Vitamin D could cut the risk of dying from cancer, according to research which suggests sunshine and supplements could save lives.
Scientists warned that modern lifestyles could be increasing the risk of disease, with ever longer hours spent indoors, or in the shadow of skyscrapers.
Research on almost 80,000 adults by Michigan State University and Hurley Medical Center found that taking a supplement for at least three years was associated with a 13 per cent drop in mortality from all cancers.
Another study by Madrid University Hospital found that taking a daily pill along with a statin was linked to a 38 per cent reduction in deaths from prostate cancer. Scientists from said the effects appeared to be independent of each other, suggesting that both the medication and the vitamin boosted survival.
A third study by Allegheny Health Network Cancer Institute, in Pittsburgh, suggested that a deficiency of vitamin D could double the risk of pancreatic cancer.
Researchers said GPs should prescribe supplements to ensure the population increased its intake of vitamin D.
The slew of studies, presented at the American Society of Clinical Oncology (ASCO) annual conference in Chicago, follow research suggesting that the vitamin could protect against heart disease, and diabetes, as well as helping bone strength.
The studies did not show why vitamin D might help cancer survival. But experts said it could enhance the body’s immune response, reducing the proliferation of tumour cells.
Dr Tarek Haykal, lead researcher from Michigan State University, said the findings were “promising” - and urged GPs to recommend supplements.
He said: “The take home message is that vitamin-D might carry a benefit for the cancer population. Patients who received vitamin-D supplementation for at least three years in any form, had significantly lower cancer-related deaths”.
Dr. Shifeng Mao, from Allegheny Health Network Cancer Institute, said modern lives made it difficult to get sufficient sunshine.
“We are living in a modern society with a fast-paced life style,” he said. “People spend significant amount of time at work in a concrete building and have much less time for leisure, let alone being exposed to nature and sunlight, so Vitamin D deficiency is prevalent.”
Three in four adults in Britain are deficient in the vitamin, some research suggests.
In 2016, health officials recommended that all adults should consider taking supplements, especially in the winter, and providing them for children over the age of one.
However, over-exposure to sunshine is linked to an increased risk of skin cancers, which have seen a sharp rise in the UK since the advent of cheaper travel, and package holidays.
Medics said pensioners could cut their risk of early death by up to 20 per cent by taking a supplement.
Dr Daniel Bikle, Professor of Medicine and Dermatology at University of California, San Francisco, said: “I’m a big believer in sensible sun exposure, getting some sun or your skin without burning. But in places such as the UK, there is not enough sun all year round, so supplements in the winter months are necessary.
Dr Rachel Shaw, from Cancer Research UK, said the studies did not prove that vitamin D prevented cancer developing.
She said: “It may improve prognosis when cancer develops - potentially in both those who take vitamin D preventatively, and those who take it in addition to their prescribed cancer treatments. “More research is required to determine who will benefit and the recommended dosage, so it’s important that cancer patients consult their doctor before taking vitamin supplements."