Confirmation of Lycopene's Benefits Remains Elusive

There's nothing quite as mouthwatering as a rich, savory tomato sauce topping off fresh pasta—unless it’s that quintessentially American summer treat, a slice of ice-cold watermelon. Though the foods differ, they share their cheerful red hue thanks to lycopene, a carotenoid pigment.

Carotenoids are the fat-soluble pigments found in numerous red, orange and yellow fruits and vegetables, some of which the body uses to make vitamin A. While the lycopene found in apricots, guavas and papayas is likely less familiar (and not a source of vitamin A), proponents say it, too, has major health benefits. And research suggests that lycopene’s effectiveness is boosted if eaten with fat because it dissolves better in fat than in water and is thus more easily absorbed by the body.

“If a chemist could make a lycopene derivative that was more potent, and still safe, that could be very useful.” — MICHAEL SPORN

Lycopene is thought to potentially lower the risk of heart disease, stroke and macular degeneration. However, the pigment’s potential to prevent and treat certain cancers has generated great interest.

On the cellular level, lycopene, like all carotenoids, has well-established antioxidant properties. Additionally, laboratory studies of prostate cancer cells have shown that lycopene promotes apoptosis (programmed cell death), interferes with cell proliferation, inhibits the expression of androgen (male hormone) receptors, and possibly affects the insulin-like growth factor 1 (IGF-1) receptor signaling pathways. (Higher-than-normal levels of IGF-1 could lead to increased cancer risk.) But what does this mean outside the laboratory?

“The epidemiologic [observational] studies tend to suggest that high consumption of lycopene or a high blood level of lycopene is associated with a lower risk of prostate cancer,” says Edward Giovannucci, a professor of nutrition and epidemiology at Harvard School of Public Health in Boston.

However, these studies need to be interpreted with caution, because numerous factors can affect outcomes, including weight, diet and geographic settings. And the Food and Drug Administration (FDA) has found no credible evidence to support an association between lycopene intake and reduced risk of cancer.

Moreover, epidemiologic studies don’t tell the whole story; interventional studies are also necessary. For instance, it is possible that those who consume more lycopene also have other lifestyle habits that account for their lower cancer risk, pointing to a need for further studies.

Still, Giovannucci says epidemiologic and interventional studies are very different and not comparable, and that “in the era of widespread PSA screening, many prostate cancers that are diagnosed are indolent and at a relatively early stage. Thus, the potential beneficial influence of lycopene has been diluted.”

Lycopene supplements are generally regarded as safe, but, like all nutritional supplements, lycopene is not regulated by the FDA, and quality and consistency among brands varies.

Whether in foods or supplements, lycopene is not very potent, according to Michael Sporn, a professor of medicine at Dartmouth College’s Geisel School of Medicine in Hanover, N.H. “So one would need to eat a huge number of tomatoes or ingest something like a gram a day of pure lycopene in order for it to be clinically useful. We have no information about the safety of giving such a high dose to people.”

The bottom line: “Lycopene itself is simply not potent enough as a cancer-preventive agent to justify further clinical trials,” Sporn says.

“If a chemist could make a lycopene derivative that was more potent, and still safe, that could be very useful,” Sporn adds. “But that’s a long-term research project, and certainly not applicable to people in the short term.”

Perhaps one dietary component might not make much of a difference, but a combination of micronutrients could.