Milk strikes a powerful chord in our imaginations. It conjures associations with infancy, nutrition, bones, and of course, cookies. Recently, however, milk has become the focus of controversy, as experts have raised doubts about the virtue of drinking animal milk.
So let’s take a closer look at milk. What is it anyway?
Mothers in every species on earth produce a unique cup of milk. The amount of fat, sugar, water, and more, that go into every cup of breast milk is precisely set by nature. A cup of human breast milk is very different from a cup from a cow or a bear. For example, human breast milk is more watery than most animals and thus requires frequent feeding. At the other extreme, polar bear milk is so high in fat that one feeding can last many days or longer.
Human breast milk represents millions of years of fine-tuning for just what the human newborn needs in the first months of its life. How an infant grows, how a mother cares for the infant, the world in which they both live, all define how that milk is created.
The delivery of iron demonstrates just how deep the level of complexity of this fit goes. Iron is both essential to life, and toxic. Too little, and there is no hemoglobin or oxygen. But too much and iron becomes as dangerous as lead. So the body tends to keep iron out. If you eat foods rich in iron, most of the iron is dumped. For this reason manufactured infant formulas add lots of iron to get a little in. Human breast milk actually contains a protein that escorts nearly every atom of iron in breast milk into the newborn. So breast milk has six times less iron than formula, but delivers the same amount.
Mother’s milk is the only food whose every molecule was designed for us to eat, but when we start talking about any milk beyond nursing, we enter a new arena—one in which the milk was not evolved to fit our needs. With these milks a new question come up: Is this milk good for me? That is never a question for human breast milk.
At birth, milk is necessary for life and defines the entire intake of nutrition. But once someone starts eating regular foods—sometime after turning a year old—milk shifts its role in life dramatically.
For most people in the world this shift means the end of milk in their diet. Roughly 80% of people worldwide live in cultures that offer no milk in the post-weaned diet. Dairy is so absent that about the same percentage of the world’s population cannot digest milk. From the world’s perspective this is only natural, as milk is not a food, it is only what you have when nursed as an infant.
In the United States, the role of milk is clouded by intensive marketing efforts to portray milk as an essential food. In the early 20th century, the U.S. Department of Agriculture conducted studies to determine the best diet. Not surprisingly they found that the key elements of the best diet were fruits, vegetables, and whole grains. The National Dairy Council then volunteered to make their findings public by creating a poster and sending it out to every classroom across the nation. The resulting poster was a complete fabrication that you might remember staring at in health class: the Four Food Groups. This notion was invented by the National Dairy Council, and in one move, every student in America was taught that milk was as vital a food as fruits and vegetables.
Over the years this has led to other assumptions, including that drinking milk is necessary to develop strong bones. Eventually, most Americans have come to believe that if you don’t drink milk as a child, you risk being impaired as an adult. This assumption has been questioned for many decades, but continues to hold sway.
In 2014, landmark studies were published in The Journal of the American Medical Association Pediatrics and The British Medical Journal that asked, how does drinking milk in childhood affect the chance of having a hip or leg fracture in elderly years. The studies took hundreds of people over age 70 and ascertained each person’s milk and calcium and Vitamin D supplement habits in childhood and numbers of fractures. Surprisingly the studies suggested that those who drank milk, took calcium, and/or took vitamin D had no fewer fractures than those who did none of these.
At the start of life, mother’s breast milk defines what the newborn should eat. It evolved to fit this purpose. But once a baby weans from breast milk or formula, the role of any milk in our lives becomes one of taste, not nutritional necessity. Milk is needed only during infancy. Once we have outgrown our need for milk, then fruits, vegetables, and whole grains take the place of milk as necessary to our well-being.
And water becomes the best beverage to drink.