Health effects of sunlight exposure

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**Vitamin D and Sunlight Exposure:**
– UVB radiation converts 7-dehydrocholesterol to previtamin D in the skin.
– Time of day, geographic latitude, and sunscreen use affect vitamin D synthesis.
– Moderate sun exposure to face, arms, and legs can produce adequate vitamin D.
– Serum 25(OH)D test quantifies vitamin D levels.
– Vitamin D deficiency is common in countries like the US, Australia, and New Zealand.
– UV exposure induces vitamin D production in the skin.
– Higher vitamin D levels are associated with lower rates of diabetes and heart disease.

**Health Benefits of Sunlight Exposure:**
– Sunlight triggers the release of serotonin, improving mood and mental health.
– Exposure to sunlight helps regulate circadian rhythm and improve sleep quality.
– Sunlight exposure can lower blood pressure and reduce the risk of heart disease.
– Sunlight exposure may improve skin conditions like psoriasis and eczema.
– Sun exposure is essential for Vitamin D synthesis in the skin.

**Skin and Eye Health Effects:**
– UV irradiation from sunlight is a human carcinogen.
– Long-term sunlight exposure is linked to skin cancer and aging.
– UV exposure can cause mutagenic and carcinogenic effects on the skin.
– Eye diseases like cataracts can result from prolonged UV exposure.
– Prolonged exposure to UV light can lead to cortical cataracts and macular degeneration.
– Bright light exposure may be necessary for children to prevent myopia.

**Risks of Excessive Sunlight Exposure:**
– Overexposure to sunlight can cause sunburn, premature skin aging, and skin cancer.
– Excessive sun exposure increases the risk of cataracts and other eye-related issues.
– Sunburns and UV exposure weaken the immune system.
– Long-term sun exposure without protection can lead to photoaging and wrinkles.
– Prolonged exposure to UV radiation can damage DNA in skin cells, leading to mutations.

**UV Radiation and Health Risks:**
– UV radiation can cause skin damage and increase the risk of skin cancer.
– Exposure to UV radiation is linked to eye conditions like cataracts and solar retinopathy.
– Solar UV radiation can lead to folate deficiency in women and affect pregnancy.
– UV exposure is associated with decreased bone health due to potential vitamin D deficiency.
– There are concerns about the impact of UV radiation on blood pressure and cardiovascular health.

Exposing skin to the ultraviolet radiation in sunlight has both positive and negative health effects. On the positive side, exposure allows for the synthesis of vitamin D3. Vitamin D has been suggested as having a wide range of positive health effects, which include strengthening bones and possibly inhibiting the growth of some cancers. A dietary supplement can also supply vitamin D, but there are also benefits to exposure not obtainable through Vitamin D supplementation. Long-term sun exposure is associated with reduced all-cause mortality and reduced mortality risk from cardiovascular disease (CVD), some forms of cancer, and non-CVD/noncancer related disease, with indications in these studies that Vitamin D is not the mediator. Supplementation offers limited bioavailability and no synthesis of subdermal nitric oxide. UV exposure also has positive effects for endorphin levels, and possibly for protection against multiple sclerosis. Abundant visible light to the eyes gives health benefits through its association with the timing of melatonin synthesis, maintenance of normal and robust circadian rhythms, and reduced risk of seasonal affective disorder.

Sunbaker, by Max Dupain

On the negative side, UV is a mutagen and carcinogen for skin. Acute exposure may lead to a painful sunburn, which can increase the chances of developing serious skin problems later in life. Long-term sunlight exposure is known to be associated with the development of some types of skin cancer, skin aging, immune suppression, eye diseases such as cataracts and maybe macular degeneration.

Since UV rays, and therefore sunlight and sunlamps, have both health benefits and risks, a number of public health organizations state that there needs to be a balance between the risks of having too much sunlight or too little. There is a general consensus that sunburn should always be avoided.

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