Responses+of+Human+Bodies+to+Sun+Exposure

toc =Introduction =

Sunlight is radiation given off by the Sun that hits the Earth. This electromagnetic radiation is what provides most of the energy required by life. There is much debate about whether sunlight is healthy for you or not. This controversy and its important implications on our health have caused this to be a hot topic of scientific research. This Wiki will begin by exploring research about how the sun interacts with our body to create vitamin D, and how much vitamin D our bodies actually need. We will continue by exploring research into the potential harms the sun poses. Lastly, this Wiki will investigate the effects and usefulness of sunscreen.

=Sunlight and Vitamin D Production =

 Sunlight contains all colors of light inside of it, and it actually peaks in the green visible light. However, studies show that the ultra violet part of the light spectrum is the part that is responsible for vitamin D production in the human epidermis. Researchers tested all common wavelengths of light on human skin and have analyzed how much pre vitamin D is produced by these different wavelengths. This pre vitamin is later used in the body to synthesize vitamin D. What the research found was a clear peak in the UVB range of about 290-315 nanometers. [1] Outside of this range pre vitamin D production quickly falls off. What we can conclude from this is that it is ultra violet rays which are most responsible for the chemical reaction that creates vitamin D in the human body. This figure shows production of 7-dehydrocholesterol to pre vitamin D. [1]

=How Much Sun do Humans Need? =

Sunlight, when it hits our skin, causes a chemical reaction that results in the production of vitamin D in our bodies. The daily recommended dose of vitamin D for people between ages 1 and 71 is 600 IU. [2] Current statistics depict that more than 50% of the world’s entire population is at risk for vitamin D deficiency. [3] The daily recommended dose of vitamin D for people between ages 1 and 71 is 600 IU. [3] A research paper on the subject posits that a person can easily achieve the benchmark vitamin D levels by incidental protected exposure of the face and back of hands to the sun. This exposure must take place three times a week and be long enough to be 25% of the time required to produce sunburn. [4] You can take a daily vitamin or drink two glasses of vitamin D fortified milk or orange juice every day in order to achieve this benchmark level of vitamin D as well. [4] These researchers recommend humans get vitamin D from supplements, as they are not known carcinogens.

=General Trends in Sunlight Exposure =

 A study that took into account 93 subjects with randomized skin pigments, gender, and BMI, shows that sun exposure doesn’t necessarily cause a general increase in the chemicals it is commonly associated with, such as serum 25(OH)D. [5] Serum 25(OH)D is synthesized by your body into pre-vitamin D, which is what your body ultimately uses to make vitamin D. [5] In this group of young adults, there was substantial variability with respect to serum 25(OH)D despite abundant sun exposure. The data for the presence of Serum 25(OH)D does not follow an obvious correlation when compared with the graph to the right. [5] This lends credence to the idea that when people in general are considered, there is not an obvious rate at which our skin receives UVB to produce vitamin D. People with different genetics, particularly skin pigmentations, all have different reactions. Humans all need similar amounts of vitamin D, but there are not strong general trends relating sun exposure to vitamin D across all skin pigmentations.

=Sunlight and Skin Cancer =

People can get skin cancer from overexposure. One study found that a sunburn leaves the skin with apoptotic cells. These are cells that are essentially dead, but they can keep reproducing, creating things such as tumors inside the body. To produce this result, researchers beamed mice with UV light, which is the harmful component of sunlight. Twenty-four hours later, sunburn cells were present in the skin of all of the tested mice. After observing the cells, the researchers saw these cells to have every physical indicator of apoptotic classification. [6] The skin of a human is chemically and biologically similar to that of the mice, so it a fair extrapolation to link these results to the skin of humans. What we can easily see from this study is that sunburns can indeed induce cells to become cancerous, being one potential harm from over exposure to the sun.

