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Background: The role of total calcium intake in the prevention of hip fracture risk has not been well established., Objective: The objective of the study was to assess the relation of calcium intake to the risk of hip fracture on the basis of meta-analyses of cohort studies and clinical trials., Results: In women (7 prospective cohort studies, 170,991 women, 2,954 hip fractures), there was no association between total calcium intake and hip fracture risk [pooled risk ratio (RR) per 300 mg total Ca/d = 1.01; 95% CI: 0.97, 1.05]. In men (5 prospective cohort studies, 68,606 men, 214 hip fractures), the pooled RR per 300 mg total Ca/d was 0.92 (95% CI: 0.82, 1.03). On the basis of 5 clinical trials (n = 5666 women, primarily postmenopausal, plus 1074 men) with 814 nonvertebral fractures, the pooled RR for nonvertebral fractures between calcium supplementation (800-1600 mg/d) and placebo was 0.92 (95% CI: 0.81, 1.05). On the basis of 4 clinical trials with separate results for hip fracture (6,504 subjects with 139 hip fractures), the pooled RR between calcium and placebo was 1.64 (95% CI:1.02, 2.64). Sensitivity analyses including 2 additional small trials with <100 participants or per-protocol results did not substantially alter results., Conclusions: Pooled results from prospective cohort studies suggest that calcium intake is not significantly associated with hip fracture risk in women or men. Pooled results from randomized controlled trials show no reduction in hip fracture risk with calcium supplementation, and an increased risk is possible. For any nonvertebral fractures, there was a neutral effect in the randomized trials.

Objective: To assess the ability of a semiquantitative food frequency questionnaire (FFQ) to measure calcium and bone-related nutrient intakes in a rural South Dakota population., Design: Intake estimates from FFQ were compared with four 24-hour recalls obtained quarterly during the preceding year., Subjects: Convenience sample of 100 participants of the South Dakota Rural Bone Health Study were recruited, with 81 completing the FFQ., Main Outcome Measures: Calcium and bone-related nutrient intakes were expressed as milligrams per day, milligrams per 1,000 kcal, or quartiles., Statistical Analyses Performed: Intakes by FFQ and 24-hour recalls were compared using paired t test and quartiles were formed to examine cross-classification., Results: Calcium intakes from FFQ and recalls were 1,287 and 1,141 mg/day (P=0.01), but calcium per 1,000 kcal did not differ. Calcium intake by FFQ correlated with intake by recall when expressed as milligrams per day (r=0.49, P<0.001) or milligrams per 1,000 kcal (r=0.59, P<0.001). Bland-Altman graphs indicated fairly good agreement between methods. Seventy-eight percent of subjects fell into the same or within one quartile category when calcium intake was expressed as milligrams per day and 83% when expressed as milligrams per 1,000 kcal. Gross misclassification occurred in 0% to 4% of the nutrients., Conclusions: Although FFQ may not be a valid indicator of an individual's intake, it does adequately classify rural populations into quartiles of calcium and bone-related nutrient intakes, making it a useful tool for assessing dietary calcium and bone related intake in rural populations.

Adequate vitamin D concentrations during pregnancy are necessary to ensure appropriate maternal responses to the calcium demands of the fetus and neonatal handling of calcium. The purpose of this report is to review studies that investigated maternal and neonatal outcomes of vitamin D deficiency or supplementation during pregnancy. Most studies reported included women at high risk of vitamin D deficiency, because of low vitamin D and calcium intake or decreased ability to synthesize endogenous vitamin D (attributable to lack of sun exposure or to heavily pigmented skin). Overall, vitamin D supplementation in these populations leads to improved neonatal handling of calcium. Results concerning benefits for fetal growth and bone development are inconclusive. There is no evidence of a benefit of supplementation during pregnancy above amounts routinely required to prevent vitamin D deficiency.

