Medical Health Encyclopedia

Note: Studies on these chemicals are not consistent. It is unlikely that individual phytochemicals offer protection, but rather that the benefits come from a collection of vitamins and plant chemicals contained in fruits and vegetables. (Fruit, especially, appears to be protective).

Fats and Oils. Some studies have indicated that diets high in animal fats increase the risk for lung cancer. Others have suggested some protection from cod liver oil, which contains omega-3 fatty acids (found in fatty fish), omega-6 fatty acids (found in flax and in soybean and canola oils), and monounsaturated oils (found in olive and canola oils). Of interest was a 2002 study reporting that women who had a high intake of cheese had a lower risk of lung cancer. Despite these intriguing pieces of information, the ability of these substances to protect against lung cancer remains controversial, and discontinuation of smoking remains the best advice.

Click the icon to see an image of fats and oils.

Vitamins Supplements. Even with a healthful diet, smoking reduces the levels of a number of vitamins, importantly vitamin C. There is no evidence, however, to support any protection from antioxidant supplements, including vitamins E, A, or beta carotene.

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In fact, evidence is now suggesting that high doses of vitamin C, vitamin E, and beta carotene supplements may have harmful effects. A 2000 study, for example, reported a higher risk for cancer in male smokers who took multivitamins plus A, C, or E. The strongest studies to date on negative effects of antioxidant supplements have reported an increase in lung cancer and overall mortality rates among smokers who took beta carotene supplements. In determining reasons for this disturbing effect, one animal study suggested that beta carotene increased enzymes in the lungs that actually promote cancerous changes. In other words, antioxidants may actually be harmful in people who already harbor cancer cells. This is particularly important information for smokers, who may carry precancerous or cancerous cells for years prior to developing the disease. The best way of achieving healthy levels of important nutrients is from healthy foods.

Click the icon to see the benefits of vitamin A.

Click the icon to see dietary sources of vitamin A.