There is something great about seeing the sun when you live in a country as wet and windy as the United Kingdom. Despite global warming we still don’t experience large amounts of sunshine in this island nation. We have seen news of flooding hitting the headlines for several years in a row. However, when the sun does manage to peek out from behind the clouds the almost knee jerk reaction from many in the population is to enjoy it while it lasts. People begin to strip off, the barbeques get cleaned up, garden parties ensue and long weekends to the stony coast lines we call a ‘beach’ all get into full swing. It is true, the British clearly love the sun. With sunshine at a premium in this country and many others, is there perhaps an underlying reason why we crave it so much? Why would avoiding the sun be beneficial for us? After all we are continually warned about the dangers of skin cancer from too much UV exposure.
Exposure to the rays of the sun is known to help generate vitamin D through conversion of a naturally occurring pre-cursor under the skin called 7-dehydrocholesterol. This is converted into pre-vitamin D3, which is then rearranged into the active form of vitamin D3. This is a vital nutrient that provides many benefits to the body. Scientific studies have shown that vitamin D:
- Is necessary for bone strength by aiding the absorption of calcium, phosphorus and magnesium
- Supports insulin response and therefore may protect against diabetes
- May be a more powerful antioxidant than vitamin E, often considered the most powerful
- Supports both infectious and inflammatory immune system response
- Supports oestrogen production and therefore plays a role in regulating the menstrual cycle and relieving PMT
- Contributes to thyroid production and so may support metabolism and protect against chronic fatigue
- Has been found to have beneficial effects on reversing learning and cognitive difficulties
How much vitamin D you get when exposed to sunlight depends upon the time of day, where you live in the world (latitude and altitude), how dark your skin colour is, and how much skin is exposed to the sun. The skin pigment, melanin, prevents UVB from passing through, which helps prevent skin damage, but this also means less vitamin D is produced. The conventional stance for the UK is that 20 minutes of exposure on the arms and face three times a week will provide enough vitamin D to meet our minimum health requirements. This seems relatively easy to achieve, but perhaps there are a few other considerations. The vitamin D council suggest that exposing large skin areas, such as the back, stomach or full legs, to sunlight is more effective at producing sufficient daily vitamin D in relatively short periods of time. This is less time than it takes to get a good tan and is certainly less time than skin burn time. Full skin exposure may only require half the time it takes for your skin to burn in order to reach sufficient amounts of vitamin D. This will be shorter for those with fair skin and longer for darker skin due to the amount of UVB protection the melanin in our skin provides. However, there is an additional concern – latitude!
The lowest tip of the UK sits at 50° north whilst the Shetland isles are almost 60° north. The further north or south the latitude the sharper the angle the UVB rays hit the earth’s atmosphere and become more dissipated in their journey to the surface. Basically, this boils down to the larger the latitude figures the less UVB exposure on the ground, hence why tanning and burning times are longer at distances further from the equator. The sharper sun angles early and late in a normal day also affect UVB light exposure and reduce the amount reaching the earth’s surface. This also affects vitamin D! Reduced UVB light exposure means a lower conversion rate of cholesterol precursors in our skin into active vitamin D. The geographical position of the UK makes it very difficult to receive enough UVB rays, limiting vitamin D production for about 5-6 months of the year. We would have to get virtually naked and sit outside for about an hour around midday to meet our daily requirements during these less than sunny months. This is hardly a practical solution, especially bearing in mind these times of year are much colder! However, this may be one of the reasons for the natural drive to get out and enjoy the sun when it does appear. Regular sun exposure, within reason, has been scientifically validated for boosting our essential daily requirements for vitamin D.
Throughout the autumn and winter months in northern or southern countries above and below 35° latitude, we need to rely a little more on dietary rich sources of vitamin D in conjunction with sun exposure. As vitamin D is a fat-soluble vitamin the foods that are rich in this important nutrient are typically higher in fat, such as high-quality cod liver oil, wild oily fish such as herring, salmon and trout, and also wild shellfish like oysters and shrimp. 100g of these foods (except cod liver oil, which provides higher dosage) will provide between 800 to 1000IU of vitamin D. A few other more commonly consumed foods provide smaller amounts of vitamin D such as grass-fed, free range butter or cream, beef liver and egg yolks which deliver between 50 to 200IU per 100g. These fatty, naturally occurring foods will help contribute to our personal vitamin D reservoir during the short days and long nights of winter. If the above foods are difficult to source or just not to your taste preferences, then the use of supplementation may be warranted. In 2011 researchers at Bastyr University in California ran a study comparing vitamin D3 supplementation in 3 different forms; oil drops, capsules or chewable tablets. They showed that when taking 10,000IU of vitamin D3 daily for 12 weeks all 3 forms proved to be safe and effective in significantly increasing levels in the body. The recommended daily intake varies depending upon the organisation you choose to rely upon from 800IU to 5000IU per day. The vitamin D council offer the higher 5000IU per day recommendation, especially in those more likely to be deficient.
When the sun does makes an appearance during the spring and summer seasons we should seek to enjoy some regular exposure on our skin to allow for vitamin D formation. This sunlight should not be hindered in any way, such as covering the skin in sun screen, which blocks the UVB rays we need to facilitate vitamin D conversion. It is also important to ensure that the amount of exposure is suitable and does not lead to burning or damage of the skin. If exposure to the sun is to go beyond 20-30 minutes and the weather is hot enough to lead to sunburn it would be appropriate to either to put on clothing or to utilise sun screen once the daily vitamin D requirements have been met. A useful guideline is to allow unprotected sun exposure for half the time it takes to burn your skin.
Following these dietary and lifestyle recommendations will help to ensure that an adequate daily supply of this essential nourishing compound is obtained throughout the year which in turn will support and maintain health and wellness. So, go ahead this summer, enjoy the sun, just not too much!