=Sunlight and Age-Related Macular Degeneration (AMD) =

Researchers conducted a long-term study of over 2,000 subjects over a 20-year term. During this time the subjects had 5 in depth ocular examinations. At the end of the study the research showed that the presence and severity of AMD were higher in people with high levels of sun exposure. However, after multiple comparisons, high sun exposure did not seem to remain significant. The significant variables seemed to be eye and hair color. With lighter hair and colored eyes making somebody more likely to develop AMD symptoms. This study shows that sunlight exposure is not necessarily a significant factor when it comes to developing AMD. [7]

=Vitamin D Over Production: = <span style="font-family: Arial,Helvetica,sans-serif;">

<span style="font-family: Arial,Helvetica,sans-serif;">Vitamin D plays an important role in bone formation and mineralization. A deficiency in vitamin D can lead to a number of issues including but not limited to: rickets, osteomalacia, and osteoporosis. On the contrary, a body that receives too much vitamin D, or produces it over actively (hypervitaminosos D), is just as problematic. Researchers used genetically altered mouse models to analyze the effects on mice due to high vitamin D activities. The results show that hypervitaminosos D can result in pre aging effects, ultimately yielding a shorter life span. Mice without hypervitaminosos D were used as a control for understanding this phenomenon.

<span style="font-family: Arial,Helvetica,sans-serif;">The figure to the right depicts an example of the two mice different mice side by side, both of these mice are 8 weeks old. The mouse on the left is the control mouse, containing average levels of vitamin D. Note how it is much larger than the mouse on the right, which has levels of vitamin D far above average. The smaller mouse also has a significantly reduced life span. This study shows that too much vitamin D is most certainly a health hazard as it can cause pre aging effects. [8]

=<span style="font-family: Arial,Helvetica,sans-serif;">The Role of Sunscreen =

<span style="font-family: Arial,Helvetica,sans-serif;"> <span style="font-family: Arial,Helvetica,sans-serif;">A study tested almost 600 people of the age of 40 over the period of one summer, making half of them apply sunscreen daily and the other half apply a fake sunscreen. They measured the amount of solar keratoses, which are brown sunspots on the skin that are related to cancer, in order to quantify their findings. The results showed that the mean number of solar keratoses increased by 1.0 per subject in the base-cream (fake sunscreen) group, and decreased by 0.6 in the sunscreen group. [9] What this means is that sunscreen doesn't just protect against UV radiation, it can reverse some of its affects.

<span style="font-family: Arial,Helvetica,sans-serif;">Another study tested sunscreens to see if they stayed in your skin and provided better overall protection from the sun. This study was conducted on 23 subjects. The subjects were to go to the dermatologist and have sunscreen applied to portions of their back. They then would go back to the dermatologist a day later at the same time and have that same region of skin tested for its sun protection factor. Afterwards, additional sunscreen was applied and this test went on for an entire week.

<span style="font-family: Arial,Helvetica,sans-serif;">Two different types of sunscreen, both rated at 30 SPF, were used in this study: an organic and a synthetic sunscreen. The findings strongly suggest that daily application of either sunscreen can result in an accumulation of sunscreen in the skin. However, the synthetic sunscreen seemed to result in higher accumulations and an overall increased mean sun protection factor (SPF) of 2. This factor of 2 is sufficient to prevent the average persons from getting sunburns during typical sun exposure times. The figure to the right displays the data. The o/w in the legend means oil and water and has to do with the ratio between the two substances. Note that the strongest accumulation comes from the particle sunscreen (synthetic) applied three times daily. [10]

=<span style="font-family: Arial,Helvetica,sans-serif;">Conclusions and Discussion =

<span style="font-family: Arial,Helvetica,sans-serif;">We can conclude a variety of different things from the vast amount of research done on this topic. One is that the human body needs vitamin D, and sunlight might not be the best way for us to get it. The ultraviolet rays in sunlight which provide the vitamin D we need are the same rays that are a proven carcinogen. If we can find alternative sources for our vitamin D, like supplementing our diets with vitamins, than we can avoid a direct intake of carcinogen. That being said, we must be careful not to over consume vitamin D and induce hypervitaminosos D.

