The Sun: Friend or Foe

By Joel Fuhrman, M.D.

Ill-Informed Fears Of The Sun Can Cause More Harm Than Good!

Now that the ozone layer has thinned, your skin is more easily damaged by sun exposure than it was in the past. But despite the aging and wrinkling and the increased risk of skin cancer, we need to remember that humans have evolved to obtain the vitamin D we need from exposure of our skin to sunlight. Humans synthesize vitamin D3 (cholecalciferol) in the skin upon exposure to UVB rays from sunlight. Plants synthesize vitamin D2 (ergocalciferol), which also has vitamin D activity in humans.

Vitamin D is a fat-soluble vitamin that is essential for calcium absorption. If you have a low level of vitamin D in your body, calcium absorption is reduced in the digestive tract. Calcium levels in the blood must be maintained within a narrow range to insure normal functioning of the heart and nervous system. If you do not absorb sufficient calcium, because of either low calcium intake in your diet or deficiency of vitamin D, your body will take the calcium it needs from the calcium in your bones. In fact, your body is so determined to keep the proper amount of calcium in the bloodstream that it will weaken and thin your bones if it has to. Without sufficient vitamin D, calcium absorption from the digestive tract is reduced, resulting in increased bone breakdown (osteopenia) and greater potential for osteoporotic fractures.1

A blood test for calcium cannot tell you if you are depleting your bones of calcium because the blood level for calcium does not go down with low calcium intake or low vitamin D intake; instead, your bones break down to keep the blood level constant. A normal calcium level in the blood offers no reassurance of adequate calcium or vitamin D intake.

Vitamin D Deficiency and Autoimmune Diseases

In addition to vitamin D’s protective effect on your skeleton, epidemiological studies and animal models suggest that maintaining sufficient vitamin D levels may help decrease the risk of several autoimmune diseases, including type 1 diabetes mellitus, multiple sclerosis, psoriasis, and rheumatoid arthritis.

Autoimmune diseases come about when your body mounts an immune response to your own tissue (rather than to a foreign pathogen). Autoimmune responses are mediated by immune cells called T cells. The biologically active form of vitamin D— 1,25(OH)2D—has been found to modulate T cell responses, so that autoimmune responses are reduced.2 Studies also have noted that the prevalence of autoimmune diseases increases as latitude (the distance you are from the equator) increases, suggesting that lower exposure to UVB radiation and associated decreases in vitamin D synthesis may play a role in these diseases.

In sunny climates, children and adults who spend time outside two or three times a week should be able to make all the vitamin D that they need. However, even the application of sunscreen with an SPF factor of 8 reduces production of vitamin D by 95%. The irony is that by protecting our skin against the sun’s damaging rays, we put ourselves at risk for osteoporosis and possible autoimmune disease. Worse, vitamin D deficiency has been linked to increased risk for cancer at different body sites.3

Cancer Prevention

Animal studies indicate that vitamin D has potent anticancer benefits, including prohibiting progression and metastasis with a wide spectrum of cancers. Higher rates of total cancer mortality in regions with less UVB radiation, and among African- Americans and overweight and obese people, each associated with lower circulating vitamin D, are compatible with a benefit of vitamin D on mortality. In addition, poorer survival from cancer in individuals diagnosed during the months when vitamin D levels are lowest suggests a benefit of vitamin D against late stages of carcinogenesis.

There is strong evidence that higher levels of vitamin D [1,25(OH)2] from sunlight exposure or supplement intake inhibit colorectal carcinogenesis and prostate cancer. The local cellular production of biologically active vitamin D [1,25(OH)2D] acts in a direct fashion to regulate cell growth and decrease the risk of cells becoming malignant. Higher circulating 1,25(OH)2D seems to be important for protection against aggressive prostate cancer.

In the Health Professionals Follow- Up Study, almost 50,000 men were followed from 1986 through 2000, with 4,286 serious cancer diagnoses and 2,025 deaths from cancer. This study found a 45% reduction in digestive cancer mortality and a 29% reduction in total cancer mortality from those whose vitamin D status was good compared to those with low levels. Results were similar when controlled further for body mass index or physical activity level. The conclusion of the researchers was that low levels of vitamin D are associated with increased cancer incidence and mortality in men, particularly for digestive-system cancers. The researchers also concluded that the vitamin D supplementation necessary to achieve a 25(OH)D increment of at least 25 nmol/L, found to be most protective in this trial, may be 1500 IU/day.4

Should We Avoid The Sun?

