Dairy Intake Tied to Lower Body Fat in Girls
August 11, 2004
NEW YORK (Reuters Health) - Girls who get enough dairy products in their diets may stay leaner than their peers, study findings suggest.
Researchers found that among 323 9- to 14-year-old girls in Hawaii, those who got more calcium from dairy sources tended to weigh less and have less fat around the middle than girls who ate less dairy. On the other hand, body weight tended to rise in tandem with soda intake.
The link between dairy intake and lower abdominal fat was particularly strong among girls of Asian descent, who made up 47 percent of the study group.
Since the 1960s, U.S. children's milk consumption has fallen off significantly, in favor of soda and sugary juices. The trend is thought to be one of the factors fueling the nation's ever-growing rate of childhood obesity and excess weight.
A number of studies, mostly in adults, have shown that calcium may be key in maintaining normal body weight and fat stores. One reason may be the nutrient's effects on hormones that help store calories as fat.
In the new study, reported in the Journal of Nutrition, calcium from dairy sources, but not non-dairy foods, was related to lower weight and less abdominal fat.
This suggests that "the dairy portion of the calcium intake is the key factor," write the study authors, led by Dr. Rachel Novotny of the University of Hawaii in Honolulu. It's possible, they explain, that other nutrients in milk play an important role in weight balance.
However, the researchers add, girls in the study got relatively little of their calcium from non-dairy sources -- perhaps too little for these foods to show an effect on weight and body fat.
Non-dairy sources of calcium include certain green vegetables such as broccoli and spinach, fortified soy milk, and calcium added to orange juice and cereals.
For the study, which was funded by the U.S. Department of Agriculture, girls and their parents kept a record of the foods the children ate over three days. The researchers found that the average calcium intake fell far short of the recommended level for children in this age group -- 736 milligrams (mg) per day, versus the recommended 1,300 mg a day.
When girls did get relatively higher levels of dairy calcium, though, it appeared to make a difference on the scale and near the waistline.
For reasons that are unclear, the effect on body fat was stronger for Asian girls than for white girls, according to Novotny and her colleagues. They speculate that ethnic differences in which dairy products are usually consumed, or in eating habits -- having small amounts of dairy throughout the day, for instance, rather than a single large serving-may help explain the finding.
According to the researchers, soda may tack on pounds by adding calories to kids' diets, or by replacing milk. Milk, they note, has a range of nutrients, including protein and fat, which means it is metabolized relatively slowly. Soda contains only sugar, which is quickly metabolized, leading to a blood sugar surge followed by a precipitous drop that triggers hunger.
Considering this, the researchers conclude, drinking soda in place of milk is likely to add on pounds.
Source: Journal of Nutrition, August 2004.