Birth Control Pills May Decrease Bone Density in Young Women, Study Shows

A new study suggests a possible link between long-term use of oral contraceptives and a decrease in bone density in women under the age of 30. Researchers studied more than 600 women, aged 14 to 30, and found a 5.9 percent decrease in bone mineral density (BMD) of the spine in young women taking birth control pills for longer than one year, as compared with those not taking oral contraceptives. BMD of the whole body was shown to be decreased by 2.3 percent in those taking the pill.

The study, published in the January issue of Contraception, measured BMD of the hip, spine, and entire body to analyze how both the duration of treatment with the pill and the estrogen dose affected bone density in young women. Low-dose estrogen pills containing less than 30 micrograms ethinyl estradiol were found to cause the most bone loss in the study. Since bone mass production is at its peak during a woman’s 20s, researchers are worried that the effects could lead to long-term bone problems such as osteoporosis or fractures.

Examples of bErand name “low-dose” estrogen pills containing 30 mcg or less of ethinyl estradiol include Loestrin, Alesse, Ocella, Desogen, Levlen, , Yasmin, Yaz, and others.

“I think the evidence is still emerging on this association, but our findings suggest that low-dose oral contraceptives with long-term use have some impact on bone density,” said Delia Scholes, the study author and senior investigator at the Group Health Research Institute of Group Health Cooperative in Seattle, Washington.

Researchers are not yet sure of the long-term impacts of bone loss from oral contraceptives, or if stopping treatment could reverse the negative effects.

Scholes states, “If oral contraceptives are indeed causing the approximately 5 percent lower spine bone density for oral contraceptive users… and if that impact is not reversed with oral contraceptive discontinuation or with other factors that may occur across the life span, a 5 percent lower bone density after menopause is associated with approximately 50 percent more osteoporotic fractures.”

Researchers are not entirely sure of the reasons for the decrease in bone mass, but it is believed that estrogen plays a role in the development and maintenance of bone mass. Hormonal contraceptives alter the body’s natural hormone levels, disturbing the estrogen levels that affect bone production as a young woman is developing.

An estimated 12 million women in the U.S. and 100 million worldwide use oral contraception as a form of birth control. The Centers for Disease Control and Prevention reports that birth control pills are the leading contraceptive method among women aged 15 to 29, with almost 20 percent of women aged 15 to 44 currently taking the pill.