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Potassium supplementation has been associated with reduced urinary calcium (Ca) excretion and increased Ca balance. Dietary interventions assessing the impact of potassium on bone are lacking. In this secondary analysis of a study designed primarily to determine blood pressure effects, we assessed the effects of potassium intake from potato sources and a potassium supplement on urinary Ca, urine pH, and Ca balance. Thirty men (n = 15) and women (n = 15) with a mean ± SD age and BMI of 48.2 ± 15 years and 31.4 ± 6.1 kg/m2, respectively, were enrolled in a cross-over, randomized control feeding trial. Participants were assigned to a random order of four 16-day dietary potassium interventions including a basal diet (control) of 2300 mg/day (~60 mmol/day) of potassium, and three phases of an additional 1000 mg/day (3300 mg/day(~85 mmol/day) total) of potassium in the form of potatoes (baked, boiled, or pan-heated), French fries (FF), or a potassium (K)-gluconate supplement. Calcium intake for all diets was approximately 700–800 mg/day. Using a mixed model ANOVA there was a significantly lower urinary Ca excretion in the K-gluconate phase (96 ± 10 mg/day) compared to the control (115 ± 10 mg/day; p = 0.027) and potato (114 ± 10 mg/day; p = 0.033). In addition, there was a significant difference in urinary pH between the supplement and control phases (6.54 ± 0.16 vs. 6.08 ± 0.18; p = 0.0036). There were no significant differences in Ca retention. An increased potassium intake via K-gluconate supplementation may favorably influence urinary Ca excretion and urine pH. This trial was registered at ClinicalTrials.gov as NCT02697708.

Increased potassium intake has been linked to improvements in cardiovascular and other health outcomes. We assessed increasing potassium intake through food or supplements as part of a controlled diet on blood pressure (BP), microcirculation (endothelial function), and potassium and sodium retention in thirty pre-hypertensive-to-hypertensive men and women. Participants were randomly assigned to a sequence of four 17 day dietary potassium treatments: a basal diet (control) of 60 mmol/d and three phases of 85 mmol/d added as potatoes, French fries, or a potassium gluconate supplement. Blood pressure was measured by manual auscultation, cutaneous microvascular and endothelial function by thermal hyperemia, utilizing laser Doppler flowmetry, and mineral retention by metabolic balance. There were no significant differences among treatments for end-of-treatment BP, change in BP over time, or endothelial function using a mixed-model ANOVA. However, there was a greater change in systolic blood pressure (SBP) over time by feeding baked/boiled potatoes compared with control (−6.0 mmHg vs. −2.6 mmHg, p = 0.011) using contrast analysis. Potassium retention was highest with supplements. Individuals with a higher cardiometabolic risk may benefit by increasing potassium intake. This trial was registered at ClinicalTrials.gov as NCT02697708.

There are limited data on phosphorus balance and the effect of dietary calcium supplements on phosphorus balance in adolescents. The purpose of this study was to determine phosphorus balance and the effect of increasing dietary calcium intake with a supplement on net phosphorus absorption and balance in healthy adolescent girls. This study utilized stored urine, fecal, and diet samples from a previously conducted study that focused on calcium balance. Eleven healthy girls ages 11 to 14 years participated in a randomized crossover study, which consisted of two 3-week periods of a controlled diet with low (817 ± 19.5 mg/d) or high (1418 ± 11.1 mg/d) calcium, separated by a 1-week washout period. Phosphorus intake was controlled at the same level during both placebo and calcium supplementation (1435 ± 23.5 and 1453 ± 28.0 mg/d, respectively, p = 0.611). Mean phosphorus balance was positive by about 200 mg/d and was unaffected by the calcium supplement (p = 0.826). Urinary phosphorus excretion was lower with the calcium supplement (535 ± 42 versus 649 ± 41 mg/d, p = 0.013), but fecal phosphorus and net phosphorus absorption were not significantly different between placebo and calcium supplement (553 ± 60 versus 678 ± 63 versus mg/d, p = 0.143; 876 ± 62 versus 774 ± 64 mg/d, p = 0.231, respectively). Dietary phosphorus underestimates using a nutrient database compared with the content measured chemically from meal composites by ~40%. These results show that phosphorus balance is positive in girls during adolescent growth and that a calcium dietary supplement to near the current recommended level does not affect phosphorus balance when phosphorus intake is at 1400 mg/d, a typical US intake level.

IGF-I is a pivotal hormone in pediatric musculoskeletal development. Although recent data suggest that the role of IGF-I in total body lean mass and total body bone mass accrual may be compromised in children with insulin resistance, cortical bone geometric outcomes have not been studied in this context. Therefore, we explored the influence of insulin resistance on the relationship between IGF-I and cortical bone in children. A secondary aim was to examine the influence of insulin resistance on the lean mass-dependent relationship between IGF-I and cortical bone. Children were otherwise healthy, early adolescent black and white boys and girls (ages 9 to 13 years) and were classified as having high (n = 147) or normal (n = 168) insulin resistance based on the homeostasis model assessment of insulin resistance (HOMA-IR). Cortical bone at the tibia diaphysis (66% site) and total body fat-free soft tissue mass (FFST) were measured by peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA), respectively. IGF-I, insulin, and glucose were measured in fasting sera and HOMA-IR was calculated. Children with high HOMA-IR had greater unadjusted IGF-I (p

Potassium is an essential nutrient of concern according to recent Dietary Guidelines for Americans Advisory Committees, with less than 3% of the population meeting the current adequate intake (AI) level of 4700mg/d. Increases in potassium intake have been linked to improvements in cardiovascular and other metabolic health outcomes. Blood pressure (BP) is currently the primary criterion for determining potassium requirements. In this clinical trial, we assessed the effects of increasing potassium intake on BP and microcirculation (endothelial function). Thirty pre-hypertensive-to-hypertensive (Systolic BP ≥ 120mmHg) men (N=15) and Women (N=15) with a mean ± SD age, BMI, and BP (systolic(SBP)/ diastolic(DBP)) of 48.2 ± 15 y, 31.4 ± 6.1, and 136.3 ± 11.9/ 86.1 ± 7.1 mmHg, respectively, were enrolled in a cross-over randomized control diet trial. Participants were assigned to a random order of four 16-day dietary potassium interventions including a basal diet (control) of 2300mg/d(~60mmol/d), and three periods of an additional 1000mg/d(3300mg/d(~85mmol/d) total) of potassium in the form of potatoes (baked, boiled, or pan-heated with no additional fat), French fries, or a potassium gluconate supplement. Each intervention period was separated by two or more weeks of wash out. Blood pressure was measured in triplicate using manual auscultation on days 1, 4, 6, 8, 11, 13, 15, 16, and 17 of each intervention. Microvascular and endothelial function were assessed via thermal hyperemia, utilizing laser Doppler flowmetry (LDF), at baseline and at the end of each intervention. Results for differences in both SBP and DBP ± SE were assessed at the end treatment (average of day 15, 16, and 17 measurements) using a mixed model with repeated measures and Dunnett adjustment (P < 0.05), with no significant differences among groups (control: 128.7 ± 2.1/ 83.6 ± 1.6, French fries: 127.7 ± 2.2/ 83.7 ± 1.6, potatoes: 127.6 ± 2.3/ 85.1 ± 1.6, supplement: 128.0 ± 2.2/ 83.7 ± 1.7). Utilizing the same statistical analysis, there were also no significant differences in endothelial function (measured as percent of cutaneous vascular conductance max (%CVCmax) ± SE) among groups (control: 87.4 ± 1.5%, French Fries: 87.7 ± 1.4%, potatoes: 88.3 ± 1.1%, supplement: 88.9 ± 1.0%). In this small, controlled feeding study of short duration, increased potassium from potatoes or supplement achieved 70% of recommended intakes, but had no significant benefit to blood pressure or microvascular function in men and women with higher cardiometabolic risk.

