A surprising new study from Rutgers Health has found that people who took penicillin antibiotics multiple times had a slightly lower risk of developing Parkinson’s disease.
While the effect is modest, the findings point to a deeper and still mysterious link between gut bacteria and brain health.
The study, published in the journal Parkinsonism & Related Disorders, looked at the medical records of more than 93,000 people in the United Kingdom.
Researchers compared over 12,000 people who were later diagnosed with Parkinson’s to nearly 81,000 people without the disease.
They found that individuals who had taken five or more courses of penicillin over a five-year period were about 15% less likely to be diagnosed with Parkinson’s than those who had not taken any antibiotics during that time.
This was unexpected. In fact, it contradicts some earlier studies, which suggested that antibiotics might increase the risk of Parkinson’s. But in this case, there appeared to be a trend: the more courses of penicillin a person had taken, the lower their risk.
Dr. Gian Pal, the study’s lead author and a neurologist at Rutgers Robert Wood Johnson Medical School, said, “We found an inverse dose-response relationship between number of penicillin courses and Parkinson’s disease risk.” In simpler terms, more penicillin use was linked to less Parkinson’s.
The study adds to a growing body of research exploring the gut-brain connection. Parkinson’s disease is a progressive brain disorder that affects movement, balance, and other body functions. Scientists have been exploring the idea that it may begin in the gut, with gut bacteria playing a key role in starting or worsening the disease.
Dr. Pal explained that one theory suggests the gut may become “leaky” due to inflammation, allowing harmful substances or inflammation itself to travel through the vagus nerve—a major communication pathway between the gut and brain—leading to damage in brain cells.
To dig deeper into these possible connections, the team looked not only at antibiotics but also antifungal medications. Interestingly, people who took two or more courses of antifungals in the five years before diagnosis were about 16% more likely to develop Parkinson’s. This supported similar results from an earlier study in Finland.
Still, Dr. Pal emphasized that these effects were small and should not guide how doctors prescribe antibiotics or antifungals. “The importance of the study is that it speaks to the idea that something is going on in the gut microbiome that could influence Parkinson’s disease,” he said.
One limitation of the study is that it couldn’t account for all factors that affect gut bacteria, such as diet. People’s eating habits, use of other medications, or illnesses may also influence their microbiome and affect their risk.
Still, the study suggests that even short-term changes to gut bacteria—such as those caused by a week of antibiotics—might have long-term effects on the brain. That’s why researchers are now turning their attention to the specific microbes living in the gut. Are there certain bacteria or fungi that protect the brain—or that raise the risk of disease?
Dr. Pal and his team plan to explore these questions in future studies. They want to know whether differences in gut microbes can help tell apart people with Parkinson’s from those without it, and whether changing the gut microbiome—possibly through diet, medications, or probiotics—could lower the risk or slow down the disease in people who already have it.
Parkinson’s disease affects more than 10 million people worldwide, and the number is growing as populations age. Although doctors have made progress in managing symptoms, there is still no cure and no simple test for early diagnosis.
Studies like this one may help scientists develop better ways to detect and prevent Parkinson’s by understanding the surprising role of gut health in brain disease.
If you care about Parkinson’s disease, please read studies that Vitamin B may slow down cognitive decline, and Mediterranean diet could help lower risk of Parkinson’s.
For more health information, please see recent studies about how wheat gluten might be influencing our brain health, and Olive oil: a daily dose for better brain health..
The research findings can be found in Parkinsonism & Related Disorders.
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