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Calcium supplements for prevention and treatment of mineral and bone disorders in chronic kidney disease (CKD) have been alternately praised and damned. Clinical evidence in favor of either attitude has been lacking. The calcium balance study by Spiegel and Brady in patients with late stage 3 and stage 4 CKD suggests that CKD subjects ingesting 2000mg of elemental calcium per day are in marked positive balance. Methodological limitations such as unproven steady state warrant caution and confirmatory studies.

The effect of dietary lentils on calcium balance was evaluated in nine healthy male subjects. The Control and Experimental (+ 130 g dry lentils) diets were each fed for three weeks in a cross-over design. Study diets were matched to subjects' usual calcium and energy intakes, and balanced for protein and phytate. Complete fecal collections were made for all weeks and 24-hour urine collections were made in Week 3 of each period. Calcium balance was maintained during both the Control (0.4 ± 0.8 mmol/day, mean ± SEM) and Experimental periods (− 0.6 ± 0.9 mmol/day); fecal calcium remained unchanged (28.5 ± 1.7 mmol/day, 29.7 ± 1.5 mmol/day, respectively). Urinary excretion, however, varied from Control to Experimental periods for the following: calcium decreased from 5.43 ± 0.44 to 4.53 ± 0.41 mmol/day (P

Calcium is an important nutrient but also contributes to the texture, taste and functionality of most dairy products. The balance between micellar and free calcium in curd and serum phase during direct acidification of bovine milk was studied by changing organic acid type, pH and acidification temperature. Concentration of free calcium increased with decreasing pH and increasing temperature. Citric acid was more efficient than lactic acid at lowering free calcium concentration, while temperature effect was larger for acidification with lactic acid. These findings are rationalized by the stronger binding of calcium to citrate compared to lactate with an almost athermal binding for citrate and an endothermal binding for lactate. Curd yield decreased by decreasing pH as solubilization of colloidal calcium phosphate causes loss of minerals into the serum phase decreasing the concentration of both calcium and phosphate left in the curd, while acidification temperature had little effect on curd yield. These results are important to improve yield and tailor the properties and functionality of dairy products, such as for example Mozzarella cheese.

Calcium balances performed on 519 individuals from birth to 30 years of age, derived from 34 published reports, were pooled by age group and the relationship between intake and balance for each group was compared at both extremes of the intake range. At all ages, from infancy through the young adult years, balance values tended to flatten and become constant at higher intakes, while at lower intakes balance was invariably highly correlated with intake. Threshold intakes and balances were estimated by fitting the data to a two-component, split, linear-regression model. The threshold values at which balance no longer rose with intake exceeded the US recommended dietary allowances for calcium for all the age groups concerned.

Calcium flux and mode of uptake were investigated in an underground dwelling mole-rat, Cryptomys damarensis, fed diets of varying Ca content. The amount of dietary Ca positively influenced the amounts ingested, absorbed and retained. The linear relationship between ingested and absorbed Ca was significantly (P less than 0.001) correlated, implying that this process is nonsaturable. When mole-rats were fed a diet low in Ca, apparent fractional absorption of Ca was high (85.88%). This increased still further when the diet was changed to a food of greater Ca content (96.13%, carrots; 96.97%, gemsbok cucumber). Mineral homeostasis is regulated at the intestinal level in most mammals. Regardless of dietary Ca content, uptake of 45Ca (examined via the everted gut sac technique) was passive, confirming that absorption is via a nonsaturable process. Plasma Ca concentrations were not tightly regulated, yet when fed the diet with the highest Ca content, mole-rats were not hypercalcemic. Regardless of diets, Ca apparent fractional retention was positive, and approached physiological maxima (greater than 97%). Cryptomys damarensis, in using highly efficient modes of mineral uptake and retention, is therefore capable of fully exploiting the limited food resources of their arid ecotope.

Calcium balance in chronic kidney disease is poorly understood as calcium deficiency is a stimulus for secondary hyperparathyroidism and consequent bone loss while calcium excess promotes extraosseous calcifications. To help resolve this, we evaluated calcium balance in normal individuals and in patients with chronic kidney disease (CKD) on daily diets containing 800 and 2000 mg elemental calcium. Both normal individuals and patients with late stage 3 and stage 4 CKD were in slightly negative to neutral calcium balance on the 800-mg calcium diet. Normal individuals were in modest positive calcium balance on the 2000-mg diet, while patients with CKD on the same diet were in marked positive calcium balance at least over the 9 days of study; and significantly greater than the normal individuals. Increased calcium intake significantly decreased 1,25-dihydroxy-vitamin D and intact parathyroid hormone levels but did not alter the serum calcium concentration. Thus, our findings have important implications for both preventing calcium deficiency and loading in individuals with late stage 3 and stage 4 CKD.

