Nutrition and oral cancer.

Epidemiologic evidence on the relationship between nutrition and oral cancer is reviewed. Ecologic and case-control studies provide most of the evidence regarding the nutritional epidemiology of oral cancer. The ecologic evidence is that the considerable geographic variation in the incidence of oral cancer is consistent with variation in nutrition. Because incipient oral cancer is likely to affect the diets of oral cancer patients, even before diagnosis, case-control studies are limited by their ability to extract comparable information from subjects regarding their pre-illness diets. The case-control evidence is that a diet that emphasizes fruit and vegetable intake may protect against oral cancer. However, this case-control evidence is not highly consistent; individual foods that appear protective in some studies do not in others, and the effects of diet appear to be modest when compared with those of smoking and alcohol consumption. The nutritional epidemiology of oral cancer is marked by two risk factors that appear far more powerful than nutrition: tobacco use and alcohol consumption. As these likely are related to nutrition, they pose as important potential confounders. Oral hygiene also may confound the association of nutrition and oral cancer risk; it is likely to be associated with dietary practice, and it has been shown to be related to oral cancer risk. Thus, studies of nutrition in the epidemiology of oral cancer also must address the effects of tobacco and alcohol consumption and oral hygiene.