Sunlight, Vitamin D and Cancer
  by James Occhiogrosso, N.D.

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The primary way the human body gets vitamin D is from the sun.  Human beings have a built in mechanism for obtaining vitamin D through the action of sunlight on their exposed skin.  Insufficient sun exposure results in vitamin D deficiency.  Many experts estimate that more than eighty percent of the U.S. population is severely deficient in vitamin D, especially during the winter months.  The effect of this deficiency on the body is profound. [1] [2]  Recent studies have concluded that vitamin D deficiency is a significant risk factor for the development of many diseases, including breast and prostate cancer. [3] [4] [5]

Resistance to change often inhibits progress.  Many of us have indeed heeded the warnings of the medical community, avoided sun exposure, and diligently used sun-blocking agents.  However, the incidence of many cancers continues to rise.  Since the early part of the last century, research has suggested that sunlight helps lower the risk of cancer.  Geographical studies show an association between living in a higher latitudes and increased cancer risk.  However, the prevailing wisdom has been to avoid sun exposure due to the risk of some skin cancers.  This long-term purveyance of the idea that any exposure to the sun increases the risk of skin cancer has induced an unreasonable fear of the sun in many people.  Such unfounded fears have led to an inordinate avoidance of sun exposure and a consequential deficiency of vitamin D. [6]

During winter months in the U.S., it is virtually impossible to get sufficient sunlight to forestall a vitamin D deficiency, even for those with fair skin. The only real exception to this is for folks that live in southern Florida, southern Texas, or Hawaii.  Nearly everyone living north of these areas is subject to a vitamin D deficiency for the greater part of the year.  Several studies have examined the geographical incidence of cancer. Virtually all of them found an increased incidence cancer in northern areas subject to long winters with little sunlight.  This correlates directly with levels of ultraviolet radiation from the sun and associated vitamin D production by the skin. [7]

The maps below show cancer mortality rates for prostate and breast cancer over the United States.  These maps show a strong relationship between latitude and these two cancers. Both maps courtesy of National Cancer Institute Cancer Mortality Maps and Graphs website. http://www3.cancer.gov/atlasplus   

 

Exposure to sunlight easily corrects vitamin D deficiencies but it is difficult to get sufficient sunlight in most areas of the country, especially in the winter months. Thus, supplementation with vitamin D is appropriate.  The current recommended daily allowance (RDA) of vitamin D is 200 IU for those under fifty, 400 IU from fifty to seventy, and 600 IU for adults over seventy.  However, this may be inadequate, especially for older adults.  A recent review of several studies noted that the concentrations of vitamin D needed to maintain good health could not be reached with the currently recommended RDA’s.  The authors of the review suggest that raising the RDA of vitamin D for all adults to at least 1000 IU will help prevent many serious chronic conditions, particularly in older adults. [8]  Most natural health practitioners recommend a daily intake of 2000 IU.

Recent studies demonstrate that avoidance of the sun and the use of sunscreens is not the best strategy for reducing the overall incidence of cancer.  Moderate exposure to the sun—rather than total avoidance—and vitamin D supplementation, is much more reasonable and effective. Vitamin D plays and important role in balancing the body’s calcium levels, and, as with most nutrients, it appears to work synergistically with other nutrients.  Maintaining optimal levels of vitamin D can reduce the risk of many illnesses, including many cancers.

References:

[1] Zitterman, A. Vitamin D in preventive medicine: are we ignoring the evidence? British Journal of Nutrition, Vol. 89, No. 5:552-572, May 2003.

[2] Zittermann, A, et al, Low vitamin D status: a contributing factor in the pathogenesis of congestive heart failure? Journal of the American College of Cardiology, Vol. 41, No. 1:105-112, Jan. 2003.

[3] Schwartz, G., et al. Vitamin D Status and Cancer Incidence and Mortality: Something New Under the Sun. Journal of the National Cancer Institute, Vol. 98, No. 7:428-430, April 2006.

[4] Garland, C., et al. The role of vitamin D in cancer prevention, American Journal of Public Health, Vol. 96, No. 2:252-261 Feb. 2006.

[5] Peehl, D., et al. Pathways Mediating the Growth-Inhibitory Actions of Vitamin D in Prostate Cancer. Journal of Nutrition, Vol. 133:2461S-2469S, July 2003.

[6] Garland, C., Sun avoidance will increase incidence of cancers overall. British Medical Journal, Vol.327:1228, Nov. 2003.

[7] Freedman, D., et al. Sunlight and mortality from breast, ovarian, colon, prostate, and non-melanoma skin cancer: a composite death certificate based case-control study. Occupational & Environmental Medicine, Vol. 59, No. 4:257–262, April 2002.

[8] Bischoff-Ferrari, H., et al. Estimation of optimal serum concentrations of 25-hydroxyvitamin D for multiple health outcomes. American Journal of Clinical Nutrition, Vol. 84, No. 1:18-28, July 2006.