Introduction: Hypertension is a major risk factor for CVD affecting 34% of American adults. High sodium (Na) intake is identified as a modifiable risk factor for high blood pressure, but our ability to assess Na intake is poor. The gold standard is to measure Na excretion in a 24h urine collection, but this is burdensome. An alternative method is to predict 24h Na excretion from a spot urine sample. However, we do not know how well predicted 24h Na excretion reflects intake, the true outcome of interest, or the ideal time to collect a spot urine sample. These gaps can only be filled using a controlled feeding study in which intake is known and timing of urine collections is controlled. Hypothesis: We hypothesized that, with currently available equations, 24h Na excretion predicted from spot urine samples will not accurately reflect intake. Methods: This is a secondary analysis of a randomized, multi-phase, crossover, full-feeding trial in healthy adults ( n = 39, aged 29.7 ± 11.2 y). Data from the two control phases were used in which dietary intake and testing conditions were identical. Participants ate three meals in a clinic setting and spot urine samples were collected every 2 hours as part of a 24h collection. Urine samples were analyzed for sodium, potassium, and creatinine. The INTERSALT equations were used to predict 24h Na excretion from each of the 9 spot urine samples collected. Predicted 24h Na excretion values were compared with observed 24h excretion and known dietary intake using repeated measures ANOVA. Intra-class correlations for each timed spot urine sample were calculated to determine the variability in average spot urine Na excretion between the two control phases. Results: Predicted 24h Na excretion using the spot urines at hour 10, 12, overnight, and early morning collection were not significantly different from observed 24h Na excretion (all p ≥ 0.21). However, predicted 24h Na excretion underestimates observed 24h Na excretion by about >600 mg. Importantly, all predicted 24h excretions as well as observed 24h excretion were significantly lower than intake by >1000 mg (all p < 0.001). Intraclass correlations were significant at hour 0, 2, 8, 12, and evening/overnight (all p < 0.05), suggesting low day-to-day variability in Na excretion at these times. Conclusions: Regardless of time of spot urine collection, predicted 24h Na excretion is lower than Na intake, suggesting currently-available equations do not provide adequate estimates of Na intake. The next step is to develop equations to accurately predict Na intake from a controlled feeding study model using spot urine samples collected at a time when Na excretion is consistent from day to day. These improved equations could be used to implement effective dietary interventions to reduce blood pressure and CVD risk.

The rare, long-lived radiotracer, 41Ca, measured by accelerator mass spectrometry in the urine or serum following incorporation into the bone provides an ultra-sensitive tool to assess changes in bone calcium balance in response to an intervention. Changes in bone balance can be followed for years with one small dose that is both radiologically and biologically non-invasive. Sequential interventions can be compared, with greater precision than they can with biochemical markers of bone turnover and with greater power than with bone densitometry. This method is especially useful to screen interventions over a period of weeks. The development and validation of this tool and its applications are reviewed. Mini abstract: Use of 41Ca measured in the urine or blood by accelerator mass spectrometry to assess bone balance provides a tool to compare the relative efficacy of multiple interventions. This perspective provides insights in the use of this novel method and comparisons with more traditional methods for evaluating the efficacy of interventions.

BACKGROUND: Soluble corn fiber (SCF; 12 g fiber/d) is shown to increase calcium absorption efficiency, associated with shifts in the gut microbiota in adolescent males and females who participated in a controlled feeding study. OBJECTIVE: We evaluated the dose response of 0, 10, and 20 g fiber/d delivered by PROMITOR SCF 85 (85% fiber) on calcium absorption, biochemical bone properties, and the fecal microbiome in free-living adolescents. METHODS: Healthy adolescent females (n = 28; aged 11-14 y) randomly assigned into a 3-phase, double-blind, crossover study consumed SCF for 4 wk at each dose (0, 10, and 20 g fiber/d from SCF) alongside their habitual diet and were followed by 3-d clinical visits and 3-wk washout periods. Stable isotope ((44)Ca and (43)Ca) enrichment in pooled urine was measured by inductively coupled plasma mass spectrometry. Fecal microbial community composition was assessed by high-throughput sequencing (Illumina) of polymerase chain reaction-amplified 16S rRNA genes. Mixed model ANOVA and Friedman analysis were used to determine effects of SCF on calcium absorption and to compare mean microbial proportions, respectively. RESULTS: Calcium absorption increased significantly with 10 (13.3% ± 5.3%; P = 0.042) and 20 g fiber/d (12.9% ± 3.6%; P = 0.026) from SCF relative to control. Significant differences in fecal microbial community diversity were found after consuming SCF (operational taxonomic unit measures of 601.4 ± 83.5, 634.5 ± 83.8, and 649.6 ± 75.5 for 0, 10, and 20 g fiber/d, respectively; P < 0.05). Proportions of the genus Parabacteroides significantly increased with SCF dose (1.1% ± 0.8%, 2.1% ± 1.6%, and 3.0% ± 2.0% for 0, 10, and 20 g fiber/d from SCF, respectively; P < 0.05). Increases in calcium absorption positively correlated with increases in Clostridium (r = 0.44, P = 0.023) and unclassified Clostridiaceae (r = 0.40, P = 0.040). CONCLUSIONS: SCF, a nondigestible carbohydrate, increased calcium absorption in free-living adolescent females. Two groups of bacteria may be involved, one directly fermenting SCF and the second fermenting SCF metabolites further, thereby promoting increased calcium absorption. This trial was registered at clinicaltrials.gov as NCT01660503.

Context: Citrus fruits contain unique flavanones. One of the most abundant of the flavanones, hesperidin, has been shown to prevent bone loss in ovariectomized rats. Objective: The objective of the study was to measure the effect of hesperidin with or without calcium supplementation on bone calcium retention in postmenopausal women. Design: The study was a double-blind, placebo-controlled, randomized-order crossover design of 500 g hesperidin with or without 500 mg calcium supplement in 12 healthy postmenopausal women. Bone calcium retention was determined from urinary excretion of the rare isotope, 41Ca, from bone. Results: Calcium plus hesperidin, but not hesperidin alone, improved bone calcium retention by 5.5% (P < .04). Conclusion: Calcium supplementation (Calcilock), in combination with hesperidin, is effective at preserving bone in postmenopausal women.

OBJECTIVES: Preclinical studies suggest that blueberry consumption is associated with improved bone health. This study quantified changes in urinary excretion of the long-lived calcium radioisotope (41)Ca to assess the dose-response effect of blueberries on bone loss in postmenopausal women. We hypothesized that blueberry consumption would reduce bone loss in a dose-dependent manner. METHODS: Healthy women at least 4 years past menopause were dosed with 50 nCi of (41)Ca and completed a 5-mo equilibration period for (41)Ca deposition in bone followed by a 6-wk control period. Subsequently, participants were assigned to a random sequence of 3 intervention periods, each corresponding to a low (17.5 g/d), medium (35 g/d), or high (70 g/d) dose of freeze-dried blueberry powder equivalent to 0.75, 1.5, or 3 cups of fresh blueberries. The blueberry powder was incorporated into granola bars, spread, and drinks consumed daily for 6 wk, followed by a 6-wk washout period. Urinary (41)Ca: Ca ratio was measured by accelerator mass spectrometry in 24-h urine collected weekly during intervention and every 3 wk during washout. Serum 25-hydroxyvitamin D and calcium concentrations were assessed prior to each intervention. Serum bone resorption biomarkers and urinary polyphenols were measured at the end of each control and intervention period. Data were analyzed using a linear mixed model and repeated measures ANOVA. RESULTS: Fourteen healthy, non-osteoporotic (mean bone mineral density t-score: −1.33) women completed the study. Net bone calcium retention increased by 6% in the low (P

There are limited data on phosphorus balance and the effect of dietary calcium supplements on phosphorus balance in adolescents. The purpose of this study was to determine phosphorus balance and the effect of increasing dietary calcium intake with a supplement on net phosphorus absorption and balance in healthy adolescent girls. This study utilized stored urine, fecal, and diet samples from a previously conducted study that focused on calcium balance. Eleven healthy girls ages 11 to 14 years participated in a randomized crossover study, which consisted of two 3-week periods of a controlled diet with low (817 ± 19.5 mg/d) or high (1418 ± 11.1 mg/d) calcium, separated by a 1-week washout period. Phosphorus intake was controlled at the same level during both placebo and calcium supplementation (1435 ± 23.5 and 1453 ± 28.0 mg/d, respectively, p = 0.611). Mean phosphorus balance was positive by about 200 mg/d and was unaffected by the calcium supplement (p = 0.826). Urinary phosphorus excretion was lower with the calcium supplement (535 ± 42 versus 649 ± 41 mg/d, p = 0.013), but fecal phosphorus and net phosphorus absorption were not significantly different between placebo and calcium supplement (553 ± 60 versus 678 ± 63 versus mg/d, p = 0.143; 876 ± 62 versus 774 ± 64 mg/d, p = 0.231, respectively). Dietary phosphorus underestimates using a nutrient database compared with the content measured chemically from meal composites by ~40%. These results show that phosphorus balance is positive in girls during adolescent growth and that a calcium dietary supplement to near the current recommended level does not affect phosphorus balance when phosphorus intake is at 1400 mg/d, a typical US intake level. © 2017 American Society for Bone and Mineral Research.

