The Summer is pretty much over. The sunniest and hottest season of the year usually leaves us with not only great memories but also the effects of exposure to Ultraviolet (UV) radiation that accumulates over a lifetime, transforming our skin and our whole body in various ways.
Vitamin D intake and sun exposure
Vitamin D is a fat-soluble molecule not typically found in very many food sources. The exceptions are fatty fish livers! Therefore, naturally derived Vitamin D is mainly the result of dermal (skin) synthesis. Exposing our skin to the sun allows UV rays to promote the synthesis of an intermediate form of vitamin D from a precursor molecule. The intermediate form of vitamin D is then further modified by the liver and then finally travels to the kidneys where the active form of vitamin D is produced. Vitamin D and it’s by-products are intimately involved in calcium balance and bone metabolism. Rickets, a childhood disease of the bones and osteomalacia (weak bones) are caused by severe vitamin D deficiency. Fortunately, these conditions have become extremely uncommon and often involve malabsorption syndromes. The amount of vitamin D an individual produces depends on several factors:
- Where you live: Geographic location and season are relatively crucial because vitamin D production is reduced in areas further away from the equator.
- Air quality: Carbon particles in the air from the burning of fossil fuels, wood, and other materials scatter and absorb UV rays, diminishing vitamin D production.
- The use of sunscreen: Sunscreens reduce sunburns and aging by blocking UV light. Theoretically, that means that sunscreens should lower vitamin D production. However, as a practical matter, very few people put on enough sunscreen to block all UV light, or they use sunscreen irregularly.
- Skin colour: Melanin is the substance in the skin that makes it dark. It “competes” for UV with the substance in the skin that kick-starts the body’s vitamin D production. As a result, dark-skinned people tend to require more UV exposure than light-skinned people to generate the same amount of vitamin D.
- Weight: Studies have also shown that being obese is correlated with low vitamin D levels and that being overweight may affect the bioavailability of vitamin D. It means people who are overweight may need higher amounts of vitamin D.
- Age: Compared with younger people, older people have lower levels of the vitamin D precursor in the skin that UV light converts into the vitamin D intermediate molecule. There’s also experimental evidence that older people are less efficient vitamin D producers than younger people.
Why we tan
Tanning of the skin is a sign of UV exposure. As a protective measure, the skin produces melanin to try and reduce UV rays from penetrating any deeper into it, but the damage has already been done. For this reason, when it comes to sun exposure, there is no such thing as a healthy tan – even if UV radiation exposure is recommended by your doctor, its therapeutic use to help to treat diseases like eczema, psoriasis, rickets, or jaundice, cannot eliminate the negative side-effects of UV radiation – treatments like these must take place under medical supervision to ensure that the benefits outweigh the risks.
Sunlight is the main source of UV radiation, even though UV rays make up only a small portion of the sun’s rays. Different types of UV rays reach the ground in different amounts. About 95% of the UV rays from the sun that reach the ground are UVA rays, with the remaining 5% being UVB rays. You can learn more about the different UV types and how to protect your skin by reading one of my Healthing.ca articles here.
Other health problems
According to the World Health Organization, the harmful effects of exposure to UV radiation usually far outweigh its benefits. People are generally aware that sunburns are a primary cause of skin cancer, however, not many are aware that any unprotected exposure to the sun can play a role in developing skin cancer. Moreover, in addition to skin cancer, exposure to UV rays can cause other health problems:
- Sunburn: UV rays, either from the sun or from artificial sources like tanning beds, can cause sunburn. Your skin will turn red due to an increase in blood flow and it can notice it right away or over time.
- Premature aging of the skin: Causing signs of sun damage such as wrinkles, leathery skin, liver spots, actinic keratosis, and solar elastosis. Talk to your doctor about screening your skin and track the appearance of any new signs you find on your skin.
- Eye problems: UV rays can damage the tissue in your eyes. They can cause the cornea (surface of the eye) to become inflamed or burned. They can also lead to the formation of cataracts (clouding of the lens of the eye) and pterygium (tissue growth on the surface of the eye), both of which can impair vision.
- Weaken the immune system: Your body has a harder time fending off infections. It can also cause vaccines to be less effective.
The sun and our mood
Nowadays, people spend more time indoors staring at computers and television screens. For this reason, scientists are starting to appreciate how exposure to sunlight affects various body systems including our mood. One Australian study that measured levels of brain chemicals flowing directly out of the brain found that people had higher serotonin levels on bright sunny days than on cloudy ones. That higher levels of serotonin correlate with better mood and feelings of satisfaction and calmness, and lower levels link to depression and anxiety.
While not everyone is as strongly affected by a lack of sunlight, for the people who are, make sure you do it in a safe way: apply and reapply your sunscreen every 2 hours; stay in the shade under an umbrella, tree, or other shelters; wear sun-protective clothes, a hat, and sunglasses that block both UVA and UVB.
After all, is said and done, the best way to get your compliment of vitamin D is still naturally via the sun. Brief (15-20 minutes) exposure of your arms and face to the sun can produce up to 200 IU of vitamin D. The actual level of vitamin D that any one individual should maintain is variable across the population. Daily supplementation for children and adults age 9 – 70 is recommended at 600 IU daily. Doses in excess of that number may be utilized as directed by a physician. If you have concerns, or questions regarding anything to do with vitamin D, please reach out to us.
Dr. Rohan Bissoondath,
Medical Director