@Mary Matsui

Ph.D.  Adjunct professor  Columbia University

Estée Lauder Companies Inc. · R&D

This sentence will not be new news to you:  Ultraviolet radiation from the sun has short term effects such as sunburn (a sign of damage to the DNA in your skin cells) and immune suppression, and longer term consequences such as skin cancers, cataracts, and photoaging (dry leathery skin, sagging, pigment spots, and red rough scaly spots called actinic (sun-related) keratoses.  The use of sunscreen is recommended to protect yourself from this damage.

Despite this, many people don’t use sunscreen or don’t use it enough.  There are several reasons for this.  First, the greasy feel of chemical sunscreens is off-putting (typically chemical sunscreens are a combination of two of these: oxybenzone, avobenzone, octisalate, octocrylene, homosalate and octinoxate), and the white semi-opaque nature of physical sunscreens (titanium dioxide and zinc oxide) can be unattractive.  Second, people often just forget to put sunscreen on when they go outside for casual activities (whereas they usually remember to take it to the beach).  People usually don’t put sunscreens on thick enough to prevent all damage either, and some people just need more protection (those with lighter skin, those who will be outside for an extended length of time, and those with rosacea or on certain medications).

For all these reasons, quite a bit of research has gone into finding safe, edible sun protection[1].  Ideally, the ingredients used for this would come from botanicals and ingredients already used as food.  There is quite a bit of appeal for this, as their efficacy does not depend on topical application, and they would be safe and affordable.  Perhaps easier than remembering to apply sunscreen or take you sunscreen with you on outdoor trips, a diet enriched in the right foods or even a pill every day could give you continuous protection and be less harmful to the environment than chemical sunscreens.  Importantly, even a modest degree of photoprotection might lead over time to a significant reduction in skin damage, photoaging and risk of skin cancer. Foods that show promise as photo-protective include red and orange fruits and vegetables, omega-3 fatty acid, cruciferous vegetables, leafy greens and black and green teas.

Foods that have shown the best potential for blocking sun damage are the ones high in antioxidants.  This is because ultraviolet radiation causes oxidative stress, especially the UVA wavelengths.  UVB wavelengths are absorbed by the DNA in your skin cells and lead to cancer-causing mutations.  Exposure to UVA is associated with oxidative stress caused by “reactive oxygen species”, which can lead to cancer, but UVA is even better at photoaging.  This is because UVA penetrates farther down into your skin, and oxidative stress there increases enzymes, like collagenase and elastase, that chew up the skin’s collagen fibers and elastic fibers, which are necessary to maintain smooth, resilient skin.  Oxidative stress clearly plays a role in fine lines, wrinkles, sagging, loss of elasticity.

So, what molecules in food have been shown to be protective against sun damage?  One big category are the carotenoids, which give pigment to orange and red fruits and vegetables and go by names such as lycopene, lutein and beta carotene. Carotenoids are good antioxidants and have been shown to protect the skin against the damage caused by sun exposure[2]. Results from a double-blinded, placebo-controlled, crossover study that looked at oral supplementation with lycopene or lutein showed that those compounds can protect human skin against ultraviolet radiation[3].  

Sweet potatoes, carrots and spinach are rich in beta carotene, another carotenoid that helps decrease the damage done by the sun.  Spinach, green beans and broccoli are also loaded with lutein, another skin-protective carotenoid.

Tomatoes are an excellent source of lycopene, and have been shown to protect against multiple aspects of sun exposure.  In studies, people who ate some tomato paste for two weeks or more showed that they were protected against sunburn, stimulation of enzymes that are linked to wrinkle formation and photoaging, and even a certain kind of DNA damage [4].

Many studies have looked at the protective effects of tea against sun damage by the sun—both the application of tea extracts to the skin [5-8] and the drinking of black and green teas.  This protection has been shown to be primarily from a class of compounds called polyphenols, and these polyphenols have been shown in numerous studies to scavenge reactive oxygen molecules before they can do damage and thereby protect against sun-induced inflammation and immune suppression.  Green tea, which contains the major polyphenol of epigallocatechin-3-gallate (EGCG), has also been shown to protect against ultraviolet radiation induced skin cancer in mice[9].  Raspberries, strawberries and pomegranate contain ellagic acid, another type of sun-protective polyphenol.

Resveratrol is a polyphenolic type of molecule found in the peels and seeds of grapes as well as red wine. The effect of resveratrol as a photoprotection agent is well documented[10, 11].  

Omega-3 fatty acid also stands out for its important role in human biology.  The most common source of omega-3 in the diet is fatty fish like salmon, tuna, herring, and trout.  There are also concentrated commercially manufactured supplements that can be from fish but are often now from blue-green algae. Evidence suggests that omega-3 fatty acid is capable of reducing UV-induced inflammation in human skin, and may be protective against sun induced immunosuppression, skin cancers, photoageing and photosensitivity disorders[12].

Finally, not exactly a food, but a plant, a fern called Polypodium leucotomos, also known as Fernblock® (IFC, Madrid, Spain)has been intensively studied in many human clinical research projects and reported on extensively in scientific journals[13-19].  It has been shown to be safe and has been effective in protecting against sun damage looking at many different endpoints and using numerous model systems.  It has even been shown to be a useful addition to melasma treatment in Asian skin.

