Drinking dairy milk may increase your risk of breast cancer, study finds

People who drink dairy milk on a regular basis could have a higher risk of breast cancer, a new study has found.

Researchers tracked the dairy intake of 52,795 North American women for nearly eight years. All were cancer-free when the study began, but by the end, researchers recorded 1,057 new incidents of breast cancer.

“Consuming as little as one-quarter to one-third of a cup of dairy milk per day was associated with an increased risk of breast cancer of 30 per cent,” said researcher Dr. Gary Fraser in a press release.

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Drinking up to one cup of dairy milk was associated with a breast cancer risk of 50 per cent, and drinking two to three cups per day increased a person’s risk by up to 80 per cent in some cases. The fat content of the dairy milk did not appear to affect the results.

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In the study, a person’s family history, physical activity, alcohol consumption, medication use and reproductive and gynecological history were also taken into consideration.

Researchers also looked at soy milk, but no association with an increased breast cancer risk was found.

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Roughly 75 per cent of dairy cows providing milk in modern dairy production are pregnant, according to researchers, which could be the reason for the increase in risk.

The study is “very strong,” according to Wendy Demark-Wahnefried, a professor of nutrition sciences and senior scientist with the O’Neal Comprehensive Cancer Centre at the University of Alabama Birmingham.

“It’s a very large sample size [and] the sample is racially and ethnically diverse,” she said. “[However], this is one study and it’s observational. There’s no cause and effect … only associations.”

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The results of this study prove that more research needs to be done — especially because milk is still widely regarded as an important part of a balanced diet, said Demark-Wahnefried.

The current U.S. dietary guidelines recommend three cups of milk per day for adults. In contrast, the Canadian food guide was updated in 2019 and dairy intake was de-emphasized relative to the prior version.

When it comes to drinks, the Canadian food guide recommends making water your beverage of choice.

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Doctors will still often prescribe more milk for women because of concerns about osteoporosis, a disease characterized by low bone mass and deterioration of bone tissue. It more commonly affects women.

“If you’re a woman … you do need to pick up that calcium,” said Demark-Wahnefried.

According to the Mayo Clinic, there are several foods other than dairy that can help with calcium levels. For example, soy and almond milk that has been fortified, tofu made with calcium sulfate, canned pink salmon with bones and greens like turnip, collard greens and kale.

If further research has similar results, the standard plan for preventing osteoporosis will need to be updated.

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Despite the “compelling” results of the study, Demark-Wahnefried says women don’t need to avoid drinking milk until further research is done.

“Whenever you look at epidemiological studies such as this [one], you can’t apply cause and effect,” she said.

“There may be some other thing that’s going on that … they didn’t control for.”

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