INDOOR living has made growing numbers of people short of vitamin D, with attendant risk of cancer, diabetes and rickets, experts on diet said yesterday. Most people in Britain get as little as a fifth of the vitamin D they need because of low exposure to sunlight and poor nutrition.
Almost all the body’s vitamin D is produced by exposure to sunlight; only very small quantities, in a handful of food groups such as oily fish, come from diet.
Fear of skin cancer, however, has made people wary of the sun, and a growing tendency to spend work and leisure time indoors also reduces their exposure. In Britain the sun is strong enough for vitamin D synthesis only between April and October.
As a result, vitamin D deficiency now affects between a quarter and half of adults. The average daily intake is between 3 and 4 micrograms, or 120 to 160 units, though experts believe about 12.5 micrograms (500 units) is required for optimum health.
The danger of deficiency is greatest among black and Asian people, as darker skin reduces the ability to make vitamin D from relatively weak sunshine. Muslim women who cover themselves fully in public reduce their synthesis of vitamin D still further.
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It is already known that vitamin D deficiency contributes to the bone deformity rickets in children and to osteoporosis in adults, but recent research links it to many other disorders, including hypertension, diabetes, autoimmune conditions such as multiple sclerosis, and breast, prostate, colon and ovarian cancer.
Birgit Teucher, of the Institute of Food Research in Norwich, one of the scientists who spoke on vitamin D in London yesterday, said that in winter about a quarter of British adults do not get enough Vitamin D for optimum bone health, and about half do not get enough for general health.
The scientists said the Government should issue a recommended daily intake of vitamin D, and consider fortifying milk, bread or orange juice to increase consumption. There is a recommended daily dose of 10 micrograms (400 units) for infants under 4 and adults over 65, but no recommendations for other ages.
More sun would do more harm than good, said Graham Bentham of the University of East Anglia, adding that deaths from melanoma grew by 7 per cent last year.