During the last decade a greater appreciation has developed for determining factors that influence bone accretion in healthy children. Nutritional factors that may contribute to bone accretion in infants and toddlers include maternal nutritional status during pregnancy, type of infant feeding, calcium and phosphorus content of infant formula, introduction of weaning foods, and diet during the toddler and preschool years. Maternal vitamin D deficiency during pregnancy is associated with disturbances in neonatal calcium homeostasis, and maternal calcium deficiency leads to reduced neonatal bone mineral content (BMC). Preterm infants are at increased risk of osteopenia, and, although the use of high mineral formula has reduced the risk of osteopenia in these infants, it has not eliminated it. The reason for the long-term bone deficiency among preterm infants is not clear, although lower physical activity levels have been suggested as a potential cause. Studies find that human milk-fed infants have lower bone accretion than do formula-fed infants; that the greater the mineral content of formula, the greater the bone accretion; and that the inclusion of palm olein oil in infant formula may reduce bone mineral accretion. Bone accretion is not influenced by the timing of the introduction of weaning foods, despite higher serum parathyroid hormone (PTH) concentrations among infants who receive solids earlier. There is evidence of calcium intake-by-gene and calcium intake-by-physical activity interactions among toddlers and young children. The long-term effects of these early nutritional influences on later bone health are unknown.

Objective: The timing of introduction of complementary food to an infant's diet is variable throughout the world. Our objective was to determine whether early introduction of complementary foods affects iron and zinc status of formulated infants at 12, 24, and 36 months of age., Design: A randomized, prospective trial was conducted. Infants were randomly assigned to receive either a) early introduction (at 3 to 4 months of age) of commercially prepared or parent's choice of complementary foods; or b) late introduction (at 6 months of age) of commercially prepared complementary foods or parent's choice of complementary foods. In addition to complementary foods, infants were fed commercial infant formula as recommended by their pediatrician. Hemoglobin, mean corpuscular volume, and serum ferritin and zinc concentrations were determined at 12, 24, and 36 months of age. Three-day diet diaries were completed at 3, 6, 12, 18, 24, 30, and 36 months of age., Subjects/setting: One hundred seventy-five infants younger than 3 months were recruited by mailings to parents in the Cincinnati area. Of these, 172 were enrolled, 90 in the early-introduction group and 82 in the late-introduction group. One hundred thirty-three infants (n = 67 in the early, n = 66 in the late group) completed the study., Statistical Analyses Performed: Student t test and regression analyses were used to determine whether there were group differences and whether there was a relationship between serum parameters and dietary intake., Results: Infants fed complementary foods early had significantly greater iron intakes until 6 months of age; however, there were no differences in the iron status parameters (ferritin, hemoglobin, and mean corpuscular volume) at 12, 24, or 36 months of age. The early introduction group consumed slightly less zinc than the late introduction group at 5 months (4.4 vs 4.8 mg/day, P < .01) and 6 months (4.4 vs 4.7 mg/day, P < .01). At all other times there were no differences between the early and late group in zinc intakes. The serum zinc concentration was not associated with dietary zinc. Both groups had normal serum zinc concentrations at 12, 24, and 36 months and there were no differences between groups., Applications/conclusions: The iron and zinc status of infants in this study was not influenced by the timing or type of complementary foods introduced. However, the infants were formula fed and the mean iron and zinc intakes that were equal or greater than the Recommended Dietary Allowances for the first 6 months of age.

Objective: To determine whether consumption of 2% milk during the second year of life leads to reduced growth or lower percentage body fat compared with consumption of whole milk., Subjects: Subjects were healthy toddlers who participated in a larger trial examining the effects of the timing of introduction of solid foods on growth., Design: Three-day diet diaries, anthropometric measurements, and body composition determined by dual-energy x-ray absorptiometry were assessed at 12, 18, and 24 months of age. At age 12 months, the toddlers were similar in length, weight, percentage body fat, and total energy intake. From 12 to 24 months of age, milk consumption consisted of whole milk exclusively in one group (n = 23) and 2% milk exclusively in another group (n = 28)., Statistical Analyses: Differences between the 2 groups in anthropometric measurements, changes in anthropometric measurements, and dietary intakes were determined by Student t tests. Mean differences were considered significant at the P = .05 level. Data are presented as mean +/- standard deviation., Results: Despite lower intakes of total fat and saturated fat in the 2% milk group, there were no differences in height, weight, and percentage body fat. Total energy intake was not reduced in the 2% milk group., Applications: Reductions in total fat and saturated fat intake in toddlers can be achieved through the use of 2% milk without compromising growth.

