Healthy Bones and Milk

March 31, 2008

I was reading through Harold McGee’s On Food and Cooking yesterday and found his discussion of milk, lactose, and osteoporosis interesting.

Milk is one of the few foods that is actually supposed to be a food, so it is unsurprising that milk contains many nutrients. All milk is primarily made of up of water, with varying levels of fat, protein, lactose and minerals. Here is an excerpt from an excellent chart in McGee’s book that breaks down the contents of milk from different animals:

(percentage of milk by weight)

Human milk has higher lactose than most, but lower protein and minerals. And the fin whale’s milk is a whopping 42% fat. It is these differences that led to the decline in use of cow’s milk for infants, a practice which apparently used to be widespread in America.

Lactose is a sugar that cannot be absorbed and used by the human body. The enzyme, lactase, must first break it down into other sugars before it can be digested. Humans have the most lactase in their body after birth, when milk is supposed to be consumed for nutrition. After a couple years, however, lactase levels decline and continue doing so throughout adulthood. Our bodies do not expect us to drink milk after our initial growth from infancy.

Lactose intolerance, then, is actually normal for adult human beings - lactose tolerant people are the weird ones. The geographical breakdown of lactose tolerance is interesting:

About 98% of Scandinavians are lactose tolerant, 90% of French and Germans, but only 40% of southern Europeans and North Africans, and 30% of African Americans. Harold McGee, On Food and Cooking

McGee attributes these differences to the colder climate in northern Europe. Even lactose intolerant adults, however, can drink about a cup of milk per day without adverse consequences.

Calcium is one of the primary minerals needed for healthy bones, but milk is not necessarily the best way to get it. McGee argues that drinking a quart of milk per day, the recommended amount by U.S. government panels, is a bad idea because the milk also replaces calories that are needed from foods that contain other nutrients. China and Japan, countries where milk consumption is much lower than the U.S., have much lower levels of osteoporosis.

Other factors also play a role in calcium absorption, as Vitamin D is needed for absorption, while high salt will lower calcium in your body. McGee recommends a well-rounded diet with multiple foods with calcium, and frequent exercise.

So, milk may not be as good for me as I originally thought. I do like the advice though of a well-rounded diet. That is my philosophy on eating, or at least the philosophy I would like to follow, namely eating a wide variety of foods (with an emphasis on fruits and vegetables) to stay healthy.

Do you drink milk frequently? Any lactose intolerant people?

Posted in Food Science, Health |