Purdue News

August 17, 2005

Purdue research shows added calcium benefits women on the pill

WEST LAFAYETTE, Ind. – Women who take oral contraceptives can counteract bone loss by making sure they have enough calcium in their daily diet, especially early in life, according to Purdue University research.

Earlier research has indicated that optimizing bone mass in adolescence and young adulthood prevents low bone density and osteoporosis later in life. On the other hand, oral contraceptives appear to decrease bone density.

"It's estimated that eight out of 10 women in the United States use oral contraceptives at some time during the years in which peak bone mass is developing," said Dorothy Teegarden, assistant professor in Purdue's Department of Foods and Nutrition. "The results of our study suggest that the loss for this group can be prevented by increasing calcium intake."

According to the National Academy of Sciences, the recommended dietary allowance of calcium for women age 19 to 50 is 1,000 milligrams a day. The recommended daily allowance of calcium for adolescents age 9 to 18 is 1,300 milligrams a day.

The 12-month study, funded by the American Dairy Association/National Dairy Council, was published in the July issue of Journal of Clinical Endocrinology and Metabolism.

The study compared 135 oral contraceptive users to non-users between the ages of 18 and 30. Three groups were randomized to receive one of three diets: control (less than 800 mg calcium a day), medium dairy (1,000-1,100 mg calcium a day) and high dairy (1,200-1,300 mg calcium a day).

At the end of the year, women using oral contraceptives and consuming the medium- or high-dairy diet gained significantly more bone mineral density in their hips and spines compared to the low-dairy group.

"These results suggest that many women who are using oral contraceptives in their peak bone-development years could reduce their risk of osteoporosis by approximately 3 percent to 10 percent over one year by making sure they get enough calcium in their diet," Teegarden said. "This demonstrates the importance of calcium intake, either by getting enough dairy or with supplements."

Teegarden's laboratory currently is involved in a number of clinical trials to investigate the effect of calcium consumption on body fat. Her studies have shown that a high consumption of calcium slows weight gain for young women, but her more recent studies show that it may take years to make a noticeable difference.

Writer: Maggie Morris, (765) 494-2432, maggiemorris@purdue.edu

Source: Dorothy Teegarden, (765) 494-8246, teegarden@purdue.edu

Purdue News Service: (765) 494-2096; purduenews@purdue.edu


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Foods & Nutrition



Dietary Calcium Intake Protects Women Consuming Oral Contraceptives From Spine and Hip Bone Loss

Dorothy Teegarden PhD*, Pamela Legowski MS, Carolyn W. Gunther PhD, George P. McCabe PhD, Munro Peacock MD, and Roseann M. Lyle PhD

Interdepartmental Nutrition Program, Purdue University; Department of Statistics, Purdue University; Department of Medicine, Indiana University; Department of Health and Kinesiology, Purdue University

It is estimated that 80% of all women have used oral contraceptives (OCP), but OCP use may prevent attainment of maximal peak bone mass in young women and thus increase the risk of osteoporosis later in life. This study examined whether increased calcium intake could reduce the detrimental effects of OCP use on bone mass in young women. Subjects were 154 women, 18-30 yr old, with a dietary calcium intake of less than 800 mg/day, and 135 completed the trial. Random assignment to one of three diet intervention groups: 1) control, continue established (< 800 mg/day) dietary intake; 2) medium dairy, increase calcium intake to approximately 1000-1100 mg/day; 3) high dairy, increase calcium intake to approximately 1200-1300 mg/day. Randomization was stratified by OCP use. Main outcome measured total body bone mineral density (BMD) and content (BMC); total hip BMD, BMC and bone area; spine BMD, BMC and bone area. Dairy product intervention positively impacted percent change of total hip BMD and BMC. In addition, dairy product intake prevented a negative percent change in total hip and spine BMD in OCP users. Conclusion: Dairy product intake, at levels to achieve the recommended intakes of calcium, protected the total hip BMD and spine BMD from loss observed in young healthy women with low calcium intakes who were using OCP.


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