We investigated whether intestinal calcium absorption and serum 1,25-dihydroxycholecalciferol (calcitriol) concentrations are higher in women during lactation and after weaning to compensate for calcium lost in breast milk. Measurements were obtained at 4.6 mo postpartum in 24 lactating women and 24 nonlactating women, at 9.6 mo postpartum in 24 lactating women (2.6 mo after complete weaning) and 24 nonlactating women. One-half of the women in each group were randomly assigned to receive 1 g supplemental Ca/d as calcium carbonate. Fractional calcium absorption was measured by using stable isotopic tracers 42Ca and 44Ca. Fractional absorption was 0.32+/-0.02 (+/-SEM) in both lactating and nonlactating women, but was higher in lactating women after weaning (0.37+/-0.02) compared with nonlactating postpartum control subjects (0.31+/-0.02). These effects were independent of calcium intake. Changes in serum calcitriol paralleled changes in fractional absorption. There were no differences in calcitriol concentrations between lactating and nonlactating women, but calcitriol was greater in women after weaning compared with postpartum control subjects. Lactating women who had resumed menses had higher fractional absorption and serum calcitriol than did lactating women who had not. Serum calcium and phosphorus concentrations were greater in lactating compared with nonlactating women; there were no differences between groups after weaning. We conclude that lactation stimulates increases in fractional calcium absorption and serum calcitriol, but the responses are only apparent after weaning or the resumption of menses.

Nutritional inadequacies during lactation may affect the well-being of the mother, infant, or both. Vitamin D and calcium status in vegetarian women may be low, resulting in maternal bone demineralization. Vitamin B-12 deficiency resulting in neurologic damage has been reported in infants of vegetarian women. A review of several studies completed on women in the northeastern United States who were consuming a macrobiotic diet is presented. Supplemental vitamin D does not appear to be necessary given sufficient sun exposure. Calcium intake in vegetarian mothers was low and differences in calcium-regulating hormones were apparent. However, it is not clear whether these hormonal changes resulted in adequate adaptation whether these hormonal changes resulted in adequate adaptation and prevented bone demineralization. The low calcium intake in the vegetarian women did not result in lower milk calcium concentrations. Elevated methylmalonic acid excretion, which is often seen in vitamin B-12 deficiency, was noted in the vegetarian mothers and their infants. Infants with high methylmalonic acid excretion were consuming milk low in vitamin B-12.

Absorption of calcium and its mobilization from bone during lactation are important for delivery of calcium to breast-feeding infants; whether calcium intake offsets bone resorption is not known. We hypothesized that calcium absorption is increased in lactation and greater in women on low calcium diets, resulting in similar rates of bone resorption and accretion. Calcium absorption and kinetic indexes were calculated by using two stable isotopic tracers in 8 women; 6 were studied both during lactation and nonlactation. Women consumed low calcium diets, with half receiving supplemental calcium. Intestinal absorption was related to serum 1,25-dihydroxyvitamin D and did not increase during lactation. Despite decreased urinary calcium excretion during lactation, especially in women with low calcium intake, net balance tended to be lower during lactation. Mean residence time decreased and bone resorption exceeded accretion in almost all lactating women. Calcium need for milk production appears to be met by decreased urinary excretion and increased bone resorption, and not by increased intestinal absorption.

