Despite its many other health benefits, a new study has linked excessive milk drinking to an increased risk of prostate cancer in men.
The American Cancer Society estimates roughly one in eight American men are diagnosed with prostate cancer annually. Besides skin cancer, prostate cancer is the most diagnosed cancer among males in the US and the second leading cause of cancer-related death among American men.
Like all cancers, prostate cancer results from mutations in cellular DNA. These mutations can be caused by hereditary factors, but in prostate cancer, it seems that more often than not, they are related to external factors like diet.
In the past, being overweight and eating a high-fat diet, particularly one high in processed meats with nitrates like deli meats, bacon, and hot dogs, have been linked to an increased risk of developing prostate cancer.
Now, a new study has found that men who consume a lot of milk are also at a high risk of developing the disease.
Research performed by the Loma Linda University and published in the American Journal of Clinical Nutrition has identified this new major dietary risk factor tied to prostate cancer.
The study indicates that men with a high intake of dairy milk face a significantly elevated risk of prostate cancer in comparison to other men drinking less milk. More specifically, the research found that men drinking about 430 grams of dairy daily (1.75 cups of milk) showed a full 25% greater risk of prostate cancer than other men drinking less milk on a daily basis (about a half a cup weekly). Prostate cancer risk among daily milk drinkers was even higher when compared to men avoiding dairy altogether.
Calcium has been linked to prostate cancer in the past, and dairy products like milk contain tons of calcium. Importantly, though, the research team says they observed absolutely no correlations between increased prostate cancer risk and ingestion of non-dairy calcium. In other words, while it’s clear that something in milk is linked to prostate cancer development – it isn’t just calcium.
“Our findings add important weight to other evidence associating dairy products, rather than non-dairy calcium, as a modifiable risk factor for prostate cancer,” says Gary Fraser, MBChB, Ph.D., the study’s principal investigator and professor at Loma Linda University School of Medicine and School of Public Health.
Interestingly enough, no associations were seen between increased prostate cancer risk and intake of both cheese and yogurt.
So, what is it about dairy milk and prostate cancer?
Dr. Fraser theorizes that the sex hormones found in dairy milk may be involved. Most (up to 75%) lactating dairy cows are pregnant, and prostate cancer just happens to be a hormone-responsive cancer. Moreover, prior research has found that ingesting dairy and other animal proteins is linked to higher levels of a specific hormone in the blood (IGF-1), and IGF-1 is believed to support the growth of certain cancers, including prostate cancer.
What Should Men Takeaway From This Study?
The study authors caution that their findings do not confirm that dairy milk causes prostate cancer, only that there is an association between milk intake and increased prostate cancer risk. More research is ultimately needed before any final conclusions can be agreed upon.
That being said, researchers still say it’s probably a prudent idea for men with a family history of prostate cancer to think twice about consuming even moderate amounts of dairy milk.
“If you think you’re at higher-than-average risk, consider the alternatives of soy, oat, cashew, and other non-dairy milks,” Dr. Fraser concludes.