by Craig Weatherby
Moderate sun exposure seems to reduce the overall risk of cancer, probably thanks to UV-induced creation of vitamin D in the skin.
Last year, we wrote about the exaggerated cancer risks of sun exposure—and the long-overlooked anti-cancer benefits of sun-generated vitamin D—see “Cancer Society's Anti-Sun Ads Decried as Deceptive.”
On a related front, recent years have witnessed a plethora of studies linking diet to protection against sun-induced skin damage, including burning, wrinkling, and pre-cancerous DNA changes.
For example, higher intake of omega-3s—and lower intake of competing, pro-inflammatory omega-6 fats—appears to blunt the adverse effects of overexposure to strong sunlight.
(Dermatologist Nicholas Perricone, M.D., deserves credit for bringing the “cosmeceutical” effects of dietary omega-3s to public attention, and for identifying wild Salmon as their healthiest food source. See “Fish Fats Called Credible Foes of Skin Aging and Skin Cancer.”)
And a fast-growing roster of research results suggest that antioxidant-rich vegetables, fruits, teas and plant extracts can reduce damage to skin cells caused by UV sunrays.
Aussies' study identifies food allies and foes
In 2001, Australian researchers published the results of a population study designed to test the proposition that food-borne antioxidants might blunt UV-induced skin damage.
They looked for correlations between dietary habits and the extent of skin wrinkling in older people of various ethnic backgrounds living in Greece, Sweden, and Australia.
Their reported results supported the food-as-sunscreen hypothesis, and pinpointed some helpful and harmful foods:
“…a high intake of … olive oil, legumes, fish, vegetables and cereal appeared to be protective [against skin damage]… In contrast, a high intake of meat, sugar and its products and [full-fat, unfermented] dairy products appeared to be adverse.”…This study illustrates that skin wrinkling… may be influenced by the types of foods consumed” (Purba MB et al. 2001).
The specific foods linked to reduced skin wrinkling included sardines, green leafy vegetables, beans, asparagus, celery, vegetable juice, cherries, grapes, melon, fruit salad, jam, multigrain bread, and somewhat surprisingly, cheese, yogurt, and non-fat milk.
The Aussies found particularly strong correlations between reduced skin damage and higher intake of three foods rich in antioxidants: prunes, apples, and tea.
Their conclusion seems reasonable: “…for skin to be an effectively functional organ, it may need to be nourished in a protective way which allows light exposure without damage” (Purba MB et al. 2001).
Tomato-rich diets seen to decrease skin damage
Two years ago, German researchers reported the positive results of a small clinical trial in which they fed some subjects tomato paste, and found that this dietary regimen reduced sun-induced damage to skin (Stahl W et al. 2006).
New clinical findings from Britain repeat the positive results of the German research and support the hypothesis that diets high in antioxidant-rich plant foods help protect the skin from damage induced by UV sunrays.
The UK team was led by Professor Lesley Rhodes, M.D., Ph.D., who also conducted the research mentioned above concerning the opposite effects of omega-3 and omega-6 levels with regard to skin protection from sun (Rizwan M et al. 2008).
Scientists from the Universities of Newcastle and Manchester recruited 20 people and randomly assigned them to receive one of two supplemental food prescriptions daily for three months:
- Two ounces (five tablespoons or 55 grams) of tomato paste plus 10 grams (one tablespoon or 1/3 oz) of olive oil*
- Olive oil* only
The volunteers' skin was exposed to UV light at the beginning and end of the three-month study.
At the end of the trial, the tomato paste group had enjoyed 33 percent more protection against sunburn, compared with the olive-oil-only group.
This level of protection was equivalent to a sunscreen with a sun protection factor (SPF) of 1.3.
While this small SPF is only 1/10 that of a typical SPF 15 sunscreen, the one-third reduction in burn risk observed by the Brits is very substantial.
In addition to this reduced burn risk, skin samples from the volunteers in the tomato group had significantly higher skin levels of pro-collagen… the protein that gives skin its structure.
The British team attributed the protective benefits of tomato paste to lycopene: a carotene-class antioxidant and red pigment known to neutralize the oxygen radicals created by exposure to UV sunrays.
The researchers told attendees at the 2008 meeting of the British Society for Investigative Dermatology that lycopene appears to reduce damage to DNA in the mitochondria (energy factories) of skin cells.
Anything that protects skin cells' mitochondrial energy factories and their DNA is likely to enhance skin health and exert an anti-aging effect.
Cocoa, tea, grapes, and berries appear protective
Lycopene-rich tomato paste and sauce aren't the only foods that may offer potent protection against sun damage to skin.
