BACKGROUND:Antioxidant defenses are one possible mechanism for decreasing oxidative damage and its potentially negative effects on age-related bone mass. OBJECTIVE:This study cross-sectionally examined whether higher dietary intakes, total intakes, and serum concentrations of antioxidants may be associated with higher bone mineral density (BMD). DESIGN:Total hip (and subregions), spine, and total-body BMDs were measured in 11,068 women aged 50-79 y enrolled in the Women's Health Initiative Observational Study and Clinical Trial at 3 clinics. Antioxidant intakes from diet (vitamin A, retinol, beta-carotene, vitamin C, vitamin E, and selenium) were estimated by using a self-reported food-frequency questionnaire. Antioxidants from supplements were estimated with an interviewer-administered questionnaire. A random subset (n = 379) had serum concentrations of retinol, carotenoids, and tocopherols measured. RESULTS:After adjustment for important BMD-related covariates, increasing intakes of antioxidants were not independently associated with BMD. A significant interaction effect was observed between intake of total vitamin C (lower three-fourths compared with highest one-fourth) and use of hormone therapy (HT) (P < 0.01). The beneficial effect of current HT use on femoral neck BMD appeared to be greater in women with higher concentrations of total vitamin C. This interaction was also significant for total-body (P < 0.045), spine (P = 0.03), and total-hip BMDs (P = 0.029). CONCLUSIONS:Our results do not support independent associations between dietary intake, total intake, or serum concentrations of antioxidants and BMD in women participating in the Women's Health Initiative. The extent to which HT use may interact with vitamin C intake and BMD warrants further exploration.

When both calcium intake and calcium absorption are measured under controlled conditions, variation in absorption efficiency explains more of the interindividual differences in balance than does actual calcium intake (1). Small wonder, therefore, that interest in measuring absorption has remained high for nearly 40 years. True calcium absorption is defined as the quantitative, unidirectional flux of calcium from intestinal lumen into the blood. It is most accurately measured by a dual-tracer method, with one tracer labeling the oral calcium load and the other labeling the miscible calcium pool into which the absorbed calcium is introduced. This approach was first developed into a practicable human test by deGrazia et al. (2). As described, it is usually time-consuming and expensive. To reduce these barriers for widespread use, Heaney and Recker (3)(4) developed a single-tracer variant for women, requiring only a single blood sample, and calibrated it against a simultaneously performed double-tracer method. The single-tracer method has been used efficiently in thousands of women (5). However, because the calibration is empirical and based on body-size variables, it is not directly suitable for use in men who, with a typically higher proportion of fat-free mass than women, would be expected to distribute absorbed tracer in a larger mass of calcium. To fill this methodologic gap, we performed a small set of parallel measurements in adult men, using the female-based algorithm together wiketh a modified double-tracer approach. Participants in the study were 30 Caucasian men (age range, 20–60 years; weight range, 63.5–104 kg; height range, 1.67–1.93 m). All participants were free of known diseases affecting bone remodeling or calcium homeostasis, and tests were not performed if the individual had experienced any gastrointestinal disturbance in the preceding 5 days. Each gave informed consent after the procedures of the study were explained. Both the project …

