Does Dairy Increase Breast Cancer Risk?

If you've been trying to figure out if eating or drinking dairy helps or hurts your risk of breast cancer, you're not alone. Dairy foods like milk, yogurt, and cheese contain chemicals and nutrients that may affect breast cancer risk. Researchers have been looking at this connection for decades. So far, they haven’t reached a definite conclusion. While some studies suggest certain types of dairy may increase the risk of breast cancer, there’s evidence that fermented dairy products — especially yogurt and cheese — may actually protect against breast cancer.

Overall, the results of studies that have looked into the effect dairy has on breast cancer risk have been mixed and inconsistent. Some review studies — including one published in early 2024 — have looked at all the evidence from previous research and found that there isn’t conclusive evidence for a relationship between dairy and breast cancer.

A 2023 review study suggested that eating certain dairy products, including yogurt and cheese, may actually protect against breast cancer. The report also highlighted several studies linking whole milk with an increased risk of breast cancer.

One large 2024 study was too new to be included in any of these reviews. For the study, researchers followed more than 63,000 women in the U.K. from 1980 to 2018. At various times, the women reported how much dairy they ate, and the researchers followed them to see if they developed breast cancer. They found that, in general, total dairy intake wasn't related to breast cancer risk, but there was a small chance that consuming milk during adolescence increased breast cancer risk. Eating cheese was linked to a lower risk of breast cancer. 

The link between dairy and breast cancer risk may be different for different kinds of tumors — specifically, for hormone receptor-positive breast cancer. This is because some ingredients in dairy foods may affect breast cancer hormone receptors, such as by making them bind less to estrogen. But the research here is also mixed. 

One 2021 study found that total dairy intake is linked to a lower risk of hormone receptor-positive breast cancer. But another 2021 review study found that eating yogurt, cottage cheese, and ricotta cheese only protects against estrogen receptor-negative breast cancer — not against estrogen receptor-positive breast cancer. 

So there isn’t clear evidence that dairy affects hormone receptor-positive breast cancer risk, but if it does, it may be related to cheese consumption and it may lower it a small amount. This is likely true whether the breast cancer is hormone receptor-positive or -negative.

It’s difficult to compare studies on dairy and breast cancer risk because different dairy products could have a different effect on breast cancer risk. That’s because each dairy product contains a unique set of nutrients and chemicals. Some of these could, in theory, raise the risk while others could lower it. 

The evidence here is also not cut-and-dried, though, and scientists aren’t sure whether — or how — any of these affects breast cancer risk. But there is some emerging research around specific ingredients, nutrients, and contaminants.

Some evidence suggests that dairy products high in fat, especially saturated fat, could increase breast cancer risk. Other studies, however, have not found a link between high-fat dairy and breast cancer risk.

Contaminants can also find their way into dairy products, and these could potentially increase the risk of breast cancer. These include pesticides, chemicals that can disrupt our hormone systems, and a hormone called insulin-like growth factor.

Calcium and vitamin D in dairy could protect against breast cancer several ways. For example, they may stop cancer cells from dividing, and vitamin D can block hormones that increase cancer risk.

Dairy foods, particularly fermented ones like yogurt and cheese, contain healthy bacteria that could help protect against cancer. They may be especially beneficial to older women, such as postmenopausal women, who are likely to have a less healthy balance of bacteria in the microbiome of their intestines.

In a word, probably not. The evidence for a link between dairy and breast cancer isn’t strong enough for science-backed recommendations. Fermented dairy and cheese seem to offer more health benefits than whole milk for breast cancer, specifically. More studies are needed to help scientists firmly answer questions about dairy and breast cancer risk.