The result of the review is published online in the Journal of the National Cancer Institute (JNCI) and is the work of Dr Claudine Kavanaugh, of the FDA in College Park, Prince George's County, Maryland, and colleagues.
The FDA has to review scientific evidence on claims linking food and supplement consumption with health benefits before any claims can be shown on labels and packaging.
About a year and a half ago the agency rejected petitions from food companies that wished to make health claims linking fresh and cooked tomatoes and lycopene to reduced risk of cancer. This review explains the grounds for the rejection.
If the requests had been granted, the food companies would have been allowed to claim that any product containing raw or cooked tomatoes (from pizzas to bottled sauce to lycopene food supplement tablets) could stop consumers getting a range of cancers.
The agency's jurisdiction does not extend to advertising, however, which is regulated by the Federal Trade Commission (FTC). There is no news on what the FTC decision is on this subject, but the two agencies have tended to make similar decisions in the past.
Several studies have suggested a link between eating tomatoes or lycopene, the compound that gives tomatoes their red colour, and a reduced risk of certain cancers such as prostate cancer.
The FDA's review was completed in November 2005 and found no evidence that eating tomatoes reduced the risk of lung, colorectal, breast, cervical, or endometrial cancer. They also found no credible evidence linking lycopene consumption, either in food or as a food supplement, with reduced risk of any cancer.
However, they did find limited evidence linking eating tomatoes and reduced risk of prostate, ovarian, gastric, and pancreatic cancer and have ruled that claims can be made for a "very limited association" between tomatoes and these four cancers.
For example, in the case of prostate cancer, the FDA said:
"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. [The] FDA concludes that there is little scientific evidence supporting this claim."
In an accompanying editorial, Dr Paul M Coates of the National Institutes of Health (NIH) in Bethesda, also in Maryland, wrote that the number of clinical studies is not great and it is not easy communicating subleties of such a decision in a way that the general public will understand.
However, he said that neither of these concerns reduces the important principle of using evidence-based reviews to evaluate claims about links between diet a and health:
"In fact," wrote Coates, "it may be argued that evaluating a diet-health relationship is precisely the circumstance in which systematic review techniques can be most appropriate and effective because they are transparent and objective, and the search and review strategies could be exactly reproduced by others."
In a second editorial, Dr Edward Giovannucci, of the Harvard School of Public Health in Boston, said he was not surprised the FDA concluded there was limited evidence to support the claims that eating tomatoes or lycopene reduced risk of prostate cancer. He wrote a paper on the subject in 2002, which also appeared in JNCI.
Giovannucci suggested the widespread use of PSA (prostate-specific antigen) screening as a way to establish the presence of prostate cancer could be distorting the evidence. PSA shows positive readings even when the cancers are clinically insignificant said Giovannucci, which would lead to inconclusive results.
"Although it may be premature to espouse increased consumption of tomato sauce or lycopene for prostate cancer prevention, this area of research remains promising," he wrote.
"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
JNCI Journal of the National Cancer Institute, Advance Access published online on July 10, 2007
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Written by: Catharine Paddock
Writer: Medical News Today