A Rutgers Health study has found that people who took multiple courses of penicillin antibiotics had a modestly lower risk of developing Parkinson's disease, a surprising finding that researchers say highlights the complex relationship between bacteria in the digestive tract and brain health. The study, published in Parkinsonism & Related Disorders , analyzed medical records from more than 93,000 people in the United Kingdom. Researchers found that those who received five or more courses of penicillin antibiotics in the five years before diagnosis had about a 15% lower risk of Parkinson's compared with those who took no antibiotics.

We found an inverse dose-response relationship between number of penicillin courses and Parkinson's disease risk across multiple durations. This was unexpected and contrasts with some prior studies." Gian Pal, neurologist at Rutgers Robert Wood Johnson Medical School and lead author of the study The findings add to increasing evidence that the trillions of microbes living in the human digestive tract may play a role in Parkinson's disease, a progressive brain disorder that affects movement and balance.

Some researchers believe inflammation or toxins from certain gut bacteria could contribute to the disease's development. "There's an idea that the disease starts in the gut and that inflammation in the gut can make the gut more leaky and allow toxins or inflammation to ascend to the brain through the vagus nerve," Pal said. To investigate potential .