ContextInsulin resistance is an adverse health outcome that accompanies obesity. Fat mass is negatively associated with the bone mass after adjustment for confounders. Insulin resistance might be an intermediary in this relationship.ObjectiveTo determine whether insulin resistance is an intermediary in the relationship between adiposity and bone mass in adolescents.DesignCross-sectional secondary analysis of baseline data from a previous randomized trial.SettingUniversity research facility.ParticipantsA total of 240 adolescents (68% female), aged 7 to 15 years.Main Outcome MeasuresUsing dual energy x-ray absorptiometry, bone mineral content (BMC), areal bone mineral density, lean mass, and fat mass were measured. Skeletal sites of interest included the total body and lumbar spine (LS). Waist circumference was measured using an anthropometric tape measure. Insulin and glucose were measured in fasting sera, and the homeostasis model assessment of insulin resistance (HOMA-IR) was calculated. Path analysis was performed to determine whether the relationship between adiposity and bone was mediated through insulin resistance.ResultsFat mass (r = 0.467; P < 0.001) and waist circumference (r = 0.487; P < 0.001) correlated positively with HOMA-IR. Controlling for race, sex, maturation, lean mass, and height, fat mass, waist circumference, and HOMA-IR were negatively associated with LS BMC and total body areal bone mineral density (P < 0.05 for all). Additionally, path models for fat mass (95% CI, −5.893 to −0.956) and waist circumference (95% CI, −15.473 to −2.124) showed a negative relationship with LS BMC via HOMA-IR.ConclusionsThese results support an intermediary role of insulin resistance in the relationship between adiposity and LS bone mass.

The biomedical program at PRIME Lab has prepared radiocarbon and 41Ca as tracers for a variety of applications. Over the last decade several hundred 14C samples and several thousand 41Ca samples have been measured per year. Biomedical samples pose challenges that are relatively rare in the AMS community. We will discuss how to prepare and compensate for samples that have isotope ratios above the dynamic range of AMS, high interference rates, and small samples sizes. In the case of 41Ca, the trade off in the chromatography between yield and sample cleanliness will be analyzed. Secondary standards that have isotope ratios commonly encountered in our applications are routinely prepared. We use material from the Joint Research Centre’s Institute for Reference Materials and Measurement: IRMM-3701/4, 3701/5, and 3701/6 and a standard produced by PRIME Lab for 41Ca. We use International Atomic Energy Agency’s IAEA C-3, IAEA C-7, IAEA C-8, and a ∼12.5× modern oxalic acid secondary standard supplied by Lawrence Livermore National Laboratory for 14C. We will discuss our precision, reproducibility, and the relative agreement between our measured and the reported values for these materials.

Background and objectives Twenty-four-hour urine phosphorus is commonly used as a surrogate measure for phosphorus intake and absorption in research studies, but its reliability and accuracy are unproven in health or CKD. This secondary analysis sought to determine the reliability and accuracy of 24-hour urine phosphorus as a biomarker of phosphorus intake and absorption in moderate CKD. Design, setting, participants, & measurements Eight patients with stage 3–4 CKD participated in 2-week balance studies with tightly controlled phosphorus and calcium intakes. Thirteen 24-hour urine collections per patient were analyzed for variability and reliability of 24-hour urine phosphorus and phosphorus-to-creatinine ratio. The accuracy of 24-hour urine phosphorus to predict phosphorus intake was determined using a published equation. The relationships of 24-hour urine phosphorus with phosphorus intake, net absorption, and retention were determined. Results There was wide day-to-day variation in 24-hour urine phosphorus within and among subjects (coefficient of variation of 30% and 37%, respectively). Two 24-hour urine measures were needed to achieve ≥75% reliability. Estimating dietary phosphorus intake from a single 24-hour urine resulted in underestimation up to 98% in some patients and overestimation up to 79% in others. Twenty-four-hour urine phosphorus negatively correlated with whole-body retention but was not related to net absorption. Conclusions From a sample of eight patients with moderate CKD on a tightly controlled dietary intake, 24-hour urine phosphorus was highly variable and did not relate to dietary phosphorus intake or absorption, rather it inversely related to phosphorus retention.

OBJECTIVES: Accurate estimates of sodium (Na) intake are critical for advancing our understanding of Na and cardiovascular disease. The aim of this study was to utilize data from a controlled feeding study to assess the agreement between estimated 24hUNa, calculated from several timed spot urine collections, and known Na intake. METHODS: This secondary analysis used data from the control phase of a potassium intervention study in normotensive men and women (n = 39) to avoid the potential confounding factor of dietary potassium manipulation. Participants followed the controlled diet containing on average 3463 mg Na/d for 3 days. On day 4, participants ate 3 meals in a clinic setting and collected urine every 2 hours starting with a fasting second void. The 24-hour urine collection was completed with the first morning void the following day. Spot urine samples were analyzed for Na and estimated 24hUNa was calculated from all samples using the INTERSALT and Tanaka equations, and from only the fasting second collection using the Kawasaki equation. The relationship between estimated 24hUNa and Na intake was assessed using Spearman correlations, and agreement between estimated 24hUNa and intake was assessed using Wilcoxon Signed Rank Tests and Bland Altman plots. RESULTS: For all timed spot urine samples, estimated 24hUNa using INTERSALT and Kawasaki were significantly correlated with Na intake (all P 0.05). For all timed spot urine samples, estimated 24hUNa using INTERSALT was significantly different from Na intake (all P

OBJECTIVES: Potassium is an essential nutrient of concern according to recent Dietary Guidelines for Americans Advisory Committees. Current recommendations established by the Institute of Medicine (IOM) are given as an Adequate Intake (AI) of 4700 mg/d, met by less than 3% of the population. Little is known about potassium (K) tissue retention and less is understood on how retention may affect health outcomes. In this clinical trial, we assessed the effects of K intake from potato sources and a K supplement on overall K balance. METHODS: Thirty pre-hypertensive-to-hypertensive (Systolic BP ≥ 120 mmHg) men (N = 15) and women (N = 15) with a mean ± SD age, BMI, and BP (systolic(SBP)/diastolic(DBP)) of 48.2 ± 15 y, 31.4 ± 6.1, and 136.3 ± 11.9/86.1 ± 7.1 mmHg, respectively, were enrolled in a cross-over randomized control diet trial. Participants were assigned to a random order of four 16-day dietary K interventions including a basal diet (control) of 2300 mg/d(∼60 mmol/d), and three periods of an additional 1000 mg/d(3300 mg/d(∼85 mmol/d) total) of K in the form of potatoes (baked, boiled, or pan-heated with no additional fat), French fries, or a K gluconate supplement. Each intervention period was separated by two or more weeks of wash out. Twenty-four hour urine and stool samples were collected throughout each intervention phase, and assessed via ICP-OES for K, sodium (Na), and calcium (Ca) content. Results for differences in mineral balance were assessed as % (%) of intake by 15-day sums as follows: retention = dietary intake – urine + stool losses. RESULTS: Using a mixed model with repeated measures and follow-up contrast analyses, initial analysis shows no significant differences (P > 0.05) in % mineral retention (± SE) for K (control: 28.92 ± 7.19, French fries: 30.37 ± 5.81, potatoes: 26.39 ± 5.11, supplement: 34.52 ± 6.53), Na (control: 23.42 ± 10.34, French fries: 30.37 ± 8.03, potatoes: 20.15 ± 6.86, supplement: 26.47 ± 10.14), or Ca (control: 25.21 ± 11.23, French fries: 16.61 ± 13.47, potatoes: 24.22 ± 4.56, supplement: 31.46 ± 8.22). CONCLUSIONS: Although there appears to be no difference in mineral retention due to source, these findings may challenge the current dogma that K and Na intake are equivalent to urinary output, and raise the question of how retention in various tissues can influence health outcomes. FUNDING SOURCES: The Alliance for Potato Research and Education.

