In a rigorously designed study to examine the issue, investigators found no evidence that calcium supplementation influenced energy expenditure or fat-burning in overweight people whose regular diets were deficient in the mineral.
Widely publicized animal and human studies that did suggest a role for calcium in weight loss led to a multimillion dollar ad campaign promoting three servings of dairy products a day with slogans like "Milk your diet. Lose weight!"
The new study was conducted in an effort to confirm or disprove the findings in these earlier studies, metabolic physiologist Hilary Green, PhD, of Nestle, tells WebMD.
"There was no evidence in this latest research to suggest that calcium helps people burn more fat through the mechanisms that were tested," she says.
Calcium and Weight Loss
The 20-week study, conducted by researchers from Switzerland's University of Lausanne and the Nestle Research Center, included 10 overweight or obese people identified before recruitment whose regular diets were low in calcium.
Study participants were randomly assigned to be given either placebo or 800 milligrams of dairy calcium daily for two five-week periods, separated by a 10-week washout phase.
Four weeks into the supplementation phases of the study, researchers performed a battery of tests designed to examine the impact of calcium on fat metabolism.
The tests revealed no differences between the people taking the placebo and the calcium in any of these measures, including resting energy expenditure, fat oxidation, and plasma-free fatty acid concentrations.
In addition, expression of seven key metabolic genes in biopsied fat tissue was not affected by calcium supplementation.
In an accompanying editorial, University of Copenhagen nutrition researcher Arne Astrup, MD, writes that the study makes a strong case against the hypothesis that calcium-controlled pathways in fat tissue help regulate body weight.
But he concludes that there is still good evidence indicating a role for dietary calcium in weight regulation.
The study and editorial appear in the October issue of the American Journal of Clinical Nutrition.
Dairy Industry Weighs In
Greg Miller, PhD, who is a spokesman for the National Dairy Council, tells WebMD that the study addressed just one of several theories about calcium and weight control.
"There is a good body of evidence that supports a relationship between calcium intake, dairy intake, and weight and body fat regulation," he says. "What we are trying to understand now is what mechanism or mechanisms are involved and under what conditions do they have an effect."
He points out that the study did not address the role of calcium and protein-rich foods in controlling appetite. New research also suggests that calcium may bind fat and decrease its absorption from the intestinal tract.
But the Dairy Council's advertising no longer makes the claim that eating dairy foods leads to weight loss. Miller confirms that the 3-a-day campaign and other promotional ads now focus on the role of dairy foods in maintaining a healthy weight.
Early last year, the Federal Trade Commission and the FDA expressed concern about the weight loss claims made in the ads, but Miller says the decision to shift the focus from weight loss to weight regulation was entirely voluntary.
"Our marketing outreach told us that consumers were tired of hearing about dieting and our current marketing reflects that," he says.