A common bacteria found in the stomachs of millions of Britons could partly explain the disturbing rise in bowel cancer cases, new research suggests.

Scientists say the bacterium, known as Helicobacter pylori (H. pylori), could be responsible for as many as one in five cases of the deadly disease. 

Around 40 per cent of people carry the bacteria in their stomach and it does not usually trigger symptoms.

However in some, it can cause indigestion, bloating and nausea and, in worst cases, ulcers that can develop into stomach cancer. 

Now scientists have suggested those exposed to the bacteria - usually as a result of contaminated food - face a 60 per cent higher risk of colorectal cancer than those not exposed. 

The research throws open the possibility that antibiotics could be offered to high risk patients in a bid to prevent cancer developing.   

Publishing their findings in the journal eGastroenterology, scientists from the University of Hong Kong said: 'H. pylori control may help prevent gastric cancer and, if the link with bowel cancer is causal, reduce the burden of disease.'

Bowel cancer is one of 11 types that are increasing among young people.

If current trends continue, colorectal cancer is projected to become the leading cause of cancer-related death among young adults by 2030. 

While obesity is the only known behavioural risk factor that is on the rise, experts say it is not sufficient to explain the overall rise. 

The current study suggests that harmful strains of H. pylori might be involved. 

Together with experts from the University of California, the Hong Kong researchers analysed health data from 43 studies, involving more than 48.7 million people worldwide.

They found that people exposed to the bacteria had a 59 per cent higher risk of colorectal cancer than those not exposed.

Using all available studies, the researchers estimated that 22 per cent of cases could potentially be linked to the bacteria. 

However, when they looked at only the strongest studies, the estimate dropped to around 12 per cent.

The link appeared strongest in the Western Pacific Region - including countries such as China, Japan and South Korea - where researchers estimate around a quarter of bowel cancer cases are linked to H. pylori. 

The researchers said this could be because H. pylori infections are more common in these areas. 

It is not completely clear exactly how the bug is passed from one person to another but poor sanitation and hygiene and contaminated food and water are common causes of infection. 

Experts have also warned that vegetables including lettuce, leeks and spinach can become contaminated if they are grown or washed using contaminated water, potentially exposing consumers to the bacteria. 

In the UK, where prevalence has been steadily falling, older adults are much more likely to carry the bug. 

It can be detected using a breath or stool test which check whether the bacteria is present in the stomach or stool. 

Treatment typically involves a seven-day course of triple therapy, combining one acid-lowering medication with two different antibiotics to kill the bug. 

Studies that followed participants for more than 10 years found that those who had the bacteria eradicated - through the use of antibiotics - had a 10 per cent lower risk of developing bowel cancer than those who remained untreated. 

The researchers concluded that while their work does not prove H. pylori causes bowel cancer, treating the infection could help minimise the risk of disease in at-risk populations. 

Commenting on the findings, Dr Rosiered Brownson-Smith, a colorectal cancer researcher at King’s College London, who wasn't involved in the current study, said: 'H. pylori is already a well-established cause of stomach cancer, and if it does turn out to meaningfully raise bowel cancer risk too, that would matter hugely for prevention.

'But this study is a careful estimate of what might be true, not proof of what is. Crucially, there is still no trial showing that treating H. pylori infection actually prevents bowel cancer.'

According to Cancer Research UK, more than half of bowel cancers are preventable, with a quarter linked to not eating enough fibre, 11 per cent driven by obesity and 6 per cent caused by heavy alcohol consumption.