Overview
Although nutrition plays a role in the development of prostate cancer, no specific diet can prevent or eradicate this disease. Prostate cancer, like other cancers, is an extremely complex process. No single factor (eg, diet) can explain the various facets of this disease. Nevertheless, the use of diet and dietary supplements for reducing the risk of developing prostate cancer or for treating prostate cancer continues to engage the interest of patients and researchers.
Before discussing or recommending a dietary or lifestyle pattern that may help prevent prostate cancer or inhibit its progression, it would seem prudent to touch on probability, which should inform discussions of the role of nutrition in the prevention of any disease. Reviewing the most common causes of morbidity and mortality allows for an easier understanding of dietary changes that should be recommended in general.
Recommendations should be simple, logical, practical, and at the very least probability-based, similar to any other evidence-based medicine topic. Additionally, with any general dietary and lifestyle recommendations, the maxim “first do no harm” should also apply, given the history of some past recommendations—especially in the area of dietary supplements whose risk was ultimately found to outweigh their benefit.
In the United States, as in virtually every region of the world, cardiovascular disease (CVD) is the number one overall cause of mortality; indeed, CVD has been the leading cause of death in the US every single year since 1919.
Cancer is the second leading cause of death in the US and in most developed countries, and is expected to mirror the number of deaths from CVD in the future in various regions of the world. Currently, however, almost 358,000 US men die of CVD every year,
whereas about 34,000 die from prostate cancer.
Thus, for the average US man, CVD prevention should take precedence over prostate cancer prevention, based on probability and cumulative research. Fortunately, most of what is known concerning lifestyle and dietary change for CVD prevention appears to directly apply to cancer prevention.
The largest US and worldwide trials of pharmaceutical-based prostate cancer primary prevention exemplify the urgent need for a more proper and balanced perspective. For example, results of the Prostate Cancer Prevention Trial (PCPT) garnered attention plus controversy regarding the use of finasteride daily versus placebo to reduce the risk of prostate cancer.
However, the PCPT results also provided information that has not received adequate exposure and debate in the medical literature: Of the almost 19,000 men included in this randomized trial, 5 men died from prostate cancer in the finasteride and in the placebo arm, but 1123 men in total died.
Thus, prostate cancer was responsible for less than 1% of the deaths; the majority of deaths were from CVD and other non-prostate causes.
The largest clinical trial ever conducted on the use of dietary supplements to prevent cancer was the selenium and vitamin E supplementation randomized trial (SELECT).
It was terminated approximately 7 years early because of a lack of efficacy, and even a potential negative impact with these supplements at the dosages used. Once again, CVD represented the primary cause of mortality overall in this study, with over 500 deaths from this cause compared with a single death from prostate cancer in 5 years of follow-up. In short, every prostate cancer study with survival as the endpoint has found that most patients die of causes other than prostate cancer, mostly CVD.
With that in mind, the lifestyle recommendations proffered in this article are intended to serve CVD and prostate health simultaneously. Lifestyle or dietary changes that can potentially impact all-cause morbidity and mortality rather than just disease-specific morbidity and mortality again appear to provide the greatest benefit-to-risk ratio. The principal message from nutritional studies in humans has been an endorsement of the benefits of a diet consisting mainly of vegetables, fruits, fiber, and fish, combined with restricted caloric intake and/or exercise to maintain or achieve a healthy weight.
These measures have been associated with a reduced cancer mortality, although no studies have indicated that they can slow the growth of an existing cancer.
However, evidence has shown that these dietary measures are effective in reducing the risk of death from CVD. Therefore, the possible merits of nutritional measures in preventing prostate cancer are compounded by their proven merits with regard to CVD.
Ideally, individuals should adopt this type of diet when they are young. Unfortunately, that has not been happening; even with the widespread publicity about the dangers of an improper diet, rates of obesity and diabetes are increasing.
The diagnosis of prostate cancer can be a trigger for dietary improvement, however. In an interview study from the United Kingdom, Avery et al found that over half of men diagnosed with prostate cancer reported making dietary changes, primarily to promote general or prostate health or to facilitate coping. Interest in dietary advice was high. Men whose treatment choice was active surveillance were especially likely to modify their diet and regard diet as an adjunct therapy.
Interestingly, clinicians dealing with prostate cancer patients are at times understandably questioned by these same patients or their family members about what they can tell their sons about prostate cancer prevention, now that there is a family history of the disease. In such cases, the emphasis on reducing CVD risk to as close to zero as possible is often initially surprising to patients and their families, but when the preventive effect on both CVD and cancer—the so-called 2-for-1 benefit—is explained, it seems likely to increase the chances of compliance within the family.