Diet Supplements & Prevention

Feb 2016

PROSTATE CANCER

DIET, NATURAL SUPPLEMENTS AND PREVENTION

Different races carry different risks of developing prostate cancer (PCa): it is low in Asian races, medium (1 in 8) in white Caucasians and highest (1 in 4) in black African and African Caribbean/American men. Perhaps diet contributes to this since east asiatic diets are often rich in soya whereas western diets are blamed for obesity - PCa is commoner in obese men. If diet is a factor, the concept of "harmless" natural foods or supplements immediately becomes attractive as a preventive measure and some studies have even suggested this is the case. So far Vitamin E, Selenium, lycopenes, polyphenols and isoflavones have been cited as beneficial - is this really true?

Vitamin E & Selenium

Vitamin E is an antioxidant found in plant oils such as soya and Selenium is found in nuts, cereals, fish and meat.

An early trial in smokers in the USA suggested a considerable drop in cancer risk and mortality of 32% and 41% respectively. However the largest prevention trial involving over 35,000 randomised men showed no benefit after 5 years but after further follow-up and recruitment of 54,000 more men, the Vitamin E arm revealed a 17% INCREASED risk of developing PCa!

Subsequent analysis of the Selenium subgroup then showed the risk of developing high grade, aggressive PCa to be 90% higher! Worrying statistics indeed and illustrative of the risks in following unproven theories or dietary fads.

Lycopene & Polyphenols

Lycopene is found in red and orange vegetables such as tomatoes and carrots but in trials so far there is no proof of benefit.

Polyphenols are found in tea but so far all studies, including small randomised trials have shown conflicting or negative results. At least there is no evidence of danger from these two!

Isoflavones

These are basically plant oestrogens - "female" hormones - found in soya. Not surprisingly as they interfere with testosterone metabolism, essential for prostate and PCa growth, there is some evidence of reduction of PCa risk. This is a valid area for further research, especially in men at risk of PCa where some trials have shown a clear reduction of PCa in the isoflavone group.

Conclusion

For western Caucasian, black African and African Caribbean men there is no clear evidence that food supplements are of any value in preventing or suppressing PCa except for the use of soya which may be of value in men at risk of PCa.