Vitamin D From Sunlight Shown to Fight Cancer

June 09, 2004 -- Yes, we are told to wear sufficient sunscreen to prevent melanoma, or skin cancer. But there is a balance point since too little sunlight or UVB radiation prevents our skin from producing sufficient vitamin D which help protect us from certain forms of cancers.

U.S. researchers have found the best source of vitamin D is ultraviolet B rays, while dietary supplement may not be as effective in preventing cancer.

It has been hypothesized that UVB radiation produces vitamin D in the skin and acts to reduce the risk of colon, rectal and nearly 12 other types of cancer, the researchers said. Geographical surveys have supported this notion, they said, because areas with more UVB in the summer have lower mortality rates from related cancers.

Vitamin D promotes the absorption of calcium and phosphate from food and is essential in the formation of bones and teeth. A deficiency of vitamin D leads to a failure of the bones to grow and causes rickets in children and osteomalacia in adults.

In a literature review in the current issue of Nutrition and Cancer, the researchers reported finding regular dietary sources do not provide the necessary amount of vitamin D to be as effective a protectant as UVB radiation.

The researchers estimate nearly 20,000 Americans die annually from cancers linked to insufficient vitamin D from UVB rays. This is a significantly higher figure than the 9,000 who die each year in the Unites States from melanoma, the researchers said, in which UVB plays a causative role.

Geographical Evidence

These results, then, help explain the geographic variation of colorectal and other cancer mortality rates in the U.S. Colon cancer mortality rates for males in the period 1970-94 were about 25 deaths/100,000/year for males and 18 for females in northeastern states but only 15 for males and 12 for females in southwestern states.

It's the Goldilocks syndrome, too much sun and you can develop melanoma, too little and you don't produce ample vitamin D which can stave off certain forms of cancer… everything in moderation.

These mortality rates are inversely correlated with July average irradiances of solar UVB radiation, which are highest in the southwest, lowest in the northeast taking into further consideration that urbanites have reduced UVB exposure compared to rural residents.

These results are consistent with those living in the southwestern states having an effective annual average vitamin D production of several hundred I.U./day more than those living in the northeastern states. In addition, these results provide further support for the idea that most Americans obtain most of their vitamin D from solar UVB radiation and not diet.

It should be noted that while UV radiation, especially UVA, plays a role in both melanoma and non-melanoma skin cancer, a number of other factors also play important roles, such as skin pigmentation, severe sunburning, a high-fat, high-protein, low-fruit and vegetable diet, and alcohol consumption and, at least for non-melanoma skin cancer, cigarette smoking. Together, these factors explain about half of melanoma and non-melanoma death rates.

Most people should be able to obtain adequate levels of vitamin D from modest daily exposures to mid-day summer sun in the southwest up through Wyoming and the southeastern states, with longer exposures required in other locations.

Earlier In a Separate UK Study

The idea that vitamin D may play a useful role in helping to prevent breast cancer was given a boost by UK research presented in March 2004. The researchers announced at a British Endocrine Societies meeting that they had found an enzyme in breast tissue that converts vitamin D into a cancer-fighting compound called calcitriol. Until now, it had been thought that this enzyme was only present in the kidneys.

Vitamin Supplements

Again, a modest amount of sunshine is sufficient for your body to generate sufficient supply of vitamin D. However, should you live in urban, cloudy, or extreme northern locations, natural sources of vitamin D can be found in:

cod liver oil
sardines
herring
salmon
tuna
milk
cheese
eggs

Source: UPI