Topic of the Month

Sun protection – as important inside as outside

August 1, 2010

Vitamins, carotenoids, minerals and nutritional lipids play important roles in maintaining healthy skin throughout life. Looking after the skin is important in order to maintain a strong barrier between the body and the environment. The right mix of nutrients help keep the skin hydrated, protect it from the ravages of time, and offer protection from the aging effects of the sun.

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The damaging effects of solar ultraviolet (UV) radiation on the skin are well recognized: UV-B radiation affects mainly the thin outer layer of the skin (‘epidermis’), and is responsible for sunburn, the most known form of skin damage. Epidemiological studies suggest that solar UV-B radiation is the primary cause of skin cancer development via damage to the genetic material (DNA). UV-A radiation, on the other hand, penetrates the thicker inner layer below the epidermis (‘dermis’) and plays a substantial role in photo-aging, causing wrinkling and skin roughness.

To prevent skin-damaging effects, the main focus is on avoiding the sun and using sun screens to reduce skin exposure to UV radiation. In addition, micronutrients, especially antioxidants, are known to offer nutritional protection against skin damage from sunlight.

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Vitamins E and C

One of the major underlying causes for skin damage is oxidative stress and the harmful effects of free radicals, which come from both the environment (e. g. UV light) and normal metabolism. Free radicals harm skin cells directly by damaging the genetic material (DNA) and other important parts of skin cells, and also reduce skin cells’ ability to repair themselves. Dietary antioxidants can boost protection against oxidative stress and free radicals in the outer skin layers.

Vitamin E is the most important fat-soluble antioxidant. It is a component of the cell membrane, where the fatty acids are often attacked by free radicals. When a radical attacks, it seems that vitamin E is able to neutralize it and therefore prevent cellular damage. Due to its special chemical structure, vitamin C can regenerate vitamin E and so maintain its antioxidant capacity. Here vitamins once more prove themselves to be team players: Both vitamins together seem to have a protective effect against harmful UV rays. If not enough vitamin E is supplied, skin can also become brittle and crack. Vitamin C also appears to positively influence the healing of skin.

References

  1. Thiele J.J. et al. Vitamin E in human skin: organ-specific physiology and considerations for its use in dermatology. Mol Aspects Med. 2007; 28(5–6):646–67.
  2. Placzek M. et al.; Ultraviolet B-induced DNA damage in human epidermis is modified by the antioxidants ascorbic acid and D-alpha-tocopherol; J Invest Dermatol. 2005; 124:304–307.
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Carotenoids

Beta-carotene is deposited in the skin, where scientists suggest it contributes to the protection of the skin against the effects of UV light exposure. Two underlying mechanisms are mainly discussed: Firstly, beta-carotene prevents the production of particular UV-activated enzymes capable of destroying collagen, which gives skin its strength. Secondly, beta-carotene may act as an antioxidant, decreasing oxidative stress caused by UV-A light, and reducing the redness from sunburn.

Lycopene and lutein are in the first line of antioxidant defense of the skin. They may be able to hinder the break-down of collagen in the skin that can happen after exposure to sunlight.

In this case, micronutrients work more effectively together than alone: The UV protection apparently improves if – in addition to the carotenoidsvitamin E, selenium and zinc are able to deliver their antioxidative properties.

References

  1. Heinrich U. et al. Supplementation with beta-carotene or a similar amount of mixed carotenoids protects humans from UV-induced erythema. J Nutr. 2003; 133(1):98–101.
  2. Palombo P. et al. Beneficial long-term effects of combined oral/topical antioxidant treatment with the carotenoids lutein and zeaxanthin on human skin: a double-blind, placebo-controlled study. Skin Pharmacol Physiol. 2007; 20(4):199–210.
  3. Greul A.-K. et al.; Photoprotection of UV-irradiated human skin: An antioxidative combination of vitamins E and C, carotenoids, selenium and proanthocyanidins; Skin Pharmacol Appl Skin Physiology. 2002; 15:307–315.
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B Vitamins

The B vitamins are needed for skin metabolism and synthesis. Vitamin B6 and B3 (niacin) are required for the synthesis of collagen, which is the protein that gives skin its strength. Vitamin B5 helps the skin maintain its barrier function. Vitamin B7 (biotin) helps skin enzymes function correctly; biotin deficiency can result in an itchy, scaly skin. In addition, vitamin B9 (folic acid), B2 (riboflavin), B6 and B12 are involved in the synthesis and repair of DNA and proteins in skin cells.

It may be that vitamin B3 (niacin) plays an important role in reducing skin cancer risk. It was found that callus-forming cells are more sensitive to light or radiation damage when they lack niacin. Damage to the genetic material (DNA) can no longer be repaired, which causes more and more cells to die. People with niacin deficiencies are more light-sensitive and could have an increased risk of skin cancer.

A positive influence on the skin, as an important part of the immune system, has also been ascribed to vitamin B3. It is thought that UV radiation can suppress the function of immune defense cells in the skin, as well as in the rest of the body. The niacin compound nicotina-mide seems to be in a position to reduce the immunosuppressive effect of sunlight.

References

  1. Kirkland J.B. Niacin and carcinogenesis. Nutr Cancer. 2003; 46(2):110–8.
  2. Yiasemides E. et al. Oral nicotinamide protects against ultraviolet radiation-induced immuno-suppression in humans; Carcinogenesis. 2009; 30(1):101–5.
  3. Damian D.L. Photoprotective effects of nicotinamide. Photochem Photobiol Sci. 2010; 9(4):578–85.
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Vitamins A and D

The vitamins A and D are required for growth and differentiation of skin cells. Vitamin D is generated in the skin in response to sunlight.

Recent research reveals that vitamin D protects against UV-B photo damage and regulates skin immune responses, as well as growth and repair mechanisms. People who protect themselves from the sun are at risk of vitamin D deficiency.

References

  1. Reichrath J. Vitamin D and the skin: an ancient friend, revisited. Exp Dermatol. 2007; 16 (7):618–25.
  2. Bell E. Vitamin D3 promotes immune function in the skin. Nature Rev Immunol. 2007; 7(3):174–75.
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Essential fatty acids

Lipids, especially those from omega-6 fatty acid gamma-linolenic acid-rich oils, play an important role in skin hydration. They can improve skin moisture, elasticity and strength.

The omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are deposited in the outer layer of the skin where they have been shown to increase the skin’s tolerance of UV light.

References

  1. Brosche T. et al. Effect of borage oil consumption on fatty acid metabolism, transepidermal water loss and skin parameters in elderly people. Arch Gerontol Geriatr. 2000; 30(2):139–50.
  2. Calder P.C. n-3 polyunsaturated fatty acids, inflammation, and inflammatory diseases. Am J Clin Nutr. 2006; 83(6):1505–19.