Taking calcium and vitamin D supplements may help overweight women to lose body fat, but only if their calcium intake from food is already quite low, a small study suggests.
The study, which followed 63 overweight or obese women, found that those who took a calcium-plus-vitamin-D supplement in addition to a lower-calorie diet lost no more body fat over 15 weeks than those given a placebo.
When the researchers looked at only those women with a very low calcium intake before the study, the supplement did seem to have a benefit.
Among the women — who had been getting less than 600 milligrams of calcium per day — the calcium/vitamin D supplement spurred greater reductions in weight and body fat.
While the reason for the benefit is unclear, there was evidence that the supplement helped curb women's appetite for fatty food, the researchers report in the British Journal of Nutrition.
During a buffet-style test meal, the study found, women who'd been taking the supplement ate less fat than they had at a test meal done at the study's start. The same was not true of women in the placebo group, however.
"Our hypothesis is that the brain can detect the lack of calcium and seeks to compensate by spurring food intake, which obviously works against the goals of any weight loss program" senior researcher Dr. Angelo Tremblay, of Laval University in Quebec, Canada, said in a news release from the university.
"Sufficient calcium intake seems to stifle the desire to eat more," he explained.
Some past studies, but not all, have suggested that calcium helps speed fat loss among dieters. The current findings, according to Tremblay's team, suggest that for overweight people with a very low calcium intake, calcium/vitamin D supplements "might be necessary" for weight-loss success.
For the study, the researchers had 63 overweight middle-aged women go on a calorie-restricted diet. All had been getting inadequate calcium in their diets — less than 800 mg, compared with the recommended 1,000 mg for women ages 19 to 50.
Half of the women were randomly assigned to take a calcium/vitamin D supplement twice a day, which provided 1,200 mg of calcium daily. The other half took placebo pills.
Only women with the lowest calcium intake prior to the study — less than 600 mg — seemed to get added fat-loss benefits from the supplement. Supplement users lost 13 pounds, on average, versus 3 pounds in the placebo group.
While the results from the test meals suggest that extra calcium may help calcium-deficient women curb their appetites while dieting, more research is needed to confirm that, according to Tremblay's team.
The study was funded by Wyeth Consumer Healthcare, Inc., which also supplied the calcium/vitamin D supplement.