The study also found a strong effect of having dairy as a calcium source followed by periods of inadequate calcium.
Over a second 10-week period, the remaining rats were fed as adults. Half of those were given adequate calcium as carbonate or milk. The other half were switched to half as much calcium as recommended, but were given calcium carbonate.
"This is comparable to humans who, during their early growth, drink a lot of milk to the age of 9 to 11, or maybe even adolescence, but then get only half as much milk calcium as they need after that," Weaver said. "Some take calcium supplements, but few adults get adequate calcium."
Weaver said the study showed the rats raised on dairy still had advantages over those who were given calcium carbonate even later when they were given half enough calcium as dairy or calcium carbonate.
"We found it was an advantage having milk or dairy while bones were growing over calcium carbonate, and it protects you later in life," Weaver said.
She is not sure why dairy is better, but said further study is needed.
"I think this will spark some people to want to figure out what it is about milk that gives it an advantage," she said.
"It's not due to increased calcium absorption. It's more about protecting against bones losing calcium, according to our results of calcium metabolism. Bones are in constant turnover, especially when they are growing. Youth need to have bone formation outweigh bone loss."
|Contact: Greg McClure|