Few calcium balance data are available from young children on which to base dietary recommendations.The objective of the study was to evaluate the relation between calcium intake and balance in healthy children aged 1-4 y consuming typical American diets.Subjects were assigned to a diet with nutrient intakes similar to those of their usual diet. Calcium absorption was assessed by using a dual-tracer stable-isotope technique. Endogenous fecal excretion was measured in a subset of children, and net calcium balance was calculated.Mean calcium intake was 551 mg/d (range: 124-983 mg/d), and mean (+/-SEM) calcium retention was 161 +/- 17 mg/d. Both linear and nonlinear modeling of balance data showed that a calcium intake of approximately 470 mg/d led to calcium retention of 140 mg/d, which is the amount that meets expected bone growth needs in children of this age. No evidence was found that calcium intakes of 800 to 900 mg/d reached the threshold intake beyond which no additional increase in calcium retention would occur.Bone growth needs in 1-4-y-old children following American diets are met by a daily calcium intake of approximately 470 mg/d, which suggests that the current Adequate Intake of 500 mg/d is close to the actual Estimated Average Requirement. The benefits and risks of higher calcium intakes consistent with threshold values should be evaluated in a controlled trial before those intakes could be used as a basis for dietary recommendations.

Objective Bone mineral density is compromised in individuals with cystic fibrosis (CF); calcium is the major bone mineral. This study examined the impact of endogenous fecal calcium (V endo ) losses on calcium balance in girls with CF. Study design V endo was measured in 12 girls with CF (aged 7-18 years): 7 younger, premenarcheal girls with compromised nutritional status; and 5 older, postmenarcheal girls with adequate nutritional status. V endo was measured as the amount of intravenously administered 42 Ca, a calcium stable isotope, in stool relative to urine over 6 days. V endo was compared between pre- and postmenarcheal girls by Student's t test. Actual calcium balance [absorbed calcium−(urinary calcium (V u )+V endo )] was compared with estimated balance (assuming V endo =1.6 mg/kg/day calcium) by paired t test. Results V endo was 99.3±42.3 mg/day. By body weight, V endo was highest among premenarcheal girls (3.37±1.09 mg/kg/day), resulting in excess losses (>1.6 mg/kg/day) of 55.0±45.7 mg/day. Over 1 year, this represents 20.1±16.7 g of unattained bone calcium or 6.7±4.2% of the bone calcium content of these girls. Conclusions V endo is a significant source of calcium loss in individuals with CF and may limit calcium availability for bone mineral deposition.

Chinese dietary reference intakes (DRIs) for calcium were developed mainly from studies conducted amongst Caucasians, yet a recent review showed that reference calcium intakes for Asians are likely to be different from those of Caucasians (Lee and Jiang, 2008). In order to develop calcium DRIs for Chinese adolescents, it is necessary to explore the characteristics and potential influencing factors of calcium metabolic balance in Chinese adolescents. A total of 80 students (15.1+/-0.8 years) were recruited stratified by gender from a 1-year calcium supplementation study. Subjects were randomly designed to four groups and supplemented with calcium carbonate tablets providing elemental calcium at 63, 354, 660, and 966 mg/day, respectively. Subjects consumed food from a 3-day cycle menu prepared by staff for 10 days. Elemental calcium in samples of foods, feces, and urine was determined in duplicates by inductively coupled plasma atomic emission spectrometry. The total calcium intake ranged from 352 to 1323 mg/day. The calcium apparent absorption efficiency and retention in boys were significantly higher than that in girls (68.7% vs. 46.4%, 480 mg/day vs. 204 mg/day, P

Vitamin K2 (menatetrenone) has been used for the treatment of osteoporosis in Japan. We investigated the effects of ovariectomy (OVX) and vitamin K2 on the calcium (Ca) balance in 20-week-old female Fischer rats. Vitamin K2 (31 mg/kg per day) was given to animals as a dietary supplement. At weeks 4 and 8 after OVX, a Ca balance study was performed for 5 days. The intestinal Ca transport was determined using the everted gut-sac technique at week 9. The Ca balance was poorer in the OVX-control group than in the sham-control group at weeks 4 and 8 after OVX. The Ca balance improved significantly in the vitamin K2 groups as compared with the sham- and OVX-control groups. The intestinal Ca transport decreased due to OVX and was higher in the vitamin K2 administration groups than in the sham- and OVX-control groups, but not to a significant extent. The bone mineral density in the femoral metaphysis as well as the cortical area and cortical thickness in the femoral diaphysis in the OVX-control group were lower than in the sham-control group. The administration of vitamin K2 significantly inhibited an OVX-induced decrease in cortical area and cortical thickness in the femur. These findings suggest that the poor Ca balance observed in ovariectomized rats may be improved by vitamin K2; vitamin K2 may be involved in preventing bone loss in vivo.

