How does Sun affect functions of Human Body

Sun is a major reason behind life on planet Earth. But effect of Sun is not just limited to creation of life on earth. It is constantly nourishing all forms of life on earth. When it comes to humans, Sun is still regulating a number of biological activities in our body. Most of us remain unaware of these facts and take Sun as just a source of light and heat. Sun Cycle which is around 11 years long also effect human behavior which is being researched by scientists.

How does Sun affect functions of Human Body

Vitamin D: This vitamin can't be obtained from any food item, but it can be generated by our body with sun light exposure. Low levels of Vitamin D increases the risk of colorectal and breast cancer. Vitamin D is also necessary to make your bones stronger. 1000 different genes in our body are regulated by presence of Vitamin D3. 15 minute exposure of sun light is sufficient to save you from this risk.
Circadian rhythm : If you have heard about biological clock, then you must know that sunlight plays an important role in keeping this clock, known as Circadian rhythm, on track. Physical mental and behavioral changes that occur during a day are also controlled by this rhythm.
Serotonin: This hormone is secreted in our body due to exposure of sunlight and it increases our activeness and alertness level. If you have faced seasonal depression and mood variation during winters then it might be due to lesser exposure to sunlight. If you can't get sufficient sunlight during winters then some bright light inside your house can save you from the side effects of lower serotonin levels.
Prolactin: It is a rest hormone which is secreted in night time. Sunlight suppresses the release of this hormone and make our know that rest time is over. As sun sets, you body start to produce prolactin and within 2 hours it gets ready for sleep. However modern lights in home interferes with this natural system.
Sun Light lowers blood pressure: Ultraviolet(UV) rays present in sun light lowers your blood pressure. Previously you must have heard about negative effect of UV rays. But this new discovery about good effect of UV is changing the perception. However too much exposure to UV might be bad but a minimum amount of UV exposure in necessary in keeping your blood pressure reduced.
Skin Diseases: Ultraviolet radiation of short wavelengths (UVB) saves you from melanoma, skin damage and skin cancer. Indoor workers often complain more skin diseases compared to those who work outdoor.

Effect of Solar Cycle on Humans

Solar Cycle is around 11 years long (Yes ! Its duration is not fixed). In this cycle sunspot activity and solar flares increase its activity and then comes down. In every cycle, once it reaches the maximum level and then returns to a minimum level. Due to this reason every 11th or 12th ring in tree's stem is larger than other rings. But some researchers have found that this solar cycle also affect human behavior. Some researches have concluded that as the solar sunspot activity increases human behavior tend to be at unrest. Most of the wars and revolution in the history happened during that period. Even most of the creative works in field of science and art happen at this time. Some Russian researchers have found that minimal sunspot activity decreases the immunity of human body and our tendency to get sick increases. Solar Cycle is being observed from 1755 and currently 24th Solar Cycle is going on. Current solar cycle started in Dec 2008 and reached maximum level on April 2014.

All of the above facts prove that sun is not just a source of light for humans, but it is a source of life. It not just helps in growing vegetation for us, but also controls various biological functions inside human body.