New Evidence Suggests Impact of Vitamins A, D on Cancer
Associations observed between vitamin A and lung cancer, vitamin D and colorectal cancer
WEDNESDAY, Oct. 31 (HealthDay News) -- Two new studies suggest an association between vitamin A and vitamin D on the incidence of lung cancer and colon cancer, respectively, according to reports published in the Nov. 7 issue of the Journal of the National Cancer Institute.
Walter N. Hittelman, Ph.D., of the University of Texas M.D. Anderson Cancer Center in Houston, Texas, and colleagues randomly assigned 225 former smokers to three months of daily oral treatments with 9-cis-RA (100 mg); 13-cis-RA (1 mg/kg) and α-tocopherol (1,200 IU); or placebo. Bronchoscopic biopsies were taken to assess changes in the basal and parabasal layers of the bronchial epithelium. In per-subject analyses, the combined treatments with 13-cis-RA and α-tocopherol were associated with a statistically significant reduction in bronchial epithelial cell proliferation. In per-site analysis, both treatments were associated with significant reductions.
In the second study, D. Michal Freedman, Ph.D., of the National Cancer Institute in Bethesda, Md., and colleagues followed 16,818 individuals 17 years old and older who were participants in the Third National Health and Nutrition Examination Survey. Data were collected by interview and physical examination, including blood samples to determine levels of 25-hydroxyvitamin D. No relation was observed between vitamin D status and total cancer mortality, but an inverse relationship was noted between vitamin D and mortality due to colorectal cancer.
An editorial commenting on the Freedman study cautioned that the results should not encourage the public to consume high amounts of vitamin D, and concludes, "More definitive data on both benefits and potential adverse effects of high doses are urgently needed."