Studies in European and other countries have shown that vitamin D deficiency during pregnancy may adversely affect fetal growth, bone ossification, tooth enamel formation, and neonatal calcium homeostasis. Whether effects of vitamin D deficiency on pregnant or lactating mothers differ from effects observed in nonpregnant or nonlactating women is not clear. Poor maternal vitamin D status during lactation results in low breast-milk vitamin D. However, human milk usually contains small vitamin D amounts and, under normal circumstances, the sunshine exposure of human-milk--fed infants is the major factor affecting their vitamin D status. Mothers at risk of vitamin D deficiency are those who avoid dairy products, which are routinely vitamin D fortified, and live in more northern latitudes. Dark-skinned women also are theoretically at risk of vitamin D deficiency. Sunshine exposure is a major vitamin D source, and given adequate exposure, supplemental vitamin D is not necessary. However, defining adequate sunshine exposure is difficult.

Vitamin B-12 status was assessed in a group of 110 adults and 42 children from a macrobiotic community in New England. Dietary and anthropometric information also was obtained. Fifty-one percent of the adults had low concentrations of serum vitamin B-12, which inversely correlated with duration of macrobiotic diet practice. Urinary methylmalonic acid (MMA) excretion was inversely correlated with serum vitamin B-12, and 30% of adults sampled had high urinary MMA. Fifty-five percent of children had high urinary MMA, and MMA was higher in the group that consumed a macrobiotic diet during their entire lifetime. Children were relatively short in stature and weight, and decreased stature was associated with high urinary MMA. In both adults and children vitamin B-12 status was better with more consumption of dairy products or with higher tertile of reported frequencies of vitamin B-12 consumption of various animal products. Vitamin B-12 status appeared to be unrelated to consumption of several vegetarian foods.

In a group of 13 strict vegetarian and 6 omnivorous lactating women, relationships were studied among maternal milk and serum vitamin B-12, and milk vitamin B-12 and infant urinary methylmalonic acid (MMA) excretion. Milk vitamin B-12 concentrations were lower in women consuming a strict vegetarian diet compared with an omnivorous diet. Milk vitamin B-12 was inversely related to length of time on a vegetarian diet and positively correlated with maternal serum vitamin B-12 concentrations. Infant urinary MMA excretion was inversely related to milk vitamin B-12 concentrations less than 362 pmol/L. The 1989 recommended dietary allowance for vitamin B-12 of 221 pmol/d for infants is close to the intake below which infant urinary MMA excretion is increased. We conclude that the current RDA for infants provides little margin of safety.

Serum vitamin B-12 and urinary methylmalonic acid (MMA) concentrations were determined in 62 healthy infants aged 1-6 mo. Urinary MMA was inversely correlated with serum vitamin B-12 concentrations (r = -0.550, p less than 0.001); serum vitamin B-12 was higher (p less than 0.001) and urinary MMA concentrations were lower (p less than 0.001) in formula-fed infants than in infants fed human milk (from the breast). Human-milk-fed infants who had received supplemental formula had higher serum vitamin B-12 concentrations than did infants exclusively fed human milk. It is not clear whether the serum vitamin B-12 and urinary MMA concentrations in infants fed human milk reflect biochemical deficiency of vitamin B-12, and the clinical significance of these findings needs to be investigated.

Increased urinary methylmalonic acid (UMMA) concentrations might indicate vitamin B-12 deficiency. Our study tested the hypothesis that elevated UMMA in breast-fed infants is associated with decreased maternal serum B-12 concentrations. UMMA concentrations were measured in 17 vegetarian mothers and their infants and in six infants of nonvegetarian mothers. Serum vitamin B-12 concentrations were determined in all mothers. Range of UMMA for vegetarian infants (3-924 mcg/mg [2.6-790.9 mumol/mmol] creatinine) was much broader than that for omnivorous infants (2-25 mcg/mg [1.7-21.4 mumol/mmol] creatinine). Maternal UMMA and serum vitamin B-12 were negatively correlated (r = -0.700, p = 0.003). Infant UMMA concentrations correlated positively with maternal UMMA concentrations (r = 0.686, p = 0.003) and inversely with maternal serum vitamin B-12 concentrations (r = -0.681, p less than 0.001). In three infants with high UMMA concentrations, vitamin B-12 treatment (oral B-12, vitamin B-12 injection, or a modification of maternal diet within the vegetarian philosophy) led to an abrupt decrease of UMMA.