There is one good thing about exposure to the sun—it does result in the synthesis of vitamin D, an important vitamin for your body’s health and well-being.  Research now links low vitamin D levels with an increased risk of heart disease and certain cancers, and new evidence shows that the "sunshine" vitamin plays other roles in good health in addition to strong bones.  Clearly, getting enough vitamin D is important to your overall health.  However, you’ve also heard that exposure to sunlight, ultraviolet radiation, leads to photoaging of your skin and is responsible for skin cancer.  

So, if you’re smart and want your older self to really be happy about your younger self, you will practice “safe sun”.  You will stay out of the sun, especially between the hours of 10am and 2pm.  You will find shade and you will use broad-spectrum sunscreen all the time.  That way you can prevent dark age spots, deep lines and leathery-looking skin, help prevent basal cell cancers, squamous cell cancers and lower your risk of melanoma.  To make sure that you get enough vitamin D, you should eat food naturally high in vitamin D such as salmon, tuna, herring, and trout, and you can eat foods that are fortified with vitamin D such as many dairy products, some soy milk, some breakfast cereals and bread.  You can also, of course, take vitamin supplements.

Key points:

· No single method of sun defense gives you total protection.

· Never use tanning beds.

· To keep your skin healthy and youthful you should do as many healthy things as possible, including staying out of the sun, covering up, using broad-spectrum sunscreen, and eating a balanced, varied, nutrient-rich diet with lots of fruits and vegetables.

· Remember to make sure you get plenty of vitamin D either through your diet or with supplements.

· A diet high in fruits and vegetables and low in simple sugar and saturated fats is good for both your heart and your skin.

1. Sondenheimer, K. and J. Krutmann, Novel Means for Photoprotection. Front Med (Lausanne), 2018. 5: p. 162.

2. Stahl, W. and H. Sies, beta-Carotene and other carotenoids in protection from sunlight. Am J Clin Nutr, 2012. 96(5): p. 1179s-84s.

3. Grether-Beck, S., et al., Molecular evidence that oral supplementation with lycopene or lutein protects human skin against ultraviolet radiation: results from a double-blinded, placebo-controlled, crossover study. Br J Dermatol, 2016.

4. Rizwan, M., et al., Tomato paste rich in lycopene protects against cutaneous photodamage in humans in vivo: a randomized controlled trial. Br J Dermatol, 2011. 164(1): p. 154-62.

5. Camouse, M.M., et al., Topical application of green and white tea extracts provides protection from solar-simulated ultraviolet light in human skin. Exp Dermatol, 2009. 18(6): p. 522-6.

6. Elmets, C.A., et al., Cutaneous photoprotection from ultraviolet injury by green tea polyphenols. J Am Acad Dermatol, 2001. 44(3): p. 425-32.

7. Matsui, M.S., The Role of Topical Antioxidants in Photoprotection, in Principles and Practice of Photoprotection, Q.S. Wang and W.H. Lim, Editors. 2016, Springer International Publishing: Cham. p. 361-375.

8. Schwarz, A., et al., Green tea phenol extracts reduce UVB-induced DNA damage in human cells via interleukin-12. Photochem Photobiol, 2008. 84(2): p. 350-5.

9. Katiyar, S., C.A. Elmets, and S.K. Katiyar, Green tea and skin cancer: photoimmunology, angiogenesis and DNA repair. J Nutr Biochem, 2007. 18(5): p. 287-96.

10. Reagan-Shaw, S., H. Mukhtar, and N. Ahmad, Resveratrol imparts photoprotection of normal cells and enhances the efficacy of radiation therapy in cancer cells. Photochem Photobiol, 2008. 84(2): p. 415-21.

11. Flamini, R., et al., Advanced knowledge of three important classes of grape phenolics: anthocyanins, stilbenes and flavonols. Int J Mol Sci, 2013. 14(10): p. 19651-69.

12. Black, H.S. and L.E. Rhodes, Potential Benefits of Omega-3 Fatty Acids in Non-Melanoma Skin Cancer. J Clin Med, 2016. 5(2).

13. Bhatia, N., Polypodium leucotomos: a potential new photoprotective agent. Am J Clin Dermatol, 2015. 16(2): p. 73-9.

14. El-Haj, N. and N. Goldstein, Sun protection in a pill: the photoprotective properties of Polypodium leucotomos extract. Int J Dermatol, 2015. 54(3): p. 362-6.

15. Goh, C.L., et al., Double-blind, Placebo-controlled Trial to Evaluate the Effectiveness of Polypodium Leucotomos Extract in the Treatment of Melasma in Asian Skin: A Pilot Study. J Clin Aesthet Dermatol, 2018. 11(3): p. 14-19.

16. Kohli, I., et al., The impact of oral Polypodium leucotomos extract on ultraviolet B response: A human clinical study. J Am Acad Dermatol, 2017. 77(1): p. 33-41.e1.

17. Murbach, T.S., et al., A 28-day oral toxicology study of an aqueous extract of Polypodium leucotomos (Fernblock((R))). Toxicol Rep, 2017. 4: p. 494-501.

18. Parrado, C., et al., Fernblock (Polypodium leucotomos Extract): Molecular Mechanisms and Pleiotropic Effects in Light-Related Skin Conditions, Photoaging and Skin Cancers, a Review. Int J Mol Sci, 2016. 17(7).

19. Torricelli, P., et al., Protective effects of Polypodium leucotomos extract against UVB-induced damage in a model of reconstructed human epidermis. Photodermatol Photoimmunol Photomed, 2017. 33(3): p. 156-163.