Relationship between vitamin A and lung cancer.

Current evidence indicates that vitamin A and carotene (a precursor) protect against cancer at many sites. The relationship with lung cancer has been studied more extensively than other cancer sites by retrospective and prospective dietary surveys and serum studies, most of which support an inverse association between vitamin A or carotene and lung cancer. Further retrospective serum studies should include family members of patients and controls for determination of what family differences are present that could not be attributed to the effect of cancer on the patients. Nutritional studies are also warranted for identification of determinants of serum vitamin A and carotene and for comparisons of dietary intake and serum levels between populations with different cancer incidence.