Case-control studies generally do not find an association between lycopene intake and prostate cancer. However, the authors note the possibility of errors in methodology as some pertinent conditions that could have affected the result were not considered (e.g. only source of lycopene considered were fresh tomatoes). Prospective studies and blood-serum-based studies are more illustrative of the relationship between lycopene and prostate cancer. Considering both fresh and processed sources of lycopene, a negative relationship is seen between intake of lycopene and the risk of prostate cancer. (Giovannucci, 2002). The possible role in preventing and treating prostate cancer has led researchers to study the possibility of the same relationship between lycopene and other types of cancer. But the researchers are yet to arrive at conclusive results.
The real mechanism of lycopene’s preventive effect on prostate cancer is unknown but several theories have been proposed to explain the relationship. Among these theories, the antioxidant theory is the most widely accepted. Free-radicals are known to cause damage to the DNA and cause cancer. Lycopene, acting as a free-radical, removes the oxygen free-radicals to prevent or reduce damage to DNA. Lycopene’s specific effect on prostate cancer may be attributed to the naturally high concentrations of lycopene found in prostate cells. Other theories of mechanism include the inhibition of tumor growth by increasing the gap-junctional communication among prostate cells (Everson and Mcqueen, 2004; Heber and Lu, 2002), and the reduction of levels of insulin growth factor by increased lycopene consumption. (Everson and Mcqueen, 2004).
There is still no standard recommended lycopene intake for the prevention or treatment of prostate cancer. But studies have used 15 mg taken twice a day in order to decrease the rate of growth of prostate cancer. A 6 mg/day intake is suggested by epidemiologic studies for prevention. (Everson and Mcqueen, 2004).
References
Everson K and McQueen C. (2004). Lycopene for prevention and treatment of prostate cancer. American Journal of Health-system Pharmacy. 61(15).
Giovannucci E. (2002). A review of epidemiologic studies of tomatoes, lycopene, and prostate cancer. Exp Biol Med. 227(10):852-859.
Heber D and Lu Q. (2002). Overview of mechanisms of action of lycopene. Exp Biol Med. 227(10); 920-3.