Oral Contraceptives May Cancel Some Bone-Building Benefits Of Exercise.

2001 JUL 12 - (NewsRx Network) -- Young women who take oral contraceptives and exercise may have increased risks of bone loss, according to recent research at Purdue University.

A two-year study headed by Connie Weaver, head and distinguished professor of foods and nutrition, suggests women ages 18 to 30 who exercise while using oral contraceptives (the pill) may lose bone density in the hip and spine, even more than women who take the pill and are sedentary. This loss of density could make a women susceptible to bone fractures later in life.

The study also indicates, however, that women in this group who get the minimum daily requirements for calcium may be able to ward off bone loss.

"The study showed that, overall, exercise had positive affects on whole body bone mineral content for everyone," Weaver says. "Only the spine and hip were compromised if subjects who were on oral contraceptives exercised, and only then if calcium intakes were inadequate."

The purpose of the study, funded through the U.S. National Institutes of Health, was to investigate the effects of exercise on bone mineral content and bone mineral density in women 18 to 30 years old who either were or were not taking birth control pills. The study started with 180 women. At the end of the two-year period, 55 women remained.

The study, published in the June 2001 issue of the scientific journal Medicine and Science in Sports and Exercise, had several unexpected results, Weaver says.

"One big surprise was that for women who use birth control pills, exercise had a negative impact on the spine and the hip, especially in the first six months," she says. "By the end of the two years, that group fell below the groups of non-exercisers or non-pill users in terms of bone mineral content and bone mineral density."