Dear Dr Cannell: Sunlight, vitamin D and the prevention of cancer

Dear Dr Cannell: Sunlight, vitamin D and the prevention of cancer
November 5, 2012 -- John Cannell, MD
Dear Dr. Cannell:

Making vitamin D through sun exposure is the natural way to maintain D levels as shown through hundreds of thousands of years of human history. I analyzed a paper on about 50 studies of various internal cancers and their relationship to vitamin D, latitude, and sun exposure. Most of the analysis was focused on four cancer types: breast, colon, prostate and lymphoma. Overall van der Rhee concluded that while vitamin D levels/supplementation was only consistently associated with a decrease in colon cancer, sun exposure was consistently associated with a decrease in all four cancers.

van der Rhee H, Coebergh JW, de Vries E. Sunlight, vitamin D and the prevention of cancer: a systematic review of epidemiological studies. Eur J Cancer Prev. 2009 Nov;18(6):458-75

I took it a step further by quantifying the percentage of studies that found a significant decrease in cancer as reported by van der Rhee.

• Sunlight and latitude studies: 77.1% show significant correlation
• Vitamin D level studies: 63.4% show significant correlation
• Diet or supplementation studies: 47.4% show significant correlation

I do acknowledge that many vitamin D supplementation studies are flawed in that the amount given are not high enough to show D’s full potential. However, let’s face it, the present results of vitamin D studies, particularly those dealing with supplementation, show that people are not getting enough sun to maintain optimal levels. Continue reading → (no membership required)