Ultraviolet radiation in the sun has positive and negative health effects, as it is the main source of vitamin D 3 and mutagen. Dietary supplements can provide vitamin D without this mutagenic effect. Vitamin D has a variety of positive health effects, including strengthening bones and possibly inhibiting the growth of certain types of cancer. UV exposure also has a positive effect on endorphin levels, and possibly for protection against multiple sclerosis. Visible sunlight to the eye provides health benefits through its association with melatonin synthesis time, the maintenance of normal and strong circadian rhythms, and reduces the risk of seasonal affective disorder.
Long-term sun exposure is known to be associated with the development of skin cancer, skin aging, immune suppression, and eye diseases such as cataracts and macular degeneration. The effects of UV radiation at high latitudes, where snow remains on the ground become early summer and the sun then remains at a low position even at its peak, has been reviewed by Meyer-Rochow. Short-term overexposure is the cause of sunburn, snow blindness, and solar retinopathy.
UV rays, and therefore sunlight and sunlight, are the only registered carcinogens known to have health benefits, and some public health organizations claim that there needs to be a balance between the risk of having too much sun or too little. There is a general consensus that sunburn should always be avoided.
Video Health effects of sunlight exposure
Sintesis vitamin D 3
UVB radiation with a wavelength of 290-315 nanometers penetrates the open skin and converts 7-dehydrocholesterolic skin into previtamin D 3 , which in turn becomes vitamin D 3 . UVB radiation does not penetrate the glass, so exposure to sunlight indoors through windows does not produce vitamin D. Day time, all year long, geographical latitude, soil height, cloud cover, smog, skin melanin content, and sunscreen are among the factors which greatly affects the intensity of UV and vitamin D synthesis, making it difficult to provide general guidelines. It has been suggested by some researchers, for example, that an adequate amount of vitamin D can be produced with moderate sun exposure on the face, arms and legs, averaging 5-30 minutes twice per week without sunscreen. (The darker the complexion, or the weaker the sunlight, the more minutes of exposure it takes, about 25% of the time for minimal sunburn.Addosis of vitamin D is not possible from UV exposure, the skin reaches equilibrium where the vitamin decreases rapidly as made.) Individuals with limited exposure to sunlight need to include a good source of vitamin D in their diet or take supplements.
The only way to measure adequate vitamin D levels is by serum 25 (OH) D 3 test (calcifediol). In the United States, serum 25 (OH) D 3 was below the recommended level for more than a third of white men in the 2005 study, with serum levels even lower in women and most minorities. This suggests that vitamin D deficiency may be a common problem in the US. Australia and New Zealand have similar findings, which indicate inadequate protection against rickets for children and osteoporosis for adults.
Over the past few years, ultraviolet radiation levels have been tracked in more than 30 locations across North America as part of UVB's US Agricultural Research and Monitoring Program at Colorado State University. The first map on the right shows the level of UVB radiation in June 2008, expressed in Vitamin D Equivalents.
Using satellite data, measurements from the European Space Agency produced a similar map expressed in units of the widely followed UV Index, for locations around the world.
Exposure to ultraviolet radiation from the sun is a great source of vitamin D. A minimum dose of UV radiation gives the equivalent of about 20,000 IU of vitamin D2, taken as an oral supplement. If an adult's arms and legs are exposed to half the minimal erythematous UV radiation, it is equivalent to taking 3,000 IU of vitamin D3 through oral supplements. This exposure for 10-15 minutes, with a frequency of two to three times per week will cause adult skin to produce enough vitamin D. No need to expose the face to UV, because the skin provides a little vitamin D3. Individuals whose metabolism makes oral vitamin D use ineffective, through exposure to ultraviolet lights that emit UV-B radiation, to achieve blood levels of 25 (OH) D.
Three benefits of UV exposure are vitamin D production, mood lift, and increased energy.
UVB induces the production of vitamin D in the skin at levels up to 1,000 IUs per minute. These vitamins help regulate calcium metabolism (vital for the nervous system and bone health), immunity, cell proliferation, insulin secretion, and blood pressure. In third world countries, foods fortified with vitamin D "are practically non-existent." Most people in the world depend on the sun to get vitamin D.
Not many foods naturally have vitamin D. Examples are cod liver oil and oily fish. If people can not get sunlight, then they will need 1,000 IU of vitamin D per day to stay healthy. One must eat oily fish three or four times per week to get enough vitamin D from the food source itself.
People with higher vitamin D levels tend to have lower rates of diabetes, heart disease, and stroke and tend to have lower blood pressure. However, it has been found that vitamin D supplements do not improve cardiovascular health or metabolism, so the association with vitamin D should be partially indirect. People who get more sunshine are generally healthier, and also have higher levels of vitamin D. It has been found that ultraviolet radiation (even UVA) produces nitric oxide (NO) in the skin, and nitric oxide can lower blood pressure. High blood pressure increases the risk of stroke and heart disease. Although long-term exposure to ultraviolet contribute to non-melanoma skin cancer is rarely fatal, it has been found in the Danish study that those who get this cancer are less likely to die during the study, and are less likely to have a heart attack than those without cancer this.
People in certain situations, such as people with intellectual disabilities and neurodevelopmental disorders who stay in most of the time have low vitamin D levels. Getting enough vitamin D can help prevent "autoimmune disease, cardiovascular disease, many types of cancers, dementia, type 1 and 2 diabetes mellitus, and respiratory infections."
