More than 1 million cases of skin cancer occur each year in the United States, which makes skin cancer the most common type of cancer that Americans develop.
We should appreciate that this is an emotional topic, especially for dermatologists. First, it is important to embrace the fact that melanomas commonly develop in places where the sun doesn't shine, such as the vulva,2 penis3 and rectum.4 Second, the epigenetics of all chronic diseases are complicated, including melanoma,5 which is why it is inappropriate to equate sun exposure with melanoma or elevated cholesterol with heart disease. Third, while painful sunburns are associated with malignant melanoma, lifetime sun exposure is associated with a decreased risk of malignant melanoma.6
Seems like we have been misled a bit. It turns out that painful sunburns before the age of 20 and lifetime sun exposure are predominantly correlated to squamous-cell carcinoma and to a lesser degree with the most common type of skin cancer, basal-cell carcinoma.6 In other words, the most common type of skin cancer, basal-cell carcinoma, is least associated with sun exposure.6
Sun Exposure and Skin Health
There is evidence that painful sunburns are clearly unhealthy; in fact, painful sunburns are associated with all forms of skin cancer.6 However, sun exposure is associated with reduced expression of most cancers,8 including melanoma.6-7 Regarding the skin, it seems that sun-derived vitamin D protects the skin against the photo-oxidizing effects caused by the sun.1 In other words, moderate sun exposure is good for our skin and does not appear to cause skin cancer.
Simply stated, we need to avoid the extremist perspective that "sun is bad." The problem is the development of sunburns due to prolonged exposure, which means that we should be encouraged to pursue healthy sun exposure. In other words, it is OK to get a tan, but burning should be avoided. Instead, Americans have been scared out of the sun and are urged to venture out only if we are slathered in sunscreen, both of which are known to promote vitamin D deficiency.9
Does Diet Combat Sun Exposure?
Research continues to support the view that a healthy, anti-inflammatory diet is preventive against chronic diseases such as diabetes, heart disease and cancer. A commonly appreciated anti-inflammatory diet is the traditional Mediterranean diet rich in fish, vegetables and fruit. But what does this have to do with skin health? When it comes to skin, we have been somewhat conditioned to believe that the skin is nourished from the outside by creams and lotions. Rarely is nutrition for skin health a consideration, despite multiple papers published on this topic.11-14
In short, the anti-inflammatory diet that is recommended for primary and secondary prevention of diabetes and heart disease15 is also known to reduce the expression of skin cancer.11-14 Compared with the United States, Australia and New Zealand, Mediterranean countries with high levels of sunlight exposure, including Greece, Spain and Italy, have a substantially lower incidence of skin cancer.11 This may be due to the anti-inflammatory nature of the Mediterranean diet. It turns out that the consumption of large amounts of vegetables and fruit and reduced consumption of pro-inflammatory omega-6 fatty acids, which is characteristic of the Mediterranean diet, is associated with reductions in the negative effects of sun damage, including oxidative, mutagenic, immunosuppressive, and inflammatory responses.11
The Mediterranean diet also appears to modify the risk for developing cutaneous melanoma. According to the authors of a 2008 study, "After careful control for several sun exposure and pigmentary characteristics, we found a protective effect for weekly consumption of fish, shellfish, fish rich in n-3 fatty acids, daily tea drinking, a high consumption of vegetables, in particular carrots, cruciferous and leafy vegetables, and fruits, in particular citrus fruits."12
A Rational Plan for Skin Health
It is extremely important to avoid excessive exposure that leads to sunburns, particularly when we are young. Otherwise, we should take a graded approach to sun exposure based on our skin pigmentation. For especially fair-skinned people, this may mean only 10 minutes without sunscreen. Because it is not normal for humans to spend multiple hours at the beach lying in the sun, after brief sun exposure, the use of sunscreen is required and a beach umbrella is recommended.