Prostaglandins (PGs) are known to have various effects on bone metabolism. The supplementation of essential fatty acids (EFAs), the precursors of PGs, leads to increased intestinal calcium absorption and calcium balance. It is, however, not known whether increased calcium absorption and calcium balance will enhance the calcium content in bone. Male Sprague-Dawley rats (n = 40) aged 5-12 weeks were supplemented with EFAs. The main dietary EFAs, linoleic acid (LA) and alpha-linolenic acid (ALA) were administered in a ratio of 3:1 as a control group. The conversion of LA to ALA to the PG precursors is slow, with the first step, delta-6-desaturation being rate limiting. Fatty acids beyond this rate-limiting step, gamma-linolenic acid (GLA, n-6) and eicoapentaenioc acid (EPA, n-3), were administered to different groups in the ratios 3:1, 1:1 and 1:3 to explore the impact of different ratios of n-6 and n-3 EFAs. Intestinal calcium absorption (mg/24 h) increased by 41.5% in the 3:1 supplemented group, compared with the control group. The decrease in urinary calcium (mg/24 h) correlated with the increase in n-3 level. The calcium balance (mg/24 h) and bone calcium (mg/g bone ash) increased significantly in the 3:1 (41.5% and 24.7%) group, compared with the control. The increase in bone calcium might be attributed to an EFA-induced increase in circulating PGs. An increased synthesis of PGs acting on target bone cells, as well as changes in membrane fluidity, may underlie these observations.

Sprague Dawley rats were supplemented with either fish oil, evening primrose oil or sunflower oil (control) for 12 weeks. Calcium balance and fatty acid analyses of plasma and intestinal membranes were performed at week 12. Fish oil decreased faecal calcium excretion significantly leading to an increased calcium balance (p < 0.05). Increased unsaturation of the intestinal membranes in the fish oil group may facilitate calcium absorption.

The effect of an acid or alkali diet was investigated in 14 mature dairy cows during the last 28 days of pregnancy. The acid diet reduced the incidence of parturient hypocalcaemia compared with the alkali diet and was associated with higher blood ionised calcium and plasma chloride concentrations and lower blood pH and acid-base excess before parturition. Plasma 1,25-dihydroxyvitamin D concentrations before parturition were increased by the acid diet but the concentrations of parathyroid hormone and intact 1–86 parathyroid-hormone-related peptide were unaffected. The estimated fractional calcium absorption and calcium mobilisation rate during an ethylenediamine tetraacetic acid infusion were increased by the acid diet 14 days before parturition. Cortical bone remodelling occurred in all the animals during late pregnancy but was particularly evident in the cows given the acid diet. The data suggest that an acid diet ameliorates parturient hypocalcaemia by enhancing calcium mobilisation before parturition by increasing calcium absorption and bone resorption, these increases possibly being mediated by increases in the plasma concentration of 1,25-dihydroxyvitamin D.

Summary The ‘meal effect’ on mineral bioavailability is evaluated in short-term studies on humans whereas feeding experiments on pigs lasting several weeks allow both mineral balance studies and measurements of bone ash contents or breaking strength. Three groups of 7 pigs were given 3 dietary treatments, differing essentially in the mode of Ca and P distribution, for 7 weeks. Group 1 received Ca and P within the meals, Group 2 was fed Ca separate from meals, and Group 3 was given both Ca and P separate from meals. Ca and P absorption were evaluated by a 10-day balance trial, then several bones were collected to determine mineral contents and breaking strength. Ca was much better absorbed and retained by giving CaC03 within meals. Simultaneous administration of Ca and P did not influence Ca absorption, but tended to improve Ca and P retention. The best bone scores were obtained when CaC03 and NaH2PO4 were given simultaneously in meals. The Ca and P balance values and bone parameters were strongly correlated. Thus meal incorporation and simultaneous intake of Ca and P are both required for the best mineral retention, evaluated by balance or bone scores.

One serious difficulty with calcium balance studies is the unpredictable fecal excretion of calcium which follows ir-regular bowel habits. The calcium balance is often impossible to evaluate because of the error introduced by inadequate demarcation of feces. The significance of the demarcation error can be evaluated in the course of a balance study by a simple, continuous registration of the cumulative calcium balance expressed in mg./day. A calcium balance study should not be discontinued before the cumulative balance has attained a plateau for at least 3–4 periods. The length of the study will thus be dependent on the bowel habits of the subject studied. At a large calcium intake the plateau is generally obtained later than at a low one.

Methods for the measurement of calcium in the diet, urine and faeces for the performance of a calcium balance study are described, along with experiments on analytical procedures including recovery values. A means of calculating the inherent “technical error” in such a balance is given, and a method for determining the significance of any change in a patient's balance is described. These are illustrated by worked examples of data from a patient suffering from Paget's disease and one with osteoporosis before and after treatment with calcitonin.

