Sensible sun exposure for vitamin D

There has been a lot in the press recently about vitamin D deficiencies, leading to rickets in children and osteomalacia in adults.

The most commonly-known benefit of vitamin D is in relation to bone health, helping to regulate blood calcium levels and promoting absorption of this vital mineral to maintain bone integrity. Calcium also has other important functions, it is essential for nerve impulse transmission, muscle contraction and blood clotting.

We can get vitamin D from the sunshine, not directly but our body uses the UV rays to synthesise vitamin D. The effect of irradiation on a cholesterol based molecule in the skin starts off a series of chemical reactions which ends with vitamin D in the kidneys. Not all sunshine is equal though, the UV rays need to be a wavelength of 290-315 nm. On average, In the UK we get the right sort of rays from April to October.

We can also get vitamin D from our diets, particularly from oily fish, e.g. salmon, sardines, trout, mackerel and pilchards. Both canned and fresh oily fish will provide you with vitamin D. Other food sources of vitamin D include eggs, fortified milk, fortified dairy spreads and fortified cereals.

For most people, adequate levels of vitamin D can be obtained through exposure to the sun and eating a healthy balanced diet. Particular groups are at increased risk of vitamin D deficiency and for these people supplementation may be appropriate. Anyone who does not get exposure to sunlight, irrespective of the reason why, is at risk of being deficient. As we age our risk of vitamin D deficiency increases, one reason being our skin becomes less effective at absorbing sunlight.  Darker skinned people also have an increased risk because the melanin in their skin naturally protects against UV rays. Young children have a greater requirement for vitamin D because their bones are growing, also making them prone to deficiency.

Although an excess of vitamin D is harmful we are unlikely to overdose through too much sun or from our food, but it is possible to get too much if using supplements.  Vitamin D supplements are readily available over the counter. Use them with caution and with appropriate medical advice.

The amount of sunlight you need varies dependent on your skin colour, as little as 10-15 minutes a day for light-skinned people.  Sun screens that block the harmful effects of UV light also prevent the synthesis of vitamin D, so spend a short period enjoying the sun before you slap on the sunscreen. 

As well as providing for vitamin D, scientific research suggests that sunlight may also:

• improve sleep quality
• improve mood
• lower risk for multiple sclerosis
• heal psoriasis
• protect against melanomas
• lower blood pressure
• reduce the risk of heart attack and strokes.

A balance between the harmful effects of the sun and the benefits of sunlight must be struck.