Context: Changes in serum vitamin D metabolites and calcium absorption with varying doses of oral vitamin D3 in healthy children are unknown. Objective: Our objective was to examine the dose-response effects of supplemental vitamin D3 on serum vitamin D metabolites and calcium absorption in children living at two U.S. latitudes. Design: Black and white children (n = 323) participated in a multisite (U.S. latitudes 34° N and 40° N), triple-masked trial. Children were randomized to receive oral vitamin D3 (0, 400, 1000, 2000, and 4000 IU/d) and were sampled over 12 weeks in winter. Serum 25-hydroxyvitamin D (25(OH)D) and 1,25-dihydroxyvitamin D (1,25(OH)2D) were measured using RIA and intact PTH (iPTH) by immunoradiometric assay. Fractional calcium absorption was determined from an oral stable isotope 44Ca (5 mg) in a 150-mg calcium meal. Nonlinear and linear regression models were fit for vitamin D metabolites, iPTH, and calcium absorption. Results: The mean baseline 25(OH)D value for the entire sample was...

Patients with chronic kidney disease (CKD) are given calcium carbonate to bind dietary phosphorus, reduce phosphorus retention, and prevent negative calcium balance; however, data are limited on calcium and phosphorus balance during CKD to support this. Here, we studied eight patients with stage 3 or 4 CKD (mean estimated glomerular filtration rate 36 ml/min) who received a controlled diet with or without a calcium carbonate supplement (1500 mg/day calcium) during two 3-week balance periods in a randomized placebo-controlled cross-over design. All feces and urine were collected during weeks 2 and 3 of each balance period and fasting blood, and urine was collected at baseline and at the end of each week. Calcium kinetics were determined using oral and intravenous (45)calcium. Patients were found to be in neutral calcium and phosphorus balance while on the placebo. Calcium carbonate supplementation produced positive calcium balance, did not affect phosphorus balance, and produced only a modest reduction in urine phosphorus excretion compared with placebo. Calcium kinetics demonstrated positive net bone balance but less than overall calcium balance, suggesting soft-tissue deposition. Fasting blood and urine biochemistries of calcium and phosphate homeostasis were unaffected by calcium carbonate. Thus, the positive calcium balance produced by calcium carbonate treatment within 3 weeks cautions against its use as a phosphate binder in patients with stage 3 or 4 CKD, if these findings can be extrapolated to long-term therapy.

In assessing the relationship between calcium supplementation and maintaining bone mass or reducing the risk of fracture, the effectiveness of calcium supplementation has never been decisive. Freshwater crayfish rely on amorphous calcium carbonate (ACC), an instable polymorph of calcium carbonate, as the main mineral in the exoskeleton and in the temporary storage organ, the gastrolith. Inspired by the crayfish model, we have previously shown an increase in calcium bioavailability in rats administered with synthetic stable ACC vs. crystalline calcium carbonate (CCC). The current study compared the effects of amorphous calcium derived from either gastrolith or synthetic ACC with those of crystalline calcium, found in commercial CCC or calciumcitrate supplements, in a bone loss prevention model. Rats were subjected to either sham or ovariectomy (OVX) operation (n~20/ group) followed by administration of food pellets supplemented with 0.5% calcium from either source over 12 weeks. Micro-computed tomography (μCT) and histomorphometric analyses revealed bone loss prevention by both gastrolith and ACC treatments, manifested by an increase in morphometric bone parameters, compared to both CCC- and calcium citrate-treated groups. Both gastrolith and ACC treatments resulted in bone formation in the tibia cancellous bone, indicated by dynamic histomorphometry parameters, compared to either the CCC or calcium citrate treatments. Levels of urine deoxypyridinoline (DPD), suggested an anti-resorptive effect of ACC, which was also the only treatment that led to a significant increase in vertebral mechanical strength, as supported by μCT analysis of topology and orientation parameters of the vertebral trabeculae. To our knowledge, such levels of bone loss prevention by calcium supplements have never been reported. These findings thus suggest the potential of both natural (crayfish gastrolith) and, to a greater extent, synthetic ACC sources for the prevention of metabolic bone disorders and possibly of osteoporotic processes.

Background According to traditional understanding of sodium homesostasis, nearly all of daily sodium intake is excreted in urine, with intra-individual variability attributed to variability in dietary sodium intake and urine collection errors. Objective To analyze the variability of urinary sodium in excretion from a balance study with fixed sodium intakes. Methods Daily 24-h urine collections were assessed for sodium, potassium, and creatinine in 22 black and 13 white adolescent girls (11-15 y, BMI 15-29 kg/m2) in a randomized, crossover design with controlled diets containing either low (57 mmol/d) or high (167 mmol/d) sodium, each fed for three weeks. Results Coefficients of variation (CV) analysis indicated higher variation in urinary sodium excretion about the mean on low (vs high) sodium (40% vs 32%, p=0.02) and in black (vs white) girls (42% vs 30%, p Conclusions The high intra-individual variability in urinary sodium excretion on a fixed diet highlights the potential for substantial error in (a) using a single 24-hr urine collection to estimate an individual’s usual sodium intake and (b) relating sodium excretion from a single 24-hr collection with outcomes. Further research is warranted to understand the causes of such variation.

Background: Calcium retention increases with increasing body mass index (BMI) on recommended calcium intakes. Dairy foods are an excellent source of essential nutrients that are needed to increase bone mineral content (BMC) and potentially decrease fracture.Objective: We compared children who were overweight with children who were healthy weight for the accrual of bone mass in response to an extra 3 servings dairy/d compared with usual intake.Design: Participants were 240 healthy boys and girls (64%), aged 8-15.9 y (mean ± SD age: 11.8 ± 1.5 y), who consumed low amounts of dairy (

Context:Vitamin D supplementation trials with diabetes-related outcomes have been conducted almost exclusively in adults and provide equivocal findings.Objective:The objective of this study was to determine the dose-response of vitamin D supplementation on fasting glucose, insulin, and a surrogate measure of insulin resistance in white and black children aged 9–13 years, who participated in the Georgia, Purdue, and Indiana University (or GAPI) trial: a 12-week multisite, randomized, triple-masked, dose-response, placebo-controlled vitamin D trial.Design:Black and white children in the early stages of puberty (N = 323, 50% male, 51% black) were equally randomized to receive vitamin D3 (0, 400, 1000, 2000, or 4000 IU/day) for 12 weeks. Fasting serum 25-hydroxyvitamin D (25(OH)D), glucose and insulin were assessed at baseline and weeks 6 and 12. Homeostasis model assessment of insulin resistance was used as a surrogate measure of insulin resistance. Statistical analyses were conducted as intent-to-treat using a mixed effects model.Results:Baseline serum 25(OH)D was inversely associated with insulin (r = −0.140, P = 0.017) and homeostasis model assessment of insulin resistance (r = −0.146, P = 0.012) after adjusting for race, sex, age, pubertal maturation, fat mass, and body mass index. Glucose, insulin, and insulin resistance increased (F > 5.79, P < .003) over the 12 weeks, despite vitamin D dose-dependent increases in serum 25(OH)D.Conclusions:Despite significant baseline inverse relationships between serum 25(OH)D and measures of insulin resistance, vitamin D supplementation had no impact on fasting glucose, insulin, or a surrogate measure of insulin resistance over 12 weeks in apparently healthy children.

BACKGROUND Dietary soluble corn fiber (SCF) significantly improves calcium absorption in adolescents and the bone strength and architecture in rodent models. OBJECTIVE In this study, we aimed to determine the skeletal benefits of SCF in postmenopausal women. DESIGN We used our novel technology of determining bone calcium retention by following the urinary appearance of (41)Ca, a rare long-lived radioisotope, from prelabeled bone to rapidly and sensitively evaluate the effectiveness of SCF in reducing bone loss. A randomized-order, crossover, double-blinded trial was performed in 14 healthy postmenopausal women to compare doses of 0, 10, and 20 g fiber from SCF/d for 50 d. RESULTS A dose-response effect was shown with 10 and 20 g fiber from SCF/d, whereby bone calcium retention was improved by 4.8% (P < 0.05) and 7% (P < 0.04), respectively. The bone turnover biomarkers N-terminal telopeptide and osteocalcin were not changed by the interventions; however, a significant increase in bone-specific alkaline phosphatase, which is a bone-formation marker, was detected between 0 and 20 g fiber from SCF/d (8%; P = 0.035). CONCLUSION Daily SCF consumption significantly increased bone calcium retention in postmenopausal women, which improved the bone calcium balance by an estimated 50 mg/d. This study was registered at clinicaltrials.gov as NCT02416947.