Calcium balance performance was evaluated in 130 normal perimenopausal women ages 35 to 50, studied on their usual, self-selected dietary calcium intakes. Two distinct balance methods were used, one based on customary intake and output measurements, and the other based on absorption and clearance of two simultaneously administered calcium isotopes. Both methods yielded essentially identical results. Under study conditions as closely approximating normal living as possible, these women averaged -24 and -31 mg Ca/day by the two balance methods (exclusive of unmeasured dermal losses). More significantly, there was a positive correlation between intake and balance, with women on higher self-selected intakes exhibiting more positive balance than women selecting lower intakes. The calcium intake predicted from our data which would be required to produce an average balance of zero was 1.241 g/day. This is significantly in excess of the current recommended dietary allowance for calcium. The implications and significance of this discrepancy are explored in detail.

A method of determining dermal calcium losses in connection with calcium balance studies is described. The method involves collection of arm sweat in a plastic bag, rinsing with deionized water, determination of the Ca K ratio in the diluted sweat, and determination of dermal potassium losses. The latter losses are determined on the basis of the potassium balance and simultaneous determinations of changes in total exchangeable potassium. Arm sweat seems to be representative for whole body sweat with respect to the Ca K ratio. The dermal calcium loss varied between 20 and 365 mg. in 13 patients (mean 120 mg./day). These losses are of considerable importance in connection with calcium balances which is illustrated in a number of cases.

BENNION and Warren (1933) and Warren and Schnepel (1940) reported that shell thickness is reduced markedly if hens are subjected to high environmental temperatures. Their experiments further suggested that the depressing effect of high temperature is accentuated by high humidity. The mechanism or mechanisms which cause poor shell quality at high air temperatures are still not definitely established. Conrad (1939) found that blood calcium levels were reduced at high environmental temperatures. From this evidence Warren and Schnepel (1940) concluded that: “The decrease in shell thickness when the birds are subjected to high temperatures is probably due to a reduction in calcium content of the blood.” Warren and Schnepel (1940) also reported that hens kept at 95°F. consumed about 26% less feed than hens kept at 60°F. It is possible that this reduction of feed intake is at least partially responsible for the poor shell quality at high air temperatures. Finally, …

Six women, aged 38 to 62 yr, participated in a 40-day metabolic study to investigate the effect of level of protein intake and of sodium bicarbonate ingestion on urinary calcium, net calcium balance, net renal acid excretion, and arterialized venous blood pH and bicarbonate ion concentration. The diet contained 44 g protein during the first 16 days and 102 g during the remaining 24 days. During the last 10 days of the study, 5.85 g of sodium bicarbonate was ingested concomitantly with the higher protein intake. Calcium, phosphorus, and magnesium intakes were held constant at 500, 900, and 300 mg, respectively. The increase in protein intake significantly increased urinary calcium and net renal acid excretion and the mean net calcium balance became negative. The ingestion of sodium bicarbonate alkalinized the urine and reversed the increase in urinary calcium associated with the higher protein intake; the mean net calcium balance became positive. The arterialized venous blood pH and bicarbonate ion concentrations were not significantly affected by dietary treatments. The results suggest that the ingestion of a small amount of sodium bicarbonate may be an effective way to increase calcium retention in women with protein-induced hypercalciuria.

Metabolic-balance studies were performed on seven patients in the last trimester of pregnancy. All had normal diets containing approximately 1 g. calcium and three had a supplement of 1 g. calcium per day. All were in positive balance and five had hypercalciuria; however, the amount of calcium retained was only equivalent to that incorporated in the fetus in patients taking the calcium supplement. These results suggest that the calcium intake during pregnancy should be 2 g, rather than 1 g. per day.

Three, 4-wk, controlled feeding periods were used to assess relationships between oxalate excretion, calcium balance, and numbers of oxalate-degrading bacteria during consumption of a baseline diet, and the baseline diet with the addition of 175 g spinach or 260 g broccoli by 8 premenopausal women. Oxalate intakes were 108, 100 and 1570 mg/day during consumption of the baseline, broccoli, and spinach diets, respectively. Numbers of oxalate-degrading bacteria (ODB) ranged from 10 6 –10 7 /g feces in 5 subjects whereas no oxalate-degrading bacteria (no-ODB) were detected in 3 subjects. Four of the 5 ODB subjects exhibited an increase (p

