Do Sunlight and Vitamin D Reduce the Likelihood of Colon Cancer?

TLDR

Colon cancer mortality rates are highest in regions with low sunlight exposure, such as major cities and high‑latitude rural areas. The study investigates whether sunlight and vitamin D reduce colon cancer risk, proposing vitamin D as a protective factor. The hypothesis is based on geographic patterns of colon cancer mortality linked to solar radiation, suggesting a role for vitamin D3 (cholecalciferol) while considering possible ecological fallacies. Comparisons of colon cancer mortality across regions with differing solar radiation support the hypothesis that sunlight and vitamin D reduce colon cancer risk.

Abstract

Garland CF (Department of Epidemiology, The Johns Hopkins University, School of Hygiene and Public Health, 615N Wolfe Street, Baltimore, Maryland 21205, USA) and Garland FC. Do sunlight and vitamin D reduce the likelihood of colon cancer. International Journal of Epidemiology 1980, 9: 227–231. It is proposed that vitamin D is a protective factor against colon cancer. This hypothesis arose from inspection of the geographic distribution of colon cancer deaths in the U.S., which revealed that colon cancer mortality rates were highest in places where populations were exposed to the least amounts of natural light - major cities, and rural areas in high latitudes. The hypothesis is supported by a comparison of colon cancer mortality rates in areas that vary in mean daily solar radiation penetrating the atmosphere. A mechanism involving cholecalciferol (vitamin D3) is suggested. The possibility that an ecological fallacy or other indirect association explains the findings is explored.