Calcium Offsets Bone Loss in Women on the Pill

WEST LAFAYETTE, Ind.--Attaining the recommended calcium intake of 1,000 mg/d appears critical for women taking oral contraceptives to maximize bone density and avoid developing osteoporosis in later life, according to a study published online July 5 in the Journal of Clinical Endocrinology & Metabolism. More than 80 percent of all women have used or currently use birth control pills; however, it appears use of the pill may adversely impact bone density.

In the new study, researchers from Purdue University recruited healthy women ages 18 to 30 with dietary calcium intake less than 800 mg/d; of the 135 women who completed the study, 57 were currently on the pill. The women were randomly assigned to one of three dietary intervention groups: control (less than 800 mg/d calcium), medium dairy (increasing calcium to 1,000 to 1,100 mg/d) and high dairy (calcium intake 1,200 to 1,300 mg/d). Randomization was stratified by use of oral contraceptives.

The main outcome measures included total body bone mineral density (BMD) and bone mineral content (BMC), hip BMD and BMC, and spine BMD and BMC. Increasing dairy intake and its concurrent increase in calcium intake benefited BMD and BMC in all measures. Dairy intake further prevented a negative change in hip and spine BMD in control women taking oral contraceptives.

Researchers concluded health care practitioners should advise women taking oral contraceptives to increase their calcium intake, as their estimates show if these women consumed 1,000 mg/d of calcium, they could reduce their risk of osteoporosis by 3 percent to 10 percent over one year.