Top cancer expert reveals only supplement that could help reduce bowel cancer risk

Taking vitamin D could help protect you from bowel cancer, a scientist says.

Professor Justin Stebbing, an expert in biomedical sciences at Anglia Ruskin University, said there was evidence the nutrient helped combat the disease.

His comments come amid a mysterious rise in bowel cancer cases among young adults, with diagnoses having shot up 80 per cent in 30 years. 

Professor Stebbing said, while not a miracle cure, evidence was promising enough to recommend it as a potential way to reduce your risk of bowel cancer. 

‘Maintaining sufficient vitamin D levels – at least 30 ng/mL – is a low-risk, cost-effective health measure’ he wrote for The Conversation. 

‘Combined other strategies like regular screening, a healthy diet, physical activity, and personalised care, vitamin D could still play a valuable role in overall cancer prevention.’

Also known as the ‘sunshine vitamin’ people get vitamin D from exposure to sunlight as well as from foods like oily fish, red meat and egg yolks. 

But people can also top up their levels using supplements, available for about 2p per pill at high-street pharmacies. 

While science has established vitamin D is crucial for keeping bones, teeth, nerves, muscles and the immune system healthy Professor Stebbing said its exact role in cancer prevention was less clear.

He said lab tests had shown the nutrient played a critical role in combatting inflammation in tissue, supporting the immune system and regulating cell growth, including in the bowel. 

All of this supports the idea that high vitamin D levels should help reduce cancer risk. 

And data does back this up, with some studies suggesting people with recommended vitamin D levels are significantly less likely to develop bowel cancer.

Professor Stebbing said: ‘This paints a hopeful picture, suggesting that something as simple as getting more vitamin D – via sun exposure, diet, or supplements – could lower cancer risk.’

But he added that when applied to real-world patients, the benefits were less clear. 

Professor Stebbing said randomised controlled trials — the gold-standard of medical research where patients are randomly assigned a treatment or a placebo — hadn’t delivered the same promising results.

He highlighted one major study, involving 25,000 patients, which found taking vitamin D supplement had no significant effect on bowel cancer risk. 

But another did find that giving vitamin D to patients who already had the disease helped boost their lifespan, implying it did help combat cancer in some capacity.

This, he said, presented a mixed picture for vitamin D and cancer risk.

Professor Stebbing said it could be that only some patients benefit from the reduced risk from taking vitamin D or it was dosage dependent, or a combination thereof. 

He also added there was also scientific debate on if a lack of the nutrient triggered the disease or if the earliest stages of cancer caused levels to drop.   

‘Does low vitamin D contribute to cancer development? Or does the onset of cancer reduce vitamin D levels in the body?’ he wrote. 

So, Professor Stebbing concluded that the evidence wasn’t yet strong enough to recommend vitamin D as cancer prevention strategy. 

However, he added that considering it is cheap, low-risk, and crucial to other aspects of health anyway, it won’t hurt to ensure you are getting enough. 

‘While it’s not time to rely on supplements alone, ensuring adequate vitamin D levels – through sun exposure, diet, or supplements – remains a smart choice for your health,’ he said. 

Charity Cancer Research UK (CRUK) states that, while research is ongoing, there is no strong evidence that having a vitamin D deficiency increases your risk of cancer. 

The body adds that there is also no firm evidence that taking a vitamin D supplement specifically helps prevent cancer.

Separate CRUK data shows bowel cancer has seen a 52 per cent increase in among young adults, those aged 25 to 49, since the early 1990s. 

The reasons behind the rise are still unknown.

But some scientists have suggested increasing pollution might be to blame, while others suggest the trend is linked to growing consumption of ultra-processed food. 

CRUK, while acknowledging the rise, stresses that bowel cancer rates in younger adults are still low, with only around one in 20 cases diagnosed in patients under 50.

There are around 2,600 new bowel cancer cases in people aged 25-49 in Britain every year, and around 44,100 new cases among all ages.

Symptoms of the bowel cancer include changes in bowel movements such as diarrhoea or constipation, needing or feeling the need to empty your bowels more or less frequently, blood in the stool, stomach pain, bloating, unexpected weight-loss and fatigue. 

Vitamin D supplements are considered more important during the colder months when Britain gets less daylight hours and people get less vitamin D from sunlight.

As such the NHS recommends all adults — and children over four — consider taking a vitamin D supplement during autumn and winter. 

British data suggests as many as two in five adults may be vitamin D deficient during the winter months when there are fewer daylight hours.

A lack of the vitamin D can lead to bone problems, including rickets, a condition that causes bone pain, bone weakness and can lead to deformities.

But people should be careful not to have too much of the nutrient.

As vitamin D helps absorb calcium too much can cause a condition called hypercalcaemia.

This can ironically cause bones to become weaker as well as damage the kidneys and the heart.

As such the NHS recommends people don’t take more than 100micrograms of vitamin D per day unless specifically advised to by their doctor.

The amount of vitamin D in the body can be determined by a blood test – with the results are reported in units of nanomoles per litre, written as nmol/l.

A level of 25 nmol/l or lower is considered a deficiency – this was set about two decades ago, as falling below this was linked to an increased risk of rickets.