Credit: Carsten Schertzer/Wikimedia Commons

Milk is a popular energy food for outdoor athletes.

It is liberally dispensed at running races, and is often carried in backpacks or panniers as a satiating beverage. While my wife, Julie, and I spent five months rowing across the Atlantic Ocean, powdered milk was one of our staples. But is milk as healthy as the dairy industry leads us to believe?

If we look to our government for an answer, we receive an overwhelming yes. Canadian food guidelines place heavy emphasis on dairy, recommending that adults consume the equivalent of at least two glasses of milk per day. In recent years, the Canadian government has added the words “and alternatives” when referring to dairy. However, the premise that dairy is an essential food group is a very Eurocentric concept considering that, according to the Journal of the American Dietetic Association, 75 per cent of the world’s population is unable to digest milk. It is mainly people of European ancestry that are able to digest dairy. In our Canadian culture of ethnic diversity, such recommendations speak more about our colonial beginnings (and perhaps lobbying from the dairy industry), rather than a food essential to the health of our population.

Take, for example, the fact that according to Scientific American more than 90 per cent of Japan’s population is lactose intolerant, and dairy has never traditionally been a part of their diet. Despite eschewing what is touted as an essential food group by our government, the Japanese have the longest life expectancy in the world. (Okinawa also has Earth’s greatest density of centenarians.)

Of course, just because the Japanese are very healthy and they don’t consume very much milk doesn’t mean that milk is unhealthy. But it does strongly suggest that dairy may not be as essential as our government leads us to believe. 

To understand the complex relationship humans have with milk, it is important to comprehend how our evolutionary development was influenced by the mammary glands of other animals.

Humans are the only mammal (and not all of us) that has the ability to digest lactose (a type of sugar found in milk) as adults. All mammalian infants have a special enzyme called “lactase” that allows them to digest lactose, so they can process their mother’s milk. But by the time they become adults, production of lactase ceases—except for humans. Without lactase, milk consumption leads to bloating, cramping and gas.

The reason why mammals stop producing the enzyme lactase into adulthood is straightforward: milk is typically not available for adults, so the enzyme is not required. Additionally, if adults were able to digest milk, desperate individuals might be inclined to rob mothers of milk intended for offspring.

About 10,000 years ago, people started domesticating livestock, and for the first time in the span of our development, it became advantageous to be able to digest milk as adults. Domestic animals offered an abundant source of nourishment without having to kill them—goats, cattle and other animals could transform grass and leaves into something much more nutritious for humans. 

The dairy revolution provided a remarkable advantage for humans adept at domesticating animals. Genghis Khan’s mighty armies were fueled by milk (how’s that for a dairy slogan!). His troops galloped for weeks on end across the steppe, subsisting on nothing other than milk and blood from their horses, drawn in small enough quantities to not harm them. To this day, milk is a primary food source for Mongolians. During our expedition voyaging the Yenisey River through Mongolia, we frequently spotted herdsman gnawing on hard chunks of dried cheese—protein bars of the steppe.

Initially, humans had to transform milk into cheese or yoghurt so that most of the lactose was consumed by bacteria, making it more digestible. Eventually, however, between about 5,000 and 10,000 years ago, one of our most recent evolutionary changes occurred: the rise of lactase persistence. Lactase persistence is a trait where the enzyme lactase (which breaks down lactose sugar) persists beyond infancy and through adulthood. This new development took place mainly in and around Europe, which is the region that gave rise to dairy farming. Today, 80 per cent of Europeans and North Americans of European ancestry have lactase persistence and can chug milk without any problems.

While some of us can digest milk, this still doesn’t answer the question as to whether it’s healthy. There is a growing—and very vocal—group touting dairy as a poison. However, their arguments are mostly backed by pseudoscience or are cherry-picked. A common refrain is that no other animals drink milk as adults, therefore it can’t be good for humans. The reality is probably somewhere between what’s touted by the dairy industry and the dairy-be-damned crowd. There’s no denying that milk is a good source of protein and also provides a range of beneficial vitamins and minerals. The fats associated with dairy provide a feeling of satiation and long-term energy, and are now considered relatively benign to cardiovascular health.

On the other hand, the commonly held belief that milk is good for skeletal health is not supported by science. In fact, population studies indicate that milk may actually have the opposite effect. A recent study published in the British Medical Journal showed a correlation in the amount of milk drunk by Swedish women and the number of hip fractures that occurred. In other words, the women who drank more milk had a significantly higher rate of bone fractures. Two other similar studies in different countries didn’t link milk to fractures, but they didn’t show that it was good for our bones, either. 

If you’re worried about osteoporosis, you’re better off increasing your calcium and vitamin D intake from sources other than milk. And science shows that the most effective way to maintain bone density is through vigorous exercise. Sitting on the couch and popping your supplements simply won’t cut it. Climbing mountains, jogging and any other exercise that stresses your bones is what will most effectively preserve them into old age.

Overall, it seems milk is neither an elixir to good health nor a slow-acting toxin clogging our arteries and promoting cancer. If you like the taste, and it doesn’t give your back-end a blowout, then go ahead and enjoy your milk. And for those of you who are lactose intolerant, don’t let the dairy advertising get you down—a Power Bar and water is just as effective to fuel you forward.