Browse evidence-based analysis of health-related claims and assertions
Eating a little dairy might be good for you, but eating a lot might not help—or could even hurt—your health; the sweet spot isn’t the same for everyone.
Correlational
People who eat more dairy—like milk, cheese, and yogurt—tend to have a slightly lower chance of dying from heart disease than those who eat very little dairy.
People who drink whole milk regularly may be a bit more likely to die from any cause, heart disease, or cancer than those who drink skim or low-fat milk — but this doesn’t mean milk is the direct cause.
Eating a lot of full-fat dairy like cheese and butter might be linked to a higher chance of dying from cancers other than breast cancer — and it could be because it harms your heart or metabolism, not just because it feeds cancer.
Eating lots of full-fat dairy—whether it’s cheese, butter, or ice cream—seems to be linked to a higher risk of dying, no matter which one you pick, so it’s probably the fat itself that’s the problem, not the food it’s in.
Eating dairy overall doesn’t seem to make breast cancer come back or kill more women from breast cancer, but it might be linked to dying from other causes — and that’s probably because the bad stuff (like full-fat dairy) is hiding in the average.
If you’ve had early-stage breast cancer, switching from full-fat dairy like whole milk or cheese to low-fat versions won’t make your cancer come back or shorten your life — so you don’t have to stress about this change.
If you've had early-stage breast cancer and eat a lot of full-fat dairy like whole milk or cheese every day, you might be more likely to die from breast cancer or other causes later on, compared to people who eat very little of it.
In Iran, women who drink skim milk or eat low-fat yogurt may be less likely to get breast cancer, but those who eat full-fat cheese or cream might be more likely—so the fat in dairy could be what makes the difference.
Eating yogurt and cheese doesn't seem to raise or lower the chance of breast cancer in Iranian women, unlike milk or fatty dairy products, which might have a different effect.
Iranian women who drink more milk are about 76% more likely to get breast cancer than those who don’t, even when you account for other dairy like cheese or yogurt—so milk itself might be doing something unique that raises risk.
Iranian women who eat a lot of full-fat dairy like cheese and butter may be nearly 9 times more likely to get breast cancer than those who eat very little of it — but this doesn’t prove the dairy causes the cancer, just that they tend to happen together.
Iranian women who eat more low-fat dairy like milk and yogurt seem to have a much lower chance of getting breast cancer compared to those who eat very little — it’s not proven to cause the protection, but there’s a strong link.
When you eat gluten, certain bacteria-made enzymes and gluten bits team up to sneak through your gut lining and get stuck underneath, where your immune system might mistake them for invaders and react.
Mechanistic
A bacterial enzyme called microbial transglutaminase might help gut bacteria grow faster by making their inside less acidic and using their energy to multiply instead of doing other jobs.
Some bacteria make an enzyme that might interfere with the gut’s natural slime layer, making it easier for more bacteria to stick to the gut wall instead of being washed away.
Some processed wheat products treated with an enzyme called microbial transglutaminase might trick the immune system of people with celiac disease into thinking they’re under attack, causing inflammation and triggering harmful antibodies.
In people with celiac disease, a bacterial enzyme called microbial transglutaminase might glue together the tiny seals between gut cells, making the gut leakier and letting more of the harmful wheat protein (gliadin) slip through, which could make symptoms worse.
When a bacteria-made enzyme called mTG mixes with gluten in food, it can glue gluten pieces together in a way that tricks the immune system of people with celiac disease into attacking their own intestines—and the more damage they have, the more of these weird antibodies their body makes.
Adding ractopamine to pig feed doesn’t make the pigs grow faster day by day, but it does help them turn food into muscle more efficiently and end up with leaner meat.
Quantitative
Pigs bred to be lean grow muscle faster in the middle of their finishing stage than pigs bred to be fat, but by the end of 28 days, both types end up with about the same amount of muscle.
When pigs are fed a special feed additive called ractopamine at a certain strength, they grow leaner muscle and less fat—especially after about a month—making their meat more muscle and less fatty.
Adding a specific feed additive called ractopamine to pig food helps pigs grow more meat while eating less feed—especially in the last two weeks of the feeding period—and this works no matter how fat or skinny the pig was when they started.
Causal
When pigs are fed a special additive called ractopamine, they eat about 10–15% less food over a month, but they still grow just as well—and they use the food they do eat more efficiently, like a smarter eater.