Wednesday, June 20, 2001

Exercise Plus Pill May Affect Bone Mass in Women

NEW YORK (Reuters Health) - Young women who exercise regularly and use birth control pills may not get a boost in bone strength seen in women who exercise and do not use oral contraceptives, results of a study suggest.

- 2001/06/20

By Suzanne Rostler The report in the recent issue of Medicine & Science in Sports & Exercise found that regular resistance training and aerobic exercise strengthened bones in women aged 18 to 31 over a 2-year period. However, oral contraceptives appeared to prevent the build-up of bone in the spine that was seen in women who exercised. The findings suggest that women who exercise and take birth control pills may be compromising their chances of attaining peak bone mass at key sites of the body, according to Dr. Connie M. Weaver of Purdue University in West Lafayette, Indiana, and colleagues. ``If you take oral contraceptives and exercise as you should, be sure to get enough calcium to protect losses at hip and spine,'' Weaver told Reuters Health. ``We think oral contraceptives may control blood estrogen levels and prevent the exercise-induced increase (in bone),'' Weaver explained. The researchers measured the density of several bones every 6 months for 2 years in two groups of women. One group did three sessions of resistance exercise and jumped rope for 60 minutes each week, and the other did not exercise. The groups were further divided into those who took birth control pills and those who did not. The investigators found that exercisers increased bone mineral content by about 1-2% at skeletal sites throughout the body after 6 months and 2 years compared with women who did not exercise, who had about a 1-2% loss in bone mineral content. And women who did not use oral contraceptives had higher bone mineral content at skeletal sites throughout their body after 2 years compared with women who used birth control pills. But among women who exercised and used oral contraceptives, the density and mineral content of one site--the spine-- decreased after 6 months and levels remained lower than those of non-exercisers who used oral contraceptives 2 years later.

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