New Study: Drinking Milk Increases Risk of Prostate Cancer by 60 Percent

A new study has found a significant link between drinking milk or consuming dairy, and increased risk of prostate cancer. Men who consumed dairy on a regular basis were found to have a 60 percent increased risk of developing prostate cancer as compared to men who steered clear of dairy, or consumed only a minimal amount (a teaspoon or less per day).

Researchers from Loma Linda University published the study in The American Journal of Clinical Nutrition, establishing the relationship between diet and an increase in the risk of prostate cancer.

The Loma Linda researchers tracked the health of 28,737 Seventh-Day Adventist men in the United States and Canada starting in 2001. During the study, the research team analyzed the dietary habits of this population over five years, examining their health and cancer incidents. Using cancer registries, the study identified 1,254 participants who developed prostate cancer during the course of the study.

The study divided the men into cohorts based on intake of non-dairy sources of calcium, versus men who consumed dairy daily. This suggested that other substances aside from calcium itself play a role in the development of prostate cancer. Men who consumed 1 ¾ cups of milk (430 grams) per day were 25 percent more likely to develop prostate cancer than men who consumed ⅓ cup of milk (20.2 grams) per week or about a teaspoon a day.

“Our findings add important weight to other evidence associating dairy products, rather than non-dairy calcium, as a modifiable risk factor for prostate cancer,” study author and professor of preventive medicine at Loma Linda University School of Medicine and School of Public Health in California Dr. Gary Fraser said in a statement.

The findings also discovered that the difference between full fat and non-fat dairy held little importance in prostate cancer risk, according to Fraser. The study authors also emphasized that non-dairy calcium did not increase prostate cancer risk.

While the Loma Linda University research team did not design the study to examine the causes of why dairy increases prostate cancer risk, the authors mentioned possible factors that could explain the increased cancer risk. Fraser noted that one potential driver could be attributed to the hormone levels of lactating cows – 75 percent of which are pregnant and produce excess hormones. Since prostate cancer is a hormone-responsive cancer, the presence of hormones in milk could offer one possible explanation for the higher risks associated with dairy consumption.

"Insulin-like growth factor-1 is known to be a risk factor for prostate and breast cancer, and it turns out that dairy consumption raises the level of this hormone," Fraser said. "This issue needs a little more clarity before we conclude that there is a causal link, but there could be, and if you had a bad family history of prostate cancer, I would be inclined to go on a plant-based diet now.”

The study also found that the prostate cancer risk factors did not correspond to incremental increases in dairy consumption, meaning that some studies could miss a link between dairy and prostate cancer if participants already consumed more than one cup of milk per day. Instead of a corresponding rise, the cancer risk showed a curvilinear spike at certain levels of dairy consumption.

“Most of the continuing increase in risk is done with by the time you get to 150 grams, about two-thirds of a cup of milk per day,” Fraser said. “It’s almost as if some biological or biochemical pathway is saturated at about two-thirds of a cup of milk per day.”

With research placing responsibility for prostate cancer on dairy, many men might not know where to start eating healthier to avoid cancer risks. Other than dairy, the worst foods for prostate health include red meat and eggs. Another study from The American Journal of Clinical Nutrition revealed that men who followed a vegan diet had a 35 percent lower risk of prostate cancer.

But cutting out animal products might not be enough. To effectively reduce risks for prostate health, introducing foods including broccoli, collard greens, avocados, extra virgin olive oil, and others is essential to combat prostate cancer risk factors. The Prostate Cancer Foundation released a Periodic Table of Healthy Foods to help men improve their diets.

Beyond prostate cancer, drinking milk and eating dairy products can present serious risks for other diseases and environmental harm. Eating dairy can lead to higher levels of cholesterol, leading to blockages and an increased risk of cardiovascular disease. Doctors warned patients that dairy consumption can lead to a higher risk of heart disease. Dairy also contains higher levels of saturated fat, and by reducing saturated fat consumption, people can lower the risk of heart disease by 21 percent.

Similar to prostate cancer, dairy is linked to increased levels of breast cancer risks. One report found that increased levels of estrogen found in milk could lead to increased breast cancer risk by 30 percent. The Loma Linda researchers released a study regarding breast cancer and dairy consumption last February.

“Consuming as little as one-quarter to one-third cup of dairy milk per day was associated with an increased risk of breast cancer of 30 percent,” Fraser said at the time. “By drinking up to one cup per day, the associated risk went up to 50 percent, and for those drinking two cups a day the risk went to 60 percent."

Whether you are concerned with prostate cancer, breast cancer or other types of cancer, studies show that avoiding dairy and switching to plant-based milk is a healthier choice.