Dietary calcium and serum 1,25-(OH) 2 -vitamin D concentrations as determinants of calcium balance in healthy men. We previously reported that experimental elevations of serum 1,25-(OH) 2 -vitamin D [1,25-(OH) 2 -D] concentrations produced by the chronic oral administration of calcitriol, 0.75 µg every 6 hr, to healthy human males eating diets providing only 4 mmoles Ca/day stimulate net bone resorption as evidenced by more negative Ca balances and higher rates of urinary hydroxyproline excretion. To determine whether increased dietary Ca intake modifies this response we have compared serum 1,25-(OH) 2 -D and iPTH concentrations, Ca and PO 4 balances, and urinary hydroxyproline excretion in three healthy human males adapted to diets providing 22.3 ± 1.3 mmoles Ca/day and three healthy human males adapted to diets providing 9.3 ± 0.7 mmoles Ca/day before and during the continuous oral administration of calcitriol 0,5 µg every 6hr. For all six subjects, serum 1,25-(OH) 2 -D levels averaged 89 ± 25 pM during control and 143 ± 26 pM during calcitriol. Net intestinal Ca absorption and urinary Ca excretion rose during calcitriol but Ca balances did not change, averaging +2.2 ± 2.2 mmoles/day during control and +4.3 ± 2,2 mmoles/day during calcitriol for the subjects fed 22 mmoles Ca/day and - 1.6 ± 1.5 mmoles Ca/day during control and - 1.7 ± 2.0 mmoles Ca/day during calcitriol for the subjects fed 9 mmoles Ca/day. Urinary hydroxyproline excretion also did not change. Thus, when serum 1,25-(OH) 2 -D levels are elevated, the availability of dietary Ca appears to prevent more negative Ca balances and increased urinary hydroxyproline excretion suggesting that net bone resorption is not stimulated. Le calcium alimentaire et les concentrations seriques de 1,25-(OH) 2 -vitamine D determinants de la balance calcique chez des hommes sains. Nous avons prealablement rapporte que des elevations experimentales des concentrations seriques de 1,25-(OH) 2 -D par administration chronique orale de calcitriol, 0,75 µg toutes les 6 heures a des hommes sains ingerant des regimes n'apportant que 4 mmoles Ca/jour stimulent la resorption osseuse nette, ce qui est mis en evidence par des balances Ca plus negatives et par des debits d'excretion urinaire d'hydroxyproline plus eleves. Afin de determiner si une augmentation de l'apport en Ca alimentaire modifie cette reponse, nous avons compare les concentrations seriques de 1,25-(OH) 2 -D et d'iPTH, les balances Ca et PO 4 et l'excretion urinaire d'hydroxyproline chez trois hommes sains adaptes a des regimes apportant 22,3 ± 1,3 mmoles Ca/jour et chez trois hommes sains adaptes a des regimes apportant 9,3 ± 0,7 mmoles Ca/jour avant et pendant l'administration orale continue de calcitriol, 0,5 µg toutes les 6 heures. Pour les six sujets, les niveaux seriques de 1,25-(OH) 2 -D etaient en moyenne de 89 ± 25 pM pendant le controle et de 143 ± 26 pM pendant le calcitriol. L'absorption intestinale nette de Ca et l'excretion urinaire de Ca se sont elevees pendant le calcitriol, mais les balances Ca n'ont pas change, etant en moyenne de +2,2 ± 2,2 mmoles/jour pendant le controle et de 4,3 ± 2,2 mmoles/jour pendant le calcitriol chez les sujets ingerant 22 mmoles Ca/jour et de - 1,6 ± 1,5 mmoles Ca/jour pendant le controle et de 1,7 ± 2,0 mmoles Ca/jour pendant le calcitriol chez les sujets ingerant 9 mmoles Ca/jour. L'hydroxyproline urinaire aussi ne s'est pas modifiee. Ainsi, lorsque les niveaux seriques de 1,25-(OH) 2 -D sont eleves, la disponibilite du calcium alimentaire parait prevenir des balances Ca plus negatives et une excretion urinaire d'hydroxyproline elevee, suggerant que la resorption osseuse nette n'est pas stimulee.

Calcium balance studies were performed to determine whether calcium supplements were necessary. Two groups of normal pregnant women in their third trimester were studied: one group had a normal diet, the other group a similar diet plus 1 g calcium/day. All 4 patients in the control group were in positive calcium balance, the mean value for the group being + 142 mg/day. All three subjects in the supplemented group had positive calcium balances, with a mean value of + 305 mg/day. The nett gain from the 1 g supplement was about 150 mg/day. If 3% of the mother's calcium stores are incorporated in the foetal skeleton then the mother should be in positive calcium balance of 300 mg/day in order that no depletion of her body stores will occur. This study showed that only the supplemented group on a total calcium intake of 2 g/day had a mean calcium balance of 305 mg/day.

