Antibiotics and bowel cancer: Study finds link

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Islamabad, APRIL 29 (ONLINE): A recent study looking for a link between antibiotics and cancer risk uncovers a complex relationship. The researchers conclude that there is an association between antibiotic use and an increase in colon cancer risk, but a decrease in rectal cancer risk.

A new study finds an association between antibiotics and certain cancers.
With the advent of antibiotic resistance, doctors are more conscious than ever before of limiting these drugs.
However, the use of antibiotics continues to grow globally. From 2000–2010, consumption increased by 35% to 70 billion doses each year.
That equates to 10 doses for each human on earth.
These staggering figures are the fuel that drives researchers to understand the impact of antibiotics on human health better.
Over recent years, scientists have begun to appreciate the significant role that gut bacteria play in maintaining a healthy body. Likewise, because antibiotics kill gut bacteria, they have the potential to make a lasting impact on human health.
In short, if antibiotics kill off a colony of “good” bacteria, it leaves a niche for “bad,” or pathogenic bacteria to colonize. These pathogenic bacteria include ones that can be carcinogenic.
Moving forward with the research base
Earlier research has found associations between antibiotics and cancer, but current evidence is limited, as the authors of the most recent study note.
For instance, some of the previous studies recruited relatively few participants; others did not account for cancer risk factors, such as smoking and alcohol use; yet more relied on participants to self-report their antibiotic usage, which is open to errors and lacks the type and dosage of the drugs.
With that in mind, the authors of a new study, now appearing in the journal Gut, set out their intent:
“Our aim was to investigate the associations between antibiotic use and site-specific colorectal cancer risk in the world’s largest primary care database.”
To investigate, they took data from the Clinical Practice Research Datalink from 1989–2012. This database carries the anonymized medical records of 11.3 million people from 674 doctor’s offices across the United Kingdom.
The records contain detailed information about the types of drugs doctors prescribed, the dosage, and how they instructed people to take them.
From this information, the researchers extracted the records of 19,726 people, aged 40–90 years, who developed colon cancer and 9,254 who developed rectal cancer. They also collected information about 137,077 people who did not develop bowel cancer who they matched by age and sex.
Dissecting antibiotics and cancer by types
When the scientists collated information about antibiotic use, they focused on pills and tablets, as science currently has limited understanding of the impact of intravenous antibiotics on gut bacteria.
They split antibiotics into categories by drug class, for instance, tetracyclines and penicillins. They also categorized antibiotics by the type of bacteria they impact, namely, aerobic or anaerobic. Aerobic bacteria need oxygen to survive, whereas anaerobic bacteria do not.
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