Calcium supplements don't help girls lose fat

Girls who normally consume lots of calcium in their diet have less body fat than their peers, but those who add calcium supplements to their diets do not lose fat or weight, new study findings show.

The current results are "extremely clear cut that there is absolutely no effect of calcium supplements on body fat and body weight," said study author Dr. Arne Astrup, of the Royal Veterinary and Agricultural University in Denmark.

"It is possible that the effect of calcium on body weight is only exerted if it is ingested as part of a meal," Astrup and his co-authors speculate "or the effect may be due to other ingredients in dairy products, and calcium may simply be a marker for a high dairy intake."

Various researchers have found that people who report an increased intake of calcium or an increased intake of dairy products have lower body weights than those who consume less calcium or dairy products. One study showed that adults who consume higher amounts of calcium may have a lower risk of obesity.

Yet, such researchers may not have taken into consideration other factors that may explain the association between calcium and body weight, the current report suggests.

Previous research conducted among 8-year-old boys, for example, showed that a high protein intake from skim milk stimulated their bodies to produce insulin-like growth factor and insulin, which is known to be involved in regulating one's appetite. What's more, studies have shown that milk protein increases a person's sense of satiety, or that feeling of being full.

To investigate, Astrup and his colleagues analyzed findings from a study conducted among 110 girls, who were all about 12 years old. Based on a food frequency questionnaire completed by the girls, they were divided into a median-calcium group, who reported consuming up to 1,304 milligrams of calcium every day or a low-calcium group that consumed less than 713 milligrams per day.

Girls from both groups were randomly assigned to receive 500 milligrams per day of a calcium supplement or placebo tablets for a year.

By the end of the study girls who had taken calcium supplements had not experienced any related changes in height, body weight, or percentage body fat, the researchers report in the American Journal of Clinical Nutrition.

Yet, those who reported consuming higher amounts of dietary calcium at the start of the study, who were initially placed in the median-calcium group, had less body fat both at the start and at the end of the year-long study period, than did girls in the low-calcium group, the study findings indicate.

How dietary calcium, rather than supplementary calcium, decreases body fat may be related to the "timing of the intake of calcium and the intake of fat," Astrup said. Supplements taken in the morning or at night are "probably absorbed before you have any food," he said, explaining that calcium "binds to fatty acids," and so must be taken with meals.