Dairy makes up about 10% of calories in the typical American adult's diet. For the last 40 years, one approach to dairy has reigned supreme: Get calcium, avoid fat.
But Dariush Mozaffarian, a cardiologist at Tufts Medical Center and a professor of nutrition, thinks that wisdom is “really terribly oversimplified.”
He argues dairy products are so varied — and their health implications so distinct — that classifying them together is a “mistake.”
Mozaffarian, who was named one of the "World's Most Influential Scientific Minds" by Thomson Reuters and was nominated by President Biden to serve on the President’s Council on Sports, Fitness, and Nutrition, believes that dairy is “one of the most interesting and understudied categories of food.”
WBUR spoke with Mozaffarian about the latest evidence on each major type of dairy food and the health implications of this research. Let's dig in!
These interview highlights have been edited for clarity and length.
Yay for yogurt
“Among dairy foods, the category with the strongest evidence for health benefits is yogurt.
“Yogurt is consistently linked to lower risk of diabetes, and lower risk of obesity and weight gain in long-term observational studies. And there have now been dozens of small, randomized controlled trials — none of which have been perfect but you can analyze them together — showing that probiotics in yogurt, and in other foods, lower weight and improve glucose and insulin levels.
“And so, it seems pretty clear that yogurt gives us a healthier microbiome, and other factors in the yogurt, which we're just starting to understand, improve our overall metabolism.”
“Cheese has been thought of as the big demon in the food supply: It's making us fat. People talk about pizza as a negative because of the cheese, when in fact, the cheese is probably much healthier for us than the crust.
“Cheese is the top fermented food consumed in the United States. Other cultures consume kimchi or sauerkraut, but in the United States it's cheese. The fermentation creates new compounds. And also, many cheeses have active bacterial cultures or probiotics in them.
"I can't say conclusively that cheese is good for you, but I can say pretty conclusively that it's not bad for us."Dariush Mozaffarian
“Again and again in long-term observational studies, cheese is not associated with higher risk of heart attacks. It's not associated with higher risk of stroke. It's not associated with weight gain. And in fact, it seems to be generally associated with trends toward lower risk of diabetes and towards lower risk of stroke.
“So, my conclusion as a cardiologist, as a nutrition scientist, is that I can't say conclusively that cheese is good for you, but I can say pretty conclusively that it's not bad for us.
“I think it's really an urgent scientific priority to put more funding into the study of cheese to really understand what its health effects are. And it actually may be good for us, which is kind of amazing.”
Mixed results for milk
“So milk is, I think, one of the most poorly understood classes of dairy. It's widely recommended for its calcium, especially to kids, and it's also widely recommended to be nonfat to avoid getting fat and saturated fat.
“But there's no evidence that higher saturated fat intake from dairy is really a problem for health. There's also not great evidence that the calcium levels that are currently recommended are actually necessary for optimal bone health.
“If you look overall at all of the long-term studies that have looked at people who drank milk — all observational, none of these are trials — on average, milk is pretty neutral.
"Take it or leave it. If you enjoy [milk], go ahead and have a glass. If you don't, don't worry about it.”Dariush Mozaffarian
“There’s a slightly higher risk of this cancer, a slightly lower risk of that cancer. No real association with heart disease. Milk consumption does seem to lower blood pressure. So there are these slight benefits here or there.
“The one more definitive thing that clearly happens is kids who drink milk are a little taller — a centimeter or two — and that's probably less because of the calcium, but more because of some of the growth hormones that are in milk.
“One of the really sad things about industrial milk production is usually we are leveraging the poor mother cows by having them give milk and be pregnant at the same time — to get milk and veal — which isn't normal. By being pregnant and producing milk, there are natural pregnancy growth hormones and other hormones of pregnancy that get into the milk that shouldn't be there.
“If you put it all together, I’d say, take it or leave it. If you enjoy it, go ahead and have a glass. If you don't, don't worry about it.”
Don't bash butter
“There's so much debate about the health effects of butter, and yet, shockingly, it's barely consumed in the United States. It represents something like 2% or 3% of all saturated fat consumption.
