"If you can put it on the shelf, what's left in it?" Johnson wonders.
Not that Johnson can take it as a given that milk is good for her daughter in the first place.
Just last month in the American Journal of Clinical Nutrition, Purdue University foods and nutrition professor Connie Weaver wrote that milk is an important source of calcium and other nutrients, improves bone health and reduces the risk of stroke and some cancers. Research has put to rest concerns that it might increase prostate cancer, she noted. But in the same issue, University of North Carolina nutrition scientist Amy Joy Lanou argued that milk increases prostate and ovarian cancers. Her advice: Stay away from the stuff.
Even the experts who think milk is healthful don't agree on much else.
The National Dairy Council and other industry groups contend that all milks are created equal. The U.S. Food and Drug Administration agrees, finding "no significant difference" between organic milk and what flows from cows given synthetic growth hormones to boost production.
"We wouldn't favor one type of milk over another," said Michael Herndon, an FDA spokesman. Like the Dairy Council, Herndon dismissed the various milk varieties as pure "marketing."
But food-safety and sustainable-farming advocates maintain that organic milk is safer. Even if the synthetic hormones, approved by the FDA in 1994, do not show up in conventional milk, they say, they seem to raise the level of other, naturally occurring hormones in the milk that could pose problems for humans. They also contend that artificial hormones are rough on the cows, causing more infections that, in turn, lead to more antibiotic use on the farm.
In any case, these advocates say, there are too many unknowns.
"I think there's a real void in the science," said Patty Lovera, assistant director of Food and Water Watch, a consumer group based in Washington. "That just wasn't where the [agricultural research] focus was. It was how to be bigger, how to get faster."
There is one point of consensus: Cows that feed on grass produce milk that's higher in omega-3 fatty acids, vitamin E, beta-carotene and an antioxidant called conjugated linoleic acid - all good stuff for the body.
But there's no way, short of farm surveillance, for consumers to know if Bessie is really munching much green.
