Calcium and fat loss: RCT adds to controversy over potential benefits
According to findings published in the American Journal of Clinical Nutrition, neither calcium supplements nor dairy were associated with any changes to energy or fat balance in a study with 42 overweight adolescents.
When the researchers disregarded the different sources of calcium pooled data from both sources, they did report an increase in fat excretion, a result that led leading dairy researcher Professor Arne Astrup from the University of Copenhagen in Denmark to comment that the data does show a potential for calcium to increase fat loss.
“When the authors pooled the results from the different calcium sources, the change in fecal calcium excretion from the control to the calcium-supplemented diets was positively associated with change in proportion of ingested fat being lost in the stools, which suggests that dietary calcium binds fat and can increase fecal excretion,” wrote Prof Astrup in his editorial in the same journal.
“There is clearly a need for larger, longer-term, controlled dietary calcium intervention studies and updated meta-analyses of these findings if we are to draw more robust conclusions on the effects of calcium on fecal fat excretion,” he added.
The potential role of dairy, and the calcium it contains, for weight management is a topic of ongoing debate. A relationship between dairy intake and weight reduction has been reported in numerous studies, including a recent review published in Nutrition Reviews: Scientists at the University of Exeter in the UK concluded that a daily dose of 1,000 milligrams of calcium was associated with a “small, significant reduction in body fat” of around 2 kg per year.
Prof Astrup co-authored a meta-analysis in 2009 that supported a causal relationship between calcium and fat loss.
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% of the effect.
The new clinical trial, led by Connie Weaver, PhD, from Purdue University, involved 25 adolescent girls with an average BMI of 33 kg/m2 and 17 adolescent boys with an average BMI of 28 kg/m2.
The randomized, crossover study assigned the teenagers to one of two groups: The first group consumed 756 milligrams of calcium per day as part of a normal diet for three weeks; while the second group received the same diet with an additional 650 milligrams of the mineral per day as dairy or calcium carbonate supplements for three weeks. After one intervention, the teens crossed over to the other group.
At the end of the study, Dr Weaver and her co-workers reported no effects of additional calcium, either as dairy or supplements, on energy or fat balance.
“No mechanisms measured in this study support previous observations that dietary calcium affects energy balance that would lead to changes in body weight if energy intake and physical activity were controlled,” wrote the researchers.
“Our data suggest that there may be a threshold for increasing fecal fat excretion with higher calcium intakes, but during periods of high calcium absorption the addition of a calcium supplement leads to decreases in fecal fat excretion.”
Despite such strong conclusions, Prof Astrup wrote in his editorial: “There is increasing evidence to suggest that insufficient dietary calcium intake produces a calcium-deficient state that is detected by the body, and one effect might be increased hunger.
“The potential for a role for calcium in the prevention of obesity and its complications is still promising,” he concluded.
Prof Astrup notes that he is a member of the scientific advisory board for The Global Dairy Platform, Kraft Foods, Danone and Jennie Craig. He has also received support from over 100 food companies. Dr Weaver in on the advisory board for Pharmavite, Nestlé, and Sara Lee.
Weight Management 2011
The topic of dairy and fat loss is one of several to be covered in the upcoming Weight Management 2011 virtual conference and expo. Hosted by NutraIngredients-USA, the event is free to attend. Click here for more information and to register.
Source: American Journal of Clinical Nutrition
Published online ahead of print, doi:10.3945/ajcn.110.010264
“Calcium, dairy products, and energy balance in overweight adolescents: a controlled trial”
Authors: C.M. Weaver, W.W. Campbell, D. Teegarden, et al
Editorial: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.111.024141
“Calcium for prevention of weight gain, cardiovascular disease, and cancer”
Author: A. Astrup