People who take antibiotics for two months or longer during their working life are more likely to develop bowel growths that can become cancerous, a new study has found.
By analysing a major study into the health of US nurses, researchers found those who had taken antibiotics for a long time between the ages of 20 and 39 were more likely to be diagnosed with a particular type of bowel polyp later in life.
Bowel polyps, small growths on the inner lining of the colon or rectum, affect 15 to 20 per cent of people in the UK and are usually harmless but sometimes develop into cancer.
The researchers said the findings add weight to emerging evidence that the type and diversity of bacteria in the gut may have a key role in the development of the disease.
However they did not look at how many of the polyps, known as adenomas, did go on to become cancerous.
The research, published in the journal Gut, examined data from 16,642 women who had taken part in the Nurses Health Study, set up to monitor the health of 121,700 nurses.
Since joining the study in 1976, the nurses have filled in detailed questionnaires every two years about aspects of their life, including lifestyle factors, medical history and disease development.
The subjects of the new research were aged 60 and older in 2004, were able to provide a history of antibiotic use between the ages of 20 and 59 and had had at least one bowel investigation between 2004 and 2010.
During this period, 1,195 abnormal growths in the colon and rectum were diagnosed in this group. Adenomas precede the development of the majority of cases of bowel cancer.
The researchers found that recent use of antibiotics within the past four years was not associated with a heightened risk of an adenoma diagnosis, but long-term use in the past was.
Those who had taken antibiotics for two months or more between the ages of 20 and 39 were 36 per cent more likely to be diagnosed with an adenoma when compared with those who had not taken antibiotics for any extended period in their twenties and thirties.
Similarly, women who had taken antibiotics for two months or more during their forties and fifties were 69 per cent more likely to be diagnosed with an adenoma than those who had not taken such medication for an extended period.
And those who had taken these drugs for 15 days or more between the ages of 20 and 39, and between the ages of 40 and 59, were 73 per cent more likely to be diagnosed with an adenoma, when compared to non-users.
13 ways to help prevent cancer
13 ways to help prevent cancer
Stopping smoking. This notoriously difficult habit to break sees tar build-up in the lungs and DNA alteration and causes 15,558 cancer deaths a year
Avoiding the sun, and the melanoma that comes with overexposure to harmful UV rays, could help conscientious shade-lovers dodge being one of the 7,220 people who die from it
A diet that is low in red meat can help to prevent bowel cancer, according to the research - with 30 grams a day recommended for men, and 25 a day recommended for women
Foods high in fibre, meanwhile, can further make for healthier bowels. Processed foods in developed countries appear to be causing higher rates of colon cancer than diets in continents such as Africa, which have high bean and pulse intakes
Two servings of fruit and three servings of vegetables a day were given as the magic number for good diet in the research. Overall, diet causes only slightly fewer cancer deaths than sun exposure in Australia, at 7,000 a year
Obesity and being overweight, linked to poor diet and lack of exercise, causes 3,917 deaths by cancer a year on its own
Dying of a cancer caused by infection also comes in highly, linked to 3,421 cancer deaths a year. Infections such as human papilloma virus - which can cause cervical cancer in women - and hepatitis - can be prevented by vaccinations and having regular check-ups
Cutting back on drinks could reduce the risk of cancers caused by alcohol - such as liver cancer, bowel cancer, breast cancer and mouth cancer - that are leading to 3,208 deaths a year
2014 Getty Images
Sitting around and not getting the heart pumping - less than one hour's exercise a day - is directly leading to about 1,800 people having lower immune functions and higher hormone levels, among other factors, that cause cancers
2011 Getty Images
Hormone replacement therapy, which is used to relieve symptoms of the menopause in women, caused 539 deaths from (mainly breast) cancer in Australia last year. It did, however, prevent 52 cases of colorectal cancers
2003 Getty Images
Insufficient breastfeeding, bizarrely, makes the top 10. Breastfeeding for 12 months could prevent 235 cancer cases a year, said the research
Oral contraceptives, like the Pill, caused about 105 breast cancers and 52 cervical cancers - but it also prevented about 1,440 ovarian and uterine (womb) cases of cancer last year
2006 Getty Images
Taking aspirin also prevented 232 cases in the Queensland research of colorectal and oesophagal cancers - but as it can also cause strokes, is not yet recommended as a formal treatment against the risk of cancer
The authors wrote: “The findings, if confirmed by other studies, suggest the potential need to limit the use of antibiotics and sources of inflammation that may drive tumour formation.”
Sheena Cruickshank, senior lecturer in immunology at the University of Manchester, said while “there is increasing evidence that our microbiota are important in regulating our immune responses and many aspects of our normal functions”, she would be concerned about advising people to avoid using antibiotics.
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