Dietary calcium and serum 25-hydroxyvitamin D status in relation to BMD among U.S. adults

Abstract

A higher calcium intake is still the primary recommendation for the prevention of osteoporosis, whereas vitamin D deficiency is often not addressed. To study the relative importance of dietary calcium intake and serum 25-hydroxyvitamin D [25(OH)D] status in regard to hip BMD, 4958 community-dwelling women and 5003 men >/=20 yr of age from the U.S. NHANES III population-based survey were studied. Calcium supplement users and individuals with a prior radius or hip fracture were excluded. We calculated standardized means for BMD by quartiles of sex-specific calcium intake for three 25(OH)D categories (<50, 50-74, and 75+ nM) among men and women, separately controlling for other important predictors of BMD. A higher calcium intake was significantly associated with higher BMD (p value for trend: p = 0.005) only for women with 25(OH)D status <50 nM, whereas calcium intake beyond the upper end of the lowest quartile (>566 mg/d) was not significantly associated with BMD at 25(OH)D concentrations >50 nM. Among men, there was no significant association between a higher calcium intake beyond the upper end of the lowest quartile (626 mg/d) and BMD within all 25(OH)D categories. Among both sexes, BMD increased stepwise and significantly with higher 25(OH)D concentrations (<50, 50-74, 75+ nM; p value for trend: women < 0.0001; men = 0.0001). Among men and women, 25(OH)D status seems to be the dominant predictor of BMD relative to calcium intake. Only women with 25(OH)D concentrations <50 nM seem to benefit from a higher calcium intake.

FIG. 1

Total hip BMD by calcium intake (corrected for measurement error) in individuals with a 25(OH)D status <50, 50–74, or 75+ nM. (A) Values for the measurement error corrected calcium intake in quartiles among women: lowest ≤566 mg/d; second = 567–671 mg/d; third = 672–825 mg/d; top = 826–2143 mg/d. p value for trend across categories of 25(OH)D concentrations was <0.0001 while controlling for calcium intake, age (10-yr age categories), race/ethnicity (white, black, Mexican American), body mass index, height, total calorie intake, estrogen use among women, physical activity, smoking, and socio-economic status. (B) Values for the measurement error–corrected calcium intake quartiles among men: lowest ≤626 mg/d; second = 627–761 mg/d; third = 762–962 mg/d; top = 963–2152 mg/d. p value for trend across categories of 25(OH)D concentrations was 0.0001 while controlling for calcium intake, age (10-yr age categories), race/ethnicity (white, black, Mexican American), body mass index, height, total calorie intake, physical activity, smoking, and socioeconomic status.