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Ultraviolet rays induce mutation and skin cancer

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By David Liu, PHD

Sunday Aug 26, 2012 (foodconsumer.org) -- Ultraviolet light or UV rays including solar UV radiation can induce mutation and skin cancers including melanoma cancer and non-melanoma skin cancers, which many preclinical, clinical and epidemiological studies have demonstrated.  UV rays are actually commonly used to induce mutation in research.

Solar UV radiation induces skin cancers by causing depletion of antioxidant defense system, inflammation, DNA damage, oxidation of lipids and proteins, disturbances in apoptotic machinery, deregulation of signaling pathways, mutation and immunosupression, according to Farrukh Afaq and Santosh K. Katiyar of University of Alabama at Birmingham, AL.

Afaq and Katiyar reported in Nutraceuticals and Cancer that in order to reduce the risk of skin cancer, phytochemicals or chemopreventatives that are able to inhibit these events should be used.

The phytochemicals or photoprotective agents that are bioactive against skin cancer are widely distributed in all types of plants including fruit, vegetables, seeds, flowers, and bark and can be classified into a number of groups of compounds including "polyphenols, flavonoids, isoflavonoids, proanthocyanidins, phytoalexins, anthocyanidins, and carotenoids." 

The authors say in their report the effects of some phytochemicals protective against the UV induced damage or skin cancer have been extensively studied, which include "green tea polyphenols, pomegranate fruit extract, grape seed proanthocyanidins, silymarin, resveratrol, genistein, honokiol, quercetin, delphinidin, curcumin, sulforaphone, lycopene and lutein/zeaxanthin."

All types of mechanisms through which UV rays induce skin cancer have also well studied, which include UV-induced skin inflammation, oxidative stress, immunosuppression, DNA damage/mutation, and deregulation of important cellular signaling pathways.

Although UV rays can induce mutation, which can further lead to the development of skin cancer.  But most skin cancers caused by UV rays are non-lethal.   Vitamin D experts warned that avoiding UV rays like sunshine can lead to vitamin D deficiency, which has been linked to up to 17 types of cancers most of which are much more dangerous than skin cancers.

Usually exposure of the hands and face to the sun for 15 to 20 minutes at the hottest hours of the day should make a person enough vitamin D.  Overexposure is not necessary, and can increase risk of skin cancer.

It should be pointed out that just because ultraviolet rays can induce mutation and cause skin cancer, it does not mean that exposure to UV rays will definitely cause skin cancer.  The dosage is key. As long as the exposure is not excessive and causes any skin damage, there are generally no risk of skin cancer.
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