Young adult male and laying female quail, fed with a diet containing 2.64% Ca and 0.70% P, were used to study nutritive utilization, corporal calcium retention and endogenous excretion, calcemia, laying and properties of the egg (including the shell structure), mineralization of the femur bone, as well as the influence of diethylstilbestrol upon these parameters. The coefficient of nutritive utilization (C.N.U.) in the female was high and logically superior to that of the male, while the corporal retention was quite similar for both sexes. Most of the Ca absorbed (81.8%) and not excreted in urine, went to the egg and only 18.2% remained in the body. The diethylstilbestrol caused a big reduction of the C.N.U. in the female, but not in the male, parallel to an inhibition of laying, and an increase of corporal retention of used calcium. In both sexes the calcemia surprisingly increased, and the calcium level of the femur bone was higher, and even though the cortical osseous zone was slightly wider, the effect of treatment was noticeable, particularly in the medular tissue, which incremented in the female and appeared in the male. When quail were fed a calcium-restricted diet, the endogenous excretion of this mineral was small in the case of the female and significantly smaller in the male. This situation suppressed egg laying and resulted in a clearly decreased bone mineralization. The ingestion of diethylstilbestrol before feeding a diet poor in calcium provoked an increase of the endogenous excretion of calcium in both female and male quail.

Ten obese adolescents consumed the protein-sparing modified fast (PSMF), a high-protein, low-carbohydrate diet, for 92 +/- 19 d and lost 14.7 +/- 5.3 kg. The effect of weight loss using the PSMF on potassium, magnesium, and calcium was evaluated using balance method at days 2-4 and 12-20, RBC-Mg, RBC-K and total body K (TBK). The vitamin- and mineral-supplemented PSMF allowed positive Ca and K balance and improved Mg balance (p less than 0.005). TBK decreased significantly, 118.7 +/- 13.7 to 97.4 +/- 1.0 g (3.04 +/- 0.35 to 2.50 +/- 0.03 mol) from baseline to 90 d (p less than 0.001), with no change in the RBC-K concentration. An unexpected finding was a significant decrease in RBC-Mg, 3.2 +/- 1.1 to 1.8 +/- 0.3 mmol/L (p less than 0.001) after 60-90 d on the diet despite maintenance of normal serum Mg level.

The physiological role of vitamin D depends on calcium supply and calcium balance. When the calcium balance is normal, the major target of vitamin D is intestine. Vitamin D stimulates mainly active intestinal calcium transport mechanism. During a negative calcium balance, bone effects of vitamin D become dominant. Thus, the role of vitamin D in maintaining normocalcemia appears to have priority over skeletal integrity in these situations.

To achieve adequate dietary calcium intake, several choices are available that accommodate a variety of lifestyles and tastes. Liberal consumption of dairy products in the diet is the approach of most Americans. Some plants provide absorbable calcium, but the quantity of vegetables required to reach sufficient calcium intake make an exclusively plant-based diet impractical for most individuals unless fortified foods or supplements are included. Also, dietary constituents that decrease calcium retention, such as salt, protein, and caffeine, can be high in the vegetarian diet. Although it is possible to obtain calcium balance from a plant-based diet in a Western lifestyle, it may be more convenient to achieve calcium balance by increasing calcium consumption than by limiting other dietary factors.

Objectives To assess selenium intakes, absorption, retention, and status in healthy adolescent girls and the effect of calcium supplementation on selenium parameters. Design Annual 2-week study conducted each year for 3 consecutive years in which yearly selenium intakes, absorption, and retention and blood selenium status were measured. Setting A metabolic unit in a large metropolitan hospital located in Columbus, Ohio—a low selenium region of the United States. Subjects Healthy white girls aged 11 to 14 years (n=16) enrolled in a calcium balance study and randomly assigned to receive a placebo of methylcellulose (n=9) or a calcium supplement containing 1,000mg supplemental calcium as calcium citrate malate (n=7). Interventions Each subject consumed a diet with ∼100μg selenium/day during the yearly 2-week balance studies. Results Selenium status measurements (serum and erythrocyte selenium and glutathione peroxidase activity) were all within normal ranges for adults during the study. Apparent selenium absorption averaged 71%, 76%, and 74% for years 1,2, and 3 of the study, respectively, and did not vary significantly ( P >.05). Average daily selenium retention did not differ among the years of the study ( P >.05) and indicated that the usual selenium intake was ∼100μg daily. Measurements of selenium status and retention did not differ between calcium-supplemented and placebo groups. Conclusions An intake of ∼100μg selenium/day is the typical intake of the mineral among the subjects and appeared adequate to maintain selenium status in these healthy adolescent girls; in addition, calcium supplementation of 1,000mg daily does not have a negative impact on selenium parameters. J Am Diet Assoc. 2002;102:1082-1087.

