Even a Small Amount of Dairy Increases Risk for Breast and Liver Cancer

No doubt you grew up believing dairy is good for you. That’s a message the industry
has fed us for generations. While dairy does contain nutrients, it also appears to be damaging to your health, and even a small amount raises your risk of certain cancers a new study has found.

Although the link between dairy and cancer is established, the evidence that even a single serving a day is enough to increase your risk of cancer significantly is a new finding. The most recent study bolsters the link between cancer and regular dairy consumption, and this is the largest review study to date to underscore the cancer-dairy connection. Here is what the latest scientific review study and the experts have to say.

In a study from BMC Medicine, researchers from Oxford working with those in China evaluated data from people living in China, a country in which people consume less milk and yogurt than Americans and also have very little butter and cheese in their diets. The findings come from a review of data from over 510,000 individuals – 59 percent female and 41 percent male – who had no previous history of cancer.

The authors divided the data into three groups of participants, all of whom were 30 to 79 when the study began. The first group consisted of those who ate dairy at least once a week; the second group was made up of those who ate dairy once a month; the third cohort comprised of those who never or rarely ate dairy at all.

Over the next 11 years, researchers looked at the health and well-being of these groups and collected health data, including cancer diagnoses, and factored in other lifestyle factors (such as smoking, alcohol intake, physical activity levels, and soy and fresh fruit consumption). The researchers tracked family cancer history and socioeconomic status among other data points.

In the end, individuals who consumed dairy regularly had a significantly greater risk of
developing female breast cancer and liver cancer as well as lymphoma. For every 50 grams (about a quarter cup of milk) per day that they consumed, the risk of breast cancer rose by 17 percent, and the risk of developing liver cancer rose by 12 percent.

“We’ve known from other studies that dairy has a strong connection to breast cancer,” says Anna Herby, R.D. nutrition education program manager for the Physicians Committee for Responsible Medicine.

“The liver cancer connection, however, was new, as we don’t have a lot of research on that.”
And while this study didn’t find a link between dairy and other cancers like prostate cancer, for
instance, there’s a reason.

“Researchers mention that there’s not a lot of prostate cancer in the Chinese population, but other studies have certainly found a strong correlation between dairy and prostate cancer,” Herby says. Take, for instance, this study from the American Journal of Clinical Nutrition, which found that a high intake of dairy products increases a man’s prostate cancer risk.

In another study, dairy consumption was associated with a higher risk of breast cancer.

That study, published in the International Journal of Epidemiology, found that while there is no apparent connection between soy intake and breast cancer risk, dairy milk is connected with elevated incidents of breast cancer. The study followed women for almost 8 years, all of them cancer-free to start, and asked them to fill out daily food logs. The researchers found that there is a clear connection between dairy intake and breast cancer.

The study looked at soy, dairy, and breast cancer over 7.9 years among 52,795 women in North America, and by the end of the study, there were 1,057 new breast cancer cases among the women, and a higher number of those cancers were among dairy milk drinkers.

So while most people avoid soy for fear that the plant-based estrogens will act as actual estrogens in the body, research has shown that soy may actually be protective, since in past studies a moderate amount of soy in the diet has been associated with lower risks of breast cancer.

Read More: Drinking Milk Increases Risk for Breast Cancer, a New Study Shows 

Researchers in the first study were quick to note that their results don’t prove cause and effect. In other words, they can’t say dairy causes cancer. However there are numerous reasons dairy has been linked to cancer, and how compounds in dairy may be the culprits.

Dairy contains an insulin-like growth factor, IGF-1, which is designed to help a baby cow grow seven times its size. That’s beneficial if you’re a cow – but not if you’re a human. “IGF-1 makes cancer cells grow in the body,” Herby says.

Another possible reason that dairy may be associated with cancer is that dairy contains the hormone estrogen. That’s because cows are being milked beyond their natural cycle, and farmers make sure cows produce milk until they get pregnant again. The hormones in the milk get passed to you, through yogurt, cheese, cream cheese, and any milk product.

“As a result, when you consume the estrogen in dairy products," Herby says, "your body can’t regulate it as well, and it can turn on cancer growth.”

Lactose is another harmful ingredient a type of sugar that’s broken into galactose. “That can
cause cancer cells to grow and multiply more rapidly,” Herby says. This is especially common
with ovarian cancer.

Dairy contains casein, the protein in milk that has been linked to cancer in lab animals. According to T. Colin Campbell, Ph.D., founder of the Center for Nutritional Studies at Cornell and co-author of The China Study, casein is a carcinogen. In an oft-cited lab experiment, mice with tumors that were fed casein experienced tumor growth, whereas those mice fed plant-based diets saw tumors shrink. When the diets were switched, the same thing happened again and the mice not fed casein experienced tumors shrinking while the mice given casein saw tumors grow.

In a 2019 interview, Campbell said, “Casein [the main protein of cow’s milk] is the most relevant chemical carcinogen ever identified.” Guilty, as charged. For the sake of this discussion, let’s call it a hypothesis, that is, “Casein causes cancer”. He explains that in his experiments, the thesis was provable and that he considers casein a carcinogen.

Finally, dairy also contains high amounts of saturated fat, which contributes to insulin resistance and can increase inflammation in the body. This is one reason researchers believe liver cancer is elevated when consuming dairy.

Getting dairy out of your diet isn’t tough, especially given the plethora of plant-based dairy
products on the market. Peruse the grocery store aisles, and you’ll find everything from cheese and ice cream to yogurt and milk.

Of course, kicking dairy out of your diet completely will give you optimal benefits. Yet if that’s
out of the question, at least start shifting your habits away from dairy in small steps. For instance, if you drink cow’s milk three times a day, cut it to once a day or if you can’t give up your cheese pizza, enjoy it only once in a while.

“The more you can change, the more results you’ll get,” Herby says. Just know, though, that dairy is addictive so it can be tough to limit it to small portions. If you find a strong urge to consume dairy, cheese, in particular, Herby advises eliminating it completely so you can break the addictive cycle.

It's easy to love the best dairy-free products, and many taste as good as the real thing.

Bonus? As soon as you ditch dairy, you’ll be helping the earth. “Cows are the number one culprit when it comes to methane production,” Herby says.

Methane is a greenhouse gas that contributes to climate change, and on a list of the top five methane-emitting foods that PCRM recently named, dairy products were number two (hamburgers took the top spot).

Even a small amount of dairy has been shown to increase your lifetime risk of certain cancers, including female breast cancer, liver cancer, and lymphoma. If you want to lower your risk, simply swap out dairy and choose dairy-free options for milk, yogurt, ice cream, and cream cheese.

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