Long-term use of antibiotics can significantly raise the risk of developing polyps on the bowel that can lead to cancer, according to findings of a US study published in the journal Gut.

Researchers looked at data from 16,600 nurses aged between 30 and 55, involved in long-term US research launched in 1976 called the Nurses' Health Study.

They found that those who had taken antibiotics for two months or more when aged between 20 and 39 were 36 percent more likely to be diagnosed with bowel polyps known as adenomas in later life compared with those who hadn’t, while women those taking antibiotics for at least two months in their 40s and 50s were 69 percent more likely to develop adenomas.

The study authors say their research is the first to link duration of antibiotic use, in a dose-dependent fashion, to colorectal adenoma, the primary precursor of colorectal cancer, and that the findings lend weight to the argument that significant changes to bacterial levels could play a key role in the development of cancer.

“Antibiotics fundamentally alter the gut microbiome, by curbing the diversity and number of bacteria, and reducing the resistance to hostile bugs.

"This might all have a crucial role in the development of bowel cancer, added to which the bugs that require antibiotics may induce inflammation, which is a known risk for the development of bowel cancer.

“Additional studies investigating the impact of antibiotic exposure with gut microbial composition and function, particularly in relation to the mechanisms underlying colorectal carcinogenesis, are warranted,” they note.