Although antibiotics can help kill harmful bacteria, the drugs may increase your risk for cancer, according to a new report.

Researchers from Johns Hopkins University School of Medicine recently conducted a study, published in the journal Gut, to determine the association between oral antibiotic use and colon cancers.

To do so, they examined the health records of nearly 30,000 people from the United Kingdom, ages 40-90, who developed either colon or rectal cancer. They also assessed individuals in the same age bracket who did not have the diseases. They followed the adults for about 8 years.

The team gathered information about the subjects' antibiotic use, focusing only on pills and tablets, and split the antibiotics into categories based on drug classes, such as tetracyclines and penicillins.

After analyzing the results, the authors found 70% of patients with colon and rectal cancers were prescribed antibiotics, compared to just 68% of those who didn't have cancer.

The link between colon cancer and antibiotic use was particularly evident among patients who'd taken antibiotics more than 10 years before their cancer diagnosis, according to the findings.

The scientists also said the risk varied based on the type and class of antibiotics prescribed. While penicillins were associated with an increased risk of colon cancer in the first and middle parts of the colon, tetracyclines were associated with a reduced risk of rectum cancer in the last part of the bowel.

The amount of time patients used antibiotics also played a role. Those who took the drugs for only 16 days had a heightened risk of cancer, and those who took them for more than 60 days had a lower risk of rectal cancer.

Despite the results, the team noted the study was observational. They did not establish cause and effect.

They concluded, "whether antibiotic exposure is causal or contributory to colon cancer risk, our results highlight the importance of judicious antibiotic use by clinicians."