Data from seven eligible trials showed that calcium may provide weight loss of around 1.5 kg per year, compared with placebo, according to results published in Nutrition Reviews.
In addition, a daily dose of 1,000 milligrams of calcium was associated with a “small, significant reduction in body fat” of about 2 kg per year, report the scientists, led by Igho Onakpoya from the Department of Complementary Medicine, Peninsula Medical School at the University of Exeter, UK.
“The present analysis indicates that evidence on calcium supplementation and weight management from published RCTs is scarce, and most RCTs have not been rigorously reported,” wrote the researcher.
“While the findings suggest that calcium supplementation for at least 6 months results in a statistically significant weight loss in obese and overweight individuals, the clinical relevance of this finding is uncertain,” they added.
Conflict or confusion?
The potential role of dairy, and the calcium it contains, for weight management is an area of ongoing debate. A relationship between dairy intake and weight reduction has been recorded in numerous studies, and dairy industries in Europe and the US have been promoting milk-based products for consumers who want to slim for some time.
There are even splits within the dairy camp, with some arguing that calcium and vitamin D are the active nutrients behind the effects. One of the lead researchers in this area, Dr Michael Zemel from the University of Tennessee, has previously said that dairy can help reduce body fat and that calcium only accounts for about 40 per cent of the effect.
In an accompanying editorial in the same journal, Robert Heaney from Creighton University in Nebraska said the meta-analysis afforded “an opportunity to clarify some of the confusion surrounding this issue”.
For a 140 kg woman seeking to lose half of her body weight, the mean weight loss calculated by Prof Ernst and his co-workers of about 1.5 kg per year would “have very limited interest.
“However, for a population confronting secular weight gain (e.g., otherwise healthy women atmid-life), this same weight effect is huge,” he said.
Prof Heaney added that there are four main conclusions that could responsibly be drawn from the meta-analysis: In addition to countering the weight gain that may occur in mid-life, calcium “should be a component of any weight loss regimen, as it augments the weight loss of a caloric deficit while protecting lean body mass; [it] is not a substitute for control of an energy intake/output imbalance; and [calcium] is not a drug and is certainly not a magic bullet”.
Onakpoya and his co-workers noted that reports in the literature do support biological plausibility for calcium to aid body weight and fat loss: One such mechanism could involve a decrease in levels of 1,25-vitamin D – the active form of the vitamin – which in stimulates the breakdown of fat and inhibits the action of fat cells.
There are also reports that indicate that a diet rich in calcium may promote the oxidation of fat, “resulting in the removal of additional amounts of calories from the body”.
Source: Nutrition Reviews
Volume 69, Issue 6, Pages: 335-343, doi:10.1111/j.1753-4887.2011.00397.x
“Efficacy of calcium supplementation for management of overweight and obesity: systematic review of randomized clinical trials”
Authors: I.J. Onakpoya, R. Perry, J. Zhang, E. Ernst