More calcium may help teens control weight
Just about the time girls get their braces off and start worrying about how their jeans fit, they also stop drinking milk.
Although calcium intake in childhood and adolescence is crucial to long-term bone health, few teenagers find this bone-protection message convincing enough to add dairy products to their diet. Surveys show most teen girls get only about half of the recommended 1,500 milligrams of calcium per day.
Now parents and doctors may have more bargaining power over adolescent consumption of calcium. Recent studies have found that the nutrient appears to help regulate weight.
The most recent research, a University of Hawaii study presented last week at the Experimental Biology meeting in San Diego, found that girls ages 9 to 14 who consumed more calcium on a regular basis weighed less and had lower body fat than their counterparts. In the study of 323 girls, Dr. Rachel Novotny showed that, when comparing daily calcium intake, the more calcium the better. For every 300 milligrams of calcium consumed, girls were on average 1.9 pounds lighter.
Although larger studies are needed (and are underway), many epidemiological studies already strongly suggest that high calcium intake, while not necessarily leading to weight loss, does not cause weight gain.
This stands in contrast to popular opinion that high-calcium foods, such as milk and cheese, contribute to weight gain because of their fat and calorie content.
“I wouldn’t have thought too much of it [the study] if it weren’t placed nicely within a body of information people are finding that is very similar,” says Novotny.
Fear of getting fat may be one reason why so many teen girls stop drinking milk, says Joan Lappe, a professor of nursing at Creighton University in Omaha, Neb., who has studied high-calcium diets in girls.
“When I first started doing this, other scientists criticized the study because they felt I would cause the girls on the high-calcium diet to get fat,” says Lappe. “But it’s safe to do this.”
In Lappe’s study, presented last year at a medical meeting in England, girls were divided into two groups: One was asked to consume more than 1,500 milligrams of calcium a day, and the other was asked to keep their regular diets, which averaged 881 milligrams of calcium per day. There was no difference in weight gain over four years between preteen girls on a high-calcium diet and those on a regular diet.
“There is this lore that dairy foods cause you to get fat,” she says. “But even though our girls were getting two-thirds to three-quarters of their calcium from dairy, they are not gaining any more than the girls getting lower calcium.”
Health experts hope that the weight-control message may convince girls not to cut back on dairy foods during the teen years. Research has already established that adequate calcium intake in childhood and adolescence is important to long-term bone health and reducing the risk of the bone-thinning disease osteoporosis.
“The problem with osteoporosis is it’s associated with old age. The younger you are, you don’t look that far ahead,” Lappe says. “But weight, you can see an effect on that in a few weeks. We may have found a new way to get women to take calcium.”
Recent studies on calcium intake in other groups of people, including men and older women, also indicate a connection between the nutrient and weight regulation.
A Purdue University study found adult women who consumed more calcium either lost weight or had a smaller weight gain over two years compared with a control group. And a University of Tennessee study of preschool children found that high-calcium intake from dairy foods was associated with lower body fat. Studies tend to show a link between weight regulation and calcium intake regardless of whether the calcium is from food or supplements, Lappe says.
Future randomized clinical studies, including a study by the National Institute of Child Health and Human Development, will examine whether giving extra calcium has an effect on weight and other health outcomes. Other research will explore whether calcium intake plays a greater role in weight regulation during certain periods of life, such as puberty and middle age, when body fat status is changing.
There is a plausible explanation for why calcium may affect weight, researchers note. Laboratory studies suggest that calcium causes the body to make less fat but increases its ability to break down fat.
The connection between calcium and weight is tentative, however, and claims that the nutrient can trigger weight loss are unfounded, experts say. In a paper published earlier this year, two leading researchers in the field cautioned against viewing calcium as a “magic bullet” and stressed that eating less and exercising more remain the keys to weight regulation.
