About one quarter of Britons may suffer from a winter deficiency of vitamin D, which can increase the risk of muscle weakness, autoimmune diseases, osteoporosis and certain types of cancer.
Britain's northern location and lack of sunshine means that during the winter months many people do not get enough of the vitamin, which the body makes when it is exposed to sunlight.
Foods such as oily fish and egg yolk are rich in vitamin D and margarines are fortified with it, but it might not be enough to get Britons through the winter months when their stores of the vitamin diminish.
Health experts say more research is needed but suggested vitamin D supplements such as cod liver oil and fortifying more foods could be a solution.
About 80 percent of vitamin D comes from exposure to sunlight. Increased time spent indoors and fears about the risks of cancer from too much sun have limited many people's exposure to sunlight.
In addition, from October to March sunlight exposure in Britain (and other countries in northern latitudes, like Canada and the northern U.S.) will not be sufficient for the body to produce any vitamin D. During these winter months we rely on what we have stored in our body from summer exposure and what we get from diet.
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