Link found between calcium and boys' metabolism
NEW YORK (Reuters Health) - Boys who get plenty of calcium in their diets may use more calories when their bodies are at rest compared with their peers who consume less of the nutrient, a new study suggests.
The findings, reported in the Journal of Pediatrics, may help explain why some studies have linked higher calcium intake to lower body-fat levels in children and adults.
They also offer one more reason for children and adults to get the recommended amounts of calcium in their diets, the researchers say.
For the study, researchers at the University of Alabama at Birmingham looked at the relationship between children's reported calcium intake and their resting energy expenditure -- the calories required to keep the body functioning at rest.
Calcium is known to help regulate metabolism, so if it has effects on body fat accumulation, it may do so by influencing calorie use at rest, the researchers reasoned.
To investigate, Dr. Jose Fernandez and his colleagues collected detailed dietary information on 315 children between the ages of 7 and 12. They tested the children's body fat levels and, after an overnight stay in the research lab, their resting calorie expenditure -- measured indirectly through a test that gauges oxygen use and carbon dioxide production as a person breathes.
Overall, the researchers found, there was no strong direct relationship between the children's calcium intake and their levels of body fat. There was, however, a correlation between higher calcium intake and higher resting metabolism. And a higher resting metabolism, in turn, was related to lower body-fat levels.
When the researchers looked at boys and girls separately, they found that the link between calcium and resting metabolism was apparent only in boys.
The findings, according to Fernandez, suggest that calcium may affect body-fat accumulation via its influence on resting energy expenditure.
It's not clear why the association was seen only in boys. "We think it may have to do with reproductive hormones," Fernandez said, "but we don't know yet."
Estrogen, he and his colleagues note, is known to encourage fat accumulation, while testosterone drives the buildup of lean body tissue.
Still, if calcium does help boost calorie-burning at rest, then it would be a good idea for everyone to fit the nutrient into their diets, according to Fernandez.
"Calcium is very important," he said, "and the general public -- children and adults -- should continue to increase their intake to the recommended levels."
Experts recommend that children and teenagers ages 9 and up get 1,300 milligrams (mg) of calcium per day, while adults ages 19 to 50 should get 1,000 mg -- increasing to 1,200 mg after age 50.
Food sources of calcium include milk, yogurt, cheese, tofu, leafy greens such as spinach and kale, and calcium-fortified cereals and orange juice.
The ultimate impact of calcium on body weight, however, remains uncertain. Many factors -- from genetics to overall diet and exercise levels to socioeconomics -- influence a person's risk of becoming overweight or obese, and the relative importance of calcium is unknown.
Much more research is needed, Fernandez said, including studies into how calcium might affect body fat differently according to age, sex and race or ethnicity.
SOURCE: here%2810%2900209-X/abstract Journal of Pediatrics, online April 19, 2010.