Vitamin D, Tanning and Sunscreen: What Patients Need to Know
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:
- Seek shade when outdoors, and avoid outdoor activities from
10:00 am to 3:00 pm.
- Wear a broad-brimmed hat and protective clothing when
- Apply sunscreen and sunblock regularly, and wear them at all
- 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
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
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
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
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.
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.
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
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
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