Increased blood levels of lycopene may reduce the risk of advanced prostate cancer by 60 per cent, but carotenoids in general do not appear to impact on the overall risk of the disease, says a large European study.Writing in the current issue of the American Journal of Clinical Nutrition, researchers taking part in the Europe-wide European Prospective Investigation into Cancer and Nutrition (EPIC) report that, despite an apparent benefit from lycopene, more research is needed before the link can be supported."To our knowledge, this is the largest prospective study to date of plasma carotenoids, retinol, tocopherols, and prostate cancer risk," wrote lead author Timothy Key from Cancer Research UK. "Overall, we observed no significant associations between plasma micronutrient concentrations and prostate cancer risk. However, we did observe significant heterogeneity between localized and advanced prostate cancer for the associations with lycopene and for the sum of carotenoids, both of which were significantly associated with a reduction in risk of advanced prostate cancer," he added.Epidemiological evidence has suggested that tomato-based foods can protect men from prostate cancer. One study found that men eating four to five tomato based-dishes per week were 25 per cent less likely to develop prostate cancer compared to men eating tomatoes only rarely. Such findings are boosting the lycopene market, with growth rates forecast at over 100 per cent by Frost and Sullivan, albeit from a low base of around €27m ($34m) in 2003.The new study followed 137,001 men from eight European countries for an average of 6 years. After this time, the researchers compared 966 subjects (average age 60.4, average BMI 26.6 kg per sq. m) who developed prostate cancer with 1064 healthy matched controls (average age 60.1, average BMI 26.8 kg per sq. m). All the subjects provided blood tests in order to quantify blood levels of certain micronutrients.After adjusting the results to account for potentially confounding factors, the researchers reported no reduction in overall prostate cancer risk for the micronutrients, which included vitamin A, selected carotenoids, lycopene, and alpha- and gamma-tocopherols (forms of vitamin E).However, when they looked at only advanced prostate cancer (accounting for 29 per cent of the cases), significant protective associations were observed, with the highest lycopene levels linked to a 60 per cent reduction, and total carotenoids linked to a 65 per cent reduction in advanced prostate cancer risk, compared to the lowest average levels."For lycopene and for the sum of carotenoids, there was weak evidence for a difference in association according to the stage of disease, which corresponded to an inverse association for advanced disease but no association with localized disease," wrote the researchers."If lycopene or total carotenoids reduce the risk of advanced disease, it would be expected that, unless these carotenoids affect only disease progression, there would also be some reduction in risk of localized disease," they added.Key and co-workers also conducted a meta-analysis, combining their results with studies from other studies, and found no overall benefit from any of the nutrients. This supports the results from clinical trials, they said, where beta-carotene and vitamin E supplements were not observed to produce benefits against prostate cancer."Although this is the largest prospective study of plasma carotenoids, retinol, tocopherols, and prostate cancer risk published so far, more data are needed to clearly differentiate the associations of lycopene and total carotenoids with localized and advanced disease, to examine whether these associations vary according to time between blood collection and diagnosis, and to examine whether these associations are confounded or modified by other potential risk factors for prostate cancer," concluded Key.According to the European School of Oncology, over half a million news cases of prostate cancer are diagnosed every year world wide, and the cancer is the direct cause of over 200,000 deaths. More worryingly, the incidence of the disease is increasing with a rise of 1.7 per cent over 15 years.
