UV protection from meat and animal products
In the last post I looked at the health benefits of sunshine, and in particular the blood pressure lowering effects due to nitric oxide synthesis when UV light interacts with skin stores of nitrites.
I ended with the idea that ‘eating your greens’ might be beneficial, as green leaved vegetables are a major provider of dietary nitrates, which can increase nitrite stores in the skin, enhancing nitric oxide synthesis when you are in the sun, and increasing the blood pressure lowering benefits. However, don’t think this means you should become a vegetarian, because animal products can provide some specific sun-protection factors that enhance your ability to safely photosynthesise.
I unearthed the research below after hearing many anecdotes from people that switched to a Paleo-type diet (no grain, increased animal products) then found that they had an increased sun tolerance – less eye glare and sun burn. Many reported that they could now stay out in the sun longer and were enjoying it more. I had a similar experience myself. This set me wondering if there was any research to explain these anecdotes.
Here is what I found…
Creatine in meat and fish [1,2]
Creatine is a involved in production of the energy molecule ATP. It is present in all vertebrate animals, concentrated in muscles (where rapid energy production is required).
It is not an essential nutrient as the body can manufacture it, but a large amount of the creatine in the body comes directly from the diet – assuming you eat vertebrates that is!
It has UV protective effects in humans:
- Creatine is found in dietary meat and fish (beef, pork, salmon ~ 4g per kilo)
- There are specific creatine transporters in the muscles and the skin – (the skin transporters are a specific adaptation in humans – part of our naked ape evolution).
- Creatine has marked protective effects against oxidative stress and UV-induced damage in the skin, including protecting mitochondrial DNA
- Topical creatine creams appear to be effective in reducing UV damage too (it is added to various skin products for this purpose)
Note: creatine is quickly destroyed by high temperature cooking: so order that steak rare!
Animal fats v vegetable oils
One way in which UV light damages cells is via lipid-peroxidation. This is when UV-induced free-radicals attack cell membranes. Polyunsaturated membrane lipids are especially susceptible. Dietary fats determine the saturation index of body cells. A higher saturation index should be protective against free-radical damage, suggesting that more saturated fat in the diet might be good, but the evidence I found was not very strong. So whilst the two studies below are interesting, they have not been born out convincingly in any human studies I could find.
- Omega-6 PUFAs in model cell membranes increase lipid oxidation, increasing risk of skin cancer, especially melanoma 
- In mice, PUFAs increased melanoma growth at lower dietary levels than did saturated fats 
Among the PUFAs omega-6 (from vegetable oils) tend to be inflammatory, whereas omega-3 (from oily fish and grass-fed meat) are anti-inflammatory. The standard western diet is too high in omega 6 fats because of the prevalence of vegetable oils – something a Paleo diet tries to avoid. The evidence here is stronger – showing increasingly that omega-3 fatty acids are protective against skin cancer, whereas at the other extreme industrial hydrogenated vegetable oils come out particularly badly.
- Omega-3 (EPA and DHA) PUFAs help prevent skin cancer [5,6]
- Trans-fats (from hydrogenated vegetable oils) increases skin UV damage in rats 
Antioxidants from animal products that protect against UV damage
Plant antioxidants are often promoted, but less attention is paid to the antioxidants in animal products, yet many of these are protective against UV skin damage.
- Lutein and zeaxanthin (from egg yolk) provide ‘significant efficacy against light-induced skin damage’ 
- Lutein and zeaxanthin increase skin elasticity, reduce lipid oxidation and photosensitiser action 
- Astaxanthin found in wild salmon, krill, lobster and crab strongly protect skin from UV damage 
- Findings from a 2014 meta-analysis suggest that intake of retinol (vitamin A from animal source, e.g. liver), but not beta-carotene (pre-vitamin A from vegetable sources, e.g. carrots), is significantly associated with reduced risk of melanoma. 
- Sun-exposed parts of the body have been found to benefit most from retinol protection, suggesting that it may act against melanoma by repairing sun-induced skin damage. Again, beta carotene showed no such protection. 
Finally, vitamin D itself is protective against UV damage and cancer formation . Maximising your intake of vitamin D from foods could also help enhance protection before you go out in the sun. The best sources are the oily fish – salmon, mackerel, herrings and sardines – the very same fish that give you the protective omega-3 fats! Vegetarians and vegans
So perhaps these tit-bits go some way to explaining how a Paleolithic diet might enhance your UV protection whilst you soak up the sunshine and photosynthesise some cardio-protective nitric oxide and vitamin D!
Read previous post: Human photosynthesis – beyond vitamin D
- Holger Lenz et al, The Creatine Kinase System in Human Skin: Protective Effects of Creatine Against Oxidative and UV Damage In Vitro and In Vivo. Journal of investigative dermatology, 2005
- Wallimann et al, The creatine kinase system and pleiotropic effects of creatine. Amino acids, Feb 2011
- Polyunsaturated fatty acids partially reproduce the role of melanocytes in the epidermal melanin unit. Cario-André , 2005
- Erikson et al, Dietary fat influences on murine melanoma growth and lymphocyte-mediated cytotoxicity. Journal of the national cancer institute, 1984.
- van der Pols, Serum omega-3 and omega-6 fatty acids and cutaneous p53 expression in an Australian population. Cancer epidemiology, biomarkers & prevention, 2011
- You-Rong Lou et al, Effects of high-fat diets rich in either omega-3 or omega-6 fatty acids on UVB-induced skin carcinogenesis in SKH-1 mice, Carcinogenesis, Jul 2011
- Barcelos RC et al, Cross-generational trans fat intake exacerbates UV radiation-induced damage in rat skin. Food and chemical toxicology, Jul 2014
- Roberts et al, Lutein and zeaxanthin in eye and skin health. Clinical dermatology, 2009
- Rao AR et al, Effective Inhibition of Skin Cancer, Tyrosinase, and Antioxidative Properties by Astaxanthin and Astaxanthin Esters from the Green Alga Haematococcus pluvialis. Journal of Agricultural and food chemistry, Apr 2013;
- Zhang YP et al, Vitamin A intake and risk of melanoma: a meta-analysis. PLoS One Jul 2014
- Asgari MM et al, Association of vitamin A and carotenoid intake with melanoma risk in a large prospective cohort. The journal of investigative dermatology, Jun 2012
- Bikle DD, The vitamin D receptor: a tumor suppressor in skin. Discovery medicine, Jan 2011