Foods rich in flavanols—the family of flavonoid-type antioxidants found most abundantly in cocoa and tea but also amply in berries—show protective effects in laboratory and clinical studies.
In 2006, German researchers reported the encouraging results of a study in which women consumed either a flavanol-rich or a flavanol-poor cocoa powder dissolved in water daily for 12 weeks (Heinrich U et al. 2006).
Following exposure of selected skin areas to a sun-simulating lamp, UV-induced reddening was significantly decreased in the women who drank the flavanol-rich cocoa—by 15 percent and 25 percent after 6 and 12 weeks of treatment, respectively, whereas no change occurred in the group drinking the flavanol-poor cocoa.
And compared with the women drinking flavanol-poor cocoa, the women in the high-flavanol-cocoa group enjoyed increased blood flow in their skin, increased skin density and moisture, and a significant decrease in skin roughness and scaling.
(Most commercial cocoa is treated with alkali—a process called “Dutching”—to make it a bit less bitter and give it a darker color. Dutching destroys a majority of the flavanols in cocoa, so look for a raw, un-Dutched brand. Our extra-dark chocolate is made from un-Dutched cocoa.)
Likewise, many cell and animal studies have shown that green tea—which contains flavanol antioxidants just like those in cocoa—offers similar protection against sun-induced damage: beneficial effects that researchers call “photoprotection”.
These excerpts from two relevant research reviews tell the tale:
- “…green tea and/or some [of its] constituents can offer some protection against UV-induced DNA damage in human cell cultures and also in human peripheral blood samples taken post-tea ingestion (Morley N et al. 2005).
- “...green tea polyphenols are photoprotective in nature, and can be used as pharmacological agents for the prevention of solar UVB light-induced skin disorders including photoaging, melanoma and nonmelanoma skin cancers... (Katiyar SK 2003).
Why would plant foods deter sun damage to skin?
Solar radiation creates unstable oxygen compounds called “free radicals” (or “oxygen radicals”) when it penetrates our skin.
These light-generated oxygen radicals grab electrons from any nearby molecules, including the fatty acids in cell membranes. The resulting “oxidative damage” resembles the process by which oxygen rusts metal.
In turn, the victimized molecules become unstable and initiate a chain of events in which molecules grab electrons from their neighbors.
The skin is at relatively high risk of damage from sunlight-generated oxygen radicals for at least two reasons.
- Skin is bathed in ambient oxygen
- Skin has high levels of oxygen by virtue of its rich blood flow
This damaging cycle only ends if and when the body's antioxidant defense system quenches the fire by “scavenging” the oxygen radicals spawned by UV rays penetrating the skin.
Oxidative damage to epidermal cells and underlying connective tissue manifests as wrinkled, leathery, sagging skin.
Bodily antioxidants found in the skin must be replaced continuously in order to keep sunlight-induced free radicals from accelerating skin aging and causing cancer.
And it's looking more and more as though internal and dietary antioxidants function independently but synergistically to provide what researchers call photoprotection: a term that covers the free-radical-neutralizing and anti-inflammatory effects of antioxidants.
Do dietary antioxidants reduce sun-induced damage?
Human, test tube, and animal studies indicate that dietary antioxidants can reduce two visible markers for UV damage to the skin:
- Reddening, which is an immediate response to sunburn or overexposure
- Wrinkles, which are a long-term result of sun-induced damage to the collagen and elastin that give skin its structure and resiliency
And as one research team wrote, “The most promising results were obtained in studies combining several compounds, often resulting in synergism of the protective effects” (Steenvoorden DP et al. 1997; Fuchs J, Kern H 1998).
They were referring to studies employing supplemental antioxidant enzymes and vitamins, but in addition to those compounds, tea and colorful plant foods—such as berries, grapes, peppers, red cabbage, and cocoa—provide a rich variety of flavonoid-type antioxidants.
In addition to being potent antioxidants, many of the flavonoids in plant foods also dampen counterproductive inflammatory responses to sun damage—and inflammatory food factors such as sugars and “browned” meats or breads—via their influence on the cellular genetic switches called nuclear transcription factors.
In fact, the influences of flavonoids on our genes may be more important to sun protection, versus the uncertain antioxidant effects that dietary flavonoids exert in living people.
(Flavonoids exert clear antioxidant effects in test tubes, but the extent of their antioxidant effects in human bodies remains unclear.)
Everything we know so far indicates that their rich blends of antioxidant vitamins and flavonoids make plant foods promising allies in the body's fight to prevent sun-induced tissue and DNA damage.