Low serum 25-hydroxyvitamin D [25 (OH) D] is common in healthy children particularly in blacks. However, serum 25 (OH) D concentrations for optimal bone turnover in children is unknown and few data exist that describe effects of increasing serum 25 (OH) D on bone turnover markers during puberty. The purpose of this study was to determine the relationships between serum 25 (OH) D and changes in serum 25 (OH) D and bone turnover in white and black pubertal adolescents. Bone turnover markers were measured in 318 healthy boys and girls from Georgia (34°N) and Indiana (40°N) who participated in a study of oral vitamin D 3 supplementation (0 to 4000 IU/d). Serum 25 (OH) D, osteocalcin, bone alkaline phosphatase, and urine N-telopeptide cross-links were measured at baseline and 12 weeks. Relationships among baseline 25 (OH) D and bone biomarkers, and between changes over 12 weeks were determined and tested for effects of race, sex, latitude, and baseline 25 (OH) D. Median 25 (OH) D was 27.6 ng/mL (n = 318, range 10.1–46.0 ng/mL) at baseline and 34.5 ng/mL (n = 302, range 9.7–95.1 ng/mL) at 12 weeks. Neither baseline nor change in 25 (OH) D over 12 weeks was associated with bone turnover. The lack of association was not affected by race, sex, latitude, or baseline serum 25 (OH) D. Serum 25 (OH) D in the range of 10–46 ng/mL appears to be sufficient for normal bone turnover in healthy black and white pubertal adolescents.

Age-related changes in calcium metabolism play a role in the development of osteoporosis. A 4-wk feeding study was conducted in 5-mo-old ovariectomized (OVX) Sprague-Dawley rats to assess the effect of various dietary fibers on mineral metabolism and bone health parameters. There were 6 treatment groups: sham-Control, OVX-Control, OVX rats receiving daily estradiol (E2) injections, and OVX rats receiving an AIN-93M diet supplement with either an inulin-based fiber (Synergy1® or Fruitafit HD®) or a novel fiber (polydextrose) at 5% wt. of diet. Calcium and magnesium metabolic balances were performed after early (3 d) and late exposure (4 wk) to dietary treatments. Rats receiving polydextrose had significantly higher net calcium absorption efficiency and retention than all control groups and a trend (P≤ 0.10) for higher calcium absorption when compared to inulin-based fibers after early exposure but the advantage did not persist over long-term exposure. The inulin-based fibers had positive chronic effects on calcium metabolism that were related to changes in the gut, that is, production of short chain fatty acids and higher cecal wall weights. All fibers improved magnesium absorption and retention in early and late metabolic balances; effects on magnesium metabolism were more pronounced than for calcium. Practical Application: Steady growth in US middle-aged and elderly populations has led to higher incidences of several chronic diseases including osteoporosis, a bone disease that primarily affects postmenopausal women. Recent research suggests that certain dietary fibers (prebiotics) enhance mineral absorption and may impart bone health benefits. This work examines the impact of prebiotic supplementation on mineral metabolism and bone health using a postmenopausal rat model. Study findings will aid future investigations in ascertaining the factors related to potential bone health benefits of prebiotic which will aid in developing an effective prebiotics food product/supplement that will address the bone health needs of consumers.

Prebiotics and phytoestrogens have sparked great interest because evidence indicates that the consumption of these dietary constituents leads to lower cholesterol levels and inhibition of postmenopausal bone loss. The aim of this study was to determine the effect of both a prebiotic (Synergy) and a phytoestrogen (genistein) on bone and blood lipid levels in an animal model of postmenopausal women.A 4-week feeding study was conducted in 5-month-old ovariectomized (OVX) Sprague-Dawley rats to examine the effect of genistein, Synergy (a prebiotic), and genistein and Synergy combined on bone density and strength, calcium metabolism, and lipid biomarkers. There were six treatment groups: sham control, OVX control, OVX rats receiving daily estradiol injections, and OVX rats receiving an AIN-93M diet supplement with 200 ppm genistein, with 5% Synergy or with 200 ppm genistein and 5% Synergy combined.The rats receiving genistein had significantly lower total serum cholesterol concentrations than OVX rats in the control group (17%), OVX rats receiving daily estradiol injections (14%), and OVX rats fed the 5% Synergy diet (19%). Consumption of Synergy improved calcium absorption efficiency (41%) compared with nonconsumption (OVX control). Sham control rats had a significantly higher femoral bone density, as determined by underwater weighing, than did the rats in all of the OVX groups. Genistein consumption restored total and trabecular bone mineral density at the distal femur similar to the levels of sham rats.Genistein supplementation imparts modest heart health benefits and improves bone geometry at the distal femur, and prebiotic consumption (Synergy) results in improved calcium utilization strength in ovariectomized rats, but the combination produced no synergistic effects.

Overweight adolescents have low bone mineral content for weight and are at increased risk for fractures.The aim was to determine whether overweight and obesity influence the positive relationship between dietary calcium intake and skeletal calcium retention in adolescents.Analysis of pooled data from calcium balance studies in adolescents.Participants each underwent a 3-wk calcium balance study in a controlled environment.Participants included 280 White, Black, and Asian boys (n = 73) and girls (n = 207) ages 10-16 yr.The relationship among body mass index (BMI), calcium intake, and calcium retention was modeled using linear regression.Calcium intake, BMI, sex, race, and age explained 27.9% of the variation in calcium retention. At low calcium intakes, there was no effect of BMI on skeletal calcium retention, but at higher calcium intakes, BMI increased skeletal calcium retention.Greater gains in calcium retention occur with increases in calcium intake in adolescents with higher BMI compared with those with lower BMI. Additional studies are needed to investigate whether increasing calcium intake reduces the increased risk of fracture associated with overweight and obesity in adolescents.

Galactooligosaccharides (GOS), prebiotic nondigestible oligosaccharides derived from lactose, have the potential for improving mineral balance and bone properties. This study examined the dose-response effect of GOS supplementation on calcium and magnesium absorption, mineral retention, bone properties, and gut microbiota in growing rats. Seventy-five 4-week-old male Sprague-Dawley rats were randomized into one of five treatment groups (n = 15/group) and fed a diet containing 0, 2, 4, 6, or 8% GOS by weight for 8 weeks. Dietary GOS significantly decreased cecal pH and increased cecal wall weight and content weight in a dose-dependent manner (p < 0.0001). Fingerprint patterns of the 16S rRNA gene PCR-DGGE from fecal DNA indicated the variance of bacterial community structure, which was primarily explained by GOS treatments (p = 0.0001). Quantitative PCR of the samples revealed an increase in the relative proportion of bifidobacteria with GOS (p = 0.0001). Net calcium absorption was increased in a dose-response manner (p < 0.01) with GOS supplementation. Dietary GOS also increased (p < 0.02) net magnesium absorption, femur ⁴⁵Ca uptake, calcium and magnesium retention, and femur and tibia breaking strength. Distal femur total and trabecular volumetric bone mineral density (vBMD) and area and proximal tibia vBMD increased (p < 0.02) with GOS supplementation. Trabecular-rich bones, that is, those that rapidly turn over, were most benefited. Regression modeling showed that GOS benefited calcium and magnesium utilization and vBMD through decreased cecal pH, increased cecal wall and content weight, and increased proportion of bifidobacteria.

Scope Resistant starch (RS) is utilized by Gram-negative Bacteroidetes through a starch utilization system (Sus), which requires physical attachment of the bacteria to the substrate. Gram-positive Firmicutes, which include butyrate producers, utilize RS by other mechanisms, such as amylosomes and secreted amylases/glucoamylases. It has been previously shown that fabricated RS [alginate-based starch-entrapped microspheres (SM)] increases butyrate in in vitro human fecal fermentation and was slow fermenting. It has been hypothesized that in vivo SM would disfavor Bacteroidetes and promote Firmicutes, leading to an increase in butyrate production. Methods and results A C57BL/6J mouse model is used to test type 2 RS (RS2, raw potato) and SM for SCFAs and fecal microbial community structure. Feeding SM for 2 weeks results in 2.4 times higher mol% butyrate in the mouse distal gut than RS2. SM reduces relative abundance of Bacteroidetes and increases Firmicutes in fecal samples at the end of the 2-week feeding. This phylum-level taxonomic shift is not observed in animals fed RS2. Conclusion Through an approach to understand bacterial requirements related to starch utilization, a designed fiber type favors butyrogenic Firmicutes bacteria and provides higher mol% butyrate in the distal gut with potential benefit as an anti-inflammatory agent and to improve gut barrier function.

