Vitamin D could help ward off cancer, a major study suggests.
Middle-aged men and women with high levels in their blood are 20% less likely to get the disease, experts found.
Vitamin D is already known to strengthen bones and muscles and growing evidence suggests it also protects against respiratory and neurological problems.
But this is the first study to find it could also prevent cancer. The vitamin, naturally produced by the skin in response to sunlight, can be gained by eating sardines, liver or eggs. But many people are deficient in vitamin D, thanks to modern diets, indoor lifestyles and grey weather.
To counter this, Public Health England advises everyone to take 10mcg daily supplements from October to April. The National Cancer Centre in Tokyo, whose work is published in the British Medical Journal, took blood samples from 33,700 people aged between 40 to 69, tracking them for 16 years, and analysed the data.
Those who came among the highest quarter of vitamin D levels were 20 % less likely to develop cancer of any type than those in the lowest quarter.
It was particularly effective at warding off liver cancer, with the highest quarter 55 % less likely to develop the disease
The researchers believe vitamin D produces an enzyme which ‘detoxifies’ natural acids in the body. Reducing the potency of these acids may help stop them causing damage to internal organs, which in turn reduces cancer risk.
The researchers said lithocholic acid, a substance produced by the liver, is a particular cancer risk – which may ‘possibly explain the strong finding for liver cancer’.
They added: ‘The anticarcinogenic effect of vitamin D is probably not limited to a single organ or tissue in the body.’
British scientists have long called for vitamin D to be added to common foods such as milk or bread – a policy already used in the US, Canada and Australia. People with dark skin and pregnant women should take vitamin D supplements all year round, Public Health England advises.