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Carrots and tomatoes protect against lung cancer

BOSTON, MASSACHUSETTS. Lung cancer is the most deadly of all cancers in the United States and kills more men and women every year than any other cancer. Smoking is the major risk factor with more than 90 per cent of all lung cancer victims being current or former smokers. Numerous epidemiological studies have found a highly significant protective effect associated with an increased intake of fruits and vegetables. It was originally thought that the protective component was beta-carotene, but several trials involving supplementation with synthetic beta-carotene did not confirm that it would help lower the incidence of lung cancer. It now turns out that the main reason why beta-carotene was selected as being the likely protective component was that it was the only carotenoid for which the concentration in various foodstuffs was actually known!

The official US nutrient databases have now been updated to include food concentrations of other carotenoids including alpha-carotene, lycopene, lutein and beta-cryptoxanthin. This development prompted researchers at the Harvard Medical School to re-examine the role of carotenoids in lung cancer prevention. Their study involved 46,924 male health professionals and 77,283 female nurses. The study participants completed comprehensive food questionnaires in 1984, 1986 and 1990 and were followed-up for 10 years from entry into the study. During the follow-up period 275 new cases of lung cancer were diagnosed among the men and 519 new cases among the women. Evaluation of the collected data showed that non-smokers with a high intake of alpha-carotene had a 63 per cent lower incidence of lung cancer than did non-smokers with a low intake. Alpha-carotene, however, had no protective effect among the smokers. Among smokers, those with a high intake of lycopene were found to have a 37 per cent lower incidence of lung cancer than did smokers with a low intake. Beta-carotene and multivitamin supplements did not affect the risk of lung cancer.

The researchers conclude that alpha-carotene is protective against lung cancer in non-smokers. They point out that carrots are the most abundant source of alpha-carotene and provide (in raw or cooked form) about 51 per cent of the daily intake of alpha-carotene. Tomatoes and tomato products are the best sources of lycopene and provide more than 85 per cent of dietary lycopene. Tomato sauce and paste are particularly good sources due to the greater bioavailability of their lycopene content. The researchers conclude that a high intake of mixed carotenoids is protective against lung cancer, but strongly emphasize that smoking is still by far the greatest risk factor. [45 references]
Heber, David. Colorful cancer prevention: alpha-carotene, lycopene, and lung cancer. American Journal of Clinical Nutrition, Vol. 72, October 2000, pp. 901-02 (editorial)
Michaud, Dominique S., et al. Intake of specific carotenoids and risk of lung cancer in 2 prospective US cohorts. American Journal of Clinical Nutrition, Vol. 72, October 2000, pp. 990-97

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