Perceived milk intolerance may weaken girls' bones

By Anne Harding

NEW YORK (Reuters Health) - Young girls who believe they are lactose-intolerant take in less calcium and have thinner bones than their peers who don't think they had any trouble consuming dairy products, a new study shows.

But when these girls were tested to determine if they actually did have difficulty digesting lactose, many did not.

"It's a little concerning that you have young girls during this period of time when they actually obtain their peak bone mass...that they have already been influenced that they are intolerant to milk for whatever reason," said Dr. Carol J. Boushey of Purdue University in Lafayette, Indiana, the study's lead author.

Boushey and her team looked for ties between perceived milk intolerance, bone mineral content, and calcium consumption in a group of 10- to 13-year-old girls. They also tested them for lactose maldigestion, which occurs when activity of the lactose-digesting enzyme lactase is reduced, and can be identified with a breath test. People with the condition can usually drink or eat a single serving of dairy, for example 8 ounces of milk, without having intolerance symptoms, but may have indigestion if they consume larger amounts.

Of the 246 girls in the study, 47 said they were milk intolerant. Forty of these girls completed breath testing, which identified only 18 as true lactose mal digesters. Girls who thought they had milk intolerance consumed 212 milligrams fewer calcium daily than their peers who didn't have this perception, and also had a lower mineral content in their spine.

Altogether, 230 girls took the breath test, and 100 were found to be lactose mal digesters. But these individuals consumed no less calcium, and had equal bone mineral content, to their peers who had no trouble digesting milk.

The fact that girls who considered themselves lactose intolerant were consuming less calcium at such a young age could put them at risk of osteoporosis later on, Boushey noted. It's not clear, she added, where this perception is coming from, but she and her colleagues are investigating whether parents' perception of their own lactose intolerance has anything to do with how their children feel about dairy products.

"I don't think that this comes from the girls, they're way too young, it has to come from something around them," she said.

SOURCE: Pediatrics, September 2007.