An experiment was conducted to evaluate the potential dietary interaction between 1,4-diaminobutane (putrescine) and calcium on eggshell quality and overall laying performance. One hundred ninety-two 30-wk-old White Leghorn hens were fed a corn-and soybean-meal-based diet supplemented with 0.00, 0.05, 0.10, or 0.15% putrescine and 2.5, 3.0, 3.5, or 4.0% calcium in a factorial design (12 birds per diet) for 4 wk. The percentage of egg production increased linearly (P < 0.05) with increasing levels of dietary calcium. Significant interactions (P < 0.05) were observed between dietary putrescine and calcium for eggshell thickness, eggshell deformation, percentage of eggshell, calcium intake, total calcium retention, total eggshell calcium, and percentage of eggshell calcium. Interactions were due to quadratic effects of putrescine or calcium on these parameters. Eggshell thickness and percent eggshell increased when hens were fed 3.5% calcium in combination with 0.1% putrescine; however, calcium intake and calcium retention were significantly lower (P < 0.05). Eggshell quality improved with increasing dietary levels of calcium due to increased calcium retention and calcium balance. Increasing levels of dietary putrescine did not have a negative effect on eggshell quality; however, calcium intake was lower at higher-supplemented levels of putrescine. It was observed that dietary calcium in excess of requirements resulted in increased egg production and eggshell quality. Eggshell quality improved when hens were fed 3.5% calcium diet in combination with 0.10% putrescine. It was concluded that small supplements of dietary putrescine may improve eggshell quality, depending on dietary calcium concentration.

Experiments were conducted to evaluate the potential for dietary 1,4-diaminobutane (putrescine) to influence eggshell quality and overall laying performance in hens. Forty-eight, 60-wk-old White Leghorn hens laying thin-shelled eggs were fed a corn and soybean meal-based diet supplemented with 0.00 (control), 0.05, 0.10, or 0.15% putrescine for 4 wk. Twelve hens that laid thick-shelled eggs were also fed the control diet. The feeding of supplemental putrescine decreased feed consumption; however, egg weight decreased only at higher levels of supplementation. Increasing dietary levels of putrescine responded quadratically in eggshell deformation, eggshell weight, and eggshell weight as a percentage of egg weight (P < 0.05). There were no significant differences in shell deformation, shell thickness, or shell weight when comparing hens laying thick-shelled eggs and those laying thin-shelled eggs that were fed 0.05% supplemental putrescine. Calcium intake, calcium retention, and calcium balance decreased linearly (P < 0.05) with increasing levels of dietary putrescine. Pancreatic putrescine concentrations were significantly higher (P < 0.05) in hens laying thick-shelled eggs compared with hens laying thin-shelled eggs. It appeared that pancreatic cells synthesized more polyamines in hens laying thick-shelled eggs. This increase in polyamines might have caused improved eggshell quality by increasing calcium transport. It was concluded that 0.05% supplemental putrescine improved eggshell quality; however, higher levels proved to be toxic.

Background: Variation in absorption efficiency explains more of the variability in calcium balance than does actual calcium intake. Several investigators have suggested that the relatively high phosphorus and protein intakes of the diets of industrialized nations reduce calcium absorption and thereby aggravate the problem of calcium deficiency. Objective: My objective was to test whether variation in phosphorus and protein intakes is associated with variation in calcium absorption. Design: One hundred ninety-one Roman Catholic nuns aged 48.7 ± 7.0 y were studied 3 times each over a >20-y period with a full metabolic balance regimen; controlled, chemically analyzed diets; and double-tracer measurement of calcium absorption. Results: Although the expected associations with absorption were found for age, calcium intake, and estrogen status, no association was observed for intakes of either phosphorus or protein. Conclusion: Phosphorus and protein intakes do not contribute to the wide variability in calcium absorption efficiency.

Bone acts as a major reservoir that is available for the maintenance of serum calcium levels. An adult loses about 200 mg of calcium per day through the faeces (100 mg), urine (100 mg), and a very small amount through the skin. In children, about 400 mg per day of calcium are deposited in bone and they will cease 1:o grow normally if not maintained in sufficiently positive calcium balance. After the cessation of linear growth, bone undergoes remodelling at a rate of about 10% per year. The overall exchange of calcium in this process of remodelling is 500 rag/day (18.4 kg/year !). In a normal individual, these calcium needs are supplied by gut absorption, and therefore with intestinal disease, maintenance of calcium homeostasis becomes a major problem.

The vast majority of peak adult bone mass is accumulated by the time longitudinal growth is complete. As peak bone mass is an important determinant of future fracture risk, the goal of the current calcium recommended dietary allowance during youth is to provide a calcium intake that allows individuals to reach their full genetic potential for acquiring skeletal mass. The advent of controlled trials of calcium supplementation and total body bone mass measurements in children and adolescents provide the first direct way of determining the amount of calcium necessary to achieve optimal skeletal accretion. These studies indicate that the current RDAs are insufficient to support optimal bone mass gain during growth and development. Based on the recent intervention trials, recommendations are made for an RDA of 1250 mg during childhood and 1450 mg during adolescence. These values are consistent with established calcium balance intake thresholds for growth during pre-adolescence and adolescence.

