Boosting vitamin D levels by taking a daily supplement could cut the risk of dying from cancer by 13 percent, according to a study.
Vitamin D is made by the body when exposed to sunshine but modern lifestyles mean many spend more time indoors.
US researcher Dr Shifeng Mao, from the Allegheny Health Network Cancer Institute in Pittsburgh, reported findings showing that people who were deficient in vitamin D were more than twice as likely to develop pancreatic cancer and also had a higher risk of bowel cancer.
A separate study involving 79,000 healthy adults found taking a supplement for at least three years was associated with a 13 percent drop in risk of dying from any form of cancer later in life.
A third study found taking a daily pill along with a statin was linked to a reduction in deaths from prostate cancer of almost 40 percent.
All three studies were presented at the American Society of Clinical Oncology conference in Chicago.
The work bolsters growing calls for the Government to add vitamin D to common foods such as milk or bread – a policy used in the US, Canada, Sweden, Finland and Australia.
While vitamin D is produced when skin is exposed to the sun, it can also be obtained by eating liver, eggs, red meat and plenty of oily fish.
But millions who do not eat enough of these foods – or fail to get sufficient sunshine, particularly in gloomy winter months – should take supplements instead.
The study that reported the 13 per cent reduction in cancer risk was conducted by Michigan State University and Hurley Medical Centre, which reviewed findings from ten trials involving adults with an average age of 68.
A study at Madrid University Hospital in Spain, involving 2,280 men, found those on standard treatments for prostate cancer who also took vitamin D and a statin had 38 per cent lower mortality rates than those who did not.
Dr Tarek Haykal, lead researcher from Michigan State University, said: ‘I would like to see more oncologists and primary care doctors consider prescribing vitamin D for their patients as it carries many benefits with minimal side effects.’
Professor Daniel Bikle, of the University of California San Francisco, said: ‘In places such as the UK, there is not enough sun all year round, so supplements in winter are necessary.’
Researchers are not sure exactly how vitamin D fights cancer but some scientists believe it produces an enzyme that ‘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.
* Prescribing Fitbits to cancer patients, encouraging them to walk more, could significantly boost their survival, research suggests.
A number of studies presented at the Chicago conference found those with higher step counts had mortality rates up to a third lower than others.