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An onion a day keeps lung cancer away

HONOLULU, HAWAII. A high intake of fruit and vegetables has consistently been linked to a lower risk of lung cancer. Early research pointed to beta-carotene as the protective component, but its role as such has not been confirmed in more recent research. Now medical researchers at the University of Hawaii provide convincing evidence that it is the flavonoids contained in many fruits and vegetables that protect against lung cancer. Their study involved 582 patients with lung cancer and 582 age-, sex-, and ethnicity-matched controls. All participants were interviewed at home and filled out a food-frequency questionnaire that tabulated their intake of 242 different foods in the year prior to their diagnosis of cancer or in the case of controls, in the year prior to their interview. As expected smoking status was found to be the main risk factor for lung cancer with there being three times as many smokers in the cancer group as in the control group. After adjusting for smoking and intakes of beta-carotene and saturated fats the researchers found a clear inverse correlation between the intakes of onions, apples, and white grapefruit and the risk of lung cancer. Study participants who consumed 20 grams of onions or more per day had half the risk compared to participants whose intake was 7.5 grams/day or less. The protective effect of onions was particularly impressive in the case of squamous cell carcinoma where heavy onion eaters had only one-tenth the risk of less enthusiastic onion consumers. Apple eaters consuming 50 grams/day (about 1/3 apple) or more lowered their risk by 40 per cent compared to participants consuming 2.3 grams/day or less. White grapefruit, but not the pink variety, also lowered lung cancer risk with participants consuming 10 grams/day having half the risk of those not consuming white grapefruit at all.

The researchers conclude that quercetin is likely to be the protective component in onions and apples while naringin is likely to be the active component in white grapefruit. They do emphasize though that the strongest protective effect was seen with the whole foods (apples, onions and grapefruit) rather than with quercetin and naringin.
Le Marchand, Loic, et al. Intake of flavonoids and lung cancer. Journal of the National Cancer Institute, Vol. 92, January 19, 2000, pp. 154-60

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