22 June 2023

Previous research showed that low Vitamin D levels are linked to worse bowel cancer survival rates.

Vitamin D levels tend to fall dramatically after surgery, leading researchers to believe that supplementation to maintain healthy levels at the time of surgery could ultimately improve long-term cancer survival rates.

The team at the Institute of Genetics and Cancer (IGC), led by Professor Malcolm Dunlop and Peter Vaughan-Shaw, advocate a full-scale randomised controlled trial to better understand the relationship between bowel cancer and Vitamin D – with supplementation potentially being introduced to support standard care from the point of diagnosis.

The reason why Vitamin D levels matter is because earlier studies have shown that Vitamin D has anti-tumour effects on bowel cells in the laboratory but also in bowel tissue sampled from volunteers (Link)

The ICG study, part-funded by national bowel health charity Bowel Research UK, has been published in Frontiers in Nutrition (Link).

The study discovered that patients who took high doses of Vitamin D for around four weeks before bowel surgery were found to approximately halve the fall in blood Vitamin D levels immediately after surgery.

Out of 122 patients enrolled in the study, 41 patients took daily supplements in the form of four jelly capsules of 800 units of Vitamin D, leading to much lower rates of Vitamin D insufficiency after surgery- just 14% compared to 84% insufficiency in the control group not receiving supplementation.

Peter Vaughan-Shaw comments: “Together with previous studies showing that higher Vitamin D levels significantly improves survival in bowel cancer patients, the current results provide a compelling rationale for early initiation of Vitamin D supplementation after a diagnosis of bowel cancer.

“We previously looked at gene activity in the rectum, and in some patients we saw anti-tumour responses with Vitamin D supplementation, but in others it was not so marked.

“Further research is needed as part of a larger, fully randomised trial so we understand why some patients have marked responses and others much less so. One theory is that it depends on baseline genetics, but it may also be linked to the general health of the patients, or it could be both. My view is that even before a larger new trial, there is a good argument for all bowel cancer patients to take Vitamin D both ahead of surgery and also after surgery.

“And it’s worth pointing out that a typical diet would not provide the levels of Vitamin D achieved through supplementation.”

Chief Executive Officer of Bowel Research UK, Lynn Dunne, added: “This is the latest piece of research by the Edinburgh team on Vitamin D and its association with bowel cancer. The next steps will be a larger, fully randomised trial. We are delighted that our ‘proof of concept’ funding has advanced the research in this promising field to the point where a large trial is now desirable.”