So says a study in July's issue of the Journal of the American Dietetic Association.
The study shows that of 5,341 women aged 53 to 57, those taking at least 500 milligrams of calcium each day gained about 11 pounds after age 45, compared to 15 pounds for those who didn't take the supplements.
Calcium gotten from foods didn't affect the results.
About the Study
Participants had volunteered for a long-term study of vitamin and mineral supplements and cancer risk.
But for this particular report, Gonzalez and colleagues didn't focus on cancer. Instead, they checked data on participants' weight gain from their mid 40s to mid 50s.
Participants had reported their weight eight to 10 years earlier, when they were 45. They also noted their physical activities, age, smoking status, height, diet habits, and current and past use of calcium supplements.
Men were "much less likely" than women to be currently taking calcium supplements, the researchers note. Fifteen percent of the men were taking calcium supplements, compared to 53% of the women.
Weight Gain Was Common
Participants typically reported gaining some weight after age 45, regardless of calcium- supplement use.
Postmenopausal women taking at least 500 milligrams daily of calcium supplements, and who hadn't taken hormone replacement therapy, gained the least weight, the study shows. Those women gained about 10 pounds, compared to the 11-pound average for all women in the study taking supplements, and the 15 pounds gained by women not taking them.
It's possible people who take calcium supplements have other healthy habits that help keep their weight in check. But the results held after researchers took that into account.
It's too soon to recommend calcium supplements for weight control, say Gonzalez and colleagues; more studies are needed first. They point out that people don't always report their weight or supplement use accurately, and that people who volunteer for studies like this one may not be typical of the general public.
Also, the study was purely observational. Participants weren't asked to take calcium supplements. So the findings don't prove that the supplements curbed weight gain by themselves.
For now, Gonzalez and colleagues write that "calcium supplements taken for other reasons (e.g., prevention of osteoporosis) may have a small beneficial influence on reducing weight gain, particularly among women approaching midlife."