A case of unusually severe soft tissue calcification with temporary loss of limb function in a patient with rhabdomyolysis-induced acute renal failure (ARF) is described. A large dose of intravenous (IV) calcium was administered early in the hospital course to treat hypocalcemia, and hemodialysis, when initiated, was with a 1.75-mmol/L calcium dialysate. This case illustrates the danger of administering calcium supplementation and raises questions about the use of normal to high dialysate calcium concentration in the early stages of rhabdomyolysis-induced oliguric ARF. Calcium supplementation should be reserved for patients with clear clinical signs of hypocalcemia and dialysate calcium should be adjusted to prevent excessive positive calcium balance.

A large percentage of subjects receiving a normal calcium intake of 800 mg per day was in negative calcium balance and increasing the calcium intake to various levels up to 2200 mg per day showed a plateau of the calcium balance at the 1200 mg per day intake, indicating a threshold of calcium absorption at this intake level. Dietary factors, such as a phosphorus intake up to 2000 mg per day and complex proteins, such as red meat, do not cause calcium loss. Several commonly used drugs induce significant calcium loss, particularly aluminum-containing antacids, and, if used for prolonged periods of time, can contribute to the development of osteoporosis.

Calcium intake has been implicated in the etiology of age-related osteoporosis. There is evidence to suggest that many postmenopausal women consume inadequate calcium to maintain calcium balance. One of the most accurate methods of calculating dietary intake is the weighed food record; however, that method is time consuming and unsuitable for large numbers of individuals. To determine the adequacy of calcium intake in the large numbers of postmenopausal women at risk of osteoporosis, simpler methods of assessing calcium intake are required. We therefore developed a food frequency questionnaire and tested it against a 4-day weighed food record in 54 Caucasian women, between 29 and 72 years of age. Twenty-six of the women (Group 1) completed a 4-day record and questionnaire within 1 week. Another 28 women (Group 2) completed the questionnaire 1 to 12 months after completing the 4-day food diary. A good correlation (r = .79, p less than .001) was found between the two methods of calculating calcium intake for the 54 women. Independent analysis of Group 1 and Group 2 showed correlation coefficients of 0.81 and 0.78, respectively. The correlation for postmenopausal women (r = .84) was similar to that of premenopausal women (r = .79). The data show that a short, simple questionnaire can be used to rank individuals according to adequacy of calcium intake as a prerequisite to nutrition intervention.

Distribution of true fractional absorption of calcium in estrogen-deprived, nonos- teoporotic, middle-aged women was examined in 273 person-studies, using a double-tracer method. Fractional absorption averaged 0.266 (±0.096). Calcium intake averaged 0.802 g/day (±0.419) and urine calcium, 0.144 g/day (±0.062). Fractional absorption was inversely correlated with intake. Using parameters ofthe regression equation for the two variables, each absorption value was adjusted to the mean intake ofthe group so that absorption could be evaluated apart from the effect of intake. The distribution of such diet-adjusted values revealed that 55% of these estrogen-deprived women had insufficient absorption to maintain calcium balance at an intake equal to the 1980 RDA. Nearly one-fourth would still be in negative balance at an intake of 1.5 g/day. Since urine calcium was positively correlated with absorbed calcium (r = 0.521), we conclude that defective absorption and not bone breakdown is the basis for low absorptive performance in these women. Am J C/in Nutr l986;43:299-305.

Integumentary calcium loss was studied in 16 healthy young men. The daily loss by the 16 ambulatory but relatively sedentary young men in 52 determinations of 6-day periods each was 8.7 ± 1.9 mgJm2 per day (average 15.8 mg/man per day). The amount lost was not influenced by calcium intake (0. 1 to 2.3 g/day). In contrast to urinary calcium excretion, which is directly related to protein intake, there was no significant change in integumentary calcium loss with varying protein intakes ( I to 96 g nitrogen per day). No compensatory relationship between urinary and integumentary calcium excretion was noted. During strenuous exercise calcium loss increased to an average of 25 mg in 40 mm. There was no compensatory decrease in urinary excretion on the day of strenuous exercise. It was also noted that integumentary calcium loss was not affected by general calcium balance. Am. J. Clin. Nutr. 32: 1699-1702, 1979.

FOURTEEN to sixteen days before the onset of egg production, (Hurwitz, 1964), the pullet undergoes profound changes in its mineral metabolism. This stage coincides with the development of the primary and secondary sex organs and is characterized by increased plasma calcium, increase in calcium retention and formation of medullary bone (Simkiss, 1961). Such an intense mineral metabolism is preceded by a period of about two months of low intensity mineral metabolism during which the calcium and phosphorus requirements are extremely low (Berg et al., 1964). During the pre-laying period the calcium and phosphate retention reach 800 and 400–500 mg./day, respectively (Taylor and Moore, 1958). It thus must follow that the mineral requirements during the pre-laying period are increased. It has been shown that during the early production period, the young hen is in a negative calcium balance (Morgan and Mitchell, 1938) which cannot be alleviated by high dietary calcium…