<span style="font-family: Arial,Helvetica,sans-serif;">The studies also provide a cautionary element when thinking about sunlight and applying these results to human beings. That the amount of sun that each person needs is strongly dependent on their genetics. This of course should come as no surprise given that our ancestors all evolved in different environments with extremely varying amounts of sunlight. In general, lighter pigmented skin requires less sunlight to produce the same amount of vitamin D as darker pigmented skin. However, replace the word vitamin D with carcinogens and the statement is still true. It is also proven that sunscreen is an adequate protection when it comes to blocking UVB rays, blocking 99% of UV rays with SPF 15. In addition, daily application of sunscreen can lead to an increased SPF factor for your body due to accumulation of the sunscreen in your skin. When you do find yourself with sunburns, many of the cells under those burns exhibit cancerous tendencies within 24 hours of getting the sunburn. If you have skin which is prone to sunburns, you should certainly be protecting your skin with adequate sunscreen.

=<span style="font-family: Arial,Helvetica,sans-serif;">References =

<span style="font-family: Arial,Helvetica,sans-serif;">[1]M. Wacker and M. Holick, "Sunlight and Vitamin D", 2017. . <span style="font-family: Arial,Helvetica,sans-serif;">[2]"Office of Dietary Supplements - Vitamin D", Ods.od.nih.gov, 2017. [Online]. Available: https://ods.od.nih.gov/factsheets/VitaminD-Consumer/. [Accessed: 01- May- 2017]. <span style="font-family: Arial,Helvetica,sans-serif;">[3]H. MF, "Sunlight, UV-radiation, vitamin D and skin cancer: how much sunlight do we need? - PubMed - NCBI", Ncbi.nlm.nih.gov, 2017. [Online]. Available: https://www.ncbi.nlm.nih.gov/pubmed/18348443. [Accessed: 01- May- 2017]. <span style="font-family: Arial,Helvetica,sans-serif;">[4]D. Wolpowitz and B. Gilchrest, "The vitamin D questions: How much do you need and how should you get it?", 2017. . <span style="font-family: Arial,Helvetica,sans-serif;">[5]N. Binkley, R. Novotny, D. Krueger, T. Kawahara, Y. Daida, G. Lensmeyer, B. Hollis and M. Drezner, "Low Vitamin D Status despite Abundant Sun Exposure", 2017. . <span style="font-family: Arial,Helvetica,sans-serif;">[6]A. Ziegler, A. Jonason, D. Leffellt, J. Simon, H. Sharma, J. Kimmelman, L. Remington, T. Jacks and D. Brash, "Sunburn and p53 in the onset of skin cancer", 2017. . <span style="font-family: Arial,Helvetica,sans-serif;">[7]B. Klein, K. Howard, S. Iyengar, T. Sivakumaran, K. Meyers, K. Cruickshanks and R. Klein, "Sunlight Exposure, Pigmentation, and Incident Age-Related Macular Degeneration", 2017. . <span style="font-family: Arial,Helvetica,sans-serif;">[8]B. LANSKE and M. RAZZAQUE, "Vitamin D and aging: old concepts and new insights", 2017. . <span style="font-family: Arial,Helvetica,sans-serif;">[9]"Reduction of Solar Keratoses by Regular Sunscreen Use — NEJM", New England Journal of Medicine, 2017. [Online]. Available: http://www.nejm.org/doi/full/10.1056/NEJM199310143291602#t=article. [Accessed: 01- May- 2017]. <span style="font-family: Arial,Helvetica,sans-serif;">[10]M. Bodekaer, U. Åkerström and H. Wulf, "Accumulation of sunscreen in human skin after daily applications: a study of sunscreens with different ultraviolet radiation filters", Photodermatology, Photoimmunology & Photomedicine, vol. 28, no. 3, pp. 127-132, 2012.