Bone mineral density, lifetime milk and supplemental calcium intake and lifetime physical activity in elderly mothers and their premenopausal daughters

Abstract

Osteoporosis is a condition in which bone mass decreases and bone fracture susceptibility increases. Approximately 40% of women in the US sustain osteoporotic fractures after age 65. We investigated the effects of lifetime and current milk consumption, calcium intake from supplements, and lifetime physical activity on the bone density of 25 elderly women (mean age 72 y) and their premenopausal daughters (mean age 41 y). Bone mineral density of the total, entire axial and entire peripheral skeleton was measured by dual energy X-ray absorptiometry. Lifetime milk consumption, calcium supplementation and lifetime physical activity were estimated retrospectively by questionnaire and interview. Neither lifetime or current milk consumption nor lifetime physical activity was correlated with bone density among the mothers. Their calcium intake from supplements after age 60, however, was positively associated (p<.05) with total and peripheral bone density as was their body weight and estrogen replacement therapy. Among daughters, lifetime weight-bearing exercise (hrs/week) was positively associated (p<.05) with total and peripheral bone density but milk consumption and calcium supplementation were not. This lack of association between intake and bone density may be explained partly by uniformly high calcium intake (mean 1032 mg/d) based on 3-day diet records. Lifetime milk consumption of mother-daughter pairs was correlated (p<.05). High current milk consumption was associated with a lifelong pattern of high milk consumption for mothers as well as daughters (p<.05). Results suggest that calcium intake plays a role in maintaining or increasing bone mass in postmenopausal years and exercise plays a role during premenopausal years.