It’s hard to believe, but the American Cancer Society (ACS) estimates that about one in eight American men will be diagnosed with prostate cancer. Next to skin cancer, prostate cancer is the most commonly diagnosed cancer in men in the United States and the second leading cause of cancer-related death in American men.
For 2022 alone, the ACS predicts approximately 268,490 new prostate cancer diagnoses and 34,500 new prostate cancer-related deaths.
Frustratingly, modern medicine still cannot pinpoint exactly what causes prostate cancer. Like any other form of the disease, prostate cancer arises at the cellular level due to DNA changes and mutations. Some of these gene mutations are inherited, but many are not. In fact, the ACS tells us that most prostate cancer-related gene mutations seen in men are not inherited but are acquired at some point in the patient’s life.
So what are some identified external risk factors that may make a man more likely to develop prostate cancer? Age. Almost 60% of all prostate cancer diagnoses affect men over the age of 65.
Another possible risk factor is obesity. Some research has found that abdominal obesity is associated with a more aggressive form of prostate cancer. Also, an unexpected factor might be being a widower. One study even reported that widowed men were more likely to develop an advanced form of prostate cancer.
Now new research has been conducted at Loma Linda University and published in American Journal of Clinical Nutrition has identified a potential new major nutritional risk factor associated with prostate cancer. Read on to find out more!
More milk can mean prostate problems
There’s a lot to like about milk. It’s absolutely chock-full of essential vitamins and minerals, great for bone health and packs a heavy protein punch to boot. However, the results of this new study suggest so Drinking milk is associated with a higher risk of prostate cancer.
Study authors report that men with a high usual consumption of milk have a significantly increased risk of prostate cancer compared to other men who drink less milk. More specifically, the study found that men who drink about 430 grams of dairy products (1.75 cups of milk) per day have a 25% higher risk of prostate cancer than other men who drink less milk per day (about half a cup per week). The risk of prostate cancer in daily milk drinkers was even higher than in men who avoided dairy products altogether.
Calcium has been linked to prostate cancer in the past, and dairy products like milk contain tons of calcium. Importantly, however, the research team says they observed absolutely no correlations between an increased risk of prostate cancer and non-dairy calcium intake. In other words, while it’s clear that something in milk is linked to the development of prostate cancer – it’s not just calcium.
“Our results add important weight to other evidence linking dairy products and not milk calcium as a modifiable risk factor for prostate cancer,” says Gary Fraser, MBChB, PhDthe study’s principal investigator and professor at Loma Linda University School of Medicine and School of Public Health, in a press release.
Interestingly, no associations were found between the risk of prostate cancer and the consumption of cheese and yogurt.
Prostate cancer risk plateaus about 150 grams of milk daily
The authors of the study emphasize that their work did not find that the risk of prostate cancer increases indefinitely with more milk intake. Increases in risk appear to level off at about two-thirds of a cup of milk daily.
“Most of the continued increase in risk is gone by the time you hit 150 grams, about two-thirds of a cup of milk per day,” explains Dr. Fraser. “It’s almost as if a biological or biochemical pathway were saturated at about two-thirds of a cup of milk a day.”
Solve milk puzzles
As previously mentioned, this study provides strong evidence that calcium alone is not responsible for the prostate cancer-dairy link. So what’s going on here?
“One interpretation is that dairy products or a closely related unknown risk factor is causally associated with prostate cancer risk,” the study states.
dr Fraser theorizes that the sex hormones found in milk may be involved. Most (up to 75%) lactating dairy cows are pregnant, and prostate cancer happens to be a hormone-responsive cancer. In addition, previous research has found that intake of dairy products and other animal proteins is linked to higher levels of a certain hormone in the blood (IGF-1), and IGF-1 is thought to support the growth of certain types of cancer, including prostate cancer .
Milk is also linked to breast cancer
This work fits well with a previous study conducted at LLU. This project found that milk consumption in women was associated with a higher risk of breast cancer.
“The parallels between our study of breast cancer in women a year ago and this study in men are striking,” comments Dr. Fraser. “It seems possible that the same biological mechanisms are at work.”
take that away
Finally, the authors of the study warn that their results do not confirm that dairy products cause prostate cancer, but that there is an association between dairy consumption and an increased risk of prostate cancer. Ultimately, more research is needed before definitive conclusions can be drawn.
That being said, researchers still say it’s probably a smart idea for men with a family history of prostate cancer to think twice about consuming even moderate amounts of milk.
“If you think you’re at above-average risk, consider the alternatives to soy, oats, cashews, and other plant-based dairy products,” concludes Dr. Fraser.
These results are not based on a small research project. Over 28,000 men living in North America participated in this study, which resulted in an average follow-up period of almost eight years.
All participants were cancer-free at baseline, but individual dairy/calcium consumption patterns varied widely. Some men drank tons of milk, others gave up dairy altogether. Each man’s usual milk intake was estimated using food frequency (FFQ) questionnaires and 24-hour diet recalls. In addition, a baseline survey conducted by each subject collected demographic data such as BMI, exercise habits, smoking habits, family history of cancer, and any previous prostate cancer screening.
After all the initial data was collected, the researchers kept tabs on state cancer registries for the next eight years. By the end of the observation period, a total of 1,254 prostate cancer diagnoses had been identified among study participants.
The research team took great care to separate non-dairy calcium intake (via nuts, fruits, seeds, legumes, vegetables, etc.) from dairy-related dietary calcium sources. A statistical model was then used to analyze the effects of dairy intake independent of other factors (calcium-free dairy consumption, family medical history, age, etc.).
Overall, the study authors say the approach they took and the large population sample they had to work with put them in a unique position to research this topic.
“Because our study cohort showed a large disparity and divergence in milk intake and calcium levels, we were able to ask the question with unusual strength,” adds Dr. Added Fraser.