Taking too many antibiotics can contribute to the development of colorectal cancer in the proximal part (upper part of the colon), according to the results of a large Swedish study. According to the authors, this work is another reason to limit the excessive prescribing of these drugs.
Antibiotics have saved millions of lives over the past decades by fighting bacterial diseases… But nature adapts. Through the use of this type of treatment, bacteria have developed resistance to the proposed treatments. And the forecasts are disappointing: WHO estimates that these resistant bacteria could kill up to ten million people by 2050. Therefore, researchers have recently drawn the attention of the authorities to the need to take urgent measures to control the use of antibiotics.
Antibiotics and colorectal cancer
However, excessive use of antibiotics can have other insidious consequences, according to a new Swedish study.
A small British study published in 2019 already suggested that taking antibiotics could increase the risk of colon cancer. A new study based on medical data from more than 40,000 Swedes recently revealed the same connection.
For this study, scientists used data from the Swedish Colorectal Cancer Registry to identify tens of thousands of patients diagnosed between 2010 and 2016. The data also allowed the team to trace the use of antibiotics by these patients between 2005 and 2016. Finally, they compared this data with the data of more than 200,000 Swedes who do not suffer from cancer.
According to the results of the study, people who took antibiotics for more than six years were 17% more likely to develop colon cancer in the proximal (upper) part of the colon.
A change in the microbiota?
It is important to emphasize that this study only reveals a correlation. In other words, this work does not prove that antibiotics directly cause colon cancer. How can this connection be explained? Researchers believe these drugs may make the gut more vulnerable to cancer growth by causing lasting changes in the gut microbiome. In fact, the researchers found that only antibiotics capable of affecting intestinal bacteria were implicated in the development of cancer.
“We think that by disrupting the balance of the microbiota, this may allow bacteria such as Escherichia coli and Klebsiella pneumoniae to become more important where they are usually displaced by other microbes,” Cynthia Sears, lead author of the study, told LiveScience. “This, in turn, can increase inflammation in the colon, generating reactive chemicals that can damage DNA and lead to the formation of tumors.”
The proximal colon may be particularly vulnerable to these changes due to its location (it connects to the small intestine). In this case, the drug molecules are more likely to break down gradually. However, further work is needed to explain this relationship more clearly. However, the study has some limitations. The data sets did not include any information about the diet, smoking habits or alcohol consumption of the subjects.
However, these factors can also increase the risk of colorectal cancer. In addition, the Swedish Prescription Drug Registry provides information about prescriptions for medications, but cannot indicate whether people actually used the prescription they were prescribed.