Reducing Prostate Cancer Risk, Part One

By Paul E. Lemanski, MD, MS, FACP

Editor’s Note: This is the 90th 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 89 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 will outline some of the evidence for reducing prostate cancer risk. Part Two (October 2019 issue) will suggest the most promising and potentially effective strategies.

The prostate is a walnut-sized gland 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, 50-80% of males have at least a small-sized prostate cancer. Fortunately, most men die with prostate cancer and not from prostate cancer. Never the less, each year thousands of men die from the disease, especially when it spreads for metastasizes from the gland to other areas of the body such as bone. Screening for the disease may be helpful, but once detected it is sometimes difficult to determine those prostate cancers that if untreated will cause death, and which will follow a more benign course. Treatment involves either the removal of the gland or irradiation of the gland, and has significant quality of life side effects, including impotence and urinary incontinence.

The epidemiology of prostate cancer in various populations in the world offers some hope, because not all populations of men get prostate cancer with the same frequency. For example, men living in Asia have lower prostate cancer rates than men living in Western countries. While you might be tempted to attribute this lower rate to the genetics of that population, Japanese men for example who migrate to Southern California within a generation or two, begin to exhibit the same rate of cancer as the US male population as a whole. Could it be, therefore, something about the environment, food, diet, or lifestyle of Western men that contributes to the increase in rate? Moreover, could changing some aspect of that lifestyle prevent disease and lower the rate?

Indeed, teasing the epidemiological data apart for associations between the dietary patterns in various parts of the world and the rate of prostate cancer, suggests that a whole food plant-based diet is protective – and a Western diet high in animal fat and processed animal protein is detrimental. But even within a population cohort, changes in diet can be shown to be associated with changes in prostate cancer. Before World War 2 Japanese men had a low rate of prostate cancer. After World War 2 there was a Westernization of the traditional Japanese diet with a seven-fold increase in egg consumption, a nine-fold increase in meat consumption, and a 20-fold increase in dairy consumption. These changes were associated with a 25-fold increase in prostate cancer in Japanese men.  

While association does not prove causality, it does lead researchers to look for other research to corroborate the observation, and possible mechanisms that could explain such an association. Indeed, a meta-analysis of case control studies in 2004, as well as cohort studies in 2007, identified milk consumption as a risk factor for prostate cancer. More recently, in 2015, a meta-analysis of cohort studies found that total prostate cancer risk increased with a high intake of dairy products. In experiments growing human prostate cancer cells in a petri dish, researchers were able to show that adding milk to nutrient broth feeding the cells, led to an 30% increase in the prostate cancer cells growth rate.

Moreover, once prostate cancer has been identified, its ability to metastasize and kill may also be related to specific dietary practices. In following men with early stage prostate cancer, Harvard researches were able to show that consuming a single egg a day, doubled the risk of cancer progression and metastasis. It has been postulated that the high choline content of eggs, may be converted by gut microbiota to high blood levels of a substance called trimethylamine, that once metabolized by the liver may lead to both increased heart disease and cancer risk.

In an elegant experiment to test the role of diet and lifestyle on prostate cancer, Dean Ornish, MD in collaboration with researchers at UCSF department of urology and Memorial Sloan-Kettering Cancer Center in New York, recruited 93 men diagnosed with prostate cancer who had decided not to undergo the conventional treatments of surgery or radiation. These 93 men were then randomized to the experimental group implementing a low fat, whole food, plant-based diet and daily aerobic exercise, or the control group who were not asked to make any change in diet or exercise. Over one-year the men had Prostate Specific Antigen (PSA) levels measured to track the growth of tumor. Biopsies of the prostate for individuals in each group were also taken at the beginning and end of the study.

After one-year of intervention, the PSA levels in the experimental group decreased 4% in comparison to the control group, in which PSA increased 6%. Moreover, those who made the greatest change in healthy lifestyle adherence had the greatest benefit. The biopsies also showed that more than 500 genes in the tumor were affected by diet and lifestyle, with genes that slow tumor progression turned on, and genes that accelerated tumor progression turned off. 

In summary, there is increasing evidence on the basis of epidemiological or population studies, case controlled and cohort studies, as well as randomized clinical trials, that diet and lifestyle change may reduce prostate cancer risk. Both the incidence of prostate cancer may be reduced as well as progression after the time of diagnosis. Part Two will offer practical strategies on reducing risk, including specific changes in dietary patterns as well as specific foods that may reduce the risk for prostate cancer, and contribute to living a truly 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.