[ weird things ] | why milk may not actually be good for you

why milk may not actually be good for you

Many humans can drink milk long after they start eating solid food. But science is still not sure if they should.
milk carton with eyes

Milk builds strong bones because it’s full of calcium. This is what we’ve been told over and over again by ad campaigns urging us to drink more of it. And with almost 10.8 million dairy cows in the U.S. and Canada producing 110.5 billion liters of milk per year, it’s a good thing we have so much of it, right? Well, the accurate answer to this question is complicated. While it’s true that milk does help bones grow, it also puts you at risk of fractures, the fat in it isn’t exactly great for you over the long term, and there’s a strong case for getting much of your calcium elsewhere.

These are the conclusions of a review published in the New England Journal of Medicine which looked at a multitude of studies showing that while milk won’t actively hurt you, there’s a case to be made for moderating dairy intake. For example, countries with the most milk consumption also see the most hip fractures, most likely because milk can add extra bone length, and then, during a fall, physics takes over. It’s not that the bones are somehow fragile, there’s just more bone to fracture or break based on body type and circumstances of the fall.

Likewise, the fat in dairy products doesn’t play well with your cardiovascular system. Cheeses, milk, and ice cream consumed at an excessive rate may mess with your blood pressure, which tends to place you at higher risk of heart attacks and strokes. And the growth hormones in milk are being correlated to certain types of cancer in those receiving hormone therapy. Again, it’s not like dairy consumption is actively hurting you, but if you’re already at risk of certain health conditions or injuries, it seems to tip the scales slightly out of your favor.

All right, fine, you may say, but didn’t we evolve to drink milk during the dawn of agriculture to capitalize on an additional source of vitamins and calories? Wouldn’t that indicate that we need dairy and should be eating it regularly? Yeah, about that. According to a massive new study of nearly half a million genomes, that hypothesis isn’t true either. Humans had mutations to drink milk for thousands of years before milk consumption became widespread. It just so happens that the genes allowing us to process lactose were useful during famines and pandemics.

Basically, a lot of humans could process dairy past age five, when lactose processing genes are normally supposed to shut down in primates. For hundreds of generations, this offered no clear advantage whatsoever, but it also didn’t hurt, so the mutation stuck around. But in hard times, it allowed dairy products and milk to be an alternative food source others couldn’t digest, so when pandemics and famines hit, the mutation spread wider through the survivors who now had extra food and were now more likely to survive.

To sum it up, milk is perfectly fine in moderation if you’re not lactose intolerant, and you should enjoy it if you want to. However, there’s no need to consume it every day, or rely on it for strong, healthy bones because a diet rich in vegetables, nuts, and leafy greens will see to that. You did not evolve to consume dairy as part of your diet, that ability was just a lucky accident for your ancestors. And if you’re receiving hormone therapy, you may want to discuss what you eat with your doctor, and go light on dairy products.

See: Willett, W., Ludwig, D. (2020) Milk and health. N Engl J Med 2020; 382:644-654, DOI: 10.1056/NEJMra1903547

Evershed, R. et al. (2022) Dairying, diseases and the evolution of lactase persistence in Europe. Nature, DOI: 10.1038/s41586-022-05010-7

# health // dairy / evolution / milk

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