Bioavailable lycopene protects against lung cancer in smokers and nonsmokers
WESTPORT, CT (Reuters Health) - Diets high in bioavailable lycopene appear to lower the risk of lung cancer in both smokers and nonsmokers, report investigators in Boston. However, while other carotenoids are inversely associated with lung cancer in non-s
Dr. Dominique S. Michaud, of the Harvard School of Public Health, and associates pooled data from the Nurses' Health Study and the Health Professionals Follow-Up Study, which included 46,924 men and 77,283 women. In multiple questionnaires, subjects reported their average frequency of intake over the previous year of a specified serving size of each food. Results appear in the October issue of the American Journal of Clinical Nutrition.
Between 1984 and 1996, a total of 519 new cases of lung cancer were diagnosed in women. Among the men, 275 new cases of lung cancer were diagnosed between 1986 and 1996.
For nonsmokers, the lung cancer risk was 63% lower for subjects in the top quintile of intake of alpha-carotene compared with those in the lowest quintile. A similar, nonsignificant trend for beta-carotene, lutein, and beta-cryptoxanthin and lower cancer risk was also noted among nonsmokers.
The associations were strongest in analyses that allowed for a lag of 4 to 8 years between time of dietary assessment and follow-up time. The authors suggest that there is "a relatively long latency period for carotenoids and lung cancer risk."
These associations between carotenoids and lung cancer were substantially attenuated after adjusting for smoking status, the investigators write. However, when they derived a bioavailability-adjusted score for the carotenoids, the inverse association between lycopene and the risk of lung cancer was stronger for both smokers and nonsmokers.
Dr. Michaud's group suggests that other phytochemicals found in similar foods may be more important than carotenoids in reducing carcinogenesis. Therefore, "it would be unwise to suggest carotenoid supplementation as an alternative to a diet plentiful in fruit and vegetables," they conclude.
In an associated editorial, Dr. David Heber, of the University of California, Los Angeles, suggests that the findings support his group's recommendation that fruits and vegetables form the base of the US Department of Agriculture food pyramid.
Dr. Heber writes, "The primary rationale for having fruit and vegetables at the base of the...pyramid is to increase the number of phytochemicals consumed for chronic disease prevention."