VALLEY — The skin is the largest organ of the human body and a barrier that protects us from microbial pathogens and other damaging elements. The health of our skin is a reflection of our overall health, and the skin’s resilience to sun exposure and outward appearance can be enhanced with high-nutrient foods.

Skin cancer is the most common cancer in the U.S., affecting one out of every five Americans. Ultraviolet radiation from the sun promotes skin aging and cancer via oxidative stress, inflammation, and damage to DNA. Ultraviolet (UV) exposure also leads to alteration of the skin’s structural proteins, causing sagging and wrinkling. Taking proactive measures such as using a safe mineral sunscreen and limiting mid-day sun exposure are crucial to protecting your skin from the sun’s UV rays. Phytochemicals from natural foods can provide an extra source of protection, by enhancing the body’s natural defenses to help prevent sun damage and slow the aging of the skin.

Carotenoids are one class of phytochemicals that offer photoprotection. After we consume carotenoid-rich foods, carotenoids accumulate in the skin, where they oppose UV-induced oxidative stress. Individual carotenoids, mixed carotenoids, and carotenoid-rich whole foods have been shown to have photo-protective qualities that prevent or repair DNA damage to the skin caused by the sun. For example, lycopene, found in tomatoes and pink fruits such as watermelon, grapefruit, and papaya, helps to protect the skin from sun damage. Similar results have been found for lutein and zeaxanthin, found in leafy greens, and beta-carotene, found in yellow and orange vegetables.

In addition to carotenoids, another class of antioxidant nutrients—polyphenols—may have photoprotective actions. There are hundreds of polyphenols, and they are present in most whole plant foods. Polyphenols from cocoa and green tea, for example, have been shown to counteract UV-induced skin damage in human studies.

Wrinkles and other signs of skin aging are related to chronological age but also strongly influenced by UV rays. It is estimated that 80 percent of the visible aging in the face is due to sun exposure. The phytochemical-rich foods that offer sun protection also offer some protection against wrinkles. In one study of older adults, higher intakes of vegetables and legumes and lower intake of dairy and sugar were associated with less visible sun damage. Another study assessed skin aging in middle-aged American women, and found that higher dietary vitamin C intake was associated with fewer wrinkles. In a study of Japanese women that related dietary variables to “crow’s feet” wrinkling, higher intake of green and yellow vegetables was associated with fewer wrinkles. In studies on green tea and cocoa polyphenols, in addition to UV protection, these interventions improved appearance factors such as elasticity, hydration, and softness.

Structural proteins in the connective tissue of the skin are also affected by diet. There is evidence that beta-carotene reduces the levels of one such protein that promotes skin wrinkling. Also, tomato paste supplementation was found to reduce the activity of an enzyme known to degrade structural proteins in the skin, presumably slowing skin aging.

In spite of the well-known damaging effects of the sun on our skin, many of us still perceive a suntan as healthy-looking. Food-derived carotenoids can also affect our skin coloration, and research has shown that carotenoid-colored skin is perceived as healthier and more attractive. In the wild, carotenoids are responsible for the bright feather colors of male birds, which make them more attractive to potential mates. There is a much more subtle, but similar phenomenon in humans. An increase in carotenoid-produced skin coloration was consistently found to be perceived as healthier in people of Caucasian, African, and Asian descent. One interesting study found that people preferred the skin color caused by eating carotenoids over the skin color from a suntan. Another study investigated skin carotenoid coloration changes in response to increased fruit and vegetable consumption. They found that photos of individuals a few weeks after increasing fruit and vegetable intake by three serving per day received higher ratings of health and attractiveness than “before” photos. Furthermore, the improvement in appearance has been shown to be a motivating factor for increasing fruit and vegetable consumption.

Each time the skin is exposed to the sun, some carotenoids are “used up” for their antioxidant activity, so they must be constantly replenished by the diet to maintain the protective effects (smoking and alcohol also deplete carotenoids from skin). Consistently consuming antioxidant-rich plant foods will build up the stores of these protective phytochemicals in the skin. You can even quantify your skin carotenoid levels using a specialized scanner to confirm the accumulation of dietary carotenoids in your skin. I use one of these scanners in my medical practice to confirm and motivate patients to eat a Nutrtarian diet, rich in these colorful phytochemicals. A nutrient-dense, plant rich (NDPR or Nutritarian) diet is designed to be rich in antioxidant phytochemicals and promotes health inside and out, protecting against chronic disease, heart disease and cancer, while at the same time protecting the skin from sun damage while giving a natural, healthy-looking glow.

Dr. Fuhrman is a #1 New York Times best-selling author and a board certified family physician specializing in lifestyle and nutritional medicine. The Eat To Live Cookbook offers over 200 unique disease-fighting delicious recipes and his newest book, The End of Heart Disease, offers a detailed plan to prevent and reverse heart disease using a nutrient-dense, plant-rich (NDPR) eating style. Visit his informative website at DrFuhrman.com. Submit your questions and comments about this column directly to [email protected]