TAKING antibiotics could increase your risk of bowel cancer, experts have warned.
They fear the drugs alter the bacteria in the gut, increasing the risk of the second deadliest cancer in the UK.
But, the drugs also appear to protect against rectal cancer, the same study found.
Second deadliest cancer
Around 42,000 new cases of bowel cancer are diagnosed in the UK, with an estimated 16,000 people losing their lives to the disease each year.
That’s why The Sun launched the No Time 2 Lose campaign – to raise awareness of the killer disease, and call for screening rates to be lowered from 60 to 50 – something the Government agreed to last summer.
Now, scientists in the US have warned antibiotics could be a risk factor – and have urged doctors to think twice before prescribing the drugs.
It comes as antibiotic resistance – from overusing the drugs – threatens to fuel the spread of superbugs and take us back to an era when minor infections proved deadly.
It’s estimated 70 billion doses of antibiotics are taken across the world each year – that’s 10 doses per person.
The drugs have a strong and lasting effect on the gut microbiome, altering the balance of good and bad bacteria.
Drugs ‘increase bowel cancer risk’
Now, experts at Johns Hopkins University in Baltimore, have looked closer at the potential link with colon cancer.
They reviewed the medical records of more than 28,900 British patients diagnosed with bowel or rectal cancer – as well as 137,077 Brits who didn’t have cancer.
They found 70 per cent of patients with bowel cancer and rectal cancers had been prescribed antibiotics, compared to 68.5 per cent of patients without the disease.
Nearly six in 10 of the study participants had been prescribed more than one class of antibiotic.
Dr Cynthia Sears, who co-authored the study at The Bloomberg Kimmel Institute for Cancer Immunotherapy, said: “The association between bowel cancer and antibiotic use was evident among patients who had taken these drugs more than 10 years before their cancer was diagnosed.”
Type of antibiotic ‘makes difference’
Dr Sears’ team believe the risk depends on the type and class of antibiotics given to patients.
Penicillins were “consistently associated with a heightened risk of bowel cancer” – in the first and middle parts of the colon.
Of those, ampicillin and amoxicillin were the penicillins most commonly prescribed to these patients.
And in contrast, prescriptions of tetracyclines were found to lower the risk of cancer in the rectum – the last part of the bowel.
The new findings, published in the journal Gut, also found that taking the drugs for just 16 days was linked to a “heightened risk of bowel cancer” – again in the upper part of the colon.
Meanwhile, antibiotic use for longer than 60 days was associated with a 15 per cent lower risk of rectal cancers, compared to no history of taking the drugs.
Public shouldn’t worry
However, the researchers admitted this is an observational study, and so can’t establish a cause.
They weren’t able to assess other lifestyle factors, or hospital treatment that could have affected a patient’s cancer risk.
It hasn’t given me, personally, any strong concerns about my own past use of antibiotics and my risk of bowel cancer
Prof Kevin McConway, a statistics expert at The Open University
Dr Ian Johnson, a nutrition expert at the Quadram Institute Bioscience in Norwich, said the findings while “interesting” should not concern the public too much.
He said: “The increased risk of colon cancer in people receiving the highest exposure to some types of antibiotics was apparently about fifteen percent, comparable in magnitude to the risk associated with, for example, regular consumption of processed meat.
“However, for some classes of antibiotic, the increased risk for cancer of the colon seems to be partially offset by a reduced risk of rectal cancer.
“In any case, the public should not be too concerned because, for individuals, the changes in absolute risk are relatively low.
Prof Kevin McConway, a statistics expert at The Open University, agreed.
He said: “It hasn’t given me, personally, any strong concerns about my own past use of antibiotics and my risk of bowel cancer.
“The risks depend on which part of the bowel might be affected, on the type of antibiotic, on how long ago the antibiotics were taken, and on how many days the antibiotics were taken for.
“One important point, though, is that most of the associations between antibiotic use and bowel cancer rates were not particularly strong.”
Dr Sears said while more research is needed, “whether antibiotic exposure is causal or contributory to colon cancer risk, our results highlight the importance of judicious antibiotic use by clinicians”.