Science Debunks a Decades-Old Myth About Drinking Milk
Milk is optional.
Americans born in the ’90s likely remember the Got milk? campaign. The rhetorical question came in slim, white sans serif text, all lowercase, on a black background. Sometimes it completed a portrait of a smiling child or adult with a white mustache coating their upper lip like an Einstein-Groucho Marx hybrid.
Since then, milk has proliferated. At first there was just whole and skim milk, but now there are whole spectra of milk containing various amounts of fat, as well as plant- and nut-based milk in varying flavors.
All that advertising may have backfired, making some ’90s and early-aughts kids into dairy-wary adults. Like calcium and Vitamin D, a healthy dose of skepticism can do a body good, so looking at whether milk is as imperative as TV led us to believe is worthwhile.
Is milk actually good for you?
Evidence does show that cow’s milk is replete with essential nutrients like calcium, zinc, magnesium, phosphorus, protein, fat, and more that help our bodies run.
Nutrition scientist Kimberly O’Brien at Cornell University says that while plant-based milks have some of these nutrients added to them, dairy milk is more of a total package. So it’s accurate that milk contains things that are good for you, but that’s not to say milk is for everyone. For a variety of reasons, someone might be lactose intolerant, which means their digestive tract can’t break down lactose, which is only present in dairy.
“There’s some validity to the backlash,” says Michelle Averill, a nutritional sciences professor at the University of Washington. “Dairy consumption is not appropriate for all cultural groups.” That’s not to say that dairy is bad, but that dairy isn’t as ubiquitous in some cultures as it is in, say, the French and American diet. East Asian diets, for example, don’t include much dairy, but that doesn’t mean they’re lacking.
“Consuming dairy, like cow’s milk, is not culturally included in all dietary patterns,” Averill says. “So it’s an assumed acculturation recommendation to say, ‘Drink milk.’”
O’Brien also acknowledges that nothing is a one-size-fits-all, not even milk. “It’s very hard to prescribe one diet for the entire planet,” she tells Inverse.
Do humans need milk?
Indisputably, humans need water, oxygen, and sleep, among other things, to live. While they require calcium, protein, fat, magnesium, zinc, and phosphorus — all of which cow’s milk is chock full — humans don’t necessarily need milk.
Calcium famously helps build strong bones. O’Brien says that by about age 20, most of a human’s bone mass has accumulated. By age 30, that person’s skeleton has reached peak bone density. This is one reason why milk is seen as a staple for kids, because the first 20 years of life are critical for fortifying the only skeleton you’ll ever have. Moreover, like so many other things, genetics determines one’s bone density. If someone’s family has a history of osteoporosis (a bone disease due to decreased bone density and mass which can increase risk of injury), drinking milk regularly in childhood might beat dealing with the consequences.
But we don’t only need calcium for our bones. Serum calcium, which is the element as it exists in our bloodstream, is crucial for healthy muscle contractions. When the nervous system jolts a muscle to flex, that muscle releases calcium from its cells’ internal stores, allowing the muscle proteins to cause a contraction. In this situation, calcium also acts as what O’Brien calls a “potent signaling agent” for cells, its release in this moment instructing muscle cells to contract. Even the heart pulls calcium from surrounding blood to keep pumping. If the body gains or loses too much calcium, that imbalance can cause contraction defects, according to O’Brien.
When there isn’t enough serum calcium — O’Brien says we have 10 milligrams of calcium per deciliter of blood — the body pulls it from our bones, which are calcium banks. Think of serum calcium as your checking account and calcium in your bones as your savings. If you keep dipping into your savings because your checking is too low for immediate expenses, you may face consequences down the line.
“Once you have demineralized your skeleton to a great extent, you can’t bring it back to normal,” O’Brien says. That can impact quality of life and even mortality should someone suffer a hip fracture.
All this is to say that calcium — of which Averill says milk is the most cost-effective source — is integral, but there are other founts.
What else has the same nutrients as milk?
While milk is a single nutrient-dense food source, it’s possible to get those nutrients from other food groups. The downside is that one must look farther afield for all those vitamins. Especially for kids, who need all the calcium they can get to fortify their skeletons, milk can be an easy single shot of good stuff. Averill suggests that non-dairy kids who are picky eaters can get much of the same nutrients from plant-based milks.
Averill also says that a varied diet consisting of many different grains, proteins, and vegetables ought to provide all the nutrients that one needs. Plant-based milk can make up for any areas where there’s something left to be desired. In her class on micronutrients, Averill shows her students that bone density in vegan populations isn’t uniformly impacted. This means that it’s not dairy alone that can keep our calcium levels afloat. A few other good sources of calcium include almonds, leafy greens, and green soybeans.
“I’m not saying that one form is better than another,” O’Brien says. “It’s good that we have alternate fortified food sources that people can substitute to get get those nutrients.”
Milk isn’t the way, but it is a way.