Is Milk Actually Good for You?

What's as American as apple pie? The glass of milk you wash it down with—and the one you guzzled as a kid in order to grow big and strong. According to the U.S. Department of Agriculture, we should still be getting our fill: The government recommends that everyone age 9 and older consume three cups of "fluid milk products" or "foods made from milk" daily. That's because dairy is vital to healthy bones. Or is it?

"Milk is not essential for good health and wellness, nor is it the best source of calcium," says Alissa Hamilton, PhD, a former Institute for Agriculture and Trade Policy fellow who spent two years researching the science behind the dairy darling for her new book, Got Milked? The Great Dairy Deception and Why You'll Thrive Without Milk. "I was surprised to learn that the calcium recommendations we rely on aren't evidence based, and I continue to be amazed by the prevalence of misleading claims about milk's benefits. I'm not saying milk is evil, but it's not a must-have that will solve our bone problems and make us super-healthy." Here, three of Hamilton's most surprising findings.

A 2011 Journal of Bone and Mineral Research review that pooled data from six studies (involving nearly 200,000 women) found no link between milk consumption and a reduced risk of hip fracture. How could that be? Some researchers believe it's the result of getting too little vitamin D, which is crucial for calcium absorption; even four 8-ounce glasses of vitamin D–fortified milk falls short of the recommended daily allowance. In fact, countries that consume more dairy and calcium have higher rates of fracture. Plus, calcium and D aren't all your bones need: One cup of milk is a poor source of vitamin K and has only 6 to 7 percent of your daily value of magnesium, both of which are important nutrients for bone health.

The USDA recommends adults get 1,000 to 1,200 milligrams of calcium daily—which Hamilton says may be excessive: "The recommendations for calcium in North America are among the highest in the world, but research is showing that calcium above 700 or 800 milligrams per day may increase risk for various health problems." A 2014 report in the journal BMJ found that women who drank three or more servings of milk daily had a higher mortality rate than those who drank less than one glass a day. The report suggests milk consumption can affect the risks of heart disease and some cancers, potentially because lactose may play a role in promoting chronic inflammation.

Many people assume that lactose intolerance (which affects about 65 percent of adults) is a type of digestive malfunction. In fact, it's just your body responding as it should. "The ability to digest milk as an adult is actually the result of a genetic mutation," Hamilton says. When we're young, our small intestines produce the enzyme lactase, which helps us digest the lactose in our mothers' milk (and cows' milk). As we grow, the body's production of the enzyme slows or stops, leaving us with unfun stomach trouble that gurgles up when we try to process lactose. Every other mammal stops drinking milk after babyhood—humans are the only ones who didn't get the memo.