The USDA, the American Academy of Pediatrics and other august institutions recommend that calorie-containing beverages should be limited in people's diets. Pretty much all, that is, except for low-fat milk. The U.S. dairy industry made the “Got milk?” slogan one of the most famous of all time—and standard dietary guidelines embrace that entreaty: three cups a day, less the saturated fat, do well by both child and adult.

Experts are starting to have second thoughts about that recommendation. Less milk than what current daily requirements call for may in fact be more healthful, and forgoing milk altogether may be fine. What's more, even low-fat milk may not be as healthy as commonly believed.

The latest broadside against the most wholesome of foods appeared in July's JAMA Pediatrics, in a commentary from nutrition scientists David Ludwig and Walter Willett of Harvard Medical School. Their rationale is simple: foods with less fat often make you feel less full. The child who drinks low-fat milk but then grabs an extra cookie because of lingering hunger pangs winds up consuming more refined carbohydrates and risks gaining extra pounds. As for the cholesterol-raising saturated fat in whole milk, Ludwig and Willett note that milk fat increases both artery-clogging cholesterol as well as the more beneficial kind, making the whole thing somewhat of a wash.

The authors' antimilk manifesto also has an evolutionary component. Grazing animals evolved to supply milk to their young, keeping them close to protect against predation. But this necessary closeness stops when calves and kids turn into cows and goats. Human adults who chug the preferred drink of suckling grazers thrice daily for decades may not fare so well. A hormone called insulinlike growth factor 1 that is found in milk products has been tied to prostate and other cancers. If bone-strengthening calcium is what you seek, the researchers suggest, you can meet your daily requirements by eating leafy greens, nuts and seeds.

More work remains to be done, but until then, Ludwig and Willett say that milk drinking should not be mandated. And there's no need to seek out the skim carton on the market shelf.

Adapted from Talking Back at blogs.ScientificAmerican.com/talking-back