Green Vegetables Protect Smokers From Genetic Changes Associated With Lung Cancer Risk. This is the best advertisement for leafy green vegetables. Lung cancer, like many other forms of cancer, are caused by a long term damaging factors. Considering that lung cancer is not just for smokers, it's hard to find a drug that would reverse this damage. Multivitamins, folate, and green vegetables protect against gene promoter methylation in the aerodigestive tract of smokers. See also: Natural Defenses in Preventing and Treating Cancer and Natural Products: Keys to Treating Cancer and Infection.