Study finds that Sunlight Actually Prevents Cancer

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Insufficient exposure to ultraviolet radiation may be an important risk factor for cancer in Western Europe and North America, according to a new study published in the prominent Cancer journal that directly contradicts official advice about sunlight.

The research examined cancer mortality in the United States. Deaths from a range of cancers of the reproductive and digestive systems were approximately twice as high in New England as in the southwest, despite a diet that varies little between regions.

An examination of 506 regions found a close inverse correlation between cancer mortality and levels of ultraviolet B light. The likeliest mechanism for a protective effect of sunlight is vitamin D, which is synthesized by the body in the presence of ultraviolet B.

The study’s author, Dr William Grant ( , says northern parts of the United States may be dark enough in winter that vitamin D synthesis shuts down completely.

While the study focused on white Americans, the same geographical trend affects black Americans, whose overall cancer rates are significantly higher. Darker skinned people require more sunlight to synthesize vitamin D.

There are 13 malignancies that show this inverse correlation, mostly reproductive and digestive cancers. The strongest inverse correlation is with breast, colon, and ovarian cancer.

Other cancers apparently affected by sunlight include tumors of the bladder, uterus, esophagus, rectum, and stomach.


Dr. Mercola’s Comments:

Most people believe that sun exposure causes cancer. Nothing could be further from the truth. As this study published in the prestigious Cancer journal indicates, exposure to sun actually decreases cancer rates.

Does this mean that one’s sun exposure does not contribute to skin cancer? Absolutely not.

However, skin cancers are more likely related to the large distortion most people have in their omega-6 to omega-3 fat ratio. The high excess of omega-6 fats in most people’s diet puts them at a much higher risk of developing skin cancer when exposed to excess sun.

It is sunburn in conjunction with excess omega-6 fats that increases your risk of skin cancer. But even with the potential increase in skin cancer, most skin cancers are relatively benign when compared with breast, colon, and prostate cancers that lack of sun exposure is associated with.

So you can’t have it both ways. Avoid the sun and don’t change your diet and you will lower your risk of skin cancer, but increase your risk of far more common and deadlier cancers. So why not change the fat content of your diet and use sensible sun exposure guidelines and reap the benefits of sunlight?

It is also important to note that many researchers are currently evaluating vitamin D and its analogs in the treatment of cancer (van den Bemd GJ, Chang GT. Vitamin D and vitamin D analogs in cancer treatment. Curr Drug Targets. 2002 Feb;3(1):85-94.)


Vitamin D can no longer properly be considered a vitamin.

Nevertheless, vitamin D resembles true vitamins inasmuch as humans — who are cut off from the critical solar ultraviolet wavelengths by reason of latitude, clothing, or shelter — depend on an external source of the substance, just as they do for the true essential nutrients.

The major biologic function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones. It promotes bone mineralization in concert with a number of other vitamins, minerals, and hormones.

However, it is quite clear that vitamin D does far more than promote optimized bone health. In addition to the strong evidence provided in this article about prevention of cancer vitamin D has also been associated with improvement in the following conditions:

  • Diabetes
  • Heart Disease
  • Arthritis
  • Infertility and PMS
  • Fatigue, Depression and Seasonal Affective Disorder
  • Autoimmune Disorders
  • Obesity
  • Syndrome X 

Some key points to remember. The vitamin D in milk, and that put in most vitamins is vitamin D2 and is synthetic. Vitamin D2 is also called ergocalciferol. It is not the vitamin D that you want to supplement with. The best place to get vitamin D is from UV-B from sunlight. However, darker skinned people require 10 to 20 times the sun exposure length than lighter skinned people do to build up the same amount of vitamin D.

That is one of the major reasons why African Americans have a much higher rate of cancer in North America than other ethnic groups. Most people, who have skin that is deeply pigmented, should take extra precautions when living in North America for health reasons. The only work around for them to maintain their health would be to optimize their vitamin D levels.

It is also very important to realize that the RDA of vitamin D of 400 units is absolutely inadequate for most people who do not have exposure to regular sunshine. Most people may need up to 10,000 units per day for a short time to build their vitamin D levels up to healthy ranges.


Source: , Cancer March 2002; 94:1867-75


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This entry was posted on Thursday, January 25th, 2024 at 5:28 pm and is filed under Research.

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