As we move out of winter and into spring, our days will inevitably start to become lighter, but what exactly is the science behind the impact of sunlight on the human body? We often hear about the damaging effects of sun to our bodies, such as causing cancer due to excessive exposure, but there are also many beneficial effects of sunlight which often go unnoticed.

Most media attention towards sunlight focusses on its damaging effects to the human body. Chemicals known as radicals are caused by Ultra Violet Radiation (UVR). These directly damage DNA and thus can result in rapid ageing of the skin and even cause various forms of skin cancers. However, a report by the World Health Organisation (WHO) in 2006 found that exposure to UVR accounts to only 0.1% of total global disease in terms of loss of years of life. When seen in conjunction with the findings, in the same report, that as many as 3.3 billion years of life may have been lost as a result of low UVR exposure, it becomes a startling figure and underlies the importance of sunlight to our health.

The primary benefit of sunlight is to aid the production of vitamin D. One of the major functions of vitamin D is to control the movement of calcium into and out of the 206 bones in the human body. A report by the BBC in 2006 stated that many women and children in Bradford were given free vitamin D tablets due an increase in the case of Rickets.  Rickets is a bone disorder resulting from vitamin D deficiency due to lack of exposure to sunlight and can be prevalent among many Muslim communities where a specific dress code is observed. Bone pain and muscle weakness is experienced but increased exposure to sunlight often relieves the symptoms.

There also appears to be evidence suggesting that sufficient levels of vitamin D in the body may help prevent the onset of Multiple Sclerosis (MS) – a highly debilitating neuromuscular disorder. It has been shown that low levels of vitamin D can predispose someone to developing MS which is shown in the fact that MS is more common in people further away from the equator, who therefore receive lower levels of sunlight.

Finally, sunlight is known to affect the mood of a person.  Seasonal Affective Disorder (SAD) is a depressive disorder only seen in the winter months and is thought to be due to decreased exposure to sunlight. Lack of sunlight is thought to affect the hypothalamus, which is the area of the brain involved in the control of mood, sleep and appetite. Symptoms of disturbed sleep, altered mood and decreased appetite are therefore seen.

In conclusion, over exposure to sunlight can have many damaging effects, most notably cancer of the skin. We must however also be aware of the importance of sunlight to our health through vitamin D production and the potentially beneficial effects of sunlight with regard to the prevention of diseases like MS and disorders such as SAD.

Tim Knight