For the average Caucasian individual, it takes only 30 minutes of summer sunbathing to produce 20,000 IU of vitamin D.16 Viewed another way, 1 minimal erythemal dose causes a slight pinkness to the skin and is equivalent to ingesting approximately 20,000 IU of vitamin D.17 Substantially longer time is required for darker-skinned individuals to generate such levels, especially very dark-skinned African Americans.18 In a Minnesota-based study, 100 percent of African Americans, East Africans, Hispanics, and American Indians had deficient levels of serum 25(OH)D.19 Supplementation with vitamin D is recommended for individuals who cannot get adequate sun exposure.
While diet may not typically be considered to influence skin health, the evidence suggests the exact opposite. In addition to healthy sun exposure, we must eat a skin-protecting anti-inflammatory diet. For the average person, this means the avoidance of sugar, flour and refined oils, and substantially increased consumption of vegetables and fruit, which provide vital antioxidants and phytonutrients.
- Bikle DD. Vitamin D receptor, UVR, and skin cancer: a potential protective mechanism. J Invest Dermatol, 2008;128:2357-2361.
- Moan J, Porojnicu AC, Dahlback A, Grant WB, Juzeniene A. Where the sun does not shine: is sunshine protective against melanoma of the vulva? J Photochem Photobiol, 2010; Mar 12 [Epub ahead of print].
- Betti R, Menni S, Crosti C. Melanoma of the glans penis. Eur J Dermatol, 2005;15(2):113-15.
- Kim KW, Ha HK, Kim TK et al. Primary malignant melanoma of the rectum: CT findings in eight patients. Radiology, 2004;232(1):181-86.
- Kyrgidis A, Tzellos TG, Triardis S. Melanoma: stem cells, sun exposure and hallmarks for carcinogenesis, molecular concepts and future clinical implications. J Carcinogenesis, 2010;9:3
- Kennedy C, Bajdik CD, Willemze R, de Gruijl FR, Bavinck JS. The influence of painful sunburns and lifetime sun exposure on the risk of actinic keratoses, seborrheic warts, melanocytic nevi, atypical nevi, and skin cancer. J Invest Dermatol, 2003;120:1087-93.
- Berwick M, Armstrong BK, Ben-Porat L et al. Sun exposure and mortality from melanoma. J Nat Can Inst, 2005;97(3):195-99.
- Grant WB. How strong is the evidence that solar ultraviolet B and vitamin D reduce the risk of cancer? An examination using Hill's criteria for causality. Dermato-Endocrinol, 2009;1(1):17-24.
- Holick MF. Deficiency of sunlight and vitamin D. Brit Med J, 2008:336;1318-19.
- Holick MF, Chen TC. Vitamin D deficiency: a worldwide problem with health consequences. Am J Clin Nutr, 2008;87(suppl):1080S-86S.
- Shapira N. Nutritional approach to sun protection: a suggested complement to external strategies. Nutr Rev, 2010;68(2):75-86.
- Fortes C, Mastroeni S, Melchi F ,et al. A protective effect of the Mediterranean diet for cutaneous melanoma. Int J Epidemiol, 2008;37:1018-29.
- Boelsma E, Hendriks HF, Roza. Nutritional skin care: health effects of micronutrients and fatty acids. Am J Clin Nutr, 2001;73:853-64.
- Ibiebele TI, van der Pols JC, Hughes MC, Marks GC, Williams GM, Green AC. Dietary pattern in assocation with squamous cell carcinoma of the skin: a prospective study. Am J Clin Nutr, 2007;85:1401-08.
- O'Keefe JH, Gheewala NM, O'Keefe JO. Dietary strategies for improving post-prandial glucose, lipids, inflammation, and cardiovascular health. J Am Coll Cardiol, 2008;51:249-55.
- Cannell JJ, Hollis BW. Use of vitamin D in clinical practice. Alt Med Rev, 2008;13(1):6-20.
- Holick MF. Vitamin D deficiency: what a pain it is. Mayo Clin Proc, 2003;78:1457-59.
- Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr, 2004; 80(6 Suppl):1678S-88S.
- Plotnikoff GA, Quigley JM. Prevalence of severe hypovitaminosis D in patients with persistent, nonspecific musculoskeletal pain. Mayo Clin Proc, 2003;78:1463-70.
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