In recent years, we have heard much about the dangers of too much sun causing skin cancer. Most people now heed the warnings about sunburn and slather on high factor sunscreen or cover up. However, what has often been missed in this discussion is that humans are not that dissimilar to plants – we need sunshine to thrive!
Humans derive most of their vitamin D from sunshine that is absorbed through the skin. It can also be found in high amounts in oily fish such as salmon and sardines, in lower amounts in eggs and liver and in fortified foods, such as milk, margarine and cereals. However, it is difficult to get the recommended intake from food alone.
Vitamin D is a nutrient that is essential to good health. The most well-known action of vitamin D is its role in assisting the absorption of calcium, to ensure strong healthy bones. In childhood, if children don’t get enough vitamin D, they can develop rickets (a disease of malformed bones and impaired growth) and in adults, it can lead to soft spongy bones and osteoporosis. However, it plays many different roles in the body and scientists are now starting to recognise that a deficiency or simply low levels of vitamin D present in the body may be linked to some common conditions.
In the immune system, there are many cells that use vitamin D. Scientists now recognise that auto-inflammatory diseases such as multiple sclerosis and rheumatoid arthritis are much more common in more northerly latitudes, where people are naturally exposed to less hours of sunshine. A link has also been found between low levels of vitamin D and the development of food allergies in young children (Baek et al, 2014) suggesting it plays a critical role during pregnancy and researchers are investigating potential links between low vitamin D levels and inflammatory bowel disease.
Adequate vitamin D levels have also been associated with lower rates of breast, prostate and bowel cancers and a decreased likelihood of developing type 2 diabetes.
Production of vitamin D by the skin naturally decreases with age and may not be adequate in people over 65. Those with darker skins are also prone to deficiency as higher levels of melanin present in dark skin may inhibit production and those who are housebound or cover up when outside. For these groups, supplements may be advisable.
Between April and October in the UK, for most people it is possible to build up enough stores to last through the cold winter months. The current recommendations are to spend 10-15 minutes in the sun without sunscreen, most days of the week. This should be done between 11am and 3pm. However, in hot countries such as Australia, the recommendation is for just a few minutes per day of incidental sun exposure, such as during a short walk, in the summer months and 2-3 hours per week in winter.
The conclusion must be that sunshine is vital to our health in many ways, so get outside and enjoy it – not too much so you burn, but regularly and certainly in spring after a long cold winter.