“There have been almost no long-term controlled trials of health outcomes [of eating butter]. We do know that butter raises LDL cholesterol, the bad cholesterol, but butter also raises HDL cholesterol, the good cholesterol. So, on average, those effects would seem to cancel each other out. And in observational studies, that's exactly what we see. Butter is pretty neutral for cardiovascular disease and relatively neutral for most health outcomes.
“So butter seems to be kind of a neutral food.
“And what do I mean by neutral? Well, there's healthier choices and there's worse choices. Fruits, vegetables, nuts, extra virgin olive oil, fish, they're all much better choices than butter. And many of the healthy oil based margarines — they are now more natural and don't have trans fats — are also healthier than butter.
“On the other hand, there are things that are much worse than butter, particularly refined bread and candy and sugar. So when people say, ‘Should I butter my bread?’ I say, ‘Skip the bread. The butter is actually neutral. The bread is bad for you because it's refined.’ ”
We all scream for...
“What's really interesting about ice cream is that in long-term observational studies — the handful of studies that have looked at ice cream — people who consume more ice cream have lower risk of diabetes long-term.
“Now, I've been involved in some of those studies, and it's hard to know how to interpret the results since it's an observational study. There are two interpretations. One, ice cream actually lowers risk of diabetes through some unknown mechanism. And second, people who have other risk factors that make them more at risk of diabetes avoid ice cream. And people who eat ice cream are pretty healthy. And so that's called reverse causation.
“Five or 10 years ago, everyone would have assumed it must be reverse causation. They’d say, ‘there's no way ice cream can actually lower risk of diabetes.’ But the more we learn about milk fat globule membrane, menaquinones [a form of vitamin K2] and cream, could it be possible that there's something beneficial in ice cream? It's possible.
“Compared to white bread, ice cream is healthier. It is well known that if you eat white bread or if you eat ice cream, and you have diabetes, you get a much healthier glucose response from eating the ice cream than eating the bread.”
[The Atlantic recently chronicled the weird and wild ice cream debate, and how it has vexed nutrition researchers.]
On what’s behind the various health effects
“Across all dairy foods, we're just scratching the surface of what it is about the different foods that relate to their health effects. I think the bottom line lesson is: It's very complicated.
“Yogurt has active probiotics. Many cheeses, in the rind, have active probiotics as well. But beyond that, fermentation of dairy changes vitamin K, a very common vitamin, to vitamin K2, which are also called menaquinones. And menaquinones may have good health effects on the pancreas and insulin function.
“There's also something called milk fat globule membrane, which we used to not really pay attention to. It is lost when you make butter but is present in cream, ice cream and cheese. And it seems to have health benefits.
“So raw milk, the precursor to all dairy, is the combination of fats and water. For the fats to be soluble in water, there's a natural set of phospholipids which are types of fatty acids called milk fat globule membrane.
“When milk is homogenized, what the homogenization is doing is breaking up the milk fat globule membrane and scattering it into millions of pieces. When butter is made, you have to destroy and remove that milk fat globule membrane, which is buttermilk and is often thrown away.
“But we've learned from human trials that milk fat globule membrane, these phospholipids, have active biologic effects. When they're consumed, they change the function of our genes. They help lower blood cholesterol. They interact with gut absorption of cholesterol in the microbiome. And in fact, in trials, cheeses that have high levels of milk fat globule membrane can actually lower blood cholesterol by 10% or 15%, like a cholesterol lowering medication.
“That's just one example of the complexity of the compounds in dairy and how this is barely, barely understood. We need to study this much more.”
Ranking different dessert options
“If I had to stratify desserts, dark chocolate — 70% cocoa — would be at the top, especially if it had nuts. And then probably a healthy, minimally processed, real ice cream — not the processed stuff that’s full of junk.
“And then you'd go down pretty quickly to other desserts that are much less healthy, particularly ones that are rich in refined grains and sugars.
“Compared to Skittles or other candy, or other bakery desserts, ice cream is healthier. It has protein. It has some medium-chain saturated fats. It has some other nutrients in it.
“As a cardiologist who studies nutrition, I often have a scoop of ice cream as a dessert. And I've had friends say, ‘I can't believe you're doing that. How are you eating ice cream?’ I say, ‘I skipped bread at dinner and so I'm going to enjoy my ice cream instead.’ I think we don't really understand enough about ice cream. My current best guess for its health effects is that ice cream is a pretty decent dessert.”