Calcium's leading role is legendary. In fact, there seems to be no end to calcium's repertoire: It strengthens bones and teeth and new studies suggest that it may also prevent colon cancer, and even keep Montezuma's revenge at bay.
There's also good evidence that diets high in calcium are associated with reduced rates of being overweight or obese.
"At midlife, women tend to gain one-quarter to one-half a pound per year whether they want it or not, and it all goes to their waist," says Robert Heaney, MD, an internationally recognized expert in bone biology and calcium nutrition with Creighton University in Nebraska.
"We've found that women with the highest dairy intake have an average weight gain of zero, and those with the lowest dairy intake gained a pound per year," Heaney tells WebMD.
There's one catch: You also must cut back on calories for weight loss to happen. "Dairy will only help you lose weight if you have reduced calories. If you add it to what you eat all the time, it won't make a whit of difference," Heaney explains.
The Science
Michael Zemel, PhD, director of The Nutrition Institute at the University of Tennessee at Knoxville, is actually the hero of this tale.
In studies of both mice and men, Zemel and colleagues have been the first to show that calcium stored in fat cells plays a crucial role in regulating how fat is processed and stored by the body. The more calcium there is in a fat cell, the more fat the cell will burn -- and the greater the weight loss, Zemel says.
The mouse evidence: In one study, Zemel used mice that were specially bred to be obese. He fed the mice a high-fat, high-sugar diet for six weeks. All had a 27% increase in body fat.
He then put the mice on a restricted-calorie diet, and gave calcium to two groups of them.
The calcium made a big difference. Mice that didn't get any calcium had an 8% loss of body fat. Mice getting calcium supplements had a 42% decrease in body fat.
But calcium from dairy products produced the best weight-loss results. Mice on a medium-dairy diet had a 60% decrease in body fat, while those on a high-dairy diet lost 69% body fat.
The human evidence: A study of 32 obese people on a low-calorie diet divided them into three groups: those whose diet was high in dairy, those who ate little dairy but took calcium supplements, and those whose diets were low-calcium and low-dairy. After 24 weeks, everyone lost a lot of fat, but those who ate the dairy-rich diet lost five pounds more.
The dairy eaters' waists also shrank by more than an inch and a half -- the others lost only about one-quarter inch. Turns out, the yogurt group lost mostly belly fat, Zemel reports. Excess fat in the abdominal area has been linked to a higher risk of heart attack and other health problems.
Heaney has found "the calcium effect" in five of his own studies, investigating close to 1,000 women over a 20-year period. "Those with highest dairy intake had an average weight gain of zero. Those with the lowest dairy intake had an average weight gain of a pound per year," he tells WebMD.
How It Works
Calcium provides small increases in thermogenesis, the body's core temperature, Zemel explains. This may boost metabolism, which can prompt our bodies to burn fat.
If weight loss is your goal, eat three servings of fat-free or low-fat dairy products every day, he advises.
But cardiologists (heart specialists) may not like this advice: Whole-fat milk works even better in a weight-loss plan, says Heaney. "In fact, whole-fat milk has a satiety value so you naturally won't eat so much. A high-carbohydrate diet leaves you feeling hungry all the time."
