At one time, milk was promoted as "the perfect food." Of course, no one food is sufficient in itself, but milk and other dairy products are very nutritious (they remain the chief source of calcium in the American diet) and can be part of a heart-healthy diet. Still, legitimate questions, plus a number of myths, have multiplied. The arguments are highly politicized, with the dairy industry on one side and milk opponents on the other. Fortunately, there is plenty of well-designed research to help answer the questions you may have about milk.
Does cow's milk cause cancer or protect against it? There’s no clear link between milk and cancer, one way or the other. Dairy opponents say milk increases breast, prostate and ovarian cancer risks. But only a few studies support this, and many studies have found no increased risk. In addition, milk may reduce colon cancer risks, because of its calcium and vitamin D. For example, a study in the British Journal of Nutrition in 2006 found that people who drank very little milk had a somewhat higher risk of colon cancer than those who drank at least a glass a day.
Don’t believe claims by anti-milk groups that dairy harms bones. Though osteoporosis rates are lower in Asia, where dairy is rarely consumed, other factors other than diet affect bones, and most studies show that calcium from dairy is protective. Dairy is protein-rich, and very high protein intake slightly increases calcium excretion. But some protein is needed for strong bones, and dairy's high calcium may more than offset any small adverse effect of its high protein. Plus, in addition to calcium, milk provides vitamin D, magnesium, potassium and other key bone nutrients.
If you consume a lot of whole milk, whole-milk yogurt and cheese, you may see your blood cholesterol levels rise, especially if these foods contribute to weight gain. But you can get dairy products in nonfat or low-fat versions, which are lower in calories. There is evidence that increased intake of milk is linked with a reduced risk of stroke and heart attack. Certain substances in milk may even help lower cholesterol. In addition, nonfat or low-fat dairy products are an important part of the DASH diet, designed to control blood pressure.
For many years, teens and their parents have blamed diet for acne outbreaks—with chocolate the prime suspect. Most experts don't think specific foods play a role. Still, some dermatologists disagree, and some blame milk. The theory is that hormones in milk interact with human hormones and cause pimples. In the Journal of the American Academy of Dermatology in 2008, researchers presented preliminary evidence that skim milk was associated with acne in young boys. There was no explanation for why only skim (not whole) milk would have this effect.
Some studies have suggested that milk (or its calcium) can help people lose weight or at least prevent weight gain. A few years ago the dairy industry trumpeted this possibility in ads, but the United States Department of Agriculture (USDA) told it to stop doing so. Even the positive studies, which were mostly funded by the dairy industry, showed only very small benefits over long periods.
Studies have consistently found no major nutrition or safety differences between conventional and organic milk. Batches of milk tested may vary—organic milk may have higher (or lower) levels of nutrients than conventional—because the composition of milk depends on the cows' diets, the season and other factors. If you feel you are voting for better agricultural and humane practices, and can afford the high price of organic milk, that’s a reason to buy it. Whatever you do, always buy pasteurized dairy products, since raw milk is dangerous.
Thus far, studies have found no connection between milk and mucus formation. This idea persists because whole milk tends to coat the mouth briefly. If you don’t like this quality of whole milk, that’s yet another reason to switch to low-fat or nonfat milk. If you find milk unpleasant when you have a cold or cough, you can simply stop drinking it until you feel better.
People who have difficulty digesting lactose (the natural sugar in dairy) can consume lactose-reduced products or take pills that contain lactase (the enzyme that breaks down lactose) before consuming dairy. Yogurt tends to be less of a problem, since bacteria in it break down some of the lactose. Still, if you don’t like dairy products, or they don’t like you, you need not eat them. You can get calcium from other foods, including leafy greens such as collards and broccoli, canned salmon with bones, soybeans and calcium-fortified foods.