K. Ishikawa-Takata*, T. Ohta**

Division of Health Promotion and Exercise, National Institute of Health and Nutrition. ** Chubu National Hospital. Correspondence to: Kazuko Ishikawa-Takata, 1-23-1 Toyama Shinjuku, Tokyo 162-8636, Japan. Tel: +81-3-3203-8061. Fax: +81-3-3203-1731. E-mail: kazu@nih.go.jp

BACKGROUND: Japanese women have a lower bone mass and smaller calcium intake than Caucasians. OBJECTIVE: To investigate the differences in the relationship between bone mass and lifestyle among Japanese women of different life stages. DESIGN: Cross-sectional and longitudinal investigations of the relationship between bone mass and lifestyle in Japanese women aged 15-69 years. RESULTS: In both cross-sectional and longitudinal investigations of high school students, exercise was shown to effectively increase bone mass. In the longitudinal investigation, bone mass was generally greater with high or increased milk consumption. In the cross-sectional investigation of nonparous women and women more than 36 months post partum, those who exercised had significantly higher bone mass. Twelve to 35 months post partum, bone mass was greater in women with higher calcium or milk intake. The effects of parity were not investigated longitudinally, but women who continuously exercised or started exercise had greater bone mass. Non-exercising women with a higher or increased frequency of intake of dairy products, small fish, and soy products had increased bone mass. The longitudinal investigations suggest that exercise increases bone mass in pre-menopausal women. In women just after menopause, it was shown cross-sectionally that bone mass was greater with a higher calcium intake, and longitudinally that exercise resulted in a slower decrease in bone mass. Among women more than 6-7 years past menopause, exercise inhibited the decrease in bone mass. CONCLUSION: The relationship between these lifestyle factors and bone mass differs according to pregnancy status and time since menopause.

Keywords: Bone mass, elderly, nutrition, exercise, calcium, life stage, aging.