Edible Skin Care—Sun Protection from the Inside Out

A Nature article “Edible skin care” underscored an opportunity provided by the skin’s rapid turnover. Our entire outer layer of skin is completely regrown every month from the nutrients we provide it, so we are what we eat not just years down the road, but on a month-to-month basis. For example, the amount of vitamin C we eat maps directly onto the amount of vitamin C we have in our skin.

Take skin frailty for example. Skin atrophy with age is not just a cosmetic issue, but can result in skin tears, bruising, and itching. A cross-sectional study of dietary intake and skin frailty found that dietary patterns characterized by higher vegetable and fruit intake were associated with better skin condition. To test the effects of greens, Korean researchers randomized women to one of two doses of chlorophyl (equivalent to up to a few tablespoons (29.60 ml) of cooked spinach a day). After three months, skin biopsies showed a significant increase in collagen production, accompanied by an increase in skin elasticity and a decrease in facial wrinkles. This may have been due in part to an “inside-out” sunscreen effect, as less DNA damage was noted after the same degree of UV radiation. Unfortunately, these were all just comparisons to baseline, as there was no control arm included. Still, this is the kind of evidence cited by dermatology journal commentaries with titles like “Eat Plenty of Green Leafy Vegetables for Photoprotection: Emerging Evidence.” (Photoprotection is protection against the sun.)

There have been placebo-controlled randomized trials. Compared to placebo, ten months (but not five) of an extract of curly kale caused a significant improvement in a noninvasive measure of skin collagen status. The researchers concluded “a healthy lifestyle including a diet rich in carotenoids is the best prevention strategy against premature skin aging.”

Randomized, double-blind, placebo-controlled clinical trials also found apple extracts can protect the skin against the sun after 12 weeks, as can a combination of rosemary and grapefruit extracts after just 2 weeks, though a blackcurrant juice drink for 6 weeks or a pomegranate extract for 4 weeks did not.

What about whole foods? Researchers burned the butts of twenty women with a UV lamp before and after half of them ate three tablespoons (44.40 ml) of tomato paste a day for three months. There was significantly less DNA damage in the derrieres of those who had been eating the tomatoes, as well as a reduction in the collagen-eating enzyme that plays a role in skin aging activated by UV-induced oxidative stress. In mice, eating tomatoes translates into fewer UV-induced skin cancers, but no such long-term studies have been performed in people.

DNA is damaged directly by UV-B rays, whereas the bulk of UV radiation from the sun—UV-A rays—damages DNA indirectly by producing free radicals that deplete the antioxidant levels in our skin. Dietary tomato paste protects against UV-induced skin redness in humans. If we eat a lot of anti-oxidant rich food, such as tomato paste, even just ten weeks before swimsuit season (but not four), we can reduce the redness of a sunburn by 40 percent. Eating grapes may also cut down on UV-induced DNA damage and inflammation. It’s like we have built-in sunscreen in our skin. Now, this isn’t as good as a high SPF sunblock, and we shouldn’t be sunbathing in the first place, but damage occurs every time we are exposed to the sun and much of that exposure occurs when our skin is otherwise unprotected. Just giving people supplements containing the same amount of the red pigment lycopene failed to have a significant effect, suggesting it’s the constellation of antioxidant constituents in whole tomatoes working together.

An excellent example of this nutrient synergy is the fact that even mega-doses of vitamin C or vitamin E alone have no significant effect on photoprotection (skin defense from UV rays), but when combined they increase the UV radiation dose needed to cause the same redness by more than 75 percent. Antioxidants often work together. Vitamin C, for example, regenerates vitamin E once it becomes oxidized itself. However, some carotenoids can stand on their own. Giving people the equivalent of one to two daily servings of dark green leafies’ worth of lutein and zeaxanthin significantly improves skin hydration, elasticity, and photoprotection starting within just two weeks.

Beta carotene works too. A meta-analysis of seven randomized controlled trials found that a daily dose as low as a cup (240 g) of sweet potatoes’ worth protects your skin from sunburn, but it takes a minimum of 10 weeks to sufficiently build up in your skin. Skin biopsies also show that diet-relevant doses of beta-carotene can boost collagen production four-fold and decrease UV-induced DNA damage by 30 percent, combined with an improvement in facial wrinkles and skin elasticity over a period of three months. There was no control group, though, and a much larger, longer study found that the same dose of beta-carotene failed to affect skin aging over four years’ time compared to placebo.

A randomized, double-blind, placebo-controlled trial of coenzyme Q10 found it didn’t provide any UV protection, but it was able to reduce crow’s feet wrinkles by about 10 percent compared to placebo within 12 weeks, with no significant difference reported between groups getting a low dose (50 mg a day) and high dose (150 mg a day).

Topical sunscreens and dietary photoprotection from foods like greens and sweet potatoes represent complementary strategies for safeguarding our skin. Sunscreens have the advantage of working almost immediately and offering much stronger shielding. Produce protection builds up slowly over weeks and only achieves an SPF (sun protection factor) of 4, compared to 10 to 40 or even higher sun protection factor with typical sunscreens. On the other hand, sunscreens have to be deliberately applied in sufficient amounts with sufficient coverage (including all the hard-to-reach places), and then still can rub or sweat off, whereas the protection from plants is ever-present and built-in all over. Combined, they naturally complement each other.