It's hard to
imagine that a vitamin could find itself in the midst of
a controversy, but that is exactly the position vitamin
D is in. The conflict is over risking sun exposure because
of our bodies' need for vitamin D. Vitamin D deficiency
can be a serious health problem, most notably by blocking
the absorption of calcium and phosphorus, causing a chronic
imbalance and bone deterioration. As luck would have it,
sunlight is the most abundant, natural source that helps
our bodies make vitamin D.
You may be unaware that, despite the name, vitamin D
is not actually a vitamin. It is a hormone known as calcitrol.
When your skin is exposed to UVB light, it converts 7-dehydrocholesterol
(present in your skin and bloodstream) into vitamin D,
where the liver and kidneys activate it and it begins
regulating and enhancing the absorption of the minerals
calcium and phosphorus in the body. Since there are very
few foods that naturally contain vitamin D (your best
options are salmon, mackerel, and cod liver oil) most
of us need to rely on either sun exposure or vitamin D-fortified
foods (such as milk and cereals) to ensure we get enough.
Where the controversy takes place is that exposing our
skin to the sun without sunscreen is dangerous, but there
are those that believe sunscreen will cancel out the body's
ability to manufacture vitamin D from sun exposure. This
concern has been expressed from several seemingly reputable
resources (Sources: http://www.intelihealth.com/IH/ihtIH/WSIHW000/325/20932/230636.html?d=dmtContent;
http://www.cnn.com/2003/HEALTH/diet.fitness/10/28/vitamin.D.ap/;
http://www.umm.edu/patiented/articles/what_sunscreen_guidelines_000020_4.htm;
American Journal of Clinical Nutrition, December 2004,
80 (Supplement 6):1678S-88S; and Archives of Dermatology,
December 1988, pages 1802-1804).
On the other side of this argument are proponents for
sun avoidance (myself included) who encourage maintaining
adequate levels of vitamin D through dietary sources and
supplements without skimping on the sunscreen because
sunscreen does not block the amount of UVB radiation needed
to help the body manufacture vitamin D.
An article reprinted in PCI Journal (Volume 12, Number
4, November 2004) refers to comments by dermatologist
Darrell S. Rigel, M.D., clinical professor, New York University
Medical Center in New York City. He reports that as someone
who sees and treats skin cancer patients on a daily basis,
it is appalling to him that anyone in good conscience
would claim that intentional sun exposure, regardless
of length of time, is beneficial. It is a fact that skin
cancer rates are rising and solid science supports the
daily application of sunscreen as the best defense against
the damaging effects of sunlight. The same article also
mentioned a 1997 study published in the Journal of the
National Cancer Institute. It concerned patients with
xeroderma pigmentosa (a disease that causes multiple skin
cancers in persons exposed to even small amounts of UV
radiation). The study demonstrated that these patients,
despite avid sun avoidance and constant UV protection,
still had normal levels of vitamin D over a period of
several years. There is also the issue that no sunscreen,
regardless of active ingredients or how often or liberally
it is applied, can provide 100% protection from UV radiation.
The tiny amount of UVB light that sunscreens do not shield
is enough to begin the synthesis of vitamin D (though
depending on your skin color and climate, supplemental
vitamin D will likely still be necessary).
Further, several large, controlled studies have shown
that vitamin D deficiency does not result from ongoing
regular sunscreen use. Vitamin D supplementation is a
good idea because most people’s diets are naturally deficient
in it, not to mention as we age our bodies' ability to
produce vitamin D naturally diminishes due to the decrease
in 7-dehydrocholesterol (a component in skin that begins
the conversion process for vitamin D). (Sources: The Journal
of the American Osteopathic Association, Volume 103, Number
8, August 2003, pages 3-4; American Journal of Clinical
Dermatology, March 2002, pages 185-191; Dermatology, January
2001, pages 27-30; British Medical Journal, October 1999,
page 1066). Before beginning any new vitamin supplement
program, make sure to consult your physician.