Regularly eating peppers may lower the risk of Parkinson's disease, a new study suggests.
The researchers said the benefit may be due to a substance in the vegetable that we've been advised to avoid: nicotine.
People in the study who ate peppers two times per week were 30 percent less likely to develop Parkinson's disease than people who ate peppers less than once a week.
Peppers and tobacco both belong to a family of plants called Solanaceae. As a result, peppers — be they red, yellow or green — contain tiny amounts of nicotine. Previous research has suggested that the nicotine in cigarettes and secondhand smoke may protect certain brain cells, or neurons, from the damage associated with Parkinson's.
In Parkinson's disease, up to 80 percent of the neurons that produce a chemical called dopamine, which controls muscle function, are damaged, according to the National Parkinson Foundation.
A neurodegenerative disease, Parkinson's causes a range of symptoms. The hallmark signs are tremors, slowness of movement, stiffness of the arms, legs or trunk and problems with balance. Approximately 1 million Americans have Parkinson's disease, reports the National Parkinson Foundation. Each year, 50,000 to 60,000 new cases are diagnosed in the United States.
The pepper advantage
In the study, the researchers looked at 490 people who had been newly diagnosed with Parkinson's disease, and compared them with 644 people who did not have the condition. Participants answered a detailed questionnaire about their lifetime dietary habits and tobacco use.
Just 11 percent of those with the disease and 5 percent of people in the control grouphad a family history of the disease, which can raise risk.
People reported how often they ate certain vegetables, and their history of tobacco use.
The researchers found that not only were peppers associated with a reduced risk of Parkinson's, but also that the more peppers people consumed, the greater the apparent benefit. People who ate peppers five to six times a week or more slashed their Parkinson's risk by about 50 percent compared with those who ate them less than once a week.
Other vegetables didn't seem to have this effect. "Benefits associated with vegetables from the Solanaceae family seemed to be fairly specific," said study researcher Susan Searles Nielsen, an environmental and occupational health researcher