Bone mineral density in mother-daughter pairs: relations to lifetime exercise, lifetime milk consumption, and calcium supplements.

This study investigated associations between lifetime milk consumption, calcium intake from supplements, lifetime weight-bearing exercise, and bone mineral density (BMD) among 25 elderly women (mean age 72 y) and their premenopausal daughters (mean age 41 y). The BMD of the total, axial, and peripheral skeleton was measured by dual-energy X-ray absorptiometry. Lifetime milk consumption, supplemental calcium intake, and weight-bearing exercise were estimated retrospectively by questionnaire and interview. In multiple-linear-regression analyses, mothers' total and peripheral BMD were positively associated with supplemental calcium intake after age 60 y, body weight, current estrogen replacement therapy (ERT), and past oral contraceptive (OC) use, and negatively associated with age and height (all P < 0.05). Mothers' axial BMD was positively correlated with body weight and past OC use. Among daughters, lifetime weight-bearing exercise was a predictor of total and peripheral BMD, whereas total lean mass was a predictor of axial BMD. Mothers' lifetime milk consumption was positively associated with that of their daughters. Mothers' and daughters' peripheral BMD values were positively correlated after adjustment for daughters' exercise, and mothers' age, body weight, and ERT. These results suggest that calcium supplementation and exogenous estrogen positively influence bone mass in postmenopausal years. Our findings lend support to recommendations for physical activity as a means of osteoporosis prevention. In the age groups studied, the effects of behavioral and hormonal factors on BMD appeared to dominate over familial similarity, which suggests that women may successfully enhance their genetically determined bone mass through weight-bearing exercise, post-menopausal ERT, and adequate calcium intake.