|Raising the Bar in Nutrition Research
CHORI Scientist Confirms that Calcium Supplementation Does Not Result in Weight Loss
In a new study published in the October issue of Obesity, CHORI senior scientist Janet King, PhD, and her doctoral student, Vanitha Sampath, have addressed the question of whether or not calcium supplementation impact weight loss. A variety of recent studies have suggested a corollary between fat metabolism and calcium, yet the results have been inconsistent. In order to get straight to the heart of those inconsistencies, Dr. King went after the suggested mechanism behind the potential calcium-dependent weight loss in a first-of-its-kind study. Others have suggested that lipolysis, or cellular fat breakdown, increases with calcium supplementation.
“We gave the subjects a calcium supplement every day for three months and measured their energy metabolism at baseline and after supplementation. The only thing that changed was an increase in urinary calcium. In particular, there was no evidence that fat breakdown increased with supplementation,” says Dr. King.
A revered expert in nutrition circles, Dr. King has made a name for herself by using isotopic tracers to elucidate nutritional impacts of calcium and zinc.
“In human nutrition, you’re always very limited as to what you can measure. Usually you can only measure the blood and urinary concentrations; yet, we want to know more than that,” explains Dr. King, who raised the bar in nutritional research by developing a method of using stable isotopes, which have no radioactivity, to measure metabolic changes in the body, a technique now used world-wide.
“Isotopic tracers allow you to measure the rate of disappearance of the isotope from the plasma into other tissues, which enables you to determine how rapidly a supplement is metabolized and what tissues are actually using the supplement. Most of my zinc research is done in that way, where we use a kinetic model so that when we give “x” supplement, we know how it changes rates of metabolism, which tissues it goes to, and how it affects absorption and excretion,” Dr. King says.
In the case of the calcium/weight loss question, Dr. King used isotopically labeled glycerol to measure whether or not the calcium was causing subjects to breakdown more body fat.
“This is a simple measurement that enabled us to determine whether or not there was an increase in lipolysis by tracing glycerol concentrations,” says Dr. King.
If the calcium had been causing subjects to break down more body fat, Dr. King would have found a decrease in the concentration of isotopically labeled glycerol, caused by non-deuterated glycerol coming into circulation as a result of lipolysis. As Dr. King had suspected all along, there was no evidence of any change in the glycerol concentrations.
“None of us were surprised,” Dr. King says. “It’s not that simple, as much as we might wish it, you really can’t increase the amount of calories you are burning by just adding a calcium supplement.”
While the study was conducted in just 15 women who normally had marginally low calcium intakes, Dr. King feels secure in the results because the mechanistic aspects of the calcium/weight-loss hypothesis was addressed specifically.
“It would be great if other researchers took the methodology we used in this study to look at this dairy question further,” says Dr. King. “I think that including dairy foods in a weight loss diet can be advantageous because of the satiating effect of dairy foods. The protein in dairy foods causes people to feel satisfied so that people who drink milk on a diet may be able to limit their food intake more easily. But I don’t think it’s because there is anything unique in milk or other dairy foods that are increasing your cellular energy metabolism.”
Tuesday, May 17, 2011 8:19 AM