What is the Dose-Response Relationship between vitamin D and cancer Risk? Cedric F. Garland DrPH, William B. Grant PhD, Sharif B. Mohr MPH, Edward D. Gorham MPH, PhD, Frank C. Garland PhD. Division of Epidemiology, Department of Family and Preventive medicine, University of California-San Diego, La Jolla, California, USA 2 nutrition and health Research Center. Nutrition Reviews Volume 65 Issue s2, Pages S91 - S95
Thousands of cases of cancer could be averted if people in colder climates increased their blood levels of vitamin D, according to authors of a paper in the August 2007 journal nutrition Reviews. Numerous epidemiological and ecological studies have shown increased cancer rates in higher latitudes around the world, especially colon, breast, and prostate cancers. With higher latitude comes a lower exposure to ultraviolet light from the sun - a critical component of adequate vitamin D levels in the blood. Pre-vitamin D is activated in skin cells via UV light into active vitamin D3.
In this study, researchers at the University of California, San Diego, analyzed worldwide data on winter vitamin D levels and found breast and colon cancer incidence rose as blood vitamin D levels dropped. A blood level above 22 ng/mL was protective for colon cancer, while above 32 ng/mL was protective for breast cancer. These were not deemed optimal levels, but levels at which a protective effect was seen. The average late winter blood level of 25-hydroxy vitamin D in the United States is well below the protective levels, at 15-18 ng/mL.
The authors of the study suggested if individuals achieved a blood level of at least 55 ng/mL, approximately 60,000 cases of colon cancer and 85,000 cases of breast cancer would be prevented annually...
In the equatorial regions, where people remain upon their natural whole-food diet, there are low incidences of cancer. As you go further away from the equator to less sunny climates the cancer incidence rises. Diet is still a factor in all situations, nevertheless.
Sources of vitamin D
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