When people find out I am studying nutrition the questions immediately start pouring out, and the topic of dairy is one of the most popular. There is tons of research on both sides, so I’ll try to sum it up for you.
Evolution and Intolerance
The number 1 argument against dairy is that it isn’t “evolutionary” for humans to consume the milk made from other animals. While it is true that humans are the only species to do this, people have been consuming animal dairy products for hundreds of years, and some research shows that our genes have changed and adapted to accommodate the dairy products we consume.
While some genes may have changed, over 75% of the world’s population is still intolerant to the natural sugars in dairy (also known as lactose intolerance). This is likely due to reduction of lactase production (the enzyme used to digests those sugars) that naturally occurs as we age. Why does it decrease with age? Probably because in distant human history, people didn’t have much dairy in their diet after they stopped breast-feeding.
Calcium and Bones
Because dairy is the optimal food for growing animals, it is packed with beneficial nutrients like calcium, vitamin D, protein, phosphorus, and some B vitamins. Dairy products often get the spotlight for calcium content and bone health – which they should since it can be extremely difficult to meet our daily calcium needs from food without dairy. Several studies have shown that people who consume dairy have improved bone mineral density, and have lower risk of osteoporosis and bone fractures. But, other studies have shown that people who are lactose intolerant often have higher bone mineral density and lower risk of osteoporosis. Confusing, right?
More and more research is showing that we should really be focusing on vitamin D when it comes to bone health, but I’ll save that post for another day.
While the research on bone health is still “up in the air”, it is pretty well proven that dairy can provide a lot of healthy fats that can decrease heart disease and stroke risk. But there is a disclaimer that comes with this one. The nutrient composition of dairy can differ depending on what the dairy producing animals eat. We only see these healthy fats when dairy comes from animals that were grass fed or pasture raised. And don’t forget, you only get these healthy fats if you buy dairy products with fat in them – low fat and skim won’t have them.
Hormones and IGF-1
Finally, the infamous hormones that people are concerned about. Dairy has been shown to increase a hormone called insulin-like growth factor (IGF-1). IGF-1 is responsible for cell growth – which can be a good thing and a bad thing. It is great for healing damaged tissues and building muscle, but it also means it might help the growth of cancerous cells (that’s why so many people say that dairy causes cancer). While there are few and inconclusive studies showing dairy may increase prostate cancer risk, there are several studies showing dairy can decrease colorectal cancer risk.
In addition to cancer, IGF-1 is also the suspected hormonal link between dairy and acne, headaches, low energy, inhibited weight loss, and many more.
So back to the original question “Should I be eating dairy?”
Do you have digestive symptoms (like abdominal pain, flatulence, and diarrhea) after eating dairy? If you do, avoid it. You can try lactose-free dairy products be those can also cause trouble sometimes.
Do you have any symptoms of hormone imbalances (like acne, headaches, low energy, inhibited weight loss, or mood swings)? If you do, try eliminating dairy and see how you respond. Maybe it will help, maybe not, but it is worth a try.
Other than that, it is really personal preference. While there are some potential health risks, the evidence isn’t conclusive and none of the studies were gold-standard clinical trials. If you aren’t sure, maybe you try to eliminate it for a week or two to see if you feel any different and then make your decision. Remember, everyone is different so just because your neighbor won’t touch a piece of cheese doesn’t mean you shouldn’t have any either.
However, nutritionally, if you choose not to eat dairy, I would suggest a daily calcium + vitamin D supplement, especially if you are under the age of 30.