Needless to say, neither tomato products nor a diet high in colorful plant foods can replace sunscreen, when it comes to protecting against overexposure to strong sun.
But it looks as though regular, abundant consumption of antioxidant-rich plant foods may well enhance our skin cells' ability to resist the cumulative, long-term sun-induced damage that leads to wrinkles, sagging, and heightened cancer risk.
- 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 Dec;25(9):1006-12.
- Fuchs J, Milbradt R. Antioxidant inhibition of skin inflammation induced by reactive oxidants: evaluation of the redox couple dihydrolipoate/lipoate. Skin Pharmacol. 1994;7(5):278-84.
- 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.
- Greul AK, Grundmann JU, Heinrich F, Pfitzner I, Bernhardt J, Ambach A, Biesalski HK, Gollnick H. Photoprotection of UV-irradiated human skin: an antioxidative combination of vitamins E and C, carotenoids, selenium and proanthocyanidins. Skin Pharmacol Appl Skin Physiol. 2002 Sep-Oct;15(5):307-15.
- Heinrich U, Neukam K, Tronnier H, Sies H, Stahl W. Long-term ingestion of high flavanol cocoa provides photoprotection against UV-induced erythema and improves skin condition in women. J Nutr. 2006 Jun;136(6):1565-9.
- Ikeda S, Toyoshima K, Yamashita K. Dietary sesame seeds elevate alpha- and gamma-tocotrienol concentrations in skin and adipose tissue of rats fed the tocotrienol-rich fraction extracted from palm oil. J Nutr. 2001 Nov;131(11):2892-7.
- Katiyar SK, Elmets CA. Green tea polyphenolic antioxidants and skin photoprotection (Review). Int J Oncol. 2001 Jun;18(6):1307-13. Review.
- Katiyar SK. Skin photoprotection by green tea: antioxidant and immunomodulatory effects. Curr Drug Targets Immune Endocr Metabol Disord. 2003 Sep;3(3):234-42. Review.
- Lasheras C, Gonzalez S, Huerta JM, Lombardia C, Ibañez R, Patterson AM, Fernandez S. Food habits are associated with lipid peroxidation in an elderly population. J Am Diet Assoc. 2003 Nov;103(11):1480-7.
- Mittal A, Elmets CA, Katiyar SK. Dietary feeding of proanthocyanidins from grape seeds prevents photocarcinogenesis in SKH-1 hairless mice: relationship to decreased fat and lipid peroxidation. Carcinogenesis. 2003 Aug;24(8):1379-88. Epub 2003 Jun 5.
- Morley N, Clifford T, Salter L, Campbell S, Gould D, Curnow A. The green tea polyphenol (-)-epigallocatechin gallate and green tea can protect human cellular DNA from ultraviolet and visible radiation-induced damage. Photodermatol Photoimmunol Photomed. 2005 Feb;21(1):15-22.
- Purba MB, Kouris-Blazos A, Wattanapenpaiboon N, Lukito W, Rothenberg EM, Steen BC, Wahlqvist ML. Skin wrinkling: can food make a difference? J Am Coll Nutr. 2001 Feb;20(1):71-80.
- Rizwan M, Rodriguez-Blanco I, Harbottle A, Birch-Machin M, Watson REB, Rhodes LE. Lycopene protects against biomarkers of photodamage in human skin. (2008) British Society for Investigative Dermatology Annual Meeting. British Journal of Dermatology 158 (4), 874–912 doi:10.1111/j.1365-2133.2008.08486.x
- Sharma SD, Meeran SM, Katiyar SK. Dietary grape seed proanthocyanidins inhibit UVB-induced oxidative stress and activation of mitogen-activated protein kinases and nuclear factor-kappaB signaling in in vivo SKH-1 hairless mice. Mol Cancer Ther. 2007 Mar;6(3):995-1005.
- Sies H, Stahl W. Nutritional protection against skin damage from sunlight. Annu Rev Nutr. 2004;24:173-200. Review.
- Stahl W, Heinrich U, Aust O, Tronnier H, Sies H. Lycopene-rich products and dietary photoprotection. Photochem Photobiol Sci. 2006 Feb;5(2):238-42. Epub 2005 Aug 12. Review.
- Steenvoorden DP, van Henegouwen GM. The use of endogenous antioxidants to improve photoprotection. J Photochem Photobiol B. 1997 Nov;41(1-2):1-10. Review.
- Thiele JJ, Schroeter C, Hsieh SN, Podda M, Packer L. The antioxidant network of the stratum corneum. Curr Probl Dermatol. 2001;29:26-42. Review.