Fetuses and children who do not get enough vitamin D can suffer from "growth retardation and bone deformity."
Maps Health effects of sunlight exposure
Prevalence is lower than multiple sclerosis
Multiple sclerosis (MS) is most rarely found in the brightest areas. Exposure to ultraviolet-B radiation of sunlight seems most important and it can operate through the synthesis of vitamin D.
Risk for skin
Ultraviolet (UV) irradiation present in sunlight is a human environmental carcinogen. The UV toxic effects of natural sunlight and therapeutic artificial lights are a major concern for human health. The main acute effect of UV irradiation on normal human skin consists of erythema of sunburn inflammation, skin tanning, and local or systemic immunosuppression. The most lethal form, malignant melanoma, is largely due to indirect DNA damage from UVA radiation. This can be seen from the absence of direct UV signature mutations in 92% of all melanomas. UVC is the highest and most dangerous type of ultraviolet radiation, and causes adverse effects that can be mutagenic or carcinogenic.
Despite the importance of sun for vitamin D synthesis, it is wise to limit skin exposure to UV radiation from sunlight and from tanning beds. According to the National Toxicology Program Report on Carcinogens from the US Department of Health and Human Services, broad-spectrum UV radiation is a carcinogen whose DNA damage is thought to account for most of about 1.5 million skin cancers and 8,000 deaths from metastasis. melanoma that occurs every year in the United States. The use of sunbeds is reported by the World Health Organization to be responsible for more than 450,000 non-melanoma skin cancer cases and more than 10,000 cases of melanoma each year in the US, Europe, and Australia. Exposure to lifelong UV rays on the skin is also responsible for age-related dryness, wrinkling, elastin and collagen damage, age spots, freckles and other cosmetic changes. The American Academy of Dermatology recommends that photoprotective steps be taken, including the use of sunscreen, whenever a person is exposed to the sun. Short-term exposure causes pain and itching from sunburn, which in extreme cases can produce more severe effects such as blistering.
Some countries (such as Australia) provide general estimates of UV irradiation in the form of UV Index. This index can be used as a guide for the public danger from excessive exposure to sunlight, especially during the day, when direct sunlight is most intense.
Benefits of optical exposure
Light to eye, especially blue-wavelength light, is essential for the entrainment and maintenance of strong circadian rhythms. Exposure to the sun in the morning is very effective; it causes the onset of melatonin earlier in the night and makes it easier to fall asleep. Bright morning light has been shown to be effective against insomnia, premenstrual syndrome and seasonal affective disorder (SAD).
Effects on the eyes
Long-term optical exposure to sunlight, particularly intense ultraviolet light, may be associated with cortical cataracts, and high levels of visible light may be associated with macular degeneration.
However, significant daily exposure to bright light may be necessary for children to avoid myopia (nearsightedness).
Short-term short-term exposure can cause snow blindness, analogous to sunburn of the cornea, or may cause solar retinopathy, which is a long-term retina damage and visual impairment caused by sungazing.
Often exposed to the sun can cause a non-cancerous yellow lump in the center of the eye sclera, called pingueculae. This is most common in younger people, especially those who spend much time outdoors and do not protect their eyes from UV rays. To reduce the risk of developing pingueculae, it may be wise to wear sunglasses when outdoors, even on cloudy days.
Folate degradation
The level of blood folate, an essential nutrient for fetal development, can be degraded by UV radiation, raising concerns about exposure to sunlight for pregnant women. Lifespan and fertility may be affected for individuals born during the peak of the 11-year solar cycle, possibly due to UV-related folate deficiency during pregnancy.
Safe level of sun exposure
According to a 2007 study submitted by the University of Ottawa to the US Department of Health and Human Services, there is not enough information to determine the safe level of sun exposure that imposes a minimal risk of skin cancer. In addition, there is no conclusive evidence of ultraviolet radiation (UVA, UVB, UVC) components that are actually carcinogenic. UVC is almost completely absorbed by the atmosphere and does not reach the surface in significant amounts. Consequently, only broad-spectrum combinations (UVA, UVB, UVC) known as "ultraviolet radiation" are listed as carcinogens; components only "may be" known carcinogens. Sun radiation (sunlight) and sunlamps are listed as carcinogens because they contain ultraviolet radiation.
Lifetime sun exposure
There is currently no recommendation at a safe level of total lifetime sun exposure. According to epidemiologist Robyn Lucas at the Australian National University, analysis of lifespan versus illness suggests that far more lives worldwide can be lost due to illness caused by lack of sun than is caused by too much, and it is inappropriate to recommend total avoidance of rays sun.
For thousands of years, in many climate zones, genetic selection has helped indigenous human populations to adapt to the level of skin pigmentation that provides healthy levels of UV exposure. This largely explains the trend of dark-skinned populations in the brightest tropical environments, and brighter skin tones in less sunny areas and for those most in need of vitamin D for rapid bone growth, especially children and women of reproductive age. The map below illustrates the geographic distribution of skin color for indigenous people prior to 1940, based on the von Luschan chromatic scale. This long-term adaptation to optimal health can be confused by diet, clothing and shelter, especially when large populations have migrated away from the climate in which their skin is genetically adaptable.
See also
- Fluorescent and health lights
- Heat stroke
- Photosensitivity in humans
- UV Index
References
Source of the article : Wikipedia
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