UVC radiation (200 to 280 nm wavelength) is successfully filtered by the ozone layer, although today,
as the ozone layer is considerably thinner, scientists are concerned that dangerous, short wavelengths
of sun radiation may be reaching Earth in higher amounts than in the past.
Health Benefits of Tanning
The main source of vitamin D in humans is sun exposure to the skin. Research in Denmark in 2007
indicates that a lack of vitamin D may influence the development of autoimmune diseases such as
inflammatory bowel disease, type 2 diabetes, multiple sclerosis, and rheumatoid arthritis (Heller et
al. 2007).
Another recent study blames the prevalence of asthma and allergic diseases on a lack of vitamin D
in human bodies (Litonjua, Weiss 2007; Shaheen 2008). Scientists from Brigham and Women’s
Hospital in Boston hypothesize that as people spend more time indoors, there is less exposure to
sunlight, leading to decreased vitamin D production in the skin. Vitamin D deficiency, particularly in
pregnant women, results in more asthma and allergies in children. Vitamin D has been linked to the
immune system and lung development in babies, and epidemiologic studies show that higher vitamin
D intake by pregnant mothers reduces asthma risk by as much as 40 percent in children
(Litonjua,Weiss 2007).
While many studies avoid mentioning sunscreens when discussing lack of sun exposure, one 2007
study directly links heavy use of sunscreens to lack of vitamin D (Alpert, Shaikh 2007). Researchers
from the University of Nevada—a state that receives a potent dose of sunshine every day!—aren’t
ecstatic about sunscreens. They say that since most sunscreens filter out UVB light, they are inhibiting
vitamin D production. In their 2007 report, they note that long-term vitamin D deficiency leads to
rickets, osteoporosis, type 1 diabetes, cancer, and multiple sclerosis. What’s more, people with
darker complexions have greater difficulty producing vitamin D because melanin acts as an effective
natural sunscreen, requiring longer sun exposure to produce an adequate daily allotment of vitamin D.
But what about skin cancers, a dangerous consequence of inadequate sun protection? As we all
know, skin cancers are associated with sun exposure—yet the same sunlight, through the production
of vitamin D, may protect against some cancers. Scientists from Finland came to a shocking
conclusion: patients with skin cancer have a lower risk of developing other cancers. Take a deep
breath and please read on.
During a massive study of 416,134 cases of skin cancer and 3,776,501 cases of non-skin cancer as
a first cancer, from both sunny countries (Australia, Singapore, and Spain) and less sunny countries
(Canada, Denmark, Finland, Iceland, Norway, Scotland, Slovenia, and Sweden), researchers found
that all second solid primary cancers (except skin and lip) after skin melanoma were significantly
lower for the sunny countries than in the less sunny countries (Tuohimaa et al. 2007). In sunny
countries, the risk of a second primary cancer after nonmelanoma skin cancers was lower for most of
the cancers except for lip, mouth, and non-Hodgkin’s lymphoma. Scientists concluded that vitamin D
production in the skin seems to decrease the risk of several solid cancers, especially stomach,
colorectal, liver and gallbladder, pancreas, lung, female breast, prostate, bladder, and kidney
cancers. The apparently protective effect of sun exposure against second primary cancer is more
pronounced after nonmelanoma skin cancers than melanoma, which is consistent with earlier reports
that nonmelanoma skin cancers reflect lifelong, cumulative sun exposure, whereas melanoma is