Adequate intake (AI) standards for water in adolescents range between 2.4-3.3 l/day for males and 2.1-2.3 l/day for females, independent of obesity status. Water intakes and excretions of this population are not well documented. The purposes of this study were to assess water turnover, inputs, and outputs in overweight adolescents, compare these parameters between males and females, and evaluate the reproducibility of water turnover. Eighteen girls (BMI 31.7 ± 4 kg/m(2); mean ± s.d.) and nine boys (BMI 26.3 ± 3 kg/m(2)) aged 12-15 years completed two 3-week metabolic balance trials. Rate of water turnover (rH(2)O) was measured by tracking the decline of deuterated water from the body over 14 days. Water inputs (diet*, ad libitum(#), metabolic(#)) and outputs (urine*, feces*, insensible(#)) were assessed (*measured, #estimated). rH(2)O was lower (P = 0.002) in girls vs. boys (3,742 ± 536 vs. 4,537 ± 623 g/day). Per kg body weight, rH(2)O was 28% lower in girls vs. boys (46 ± 7 vs. 64 ± 9 g·kg(-1)·day(-1)). Water input from food and beverages provided and metabolic production were 44 and 28% lower, respectively, in girls vs. boys. Urine and insensible water losses were 21 and 17% lower in girls vs. boys. BMI was positively associated with water turnover in both sexes (girls P = 0.037; boys P = 0.014). The intraclass correlation of rH(2)O between trials was 0.981 (P0.001). In conclusion, these overweight adolescents consumed water well in excess of sex-specific AI standards. The lower rH(2)O in girls compared to boys is consistent with adult females and males.

Simultaneous and accurate measurement of vitamin D and 25-hydroxyvitamin D in biological samples is a barrier limiting our ability to define "optimal" vitamin D status. Thus, our goal was to optimize conditions and evaluate an LC-MS method for simultaneous detection and quantification of vitamin D(2) , vitamin D(3) , 25-hydroxyvitamin D(2) and 25-hydroxyvitamin D(3) in serum. Extraction and separation of vitamin D forms were achieved using acetone liquid-liquid extraction and by a reversed phase C8 column, respectively. Detection was performed on a triple quadrupole tandem mass spectrometer (QQQ-MS/MS) equipped with atmospheric pressure photo ionization source. The LOQs for all analytes tested were 1 ng/mL for hydroxylated molecules and 2 ng/mL for the parent vitamin Ds. RSD at lower LOQ (2 ng/mL) and in medium (80 ng/mL) and high (200 ng/mL) quality control samples did not exceed 20 and 15% CV, respectively. Accuracy of the method for determination of hydroxylated molecules was also validated using National Institutes of Standards and Technology standard samples and found to be in the range of 90.9-111.2%. In summary, a sensitive and reproducible method is reported for simultaneous quantification of vitamin D(2) , vitamin D(3) , 25-hydroxyvitamin D(2) and 25-hydroxyvitamin D(3) molecules in biological samples.

We extended a simple oral method for estimating fractional calcium absorption determined by double isotopic methods using radioactive or stable isotope across wide age of adult women. Fractional calcium absorption can be estimated by using either a radioactive or stable oral isotope across the entire age spectrum of adult women. A method for estimating fractional calcium absorption using a single serum collection following a single oral radioactive isotopic tracer has been validated against a classical double isotopic tracer ratio method in adults. Our goal was to extend this simplified method to include use of stable isotopes and a broad age range. We used our database of 56 observations from 26 white adult women aged 19–67 years receiving either radioactive or stable isotopes. Reference values for fractional calcium absorption were determined from 24-h double isotopic ratios in serum and urine and from full kinetic modeling. Equations for estimating fractional calcium absorption were developed from isotopic enrichment in serum and urine from an oral tracer and measures of body size using the multiple linear regression analysis. Equations using a 4- to 6-h sample following an oral dose of either a stable or radioactive isotope corrected for body size were highly correlated with the reference values for fractional calcium absorption across different aged populations (r > 0.8, p

3H-tetracycline (3H-TC) is thought to be superior to calcium (Ca) isotopic tracers for estimating bone resorption rates due to the less redeposition upon release in animal models. However, these 2 tracers have not been compared directly using complete kinetic studies with sampling of blood, urine, feces, and bone. Our goal was to compare the 2 isotopes for evaluating bone turnover. We firstly developed a model for 3H-TC kinetics in 4-mo-old female rats (n = 3) by measuring the tracer in serum, urine, and feces over 4 d. Then, 9-mo-old ovariectomized (OVX) rats (n = 6) were given both 45Ca and 3H-TC subcutaneously. Urine was collected in 24-h pools and assayed for both tracers. Rats were killed 7 and 46 d after the dose and whole skeleton was harvested. We calculated bone resorption rates by modeling the 45Ca and 3H-TC data in urine and bone. 3H-TC kinetics revealed that, like Ca, there are 2 exchangeable compartments between serum and bone. An additional pool was required to account for bone mass of Ca. Bone resorption rates determined from urinary 45Ca and 3H-TC did not differ significantly. The tracers 45Ca and 3H-TC can be used interchangeably to determine bone resorption rates in OVX rats. Thus, both labels can be used to screen dietary and other interventions for beneficial effects on bone.

Several studies have shown a positive effect of fructo-oligosaccharides on calcium absorption and retention in animals and humans. Effects of levels of these pre-biotics that can be functionally incorporated into manufactured foods, have not been studied in controlled feeding studies.This study was designed to evaluate the effect of 9 g/d of fructo-oligosaccharides as part of a controlled diet on calcium absorption and retention in adolescent girls.Fourteen healthy adolescent girls aged 11-13 y were studied in a metabolic setting for two 3-week periods separated by a 2-week washout period. In a randomized, double-blinded, crossover design, the teens received a diet containing either 9 g/d oligofructose-enriched inulin in a calcium-fortified cereal or the control cereal with no inulin. Both diets contained ~1500 mg calcium daily. Calcium retention was determined on the third week of each period. On day 14 of the diet period, fractional calcium absorption was determined from the enrichment of (44)Ca in 4-day urine collections.Calcium absorption (67 ± 3 vs. 66 ± 3%) and retention (409 ± 394 vs. 464 ± 241 mg/d) were not significantly different when diets contained 9 g/d oligofructose-enriched inulin or not in a calcium-fortified cereal.Daily consumption of cereal containing a combination of short- and long-chain fructo-oligosaccharides as part of a controlled diet did not benefit calcium absorption or retention in adolescent girls. Lack of response to the prebiotic in this cohort may relate to their already high calcium absorption efficiency.

We validated a single oral isotope method for estimating fractional calcium absorption determined by double isotope methods in adolescents. Developed equations with an oral isotope including a single blood draw or spot urine collection can be used to evaluate fractional calcium absorption in adolescents which allows flexibility in developing protocols. This study was designed to develop and validate a simpler, less expensive single oral isotope method for determining fractional calcium (Ca) absorption in adolescents. We used our database of 31 observations from ten white and 12 black adolescent girls aged 10-15 years who participated in metabolic and kinetic studies. Tracer data following oral (44Ca) and intravenous (IV, 42Ca) administration of calcium stable isotopes and samples in serum and urine from various time points up to 4 days were used to develop methods using multiple regression analysis based on a single measurement of enriched stable isotope/tracee defined as tracer/tracee (TT) in serum (TTserum) or urine (TTurine). Reference values for fractional calcium absorption were from oral/IV stable isotope ratios in 24-h serum or urine and full kinetic modeling. The strongest equation using a single blood sample had R 2 = 0.94 (p

Calcium requirements of North American adolescents were set at 1300 mg/day based on data from white girls. Calcium requirements for Asian-American adolescents have not been studied. Using metabolic balance protocols and a range in calcium intakes, skeletal calcium retention was determined in Chinese-American adolescents. A sample of 29 adolescents, 15 boys aged 12 to 15 years and 14 girls aged 11 to 15 years, was studied twice on paired calcium intakes ranging between 629 to 1835 mg/day using a randomized-order crossover design. Calcium absorption and bone turnover rates using double-stable calcium isotope kinetic analysis on two calcium intakes per subject were measured and compared in boys and girls. Girls and boys had low habitual mean calcium intakes of 648 and 666 mg/day, respectively, and low mean serum 25-hydroxyvitamin D concentrations of 19.1 and 22.2 ng/mL, respectively. True fractional calcium absorption varied inversely with calcium load. Boys had significantly higher bone turnover rate than girls at the same calcium intake. Calcium retention increased with calcium intake; calcium intakes to achieve maximal calcium retention were 1100 mg/day in boys and 970 mg/day in girls. Recommendations for calcium requirements should be lowered for Chinese-American adolescents. © 2010 American Society for Bone and Mineral Research.

