Taking regular Vitamin D supplements may reduce cancer deaths in the population by 15%, according to scientists.

Data gathered from the UK Biobank, an online database of medical and lifestyle records of around 500,000 Britons, indicates vitamin D deficiency is linked to an increased cancer mortality risk – particularly in relation to bowel, stomach, prostate, and lung cancers.

The researchers said their work, published in Elsevier’s European Journal of Cancer, adds to evidence that vitamin D may have a protective effect against cancer.

While the findings do not explain why this happens, the team said one possibility is that vitamin D supplements may induce anti-inflammatory, antioxidant, and DNA damage repair mechanisms, which can thwart mutations that allows tumours to grow.

Study author Ben Schottker, an epidemiologist at the German Cancer Research Centre, said: “Our findings identified a statistically significant relationship between vitamin D deficiency and increased mortality among several cancers.

“These results can be explained by other studies, which found mechanisms by which vitamin D inhibits cancer growth and metastasis.”

The NHS advice is that adults and children over four take a daily supplement containing 10 micrograms of vitamin D throughout the year.

According to the Department of Health and Social Care, around one in six adults and almost 20% of children in the UK have vitamin D levels lower than government recommendations.

Older people, the housebound and people from black and South Asian communities are more likely to have lower levels of vitamin D.

For the study, the researchers looked at data from more than 400,000 people aged 40–69.

In-depth medical information was gathered through blood, urine and saliva samples.

A short interview and a questionnaire as used to assess vitamin D consumption as well as lifestyle factors such as alcohol consumption, smoking.

Follow-up data on health outcomes were gathered through NHS links as well as care data, cancer screening data, and disease-specific registers.

Over a period of nearly 13 years, close to 13,000 people died of cancer.

Results showed a majority of the study population had either vitamin D deficiency (21.1%) or insufficiency (34.4%) – used to describe low levels of vitamin D.

Of the people involved in the study, only 4.1% regularly took a vitamin D supplement and 20.3% regularly took a multivitamin.

Results showed that vitamin D supplement users had 15% lower total cancer mortality and 25% lower lung cancer mortality compared to those who did not take the supplement.

The also found researchers found that those with vitamin D deficiency had 42% increased mortality for stomach, 27% for bowel, 24% for lung, and 36% for prostate cancers.

Meanwhile those with vitamin D insufficiency were found to have 14% increased bowel cancer mortality and 19% increased lung cancer mortality.

The scientists said that the potential to reduce cancer mortality by vitamin D supplementation in populations with low levels should be further explored in new research.

Commenting on the study, Dr Jenna Macciochi, senior lecturer in immunology at the University of Sussex, said: “This study adds to the growing body of evidence on vitamin D and cancer.

“Vitamin D plays multiple key roles in immune health and the immune system is part of the body’s cancer defence system.

“With cancer rates rising and presenting a serious public health issue, its useful to have further insight into the role of vitamin D in the prevention of cancer.”

But Dr Macciochi also cautioned that the Biobank data might not be diverse and representative of the whole of the UK population.

Alex Ruani, doctoral researcher at University College London and chief science educator at The Health Sciences Academy – who was not involved in the study, said that the exact dosage taken by participants was not ascertained and the risk reduction was not the same for all cancers.

She said: “This research doesn’t imply that taking vitamin D3 supplements will for sure lower your risk of death from cancer.

“Supplementation may help with consistent vitamin D levels, whereas production from sunlight can be variable and dependent on weather, time of the day, exposure duration, being outdoors or indoors, protective UV wear or sunblock, and many other factors.”

She added: “Common food sources of vitamin D3 include full-fat dairy, egg yolks, and fish.

“Although toxicity is rare, there is an upper tolerable limit set in the UK, where vitamin D3 supplementation shouldn’t exceed 100 micrograms a day.”