Vitamin D may improve athletic performance in vitamin D-deficient athletes. Peak athletic performance may occur when 25(OH)D levels approach those obtained by natural, full-body, summer sun exposure, which is at least 50 ng x mL(-1). Such 25(OH)D levels may also protect the athlete from several acute and chronic medical conditions.

Based on a review of the literature, ethnic and genetic factors are significant determinants of bone mass, along with such environmental factors as diet and exercise. Differences in bone density between blacks and whites remain even after adjustment for body mass. Black-white differences in bone mass appear to be related to ethnicity because blacks have not only greater skeletal calcium content, but also greater total body potassium and muscle mass. Genetic studies of twins and parent-offspring pairs reflect strong constitutional associations of both bone mineral content and bone density at commonly measured skeletal sites. At least for females, bone mass accumulation by age 20 y is highly associated with maternal bone mass; up to menopause it is enhanced by child-bearing and lactation; beyond menopause environmental factors seem to dominate. Dietary calcium and physical activity are significant in the control of bone mass. These findings are important for osteoporosis and fractures, especially in elderly people.

BackgroundRecent randomized data suggest that calcium supplements may be associated with increased risk of cardiovascular disease (CVD) events. Using a longitudinal cohort study, we assessed the association between calcium intake, from both foods and supplements, and atherosclerosis, as measured by coronary artery calcification (CAC).Methods and ResultsWe studied 5448 adults free of clinically diagnosed CVD (52% female; aged 45–84 years) from the Multi‐Ethnic Study of Atherosclerosis. Baseline total calcium intake was assessed from diet (using a food frequency questionnaire) and calcium supplements (by a medication inventory) and categorized into quintiles. Baseline CAC was measured by computed tomography, and CAC measurements were repeated in 2742 participants ≈10 years later. At baseline, mean calcium intakes across quintiles were 313.3, 540.3, 783.0, 1168.9, and 2157.4 mg/day. Women had higher calcium intakes than men. After adjustment for potential confounders, among 1567 participants without baseline CAC, the relative risk (RR) of developing incident CAC over 10 years, by quintile 1 to 5 of calcium intake, were 1 (reference), 0.95 (0.79–1.14), 1.02 (0.85–1.23), 0.86 (0.69–1.05), and 0.73 (0.57–0.93). After accounting for total calcium intake, calcium supplement use was associated with increased risk for incident CAC (RR=1.22 [1.07–1.39]). No relation was found between baseline calcium intake and 10‐year changes in log‐transformed CAC among those participants with baseline CAC >0.ConclusionsHigh total calcium intake was associated with a decreased risk of incident atherosclerosis over long‐term follow‐up, particularly if achieved without supplement use. However, calcium supplement use may increase the risk for incident CAC.

The pattern of blood lead during pregnancy was investigated in a cohort of 195 women who, between October 1992 and February 1995, entered prenatal care at Magee-Womens Hospital in Pittsburgh, Pennsylvania, by week 13 of pregnancy. Blood was drawn as many as five times, once in each of the first two trimesters and a maximum of three times in the third trimester. Blood lead determinations were made by atomic absorption spectrophotometry. Potential sources or modifiers of lead exposure were collected by interviews, including sociodemographic, pregnancy history, occupational, and lifestyle data. Results confirmed a previously reported U-shaped curve in blood lead concentration during pregnancy as well as findings that blood lead levels increase with age, smoking, lower educational level, and African-American race and decrease with history of breastfeeding and higher intake of calcium. Additionally, interactions were found between time since last menstrual period and both maternal age and calcium. Specifically, older mothers showed steeper increases in blood lead concentrations during the latter half of pregnancy than did younger mothers, and intake of calcium had a protective effect only in the latter half of pregnancy, an effect that became stronger as pregnancy progressed. These findings provide further evidence that lead is mobilized from bone during the latter half of pregnancy and that calcium intake may prevent bone demineralization.

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The precaution adoption process model was used to examine the predictors of 2 behaviors recommended to reduce the risk of developing osteoporosis: calcium consumption and weight-bearing exercise. A total of 452 premenopausal women completed a mailed questionnaire assessing stage in the precaution adoption process and 12 knowledge and attitudinal variables. Participants were also given an opportunity to request information about osteoporosis. In all, 11 of the 12 knowledge and attitudinal variables were associated with calcium stage; 8 were associated with exercise stage. Information requests were associated with both calcium and exercise stage. Findings provide substantial support for the precaution adoption process model and suggest that the model can be usefully applied in this area to increase understanding of why many women do not practice behaviors that could reduce their risk of developing osteoporosis.

The ovariectomized (OVX), lactating rat model has been used to investigate the skeletal effects of the plant estrogen, genistein, over a 14-day period. The OVX, lactating rat on a low-calcium diet loses slightly more than 50% of its bone mineral mass during the first 2 weeks of lactation, and we have demonstrated that estrogen treatment can significantly reduce the loss of femoral mass (ash weight). Following OVX, the rats were assigned to treatment or control groups (both placebo and positive control with estrogen replacement). The treatment groups received one of three doses of a genistein-rich preparation each day via the feed for 2 weeks, after which time the pups began to have an interest in solid feed. A positive control group received conjugated estrogen in the feed. The genistein doses were: low (0.5 mg/d); intermediate (1.6 mg/d); and high (5.0 mg/d). Measurements included ash weights of the femur, scanning electron microscopy (SEM) of the proximal tibia, and uterine weights. SEM results were as follows: (1) at the low dose genistein was approximately equally effective to estrogen in the retention of cancellous bone tissue, as reflected in the number and density of trabeculae in hemisections of the tibial subepiphyseal region, but at high doses genistein was less effective; and (2) rats treated with low-dose genistein, like estradiol, had rougher endosteal surfaces and smaller pores on these surfaces than untreated control rats. Mean ash weights of the entire femur were highest in the rats treated with the low dose compared to control rats (P < 0.05), and they were higher than ash weights of rats administered the intermediate or high doses of genistein. The mean ash weights of the femurs were consistent with the genistein effects on the tibias observed by SEM. In summary, a biphasic response to the genistein preparation was found in this OVX rat model. Interpretation of the results suggests that, at the low dose, genistein appears to be an agonist at the estrogen receptor locus, whereas at higher doses the genistein is less effective and may even have adverse effects on bone cells. These findings of a biphasic effect of genistein (i.e., an inverted U effect) are consistent with those of other recent reports in the literature on isolated bone cells and on reproductive tissues. In summary, lower doses of genistein from soy foods would be expected to act similarly to estrogens with a beneficial effect on bone tissue, but at high doses that are unlikely to be consumed in human diets, this soy derivative may have potentially adverse effects on bone cell functions and thereby on bone tissue.

A cross-sectional study of 38 24-28-y-old Caucasian women was undertaken to identify associations between dietary factors, physical activity (PA), and radial bone measurements during the third decade. Measurements included radial bone mineral content (BMC) and bone density (BD), nutrient intakes, and PA patterns. PA and calcium intake were positively associated by multiple linear-regression analysis whereas protein and phosphorus were negatively associated with radial bone measurements (P < 0.05). Lean body mass was positively associated with mid BMC only (P = 0.0203). No significant effect of age on BD or BMC was observed. We conclude that in this sample of 24-28-y-old women BD and BMC did not differ by age, and behaviors that had a positive impact on radial bone measurements included at least moderate PA and adequate dietary calcium intake, whereas adverse dietary practices for BD included intakes of protein and phosphorus greater than recommended amounts.