Jo Lewin

With the recent spell of sunshine, I thought it might be timely to write a piece about vitamin D. Heralded as the wonder-vit but somewhat misunderstood as to the what-where-how much we need, I aim to provide you with a bit of clarity.

Vitamin D deficiency is an important health issue. According to the National Diet and Nutrition Survey, 90% of the population have an ‘insufficient’ amount of serum circulating vitamin D.  This vitally important vitamin (which is actually a steroid hormone) can help to support immune function, healthy bones and teeth, inflammation and balance hormone levels. Low levels are linked to a wide range of health problems, from cancer and cardiovascular disease to cognitive impairment and auto immune conditions. Risk factors for vitamin D deficiency include age, pregnancy and darker skin pigmentation.

Vitamin D comes from sunshine!

The major source of vitamin D is sunshine as it is manufactured in the skin on contact UV rays. The risk of skin cancer from excessive sunlight or sunbeds opens up an important debate as to whether it is beneficial to spend more time in the sun to increase vitamin D levels. Very few foods naturally contain vitamin D. Fortified milk, egg yolks and oily fish are the best sources, but you can’t really rely on food to provide you with optimal amounts of vitamin D on a daily basis. Salmon, mackerel, sardines, herring and trout are particularly rich sources with wild salmon providing 500-1000IU vitamin D per 100g. To put this into perspective, an adult would have to eat 2-4 servings of wild salmon a day to maintain daily vitamin D requirements. Fortification of foods with vitamin D is limited to margarine, some breakfast cereals, some cheeses and yoghurts but the amounts are negligable.

Supplementation is seen by some as the safest and most effective method of achieving optimal vitamin D status. If you are choosing a supplement, it is important to consult a qualified healthcare practitioner who can advise on the appropriate dose for your individual requirements. Supplements should contain vitamin D in the form of D3 (cholecalciferol) since this is the form naturally produced by the skin.

“Vitamin D deficiency is now recognised as a pandemic, with more than half of the world’s population currently at risk” (Pizzorno J., 2010) but why is this so? Sunlight’s ability to help us produce vitamin D is hampered by season, latitude, time of day and sunscreen (SPF8 and above). Not to mention evolutionary and behavioural changes such as wearing clothes, working inside and the anxiety around sun exposure and skin cancer which means that during the winter months, many of us are simply not getting enough. Skin will naturally produce approximately 10,000 IU vitamin D after 20-30 minutes summer sun exposure (April – October). The current recommended daily requirement for 19-70 year olds is 600 IU, however researchers now suggest that an average daily maintenance dose of 5000 IU is more realistic to promote optimal vitamin D levels.