Background: Decreased ability to absorb calcium with age limits adaptation to low calcium intake and is thought to lead to secondary hyperparathyroidism and increased risk for hip and other fractures. However, the associations between fractional calcium absorption, dietary calcium intake, and risk for fracture have never been studied.Objective: To determine whether low fractional calcium absorption in women with low calcium intake increases the risk for subsequent hip and other nonspine fractures.Design: Prospective cohort study. Setting: Four clinical centers in Baltimore County, Maryland; Portland, Oregon; Minneapolis, Minnesota; and the Monongahela Valley, Pennsylvania. Derv participants: 5452 nonblack women 69 years of age or and subsequent older participating in the fourth examination of the Study studied. of Osteoporotic Fractures.Measurements: Fractional calcium absorption was measured by using a 3-hour single isotope (Ca-45) technique. Incident fractures were identified prospectively and were confirmed by radiographic report,Results: During an average of 4.8 years, 729 women (13%) experienced at least one nonspine fracture; 153 of these women had hip fractures. After adjustment for age, women with lower fractional calcium absorption were at increased risk for hip fracture (relative risk per 1-SD [7.7%] decrease in fractional calcium absorption, 1.24 [95% CI, 1.05 to 1.48]). Women with low fractional calcium absorption and low calcium intake were at greatest risk for subsequent hip fracture; among women whose dietary calcium intake was less than 400 mg/d, those who had fractional calcium absorption at or below the median value of 32.3% had a 2.5-fold (CI, 1.29-fold to 4.69-fold) increase in risk for hip fracture compared with those who had greater absorption efficiency. Fractional calcium absorption was not related to risk for other nonspine fractures (relative risk per 1-SD [7.7%] decrease in fractional calcium absorption, 1.05 [CI, 0.96 to 1.14]).Conclusions: In elderly women, low fractional calcium absorption in the setting of low calcium intake increases the risk for hip fracture. Our findings support the hypothesis of type II osteoporosis, which postulates that decreased calcium absorption is an important risk factor for hip fracture in older persons.

Quantitative ultrasound (QUS) assessment of bone is a strong predictor of hip fractures and is currently an FDA-approved tool to identify women at risk of osteoporosis. However, few studies have investigated the lifestyle and genetic correlates of QUS in women. This study investigated the cross-sectional associates of several lifestyle, demographic and genetic factors with calcaneal QUS parameters (broadband ultrasound attenuation (BUA) and speed of sound (SOS)) in 393 women aged 45–53 years. Leisure-time and historical physical activity, dietary calcium and protein, body composition, vitamin D receptor genotypes, menopause status, other health behaviors, calcaneal QUS parameters and bone mineral density (BMD) were assessed at a single clinic visit. Lean mass, recent physical activity and African-American race were the strongest correlates of SOS whereas dietary protein, calcium and recent physical activity were the strongest correlates of BUA. These predictors explained 13% and 6% of the variance in SOS and BUA, respectively. Smoking, alcohol intake, education, hormone replacement therapy, calcium and vitamin D supplements, historical physical activity and vitamin D receptor genotypes were not significantly associated with BUA or SOS. Lean body mass and premenopausal status were the strongest correlates of lumbar BMD whereas lean body mass, physical activity, African-American race and body mass index were significantly related to femoral neck BMD. Physical activity remained predictive of SOS after controlling for lumbar BMD. The spectrum and magnitude of risk factors for SOS and BUA, including lean body mass, physical activity, race, protein and calcium intake, parallel previously observed predictors of BMD.

Bone mineral density (BMD) is under genetic control. Some studies in Caucasian and Asian women suggest that polymorphisms in the vitamin D receptor (VDR) gene are associated with BMD and the rate of postmenopausal bone loss. We determined if similar associations exist in 101 African‐American women aged 65 years and older (71 ± 5 years, mean ± SD). We also examined the relation between VDR genotype and fractional 45 Ca absorption and markers of bone formation (osteocalcin) and resorption (N‐telopeptides) in these women. BMD was measured at the proximal femur and whole body at baseline and after 1.9 ± 0.4 years (femur only) on a Hologic QDR‐2000 densitometer using dual‐energy X‐ray absorptiometry. Calcaneal BMD was measured with single x‐ray absorptiometry. VDR gene polymorphisms were defined by the endonucleases Bsm I, Apa I, and Taq I. These polymorphisms were not associated with BMD at any skeletal site or with markers of bone turnover. There was a significant interaction between age and VDR genotype where the oldest women (>70 years) with the tt genotype experienced greater hip bone loss than women with the TT genotype (−2.1%/year vs. −0.4%/year, respectively), whereas heterozygous women experienced an intermediate rate of bone loss (−1.3%/year). Women homozygous for the B allele had 14% lower fractional 45 Ca absorption compared with women homozygous for the b allele, although this difference was not statistically significant ( p = 0.08). We conclude that VDR gene polymorphisms are not associated with BMD or indices of bone turnover in this population of older African‐American women. However, DNA sequence variation in the VDR gene or a nearby locus may influence intestinal calcium transport and the rate of postmenopausal bone loss in African‐American women.