Bring me sunshine, make me smile

Many factors affect how we feel each day, but weather has a significant influence. Studies show that high humidity tends to lower concentration and increase fatigue whilst hours of sunlight are directly related to a positive mood and optimism.

Sunlight is also an important source of vitamin D – which is useful as the modern foods are not good sources.

In the past, beef and milk were produced from animals which grazed on outdoor pastures. Eggs, with bright yellow yolks and rich in vitamin D, came from proper free range hens -living outdoors and fed on insects and fishmeal. These eggs, along with mackerel, salmon, herring, full fat milk and cream would provide you with enough vitamin D during the winter months. Nowadays we opt for skimmed or semi-skimmed milk. Fish get their source of vitamin D from eating plankton and smaller fish. Modern farmed salmon, unless artificially supplemented, is a poor source of vitamin D.

Thankfully sunshine can top up your levels. When sunlight is absorbed into our skin, a substance in the sub-cutaneous layer is converted to cholecalciferol – otherwise known as vitamin D. This conversion is rapid but the actual amount of vitamin D that you make will depend on the colour of your skin and where in the world you spend your time outdoors.

A very fair skinned person standing in short sleeves outside in Florida will make about 5,000 International Units (IU) of vitamin D in approximately 15 minutes, but a very dark skinned person will need about 2 hour exposure to make the same amount. Many researchers suggest that we need about 4,000 IU of vitamin D each day from all sources. However EU countries vary in their recommendations. The UK has set a level of 5ug per day, whilst the Government in Norway recommends 20ug and in Italy it is 25ug (1,000 IU).

It is the ultraviolet (UV) light which is effective, but UV light is divided into 3 bands; UV-A; UV-B and UV-C. The latter is the shortest but most damaging of the UV bands, and will burn human skin rapidly, even in small doses. Fortunately, the ozone layer absorbs the UV-C light. UV-A is known as the tanning ray, as it stimulates the production of melanin – the brown pigment produced to protect the skin. UV-A penetrates deeply into the skin and is considered to be a major contributor to the high levels skin cancers. Sun beds and tanning bulbs have a high UV-A output.

The UV band which stimulates the production of vitamin D is UV-B. It is sometimes called the “burning ray” because it is the main cause of sunburn. It can be difficult to get enough vitamin D from sunlight if you spend long hours indoors. Only 5% of the UV-B light range goes through glass and it does not penetrate clouds, smog or fog.

Whilst UV-A is present throughout the day, the amount of UV-B will depend on where you are in the world. In Scotland, the rays during May to September will be most effective in making vitamin D. At this time of year, the minimum dose of effective sunshine which you should aim for is 20-30 minutes on your face and bare forearms, 2-3 times per week. Darker skinned people need more and those with very fair skins need less. As a general rule, if your midday shadow is shorter than your height, then you are making vitamin D. However, production of vitamin D from UV-B occurs before your skin turns pink. It is never necessary to tan or burn to obtain enough vitamin D.

Other countries, such as Iceland and Canada, recognise that vitamin D may be deficient due to a lack of effective sunshine. Consequently, many foods (such as orange juice, bread, breakfast cereals) are legally required to be fortified in these countries. In the UK, only margarine must be fortified by law (and this requirement is due to be dropped soon). However, the vitamin D it contains is not a reason for eating margarine. This highly processed spread contains damaging trans fatty acids which you do not want to put into your body for any reason. These fats also interfere with the enzymes which are needed to activate vitamin D in the liver.

If you prefer to take a vitamin D supplement make sure you also have enough calcium and magnesium in your diet – as these minerals all work together. Foods which are good sources of calcium include almonds, Brazil nuts, tinned sardines, sunflower seeds, muesli, bread, tahini, dried figs and dairy products such as milk and cheese. Magnesium is likewise found in Brazil nuts, bread and dried fruit and also in beetroot, broccoli, kale and cabbage. Another reason to eat your greens!

Any easy to use, DIY, home testing kit is available from City Assays. This kit will allow you to measure your own vitamin D level, and to assess if you would benefit from taking a supplement.

 

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