Types of rays in the sun
To know the best time to sunbathe, it is first necessary to understand what role the sun’s rays play in affecting and stimulating the synthesis of vitamin D, thereby knowing which rays are harmful and which rays are beneficial. for the skin.
Sunlight consists of visible rays (rainbow) and invisible rays which are ultraviolet or UV rays. UV rays are divided into 3 types: UVC rays, UVA rays and UVB rays.
UVC rays: have a short wavelength of about 200 – 190 nm. This type of radiation is the most harmful to human health. But UVC rays are absorbed by the ozone layer before reaching the ground, so they have almost no effect on the skin and do not synthesize vitamin D. UVA rays: accounted for 95% of total UV radiation in sunlight. to the ground, has the longest wavelength about 320-400 nm. UVA rays have the ability to penetrate the ozone layer, clouds, water, glass, thin clothing. Even some sunscreens do not block the effects of UVA rays. Thus, UVA rays appear throughout during sunlight, even when it is cloudy or rainy, UVA rays still appear. UVA rays are the main cause of skin darkening, skin aging, tanning, freckles and increasing the risk of skin cancer. Like UVC rays, UVA rays are completely incapable of synthesizing vitamin D. UVB rays: The only rays in sunlight that can stimulate vitamin D precursors, support calcium absorption in the body. People. UVB rays have a shorter wavelength than UVA rays, about 290 – 320nm. Up to 95% of UVB rays are absorbed by the ozone layer. Only very few UVB rays penetrate the ozone layer to the Earth’s surface.
UVB rays are the only rays capable of synthesizing healthy vitamin D, so it is necessary to choose the time with the most UVB rays to sunbathe.
The time when UVB rays can penetrate the ozone layer the most is between 9am and 4pm. However, during this time in the sun, there are a lot of harmful UVA rays that are harmful to the skin, especially for the delicate skin of babies and children.
Therefore, the best time to sunbathe is before 9am and after 4pm, when the sun is not too strong.
Unlike other essential vitamins, which must be obtained from food, vitamin D can be synthesized in the skin through a photosynthetic reaction triggered by exposure to UVB radiation. The efficiency of production depends on the number of UVB photons that penetrate the skin, a process that can be curtailed by clothing, excess body fat, sunscreen, and the skin pigment melanin. For most white people, a half-hour in the summer sun in a bathing suit can initiate the release of 50,000 IU (1.25 mg) vitamin D into the circulation within 24 hours of exposure; this same amount of exposure yields 20,000–30,000 IU in tanned individuals and 8,000–10,000 IU in dark-skinned people.The initial photosynthesis produces vitamin D3, most of which undergoes additional transformations, starting with the production of 25-hydroxyvitamin D (25[OH]D), the major form of vitamin D circulating in the bloodstream and the form that is routinely measured to determine a person’s vitamin D status. Although various cell types within the skin can carry out this transformation locally, the conversion takes place primarily in the liver. Another set of transformations occurs in the kidney and other tissues, forming 1,25(OH)D. This form of the vitamin is actually a hormone, chemically akin to the steroid hormones.1,25(OH)D accumulates in cell nuclei of the intestine, where it enhances calcium and phosphorus absorption, controlling the flow of calcium into and out of bones to regulate bone-calcium metabolism. Michael Holick, a medical professor and director of the Bone Health Care Clinic at Boston University Medical Center, says, “The primary physiologic function of vitamin D is to maintain serum calcium and phosphorous levels within the normal physiologic range to support most metabolic functions, neuromuscular transmission, and bone mineralization.”
Without sufficient vitamin D, bones will not form properly. In children, this causes rickets, a disease characterized by growth retardation and various skeletal deformities, including the hallmark bowed legs. More recently, there has been a growing appreciation for vitamin D’s impact on bone health in adults. In August 2007, the Agency for Health Care Policy and Research published Effectiveness and Safety of Vitamin D in Relation to Bone Health, a systematic review of 167 studies that found “fair evidence” of an association between circulating 25(OH)D concentrations and either increased bone-mineral density or reduced falls in older people (a result of strengthened muscles as well as strengthened bones). “Low vitamin D levels will precipitate and exacerbate osteoporosis in both men and women and cause the painful bone disease osteomalacia,” says Holick.
Here are ways in which sunbathing benefits us:
1. Improves sleep
Melatonin is a hormone secreted that is produced by your body and is essential for promoting sleep. You often start to feel drowsy two hours after the sun sets since your body produces it when it is dark, which is among the reasons our body will naturally stay awake during the summer months. By instructing your body when to produce more and less melatonin, sunlight controls your circadian rhythm.
2. Helps manage stress
Being outside will assist your body in naturally regulating melatonin, which can help lower your stress level. Melatonin also lowers stress reactivity. Additionally, the additional exercise you get from being outside, where you are frequently engaged in physical activity, reduces stress.
3. Improves bone health
Sunbathing increases vitamin D in the body. To maintain optimal blood levels of calcium and phosphorus, which are required for proper bone mineralization, vitamin D stimulates intestinal calcium absorption. Children who are vitamin D deficient may develop rickets, which causes the bones to weaken and give the impression of having bow legs. Similar to children, adults who are vitamin D deficient experience osteomalacia or a softening of the bones.
4. Boosts immunity
Sufficient vitamin D consumption may promote healthy immune function and lower the risk of autoimmune disorders. According to research vitamin D is crucial for immune system health. The development of autoimmune diseases like diabetes, asthma, and rheumatoid arthritis are thought to be associated with long-term vitamin D insufficiency, although further study is required to prove this association.
5. Regulate blood pressure
The body’s stocks of nitrogen oxides are released into circulation when exposed to sunshine, which lowers blood pressure by expanding blood vessels. The same analysis also suggests that sunshine may directly impact the risk of heart disease. Among the most potent hormones for controlling blood pressure appears to be vitamin D.
6. Improves mental health
There is a scientific explanation for why going outside in the light makes you feel better; it’s not all in your brain. Serotonin is a hormone that elevates your mood and aids in maintaining calm and concentration. Sunshine raises your body’s amount of serotonin. The symptoms of seasonal affective disorder, a change in mood that normally happens in the fall and winter months when there are fewer daylight hours, maybe lessened with increased exposure to natural light.
Make sure to sunbathe adequately and safely to ensure you achieve all the benefits of sunbathing.
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