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Skin Cancer and Nutritional Supplements
by Jim English
Over the past few months night gazers across North
America have been treated to stunning display of the aurora borealis,
as sightings are reported as far south as the Mexico border. This
unusual and unexpected appearance of northern lights is the result
of a stupendous outburst of radiation during the peak of the 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 — in addition to providing life-giving light
and heat — also produces dangerous, life-threatening radiation
that can cause cancer.
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.
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, 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 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, 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.
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 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)
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.
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 C's ability to recycle vitamin E.
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)
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.
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. |
