Skin Damage from Solar Radiation
Growing Role for Supplements in Protection
Against Sun-Damaged Skin
Jim English
Over the past few months night gazers
across North America have been treated to the stunning light
displays of the aurora borealis, with sightings being reported
as far south as the Mexico border. The unusual and unexpected
appearance of northern lights is the result of a stupendous
outburst of radiation as sun reaches a peak in its eleven-year
solar cycle. This period of activity, notable for the passage of
dark spots across the surface of the sun, serves to remind us
that our local star -- provider of light and heat for the earth
-- is the source of dangerous and potentially life-threatening
radiation that causes sunburns and cancer. For millions of
Americans the reminder may come too late.
Photoaging
What we think of as visible light is actually a spectrum
composed of over 1,500 different wavelengths that includes
ultraviolet (UV) radiation. Short-term exposure to UV rays can
result in a tan or sunburn, depending on length of exposure,
skin color and other genetic factors. Prolonged exposure to
ultraviolet A (UVA) or ultraviolet B (UVB) increases photoaging,
including wrinkles and hyperpigmentation that becomes more
evident with advanced age. (1) UV radiation at high doses is
responsible for increased incidence of skin cancer, the most
common form of human cancer.
Skin Cancer
Many skin tumors are not malignant, and in time may
spontaneously regress. Examples of benign tumors include moles,
seborrheic keratosis keratoacanthoma, and the often premalignant
actinic keratosis. Malignant tumors include basal cell
carcinoma, squamous cell carcinoma and malignant melanoma. (2)
More than 1.3 million cases of basal cell and squamous cell skin
cancer will be diagnosed this year.
Basal Cell Carcinoma
Basal cell carcinoma, the type of skin cancer that struck former
President Bill Clinton last year, is one of the most common --
accounting for about 75 percent of all cases -- and most curable
forms of skin cancer. Men are more than twice as likely as women
to get basal cell cancers. Exposure to the sun and having fair
skin are significant risk factors for both basal cell carcinoma
and the more deadly malignant melanoma. Basal cell carcinoma
begins in the epidermis, the top layer of skin, usually on the
neck and head -- areas that are most exposed to direct sunlight
or previously burned. Lesions are usually smooth, surrounded by
a pearly border that may be pigmented or have an ulceration in
the center. Lesions grow slowly, rarely spread into other parts
of the body (metastasize) and rarely cause death. Treatment for
basal cell carcinoma involves surgical removal, freezing or
local chemotherapy.
Squamous Cell Carcinoma
Squamous cell carcinoma is a cancer that can affect both skin
and mucous membranes. Often occurring in sun exposed or burned
areas, lesions appear as rough scaly nodules that can ulcerate
and metastasize. The cancerous keratinocyte cells often extend
down into the dermis, requiring surgical removal and the
possible removal of enlarged lymph nodes for all but the
smallest of lesions.
Malignant Melanoma
Malignant melanoma, the form of skin cancer that Arizona Senator
John McCain was diagnosed with on the campaign trail last year,
is the most serious and deadly form of skin cancer. Melanoma is
increasing at an alarming rate. Ten years ago chances of
developing malignant melanoma were 1 in 250; today estimates
that an individual will
have malignant melanoma are 1 in 70. In raw numbers, nearly
50,000 cases of melanoma will be diagnosed in the United States
this year. And while melanoma accounts for just four percent of
skin cancer cases, it causes 79 percent of skin cancer deaths,
according to the American Cancer Society.
Risk of developing melanoma increases with sun exposure,
particularly early childhood sunburns. While in its earliest
stages melanoma may only be present on the surface of the skin,
it is a highly invasive cancer that spreads easily. Prognosis is
dependent on the depth of invasion of the tumor; therefore early
detection and removal are
critical.
Nutritional Protection
Solar radiation is one of the most important environmental
stress agents for human skin, causing sunburn, premature skin
aging, and skin cancer. (3) Using sunscreens, staying in the
shade and covering exposed skin are still among the best methods
for protecting skin. Additionally, research now indicates that
several nutrients and antioxidants can aid in protecting and
healing damaged skin and may contribute to lowering the risk of
developing skin cancer.
Green Tea
Green tea contains natural antioxidant polyphenolic compounds
known as epicatechins. Researchers have shown that green tea
polyphenols -- taken orally or applied topically -- exert
photoprotective effects that inhibit ultraviolet
radiation-induced skin tumors (tumorigenesis). Studies have also
shown that green tea extract possesses anti-inflammatory
activity, protecting against ultraviolet (UV) light-induced skin
inflammation (erythema). (4) The major polyphenolic
chemopreventive constituent in green tea responsible for these
biochemical or pharmacological effects is
(-)-epigallocatechin-3-gallate (EGCG).
