Fifty-eight pre-menopausal women were randomly assigned to receive calcium lactate, calcium phosphate, low fat milk, or placebo during a 12-week weight loss plan, but no effect on weight loss was observed for any of the interventions, state the researchers, led by Robert DiSilvestro.
"None of the calcium sources tested here accelerated loss of body weight or of fat," they wrote in the Journal of the American College of Nutrition .
"This study is the third intervention that has not shown an effect of manipulated calcium intake on weight loss."
The research adds to the on-going debate of the role of calcium, mainly from dairy products, in weight loss.
The topic is a source of controversy with both camps able to quote research that supports their side and undermines the other.
The study, sponsored by Purac, recruited the women and supplemented their weight loss diet (restricted to 500 kilocalories per day) with calcium lactate or calcium phosphate capsules, low fat milk or placebo.
All calcium sources supplied about 800 mg daily doses of calcium.
Purac provided both calcium lactate and calcium phosphate.
The supplements and milk were not the only sources of calcium in the women's diets, and diet record showed the placebo group had a daily average intake of 788 mg, while calcium lactate, calcium phosphate, and milk groups consumed 1698, 1566, and 1514 mg, respectively.
All women showed reductions in weight over the 12-week programme, with no significant difference between the groups.
Body fat was also changed significantly in each group.
It should be noted that the weight loss program also included three periods of exercise per week.
"A still unresolved issue is why there are conflicting results concerning calcium and weight loss," stated the researchers.
"A simple explanation may be that an effect on weight loss requires a swing from a very low calcium intake, such as 400-500 mg/day, to a considerably higher calcium intake."
"In support of this concept, 400-500 mg calcium/day is the lower intake range for the intervention studies reporting a calcium or dairy intervention effect on weight loss," they added.
DiSilvestro and co-workers also examined markers of bone health among the women, and report similar values of serum bone specific alkaline phophatase activity, a marker of bone formation, increased by similar amounts in all groups.
Interestingly, the group consuming calcium in the lactate form, but not the other groups, did experience a drop in urine values for the bone resorption marker alpha helical peptide.
In attempting to explain this observation, the researchers suggest that absorption of calcium lactate is superior to the other calcium sources tested, and thus has the greatest effect on bone health.
But the debate over whether calcium from dairy sources does enhance weight loss seems set to rumble on. "
Despite this lack of effect, it is possible that calcium may enhance weight loss in certain, as of yet undefined circumstances," they concluded.
Previously, a study from Purdue University claimed that young women could burn more calories if they ate three or four dairy servings per day.
However another report, also from Purdue, reported that increased dairy consumption had no effect on weight gain or loss.
On the other hand, Dr. Michael Zemel from the University of Tennessee told attendees at last year's Paris Anti-Obesity Therapies 2006 conference that dairy can help reduce body fat and that calcium only accounts for about 40 per cent of the effect.
Dairy industries in Europe and the US have been promoting milk-based products for consumers who want to slim for some time but the new findings underline that further work needs to be done to support such claims.
Source: Journal of the American College of Nutrition Volume 26, Number 5, Pages 456-461 "Effects of Various Forms of Calcium on Body Weight and Bone Turnover Markers in Women Participating in a Weight Loss Program" Authors: G. Wagner, S. Kindrick, S. Hertzler, R.A. DiSilvestro