The combination of supplements and additional sunshine is the most logical and practical way for Americans to achieve these benefits from adequate vitamin D status. Vitamin D deficiency is an unrecognized epidemic in most adults who are not exposed to adequate sunlight. Sensible sun exposure (usually 5-10 minutes of exposure of the arms and legs or the hands, arms, and face, 2-3 times per week) and increased dietary and supplemental vitamin D intakes are reasonable approaches to help establish vitamin D sufficiency, without significant increased risk of skin cancer.

Certainly, we want to avoid excessive sun exposure, given our thinning ozone layer surrounding the Earth, and we want to protect the most sun-exposed areas such as the nose, cheeks, shoulders, and neck from the damage and wrinkling that ensues from overexposure to the sun. However, fear of skin cancer (and the resulting sun avoidance and use of chemical sunscreens) may actually be a bigger problem than skin cancer. Research has shown that sun avoidance and the vitamin D deficiencies associated with it cause more overall cancer deaths than would have resulted from the skin cancers the sun avoidance was designed to prevent.

Proactive Approach To Vitamin D And Sunshine

Fortunately, you need not get skin cancer or promote other cancers with vitamin D deficiency. You just need to be sensible about sun exposure. Use mechanical, not chemical, sunscreen when outdoors for too long, and take a vitamin D supplement in addition to your routine multivitamin. The vitamin D in a typical multivitamin is insufficient for optimal protection. Vitamin D syntheses also is dependent on where in the world you live. At latitudes around 40 degrees north or 40 degrees south (Boston is 40 degrees north),there is insufficient UVB radiation available for vitamin D synthesis from November to early March. At 10 degrees further north (Edmonton, Canada), this lack of UVB rays extends from mid October to mid March.5 In much of the U.S., which is between 30 and 45 degrees latitude, six months or more during each year have insufficient UVB sunlight to produce optimal vitamin D levels.

It is also difficult to get adequate vitamin D because UVB rays are related to the angle of the sun’s rays. They are strongest during midday hours, which is when people are instructed to avoid the sun. The elderly and darker skinned people also have a diminished capacity to synthesize vitamin D from the sun.6

Strategies To Match Your Individual Circumstances

As people relocate around the globe and live and work in places far from where their ancestors lived, unexpected health consequences can result. Darker skinned people are adapted to withstand longer periods of intense sun exposure. Increased skin pigmentation, however, means it takes more exposure to the sun to produce enough vitamin D.7 When these people migrate to parts of the world with less UVB radiation, they are at higher risk of vitamin D deficiency. On the other hand, fair-skinned people who migrate to parts of the world with the strongest sun are not able to expose their skin long enough to synthesize sufficient vitamin D without risking skin damage.

Factors such as how much exposure to the sun you get, how much of your skin your clothing covers, how dark or light your skin is, and at what latitude you live all determine how much supplemental vitamin D you need to take. Most people who are not getting lots of sun in a warm climate should take the standard dose in a supplement such as my OsteoSun, in which 4 capsules has 800 IUs of vitamin D3. Most of the standard calcium/magnesium/vitamin D products contain much too much calcium and much too little vitamin D. If you prefer my Vegan OsteoSun, note that it contains 2000 IUs of vitamin D2 per 4 tablets. The higher dose is needed because vitamin D2 is not as effective at raising blood levels of vitamin D compared with D3.

Since it is still important to use sun protection if you’ll be outdoors too long in today’s harsh sun, I have searched to find the best sunscreen products (that contain neither chemicals nor nanoparticles). Levera sun protection products meet my high standards and are the very best products available.


1. Lips P. “Vitamin D deficiency and secondary hyperparathyroidism in the elderly: consequences for bone loss and fractures and therapeutic implications.” Endocr Rev 2001;22(4):477-501.

2. Deluca HF, Cantorna MT. “Vitamin D: its role and uses in immunology.” FASEB J 2001;15(14):2579- 2585.

3. Giovannucci E. “The epidemiology of vitamin D and cancer incidence and mortality: a review (United States).” Cancer Causes Control 2005; 16(2):83-95.

4. Giovannucci E, Liu Y, Rimm EB, et al. “Prospective study of predictors of vitamin D status and cancer incidence and mortality in men.” J Natl Cancer Inst 2006; 98(7):451-9.

5. Webb AR, Kline L, Holick MF, et al. “Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin.” J Clin Endocrinol Metab 1988;67:373-8.

6. Holick MF. “Vitamin D deficiency: what a pain it is.” Mayo Clin Proc 2003;78(12):1457-1459.

7. Matsuoka LY, Wortsman J, et al. “Racial pigmentation and the cutaneous photosynthesis of vitamin D.” Arch Dermatol 1991;127:536-8.

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