Nondigestible oligosaccharides may increase mineral absorption by changing the intestinal environment. The effect of feeding a diet containing 5% resistant starch, RS2 (uncooked native) or RS3, (cooked and retrograded) on cal- cium absorption and bone mineral status was studied in growing male rats for 4 weeks. Almost 100g more feed was con- sumed with resistant starch compared to control in four weeks. Mineral status improved as determined by femur concen- tration, but not through absorption. Mineral content of femurs increased 12, 10 and 9% for Ca, Mg and Zn respectively, while Fe decreased 23% after feeding RS3, but not RS2, compared with the control group. There was no increase in the percent retention for any of the tested minerals. 45 Ca absorption capacity was not affected by either resistant starch. We conclude that resistant starches improve mineral status possibly through increased food consumption, but not through in- creased absorption efficiency. potato and high amylose starch, were compared at the same level and fed to rats for 7 days (12), no differences were found in calcium and magnesium absorption. Cecal concen- trations of calcium, potassium, and phosphate, but not of magnesium, were significantly increased in rats fed either 25% or 50% amylose-rich starch, 10% lactulose or 10% pec- tin compared to the control (13). The cecal pool of all these minerals was increased in a dose-dependent manner with the 25% and 50% amylose. All of the studies cited above used high levels of resistant starch (15 to 50%) and some (9,10) used higher levels of dietary calcium (up to 0.75%). The calcium requirement for rats is 0.5%. It is likely that any effect of calcium-absorption enhancers would be dampened above this level. The present study was designed to investigate the effect of two resistant starches, high amylose resistant cornstarch containing 60% resistant starch (RS2) and a high amylomaize retrograded resistant cornstarch containing 55% resistant starch (RS3), at 5% by weight on calcium absorption, mineral balance and bone mineral concentration in rats fed a 0.5% calcium diet.

Adolescence is a critical time to achieve peak bone mass. However, results of national surveys suggest that young people are not consuming adequate amounts of calcium. A simple calcium self-assessment tool with low respondent burden could provide immediate feedback that may encourage calcium consumption. This study used data reduction methods to shorten a previously evaluated calcium-specific food frequency questionnaire to the 15-item Brief Calcium Assessment Tool (BCAT). Sample 1 was a cross-sectional sample of 1,426 students in sixth and 11th grades (April 2002 to February 2003) who completed the calcium food frequency questionnaire. Sample 1 was divided into two matching samples (Group 1 and Group 2). Sample 2 was a cross-sectional sample of 745 girls in sixth grade that completed the calcium food frequency questionnaire (July 2002 to February 2005). The development of the BCAT and its calcium score used two unique samples (Group 1 of Sample 1 and Sample 2) followed by confirmation of the score in a second sample (Group 2 of Sample 1). Bone mineral content was measured among the girls in Sample 2. The BCAT calcium score was associated with total hip bone mineral content (beta=.014, P=0.003) and femoral neck bone mineral content (beta=.002, P=0.006) while adjusting for covariates. Sample 3 (n=265), a subsample of Sample 2, completed bone measures 12 months later. The BCAT calcium score at the baseline was a predictor of total body bone mineral content (beta=.279, P=0.041) at 12 months. The correlation of BCAT scores 1 week apart was .76 (P0.001) among a convenience sample of 41 boys and girls aged 9 to 17 years (October 2005 to December 2005). The BCAT took about 5 minutes to complete. The significant relationship between bone mass and the BCAT calcium score supports the use of BCAT as a tool to assess food calcium intake among adolescents, especially Asian, Hispanic, and non-Hispanic white girls. The reliability and low respondent burden of the BCAT make the tool useful for large-scale studies and community-based programs.

Soy isoflavones and their metabolites, with estrogenic activity, have been considered candidates for reducing postmenopausal bone loss. In this study, we examined the effect of dietary equol, a bioactive metabolite of the soy isoflavone daidzein, on equol tissue distribution, bone parameters, and reproductive tissue activity using an adult ovariectomized (OVX) rat model. An 8-wk feeding study was conducted to compare 4 dietary treatments of equol (0, 50, 100, 200 mg/kg diet) in 6-mo-old OVX female Sprague-Dawley rats. A dose response increase in tissue equol concentrations was observed for serum, liver, kidney, and heart, and a plateau occurred at 100 mg equol/kg diet for intestine. In OVX rats receiving 200 mg equol/kg diet, femoral calcium concentration was greater than those receiving lower doses but was still less than SHAM (P < 0.05), and other bone measures were not improved. Tibia calcium concentrations were lower in OVX rats receiving 100 and 200 mg equol/kg diet compared with the OVX control rats. Trabecular bone mineral density of tibia was also lower in equol-fed OVX rats. At this dietary equol intake, uterine weight was higher (P < 0.05) than in other OVX groups but lower than the SHAM-operated intact rats. The 200 mg/kg diet dose of dietary equol significantly increased proliferative index in the uterine epithelium. Dietary equol had no stimulatory effect on mammary gland epithelium. We conclude that in OVX rats, a dietary equol dose that had modest effect on bone also exerts mild uterotropic effects.

Introduction: Reduction of ovarian estrogen secretion at menopause increases net bone resorption and leads to bone loss. Isoflavones have been reported to protect bone from estrogen deficiency, but their modest effects on bone resorption have been difficult to measure with traditional analytical methods. Methods: In this randomized-order, crossover, blinded trial in 11 healthy postmenopausal women, we compared four commercial sources of isoflavones from soy cotyledon, soy germ, kudzu, and red clover and a positive control of oral 1 mg estradiol combined with 2.5 mg medroxyprogesterone or 5 mg/d oral risedronate (Actonel®) for their antiresorptive effects on bone using novel 41Ca methodology. Results: Risedronate and estrogen plus progesterone decreased net bone resorption measured by urinary 41Ca by 22 and 24%, respectively (P < 0.0001). Despite serum isoflavone profiles indicating bioavailability of the phytoestrogens, only soy isoflavones from the cotyledon and germ significantly decreased net bone resorption by 9% (P = 0.0002) and 5% (P = 0.03), respectively. Calcium absorption and biochemical markers of bone turnover were not influenced by interventions. Conclusions: Dietary supplements containing genistein-like isoflavones demonstrated a significant but modest ability to suppress net bone resorption in postmenopausal women at the doses supplied in this study over a 50-d intervention period.

Dairy products provide most of the calcium in the diet, but consumption of milk has declined steadily over the last six decades. We determined (1) benefits to bone formation in growing female Sprague-Dawley rats when calcium is derived from dairy versus CaCO(3) and (2) residual benefits of calcium provided by dairy to rats subsequently receiving a low-calcium diet. During growth, femurs from rats fed nonfat dry milk solids (NFDM) had 8.4% higher peak breaking force, 6.4% greater Ca content, 4.8% greater weight, 4% greater width, 1.2% greater density, 13.1% greater midshaft cortical thickness, and 16.7% greater midshaft cortical area than from rats fed CaCO(3). These effects were unrelated to differences in calcium absorption or serum IGF-1, but the NFDM group had higher rates of bone formation. If maintained on an adequate calcium diet, many of these advantages disappeared. However, rats fed adequate Ca as NFDM versus CaCO(3) during growth and subsequently switched to deficient Ca as CaCO(3) had significantly (p < 0.0001) higher femoral BMD (1.3%), total bone Ca (7.2%), Ca concentration (4.6%), and cortical thickness (9.4%) and a trend (p = 0.02) toward greater peak breaking force (17%). Thus, NFDMs improved bone measures during growth and protected bone against a subsequent period of calcium depletion compared with CaCO(3).

Background: The accuracy of dietary energy assessment tools is critical to understanding the role of diet in the increasing rate of obesity. Objectives: The purposes of our study in overweight adolescent boys and girls were 1) to assess the energy reporting bias of diet records against the referent of total energy expenditure (TEE) and 2) to compare the methods of determining energy needs by using measured metabolizable energy intake (MEI) and TEE. Design: Twenty girls [12–15 y, body mass index (in kg/m2) = 33.0 ± 5] and 14 boys (12–14 y, body mass index = 27.4 ± 4) participated in two 3-wk metabolic balance studies. TEE was measured by using doubly labeled water (TEEDLW), and MEI was measured by bomb calorimetry of composite daily diet, urine, and fecal collections. Food records were collected before each study. Results: Food records underreported TEEDLW by 35 ± 20%. Underreporting of energy intake was correlated with all macronutrient intake concentrations (g or kcal) (P < 0.0001). A multiple regression model showed that 86.4% of the variance in underreporting error was explained by dietary fat (g), BMI, and sex. The intrasubject CV was 3.9% for TEEDLW and 9.9% for MEI. MEI for weight stability (MEIwtstb) averaged 99 ± 11% of TEE. Conclusions: The increased underreporting of dietary intake with increasing body weight in teens may explain in part previous reports noting that there has been an increased incidence of obesity, although energy intakes have not appeared to increase. MEIwtstb and TEEDLW gave similar estimates of energy needs. This trial was registered at clinicaltrials.gov as {"type":"clinical-trial","attrs":{"text":"NCT 00592137","term_id":"NCT00592137"}}NCT 00592137.

