Lifestyle and Prostate Cancer Risk

written by Dr Loh Chit Sin on 6 April 2011

Prostate cancer is now the most common cancer in men in many Western countries and incidence is increasing. Globally, the cancer is less common in Eastern countries like Japan and China where the incidence is almost 50 times less common than some Western countries. Lifestyle is now believed to play a very important role in the promotion of this cancer. As an example, prostate cancer in Japanese men who live in America is many times more common than their counterparts in their native country. Observations such as this increasingly question the detrimental effect of Western lifestyle / diet on the prostate and focus many research efforts on the issues of lifestyle and pathogenesis of prostate cancer.

Over the last 40 years, many studies had been done to identify dietary risk factors. Many of these are based on questionnaires of specific food components intake. Analysis of these types of studies is difficult because the collected data are often not objective and lack specificity. Many studies yield mixed or contradicting results and conclusions can often only be drawn based on analysis of many similar studies based of reproducibility of the results. Studies on manipulation of specific dietary component (withdrawal or supplementation) are easier to interpret and often regarded as more conclusive as long as the other dietary components among different studies groups are broadly similar. Other lifestyle issues such as physical activities and sexual activity have also been studied. Contradicting results have been reported. Interpretation of these results requires careful thoughts and a good understanding of statistic. With these limitations in mind, general consensus can be said to prevail on the following factors:

Food components:

Meat and dairy products consumption appears to correlate with increased risk of prostate cancer. Similar observation is made with fat consumption. Blood cholesterol levels appear to have an influence on prostate cancer behaviour and at least in animal models, the use of cholesterol lowering drugs appears to modulate prostate cancer growth. There is a strong inverse correlation between consumption of vegetables, especially uncooked green vegetable as in salads, and prostate cancer risk. Evidence on protective effect of tomato (which is rich in lycopene) on prostate cancer is also strong but data on consumption of pulse, cruciferous vegetable and alliums (onions, leeks etc) are scanty or weak. Evidence on fruit consumption is mixed and it is difficult to draw any conclusion.

Dietary Supplements:

Studies on supplementation of vitamins A, vitamin C and beta carotene showed inconclusive results but good evidence exist on the protective effect of vitamin E supplementation. A very high calcium intake appears to be associated with an increased risk of prostate cancer. Vitamin D has been shown to slow down cancer cell growth in test tube culture experiments and disease activity has also been inversely correlated in many studies with blood level of vitamin D in sufferers. It had also been observed that exposure to sunlight offered a protective effect (sunlight is required by the skin to synthesize vitamin D). However, dietary vitamin D supplementation has not yet been conclusively shown to offer protective effect against prostate cancer. Strong direct and indirect evidence exist on the protective effect of the rare metal selenium which can now be freely obtained at many pharmacy outlets.

Beverage:

Majority of studies on coffee consumption fail to show any correlation with prostate cancer risk but recently, protective effect of green tea has been reported. Overall, consistent effect of alcohol consumption has not been observed although a small number of studies showed an increased risk with alcohol consumption.

Smoking:

Smoking had been incriminated in the pathogenesis of many cancers, notably cancer of the lung, mouth, gullet, stomach and bladder. Studies on the effect of smoking on prostate cancer yield inconclusive results.

Body weight:

Prostate cancer risk has also been correlated with body mass index and being over weighed carries a slightly higher risk of prostate cancer development.


Physical activities:

Several studies had been carried out on the effect of physical activities on the progression of established prostate cancer whilst others on the protection of physical activities on the development of prostate cancer. Most of these studies have showed a protective effect of moderate to rigorous exercise against prostate cancer.

Sexual activity:

There has been a postulate that frequent sex predisposes one to prostate cancer. This could have arisen from the observation of a very high prevalence of prostate cancer in the American black population and the unfounded assumption that this population is sexually very active. However, several studies have failed to linked sexual activity with prostate cancer to date.

Conclusion:

Whilst we can feel pretty helpless on an inherited genetic risk of prostate cancer, better understanding on lifestyle risk factors at least affords us some ability to do something about prostate cancer risk. Consensus exists on the protective effect on an active outdoor life, physical activities, a high consumption of green vegetables, tomatoes, green tea and reduced consumption of meat, dairy products and fat. Dietary supplements such as selenium and vitamin E also offer protection but high dose calcium intake should be avoided. Smoking, though not conclusively shown to predispose to prostate cancer, should be discouraged because of its many other risks. Finally, effort should also be made to avoid obesity and maintain low serum cholesterol.