A review by the Food and Drug Administration concludes for now that there is little evidence to suggest eating tomatoes and lycopene supplements would reduce risk of many forms of cancers.   But the agency also concludes that "very limited evidence" suggests that consumption of tomatoes may reduce risks of prostate, ovarian, gastric and pancreatic cancers.

In response to two petitions submitted to the FDA in 2004 for qualified health claims regarding tomatoes, lycopene, and the risk reduction for some forms of cancer, Claudine, J. Kavanaugh, PhD and colleagues from the Center for Food Safety and Applied Nutrition conducted and reported the review.

In their report published in Journal of the National Cancer Institute Advance Access published online on July 10, 2007, Kavanaugh and colleagues write that "The FDA found no credible evidence to support an association between lycopene intake and a reduced risk of prostate, lung, colorectal, gastric, breast, ovarian, endometrial, or pancreatic cancer."

They also say there is no credible evidence for an association between tomato consumption of a reduced risk of lung, colorectal, breast, cervical or endometrial cancer.

However, the authors do acknowledge that some, but very limited evidence supports an association between tomato consumption and reduced risks of prostate, ovarian, gastric, and pancreatic cancers.

In response to a petition submitted by H.J. Heinz Company, the FDA wrote a letter in November 8, 2005 to the company rejecting 11 health claims over the possible preventative effect of tomatoes against prostate cancer, but allowing the company to use a claim that "Very limited and preliminary scientific research suggests that eating one-half to one cup of tomatoes and/or tomato sauce a week may reduce the risk of prostate cancer. FDA concludes that there is little scientific evidence supporting this claim."

In an editorial accompanying the review report, Edward Giovannucci, MD, ScD from Department of Nutrition Harvard School of Public Health, calls the FDA conclusion "disappointing".   But he says the findings by the FDA should not be a surprise.

Dr. Giovannucci, who conducted epidemiologic studies on tomatoes and cancer, says that the recent studies that are not included in Kavanaugh's review are also not supportive of an association between eating tomatoes and reduced risk of cancers.

However, he points out that that does not mean that eating tomatoes has no rule in cancer prevention, particularly, prevention of prostate cancer.

One of the possible reasons as he explains for the recent studies to fail to detect any association between tomatoes and total prostate cancer incidence is that they used prostate specific antigen screening as a tool for diagnosis of prostate cancer.   When PSA is used, many clinically unimportant, latent or asymptomatic tumors may be counted in the total prostate cancer incidence, resulting in an increased number of total prostate cancer and overwhelming the possible preventative effect of tomatoes.

Taking his own study as an example, which was published in 1995 in Journal of the National Cancer Institute, , he writes in his editorial that "initial analyses of the HPFS cohort for 1986–1992 found an inverse association between tomato sauce intake and total prostate cancer incidence; the association was stronger for advanced-stage cancer. In subsequent analyses of the HPFS cohort during the PSA era (1992–1998), the association was attenuated and weak, but a strong inverse association persisted for metastatic prostate cancer (combining the data from 1986 through 1998, the relative risk [RR] of metastatic prostate cancer for 2 servings per week of tomato sauce versus <1 serving per month = 0.34; 95% confidence interval [CI] = 0.19 to 0.90; Ptrend = .01) (14). Of note, the metastatic cases (n = 90) represented only about 4% of the total number of cases."

What does that mean is that eating tomatoes may help prevent advanced prostate cancer, but may not be effective in preventing the early stage form of cancer.

The review was based on 39 out of 145 research reports published before 2005.   All of the 81 observational studies of lycopene and cancer were rejected because the reviewers believe they did not meet the scientific standards for a claim of a cancer prevention benefit, according to Medpage Today. Among 64 studies of tomatoes and various forms of cancer, 25 were excluded.

In explaining why lycopene, an antioxidant found in tomatoes, does not seem to have an preventative effect against cancer, Keith Ayoob, associate professor of pediatrics at the Albert Einstein College of Medicine said, cited by abcnews.go.com, "Even if lycopene is the key nutrient in the tomato, it may need the other compounds in the tomato to do its best work,"

For more information, read the following

Qualified Health Claims: Letter Regarding
Tomatoes and Prostate Cancer

http://www.cfsan.fda.gov/~dms/qhclyco2.html

Does Prostate-Specific Antigen Screening Influence the Results of Studies of Tomatoes, Lycopene, and Prostate Cancer Risk? By Edward Giovannucci

http://jnci.oxfordjournals.org/cgi/content/full/djm048v1#BIB2

FDA Finds No Strong Link between Tomatoes and Reduced Cancer Risk

Liz Savage, Andrea Widener (a news release)

http://jnci.oxfordjournals.org/cgi/content/full/djm087v1

The U.S. Food and Drug Administration's Evidence-Based Review for Qualified Health Claims: Tomatoes, Lycopene, and Cancer

Claudine J. Kavanaugh, Paula R. Trumbo, Kathleen C. Ellwood

http://jnci.oxfordjournals.org/cgi/content/abstract/djm037v1

A Prospective Study of Tomato Products, Lycopene, and Prostate Cancer Risk

Edward Giovannucci, Eric B. Rimm, Yan Liu, Meir J. Stampfer, Walter C. Willett

http://jnci.oxfordjournals.org/cgi/content/abstract/94/5/391