The short answer is that if you really want to be sure your kids aren’t drinking milk containing bovine growth hormone, you could buy organic milk, or specially labeled milk from farms that avoid the hormone.

But that degree of concern is probably unnecessary, said Dr. Ronald E. Kleinman, cq chief of pediatric gastroenterology and nutrition at Massachusetts General Hospital. Milk from treated cows is just as safe as that from untreated cows, he said.

That said, there’s been a vitriolic controversy raging ever since farmers began injecting bovine growth hormone, also known as Posilac, into cows in 1994, following approval by the US Food and Drug Administration. One issue is labeling — there’s no way for consumers to know which containers of milk come from treated cows and which don’t.

Thirty-five percent of American cows are in herds where growth hormone is used, according to Monsanto, the only manufacturer of Posilac.

Monsanto spokesman Brian Lowry said milk from treated and untreated cows is identical. Kleinman agrees. If there is an increase in an insulin-like growth factor, as the Consumers Union and others charge, Kleinman said he doesn’t think that increase causes any health problems.

Consumers Union senior research associate Michael Hansen said there has not been enough rigorous research to know for sure. “My take is there’s an unknown risk there,” he said.

It’s clear that Posilac may not be great for cows. It can raises the risk of mastitis, which can necessitate giving cows even more antibiotics than they are already given.