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Surgery and Cosmetics

James M. Spencer, MD, MS

Vitamin D, Tanning and Sunscreen: What Patients Need to Know

James M. Spencer, MD, MS

Wednesday, December 08, 2010

During the past 30 years, dermatologists have consistently advocated that the public reduce their exposure to ultraviolet (UV) radiation in order to reduce the incidence of skin cancer, with the added benefit that reduced UV exposure will also reduce wrinkles and other signs of photoaging. Specifically, we have recommended the following guidelines:

  1. Seek shade when outdoors, and avoid outdoor activities from 10:00 am to 3:00 pm.
  2. Wear a broad-brimmed hat and protective clothing when outdoors.
  3. Apply sunscreen and sunblock regularly, and wear them at all times.
  4. Avoid indoor tanning.

All of these measures are designed to achieve decreased cutaneous exposure to UV radiation.

Although it is debatable how successful our efforts have been (one need only to look at the booming growth in indoor tanning to see that this message often falls on deaf ears), it is certainly true that dermatologists have remained steadfast in the belief that these recommendations are wise public health policy. Therefore, it comes as a surprise to many dermatologists to hear that some physicians in other fields are questioning the wisdom of sun protection. This article explores the drive behind this re-evaluation of our sun-protection message. It also discusses the purported role of vitamin D in maintaining health, which proponents argue outweighs the risks of skin cancer.

Maintaining Vitamin D Levels - Diet versus UVB Exposure

Vitamin D can be obtained through our diet, as well as being manufactured in the skin from cholesterol. UVB is a critical component in the first step of the biosynthetic pathway through which previtamin D3 is manufactured in the skin. This product is, in turn, hydroxylated in the liver to give 25-hydroxyvitamin D, and then again in the kidneys to give the active form 1,25 dihydroxyvitamin D.

Since the 1920s, it has been clear that vitamin D is critical for bone health and calcium metabolism. Severe vitamin D deficiency results in rickets in children (a disease rarely seen today) and osteomalacia in adults. The concern has been raised that sunscreen use and sun avoidance may decrease vitamin D production, and thus circulating vitamin D levels. However, it is well documented that one can practice rigorous sun protection and not develop rickets or osteomalacia.1,2 Consequently, it was accepted for many years that one could maintain normal levels of vitamin D essentially through diet alone.

In contrast, some physicians have been advocating markedly elevated levels of vitamin D for "optimal health" that may be difficult to obtain casually through our diet. They have raised the alarm that there is a national epidemic of hypovitaminosis D that must be corrected through UVB exposure.

The notion that markedly elevated vitamin D levels could optimize health through the prevention of a range of illnesses comes principally from the observation that some diseases vary by latitude.

Vitamin D - Responsible for a North-South Variance?

As far back as the 1940s,3 it was noted that the incidence of, and/or mortality from, some cancers decreases as one moves south towards the equator. This north-south variance has been noted for breast, colon, and prostate cancers, among others. Since this initial finding for cancer, the same observation has been made for a number of diseases, including multiple sclerosis, hypertension, schizophrenia, and Type II diabetes.

Although a north-south gradient for these diseases is well documented in the literature, these papers do not address in any way what causes this effect. One could imagine many possible explanations, including genetic factors, environmental pollutants in the industrialized north, and diet, etc.

One of the many possible explanations put forward to explain the observed gradient is the fact that there is greater sun exposure as one moves south, resulting in increased exposure to ambient UVB. Some have speculated that this would, in turn, presumably generate higher circulating levels of vitamin D through cutaneous synthesis. Thus, the argument is put forward that increasing vitamin D levels prevents cancers and the other diseases listed above.

The geographic studies really provide little support to the rather extraordinary claim that vitamin D prevents so many serious diseases, yet these claims about vitamin D have found widespread acceptance, including a recent review article in the New England Journal of Medicine.4

Role of Vitamin D in Disease Prevention

Measuring vitamin D levels in various populations could shed some light on the role of vitamin D in disease prevention. Surprisingly, the literature is fairly sparse for such an obvious study on an important topic. Results have been mixed, and no clear trend has emerged; however, even in the studies that find an inverse correlation between vitamin D and disease (ie, higher vitamin D levels correlate with lower disease incidence), no suggestion of causality can be made. Correlation does not show causality.

Higher vitamin D levels, for example, could be an indirect measure of an individual's overall nutritional status, and therefore any health correlates might not be due to an effect of vitamin D itself. Most importantly, such correlations do not suggest that, were patients with low vitamin D to elevate their vitamin D levels, disease would have been prevented.

Prospective interventional trials would be extremely valuable in understanding the role, if any, of vitamin D in disease prevention. Only a handful of such studies have been completed and, again, the results are mixed. In these studies, patients were randomized to receive oral supplementation with vitamin D or placebo. They were then followed prospectively for the development of future disease. Some studies showed a protective effect of oral vitamin D, whereas others showed no effect.

Unfortunately, the question of whether significantly elevating patients' vitamin D levels prevents disease remains unanswered.

The Dangers of Abandoning Sunscreen

Despite the lack of proof, passionate advocates of vitamin D are urging the public to abandon their sunscreen and go to the beach or the tanning salon for UVB exposure.4 This anti-sun-protection message has rapidly caught on, and one often hears internists and family practitioners advising their patients to seek some unprotected sun exposure. How should dermatologists respond?

It is important to let patients know that there is not an epidemic of hypovitaminosis D. Ricketts and osteomalacia are not common diseases. The public's vitamin D levels can be maintained in what was historically considered the normal range through a normal diet. (It is important to point out that "normal" and "optimal" are not the same thing.)

If patients wish to have significantly elevated levels of vitamin D, as is currently the fashion, they can safely supplement their diet with foods rich in vitamin D or through vitamin pills. Oily fish, such as salmon, are a rich source of vitamin D, and oral supplementation of up to 2000 IU per day of vitamin D is safe.

One often hears the simple advice that 10-15 minutes of unprotected sunexposure a few times week on the forearms will produce more than enough Vitamin D. This is not wise public health policy. A young healthy person will make vitamin D from about a quarter of their minimal erythemal dose (MED) exposure. For a fair-skinned person in a sunny area, this may indeed be 10-15 minutes. For a dark-skinned type V or VI, this could require many hours. Furthermore, north of Atlanta, USA, from November to May, the incident UVB exposure is not sufficient for significant vitamin D production.4 Lastly, the elderly have a significantly diminished ability to produce vitamin D in response to any amount of sun exposure. For all of these reasons, intentional sun exposure simply is not a reliable way to elevate vitamin D levels.

Conclusions

There is no justification for intentionally tanning in order to elevate vitamin D levels: excessive UV light is a known carcinogen and cannot be a recommended source of vitamin D.

References

1. Sollitto RB, Kraemer KH, DiGiovanna JJ. Normal vitamin D levels can be maintained despite rigorous photoprotection: six years' experience with xeroderma pigmentosum. J Am Acad Dermatol 1997;37:942-946.
2. Marks R, Foley PA, Knight KR, et al. The effect of regular sunscreen use on vitamin D levels in an Australian population. Results of a randomized controlled trial. Arch Dermatol 1995;131:415-421.
3. Apperly FL. The relation of solar radiation to cancer mortality in North America. Cancer Res 1941;1:191-195.
4. Holick MF. Vitamin D deficiency. N Engl J Med 2007;357:266-281.

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