Why do you need dairy in your diet?

Milk plays a big part in the dietary guidelines released by the U.S. government. Anyone aged 9 or older is urged to drink three cups of low-fat or fat-free milk or eat an equivalent amount of yogurt or cheese each day. (Health Canada recommends two cups of low-fat or nonfat milk per day, but also recommends fortified soy beverages for anyone who does not drink milk.)

Milk contains calcium which cows get from eating plants. Most milk is also fortified with added vitamin D. The common belief is that because milk contains calcium and vitamin D, it is good for building strong bones and warding off osteoporosis, a disease in which bones become porous and break easily. While calcium and vitamin D do help to build strong bones, it's not certain if the calcium and vitamin D in milk are the best way to get these nutrients to your bones.

The U.S. dairy industry earns over $50 billion per year and spends over $200 million annually to convince people that dairy products are necessary for human health. Soon after World War II, ads began to appear portraying soldiers with milk mustaches. Today, the National Dairy Council uses Dara Torres, Matt Hasselbeck, Serena Williams, and Taylor Swift: all household names, all young and healthy, all good “spokesmodels” for selling milk.

Not everyone, however, believes the conventional wisdom. Researchers are even raising questions about whether children need as much milk as guidelines recommend. A 2005 review article in the journal Pediatrics concludes that there is "scant evidence" that dairy is the right way to promote bone health in children.

Many highly respected scientists say that people need less calcium than government dietary guidelines recommend, and that drinking milk is not the best way to get it. Cow's milk wasn't a part of early human diets. Humans are the only species who, as adults, not only consume milk meant for infant mammals, but are the only species that drinks the milk of an entirely different species.

Up to 75% of people in the world can’t consume dairy: when they drink milk, they experience digestive problems or allergic reactions, especially those with Mexican, African, Native-American or Asian heritage. Some people have a tough time digesting the milk sugar, called lactose, and so they get stomach pains or gas. And some people experience allergic responses to protein in the milk, which triggers an immune response in their bodies as if they were warding off invaders. Symptoms can include excess mucous in the throat, shortness of breath, nausea, headaches and even hives.

Even people who can drink milk are concerned about the drugs such as antibiotics or growth hormones that are given to dairy cows and how they affect human health.

By 2020, one in two Americans older than 50 will be at risk for fractures from osteoporosis or low bone mass, according to an October 2004 U.S. Surgeon General report. In fact, the U.S. consumes more than double the amount of milk and dairy than the second-highest dairy-consuming country, and yet has one of the highest rates of osteoporosis and dental decay in the world. The other highest osteoporosis countries are the other highest milk-drinking countries (in Europe and Scandinavia).

Milk and other dairy products increase the net acid load on your body, causing your bones to lose calcium and preventing the calcium in milk from being absorbed. According to Dr. Michael Colgan, a researcher in the fields of nutrition and exercise, acidic foods cause your bones to leach calcium and your kidneys to expel calcium, so there is no way milk can protect your bones.

Nutrition researchers from Harvard and Cornell universities believe that exercise, heredity, hormone levels, smoking, and intake of protein and vitamins D and K are more important factors to consider than how much milk you should drink.

Dr. Walter C. Willett, chairman of the Department of Nutrition at the Harvard School of Public Health, does not believe that milk protects bones. Willett bases his conclusions on decades of research that he and his team at Harvard have done. When Willett and his colleagues investigated the milk-drinking habits of 72,000 women in the Nurses' Health Study, they found that milk consumption was not associated with a lower risk of hip fracture. In fact, women who drank milk twice a day were as likely to suffer a bone break as women who drank it once a week.

Dr. T. Colin Campbell, who grew up on a dairy farm and is now professor emeritus of nutritional biochemistry at Cornell University, also questions the amount of dairy you need each day. Campbell's views come from observations he and his colleagues made during a series of nutritional studies that began in 1983 and are collectively known as the China Study. In these studies, Campbell found that Asians, who consume far less calcium than Americans, have one-fifth the bone fracture rate of Americans. In Asian countries, people can get all the calcium their bodies need from plant sources such as leafy green vegetables.

Calcium isn’t the only nutrient important for bone, though. Vitamin D, which is generated in your body from exposure to the sun, Vitamin K, magnesium, and other minerals all help bones get stronger. Fortunately, there are very good sources of these nutrients other than milk. The best sources for absorbable calcium are dark leafy vegetables: spinach contains twice the amount of calcium as cheese. Collard greens, turnip greens, bok choy, and mustard greens are also Excellent bone-building foods, not only for their calcium, but also for their vitamin K and magnesium. Vegetables also create an alkaline environment inside your body so that the calcium in your diet can be absorbed.