When researchers tested green tea extracts in animal models they
found that these polyphenolic compounds afforded protection
against chemical carcinogenesis and photocarcinogenesis in mouse
skin. In similar experimental studies with human skin, green tea
polyphenols again demonstrated anti-inflammatory and
anticarcinogenic
properties. (5)
Antioxidants
When sunlight strikes exposed skin the resulting cascade of free
radicals causes damage to skin tissues, reduces elasticity and
contributes to the formation of age spots,
wrinkles, increasing the risk of developing skin cancer. In
clinical trials, a number of antioxidants, including carotenoids
and vitamins E and C, have been found to be capable of
scavenging reactive oxygen species generated during
photooxidative stress caused by sunlight.
Vitamin C and E
In one prospective, randomized, placebo-controlled study, a
group of 40 healthy volunteers were given either 1] vitamin E
(as alpha tocopherol), 2] vitamin C (as ascorbic
acid), 3] a combination of both E and C, or 4] a placebo. After
fifty days of supplementation the researchers found that levels
of vitamin E and C were elevated in skin tissue samples from
volunteers receiving either the single or combination
antioxidants. Additionally, when researchers exposed the
volunteers to UV radiation to induce erythema (sunburn), the
combination of C and E together protected the skin and
suppressed the sunburn reaction. (6)
In a second study investigators measured the effectiveness of
oral supplements of vitamin E and C to prevent suppression of
the immune system in skin exposed to photooxidative stress. They
found that the combination of vitamin E and C prevented the
suppression of the local immune response, concluding that the
combination could be exploited for the prevention of solar
radiation-induced skin cancer in an antioxidant intervention
study. (7) These and other studies suggest that vitamin E has a
synergistic effect with ascorbic acid, due to vitamin Cs ability
to recycle vitamin E.
Carotenoids
Researchers from the Arizona Prevention Center, School of
Medicine at the University of Arizona tested the protective
effects of oral carotenoids on skin exposed to UV radiation. The
researchers supplemented 22 subjects with natural carotenoids
for a period of 24 weeks. Daily dosages started at 29.4 mg of
beta-carotene, and 0.36 mg of alpha-carotene and increased to
88.2 mg of beta-carotene, and 1.08 mg of alpha-carotene by the
end of the study. During the test period researchers exposed
small areas (1 cm2) of skin to increasing doses of UV light to
determine the minimal erythema dose (MED), defined as a uniform
pink color with well-defined borders. During natural carotenoid
supplementation, the amount of solar radiation required to
induce erythema increased significantly, suggesting that
supplementation with natural carotenoids may partially protect
human skin from UV-induced erythema. (8)
A second study examining the protective properties of oral
carotenoids found that sunburn was suppressed significantly with
a combination of carotenoids and vitamin E. The
researchers concluded that the antioxidants provided protection
against erythema in humans and were effective in diminishing
sensitivity to ultraviolet light. (9)
Conclusion
Many people reduce their intake of supplements during the
summer. While colds and flu may occur less frequently in warmer
months, excess exposure to sunlight can impair the immune system
and increase risk of cancer. Antioxidants and carotenoids are
just a few of the nutrients that have been shown to shield the
skin from UV radiation and suppress sunburn. Continued intake of
antioxidants and carotenoids, in conjunction with sunscreen and
protective clothing, may pay off in the long run with smoother
unblemished skin and reduced risk of developing skin cancer.
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References:
1. Cerimele D, Celleno L, Serri F. Physiological changes in
ageing skin. Br J Dermatol. 1990; 122 (Suppl 35):13-20.
2. http://www.skin-cancers.net/
3. Biesalski HK, Obermueller-Jevic UC. UV light, beta-carotene
and human skin -- beneficial and potentially harmful effects.
Arch Biochem Biophys 2001 May 1;389(1):1-6.
4. Katiyar SK, Elmets CA.. Green tea polyphenolic antioxidants
and skin photoprotection (Review). Int J Oncol 2001
Jun;18(6):1307-13.
5. Katiyar SK, Ahmad N, Mukhtar H.. Green tea and skin. Arch
Dermatol 2000 Aug;136(8):989-94.
6. Fuchs J, Kern H. Modulation of UV-light-induced skin
inflammation by D-alpha-tocopherol and L-ascorbic acid: a
clinical study using solar simulated radiation. Free Radic Biol
Med. 1998; 25(9):1006-12.
7. Fuchs J, Packer L. Antioxidant protection from
solar-simulated radiation-induced suppression of contact
hypersensitivity to the recall antigen nickel sulfate in human
skin. Free Radic Biol Med 1999 Aug;27(3-4):422-7
8. Lee J, Jiang S, Levine N, Watson RR. Carotenoid
supplementation reduces erythema in human skin after simulated
solar radiation exposure. Proc Soc Exp Biol Med 2000
Feb;223(2):170-4
9. Stahl W, Heinrich U, Jungmann H, Sies H, Tronnier H.
Carotenoids and carotenoids plus vitamin E protect against
ultraviolet light-induced erythema in humans. Am J Clin Nutr
2000 Mar;71(3):795-8
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