DIJON, France--Vitamins C, B6, D and folate appear to reduce risk of colon adenoma in both smokers and non-smokers, whereas beta carotene may only have a protective effect in non-smokers and an adverse effect in smokers, according to a study published in the October issue of the Journal of Nutrition (135:2468-72, 2005).
French scientists investigated the effect of dietary vitamins and beta-carotene on the risk of adenomas and a potential interaction with smoking status as part of a case-control study of environmental factors associated with the risk of colorectal adenomas and cancers. The researchers compared nutrient intakes in polyp-free controls (n = 427) and adenoma cases (n = 362), globally and using models stratified by smoking status, adjusted for age, sex, BMI, and energy and alcohol intakes. Folate, vitamin C and vitamin B6 were inversely related to adenoma risk, whereas vitamin D tended to be inversely associated with risk. There was a significant interaction between beta-carotene and smoking. In nonsmokers, beta-carotene was inversely associated with adenoma risk, especially that of colon adenomas; whereas in past or current smokers, beta-carotene was not associated with a significant increase in the risk of colon adenomas.
The research findings support a chemoprotective effect of folate, vitamin C and vitamin B6, irrespective of smoking habits, and a protective effect of beta-carotene in non-smokers only. Based on the adverse effect of beta-carotene in smokers, researchers concluded smokers should be cautious about taking high doses of this micronutrient.
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