Background: There are limited data in adolescents on racial differences in relationships between dietary calcium intake, absorption, and retention and serum levels of calcium-regulating hormones. Objectives: The aim of this study was to investigate these relationships cross-sectionally in American White and Black adolescent girls. Methods: Calcium balance studies were conducted in 105 girls, aged 11–15 yr, on daily calcium intakes ranging from 760–2195 mg for 3-wk controlled feeding periods; 158 observations from 52 Black and 53 White girls were analyzed. Results: Black girls had lower serum 25-hydroxyvitamin D [25(OH)D], higher serum 1,25-dihydroxyvitamin D, and higher calcium absorption and retention than White girls. Calcium intake and race, but not serum 25(OH)D, predicted net calcium absorption and retention with Black girls absorbing calcium more efficiently at low calcium intakes than White girls. The relationship between serum 25(OH)D and serum PTH was negative only in White girls. Calcium intake, race, and postmenarcheal age explained 21% of the variation in calcium retention, and serum 25(OH)D did not contribute further to the variance. Conclusions: These results suggest that serum 25(OH)D does not contribute to the racial differences in calcium absorption and retention during puberty.

Background The black American population has a higher prevalence of salt sensitivity compared with the white American population. Dahl salt-sensitive rats, models of salt-induced hypertension, excrete protein-bound vitamin D metabolites into urine, a process that is accelerated during high salt intake. We tested the hypothesis that urinary vitamin D metabolite content and 25-hydroxyvitamin D (25-OHD) binding activity of black female adolescents would be greater than that of white female adolescents. Methods Female adolescents (11–15 years old, 11 black and 10 white) were fed low (1.3 g, 56 mmol/24 hours sodium) and high salt (3.86 g, 168 mmol/24 hours sodium) diets for 3 weeks in a randomized order cross-over study design. Results White and black adolescents had similar mean urinary vitamin D metabolite content (low salt, black versus white: 50 ± 10 versus 58 ± 17 pmol/24 hours; high salt, black versus white: 47 ± 7 versus 79 ± 16 pmol/24 hours). Mean urinary 25-OHD binding activities of the black and white adolescents did not significantly differ. Urinary 25-OHD binding activity of 10/11 black adolescents and 7/10 white adolescents was greater at week 3 of high salt intake than at week 3 of low salt intake (r = 0.50, P = 0.002, n = 17). Plasma 24,25-dihydroxyvitamin D concentrations of the white female adolescents were significantly higher than that of the black female adolescents ( P Conclusion Urinary loss of vitamin D metabolites may be one cause of low vitamin D status, in addition to low dietary intake and reduced skin synthesis.

Background: Higher bone mass in blacks than in whites has been related to greater calcium utilization efficiency. Dietary calcium requirements for maximal skeletal calcium accretion during puberty may differ between the races. Objective: This study compared the relation between calcium intake and calcium retention in black and white adolescent girls. Design: A range of controlled calcium intakes (760-1981 mg Ca/d) were used in 3-wk controlled balance studies. Some subjects were studied more than once; a total of 182 observations from 55 black girls and 66 white girls were analyzed. Results: Blacks had 185 ± 32 mg/d greater mean skeletal calcium retention than did whites (P < 0.0001) at all calcium intakes as a result of significantly greater net calcium absorption (P < 0.001) and lower calcium excretion (P < 0.0001). Conclusions: Dietary calcium requirements did not differ with race. Higher calcium retention at all calcium intakes during adolescence may underlie the higher bone mineral content of adult blacks than of adult whites.

Our group is interested in evaluating early effects of dietary interventions on bone loss. Postmenopausal women lose bone following reduction in estrogen which leads to increased risk of fracture. Traditional means of monitoring bone loss and effectiveness of treatments include changes in bone density, which takes 6 months to years to observe effects, and changes in biochemical markers of bone turnover, which are highly variable and lack specificity. Prelabeling bone with 41Ca and measuring urinary 41Ca excretion with accelerator mass spectrometry provides a sensitive, specific, and rapid approach to evaluating effectiveness of treatment. To better understand 41Ca technology as a tool for measuring effective treatments on reducing bone resorption, we perturbed bone resorption by manipulating dietary calcium in rats. We used 3H-tetracycline (3H-TC) as a proxy for 41Ca and found that a single dose is feasible to study bone resorption. Suppression of bone resorption, as measured by urinary 3H-TC, by dietary calcium was observed in rats stabilized after ovariectomy, but not in recently ovariectomized rats.

The bioavailability of potassium should be considered in setting requirements, but to our knowledge, the bioavailability from individual foods has not been determined. Potatoes provide 19-20% of potassium in the American diet.We compared the bioavailability and dose response of potassium from nonfried white potatoes with skin [targeted at 20, 40, and 60 milliequivalents (mEq) K] and French fries (40 mEq K) with potassium gluconate at the same doses when added to a basal diet that contained ∼60 mEq K.Thirty-five healthy, normotensive men and women with a mean ± SD age of 29.7 ± 11.2 y and body mass index (in kg/m(2)) of 24.3 ± 4.4 were enrolled in a single-blind, crossover, randomized controlled trial. Participants were partially randomly assigned to the order of testing for nine 5-d interventions of additional potassium as follows: 0 (control; repeated at phases 1 and 5), 20, 40, and 60 mEq K/d consumed as a potassium gluconate supplement or as unfried potato or 40 mEq K from French fries completed at phase 9. The bioavailability of potassium was determined from the area under the curve (AUC) of serial blood draws and cumulative urinary excretion during a 24-h period and from a kinetic analysis. The effects of the potassium source and dose on the change in blood pressure and augmentation index (AIx) were determined.The serum potassium AUC increased with the dose (P0.0001) and did not differ because of the source (P = 0.53). Cumulative 24-h urinary potassium also increased with the dose (P0.0001) and was greater with the potato than with the supplement (P0.0001). The kinetic analysis showed the absorption efficiency was high across all interventions (94% ± 12%). There were no significant differences in the change in blood pressure or AIx with the treatment source or dose.The bioavailability of potassium is as high from potatoes as from potassium gluconate supplements. Future studies that measure the effect of dietary potassium on blood pressure will need to evaluate the effect of various dietary sources on potassium retention and in both normal and hypertensive populations. This trial was registered at clinicaltrials.gov as NCT01881295.

Background Calcium is a shortfall essential nutrient that has been a mainstay of osteoporosis management. Recent and limited findings have prompted concern about the contribution of calcium supplementation to cardiovascular risk. A proposed mechanism is through the acceleration of coronary artery calcification. Determining causality between calcium intake and coronary artery calcification has been hindered by a lack of sensitive methodology to monitor early vascular calcium accumulation. The primary study aim was to assess the impact of high calcium intake on coronary artery calcification using innovative calcium tracer kinetic modeling in Ossabaw swine with diet‐induced metabolic syndrome. Secondary end points (in vitro wire myography, histopathology, intravascular ultrasound) assessed coronary disease. Methods and Results Pigs (n=24; aged ≈15 months) were fed an atherogenic diet with adequate calcium (0.33% by weight) or high calcium (1.90% from calcium carbonate or dairy) for 6 months. Following 5 months of feeding, all pigs were dosed intravenously with 41 Ca, a rare isotope that can be measured in serum and tissues at a sensitivity of 10 −18 mol/L by accelerator mass spectrometry. Kinetic modeling evaluated early coronary artery calcification using 41 Ca values measured in serial blood samples (collected over 27 days) and coronary artery samples obtained at sacrifice. Serum disappearance of 41 Ca and total coronary artery 41 Ca accumulation did not differ among groups. Secondary end points demonstrated no treatment differences in coronary artery disease or function. Conclusion There was no detectable effect of high calcium diets (from dairy or calcium carbonate) on coronary artery calcium deposition in metabolic syndrome swine.