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Antioxidants and risk of lung cancer

(May 2003)

Cigarette smoking is, of course, by far the most important risk factor for lung cancer. Several studies have suggested that various antioxidants may lower the risk of lung cancer to a modest extent among heavy smokers. An interesting and well-conducted study from Finland is reported in the American Journal of Epidemiology in September 2002. More than 27,000 male smokers ages 37 to 69 years were followed for fourteen years; during that time, there were 1,644 lung cancer deaths. At enrollment, the investigators measured dietary intake and blood concentrations of various carotenes and carotenoids and vitamin A, as well as intake of various fruits and vegetables.

The results were as follows:

The authors concluded "results of this study suggest that the consumption of several carotenoids from carotenoid rich food sources is inversely related to lung cancer risks. Moreover, dietary lycopene was associated with stronger and more significant reduction in risk. High fruit and vegetable consumption, particularly a diet rich in carotenoids, tomatoes, and tomato-based products may lower the risk of lung cancer, but dietary modification should not be considered a substitute for smoking prevention and cessation".

Commentary: It is said that 35 to 70 percent of cancer is caused by our diets. There is no good evidence to support that claim, but it is clear that our diets can modify the risk of certain cancers. That is particularly true of fruits and vegetables which, taken together, can reduce the risk of several cancers. Fruits and vegetables contain many ingredients. It has not been possible to ascribe the moderately reduced risk to specific fruits or vegetables, though it is generally agreed that the cruciferous vegetables (broccoli, brussel sprouts, cauliflower, cabbage) are important. The finding here that the foods with the strongest association were the lycopene-rich tomatoes, tomato paste, and tomato-based products is of considerable interest. Some studies suggest that lycopenes offer some protection against severe prostate cancer, but it is unclear whether lycopenes reduce the risk of prostate cancer or reduce the severity of progression once the cancer has appeared - and about one-half the studies on lycopenes and prostate cancer show no relationship at all. There are other studies supporting the claim about lycopenes made in this study on lung cancer. However, it may be other constituents in the tomatoes, not the lycopenes, that provide the benefit (for example, the polyphenols).

The evidence is pretty good that some foods (fruits and vegetables) reduce somewhat the risk of lung cancer among smokers. Some of the active substances are almost certainly antioxidants such as carotenoids. The findings regarding lycopenes are particularly interesting. The potential role of dietary lycopenes in reducing cancer risk merits a lot of additional study.

In contrast to the dietary evidence, there is, at present, no evidence that taking supplements containing carotenes, lycopenes, or other carotenoids can reduce the risk of any cancer.

As noted by the authors, the way to prevent 80 percent of lung cancer is not diet; it is not smoking.

Although we have a lot to learn about lycopenes and lycopene containing foods, it surely makes good sense to include tomatoes, tomato paste, and tomato products in your diet.

CLICK HERE for foods high in lycopenes.

Holick, C.N., et al. Dietary carotenoids, serum B carotenes and retinol and risk of lung cancer in the alpha-tocopherol, Beta carotene cohort study. American Journal of Epidemiology. Vol 156 (September 15) Pgs 536-547. 2002.

One of our Scientific Advisory Board members notes "the effect of diet on lung cancer prevention in smokers is trivial. To avoid lung and other tobacco-related cancers (about one-quarter of all cancers in man, about one out of seven in women), don’t smoke."

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