Reducing Prostate Cancer Risk, Part Two

By Paul E. Lemanski, MD, MS, FACP

Editor’s Note: This is the 91st in a series on optimal diet and lifestyle to help prevent
and treat disease. Any planned change in diet, exercise or treatment should be discussed
with and approved by your personal physician before implementation. The help of a
registered dietitian in the implementation of dietary changes is strongly recommended.

Medicines are a mainstay of American life and the healthcare system not only because they are perceived to work by the individuals taking them, but also because their benefit may be shown by the objective assessment of scientific study. Clinical research trials have shown that some of the medicines of Western science may reduce the risk of heart attacks, strokes and cardiovascular death.

In the first 90 installments of the Non-Medicated Life, certain dietary practices and a healthy lifestyle have been shown to accomplish naturally for the majority of individuals most of the benefits of medications in the treatment of chronic medical conditions such as hypertension, high cholesterol, pre-diabetes, diabetes and heart disease. However, apart from certain medications that have shown to be successful for preventing breast cancer, and possibly aspirin use for colon cancer, medications for cancer prevention have been few. This is also unfortunately true for prostate cancer. Medications may be very helpful in slowing and managing an already diagnosed prostate cancer, but have not generally proved successful in primary prevention of the disease. 

Diet, exercise and lifestyle change, however, may offer effective prevention strategies. Part One (see Non-Medicated Life, August 2019) outlined some of the evidence for reducing prostate cancer risk. Part Two will now suggest the most promising and potentially effective strategies.

As described in Part One, the prostate is a walnut-sized gland in men that is located beneath the bladder, and provides some of the fluid for semen. Cancer of the prostate is the second most common cause of cancer in males and autopsies have shown that by age 80, 50 to 80% of males have at least a small-sized prostate cancer. Epidemiological data suggests that populations that eat a plant-based diet lower in red meat, chicken, eggs, and dairy products have lower rates of prostate cancer. Moreover, in men diagnosed with early stage prostate cancer that have chosen not to have surgery or radiation, a plant-based diet appears to slow the growth of the cancer. This lower risk may be due to protective factors in plants, or a relative avoidance of risk caused by the consumption of animal protein, or both.

Why the consumption of red meat, chicken, eggs and dairy appear to increase prostate cancer risk is not clear but several possible mechanisms may be considered. In the case of red meat and chicken the means of preparation may confer risk. We know that animal protein cooked at high temperature – grilling, broiling, baking and deep frying – produces carcinogens called heterocyclic aromatic amines. These carcinogens may increase the risk of malignant cellular change in a variety of organs and may be augmented by genetic predisposition to specific cancers. 

Red meat and chicken also contain carnitine that is broken down by gut bacteria to trimethylamine, a substance that the liver then converts to trimethylamine N-oxide, a toxin that increases cardiovascular risk for stroke, heart attack and early death. Whether it increases cancer risk is not clear. Eggs contain large amounts of choline that are also converted to trimethylamine N-oxide. High blood levels of choline have been associated with an increased risk of prostate cancer and an increased risk of cancer death. Indeed, men who consume more than one egg every three days may have an 81% increased risk of dying from prostate cancer. In 2015 meta-analysis – a sort of statistical analysis of a number of different studies – found that milk and cheese consumption in large amounts, likewise increased prostate cancer risk.

From a practical perspective, minimizing exposure may help reduce risk. Simply eating less red meat, less chicken, less milk and cheese, and fewer eggs may lower risk. When red meat and chicken are consumed, cooking them using lower temperature methods such as boiling, steaming, slow cooking or in soups, will reduce the production of heterocyclic amines. In the case of red meat, cooking till rare or medium-rare instead of well-done will also decrease carcinogen production. Finally, when cooking red meat and chicken, marinating the meat in an acid-based marinade containing either lemon juice or vinegar has been shown to decrease the production of heterocyclic aromatic amines substantially.

Consuming more vegetables has also been shown to reduce the risk of developing prostate cancer, and not simply by displacing, and thus reducing the amount of animal protein consumed. The most beneficial vegetables for reducing cancer risk include the cruciferous vegetables, such as broccoli, cauliflower, kale, cabbage and Brussels sprouts. One mechanism by which this reduced risk may be achieved is the induction of enzymes in the liver that normally break down carcinogens. 

Broccoli, for example, contains a substance called glucoraphanin. When raw broccoli is chewed an enzyme in the plant called myrosinase is released that acts upon glucoraphanin to produce sulforaphane. Sulforaphane, in turn, once absorbed causes a substantial increase in the phase-2 detoxifying enzymes in the liver that are responsible for breaking down and destroying carcinogens. From a practical standpoint eating raw or minimally-steamed broccoli (three minutes) allows maximal production of sulforaphane. Additionally, consumption of tomatoes and tomato sauce, both of which contain the antioxidant lycopene, also seems to be associated with lower risk.

Other constituents of a plant-based diet that may reduce the risk of prostate cancer include certain types of beans and seeds and the phytoestrogens they contain. Asian populations appear to have lower rates of prostate cancer, which increase after migrating to Western countries. It is postulated that the higher consumption of soybeans and soybean products in Asia reduces risk because of an increased content of a type of plant-based phytoestrogen called isoflavones, which may modulate hormone sensitive tissue like prostate. With the current availability of soy products, incorporation of soy into your weekly diet – in place of meat or chicken – would be relatively simple as a risk reduction strategy.

Another class of phytoestrogen called lignans is found in flaxseed. In men with prostate cancer, consumption of three tablespoons a day of ground flaxseed in the month prior to surgical removal of the prostate has been shown to lower cancer cell proliferation rates, and increase the rate of cancer cell clearance. Moreover, in men followed with repeat prostate needle biopsies for a pre-cancerous condition called prostatic intraepithelial neoplasia, consumption of three tablespoons of flaxseed per day for six months reduced cell proliferation rates – suggesting this could help prevent progression to cancer. Again, consumption of three tablespoons of ground flaxseed per day in oatmeal or a smoothie is relatively simple and straightforward as a prostate cancer risk reduction strategy.

In summary, prostate cancer risk may be decreased by a reduction in red meat, chicken, eggs and dairy. When red meat and chicken are consumed, they should be marinated in lemon-based or vinegar-based marinade, and not overcooked on high heat. The reduction in animal protein should be combined with an increase in vegetables, grains, legumes and seeds. Cruciferous vegetables, tomatoes, soybeans, and ground flaxseed may all help decrease prostate cancer risk. In this way, a predominantly plant-based diet may help you to lead the non-medicated life.

Paul E. Lemanski, MD, MS, FACP (plemanski3@gmail.com) is a board-certified internist practicing internal medicine and lifestyle medicine in Albany. Paul has a master’s degree in human nutrition, he’s an assistant clinical professor of medicine at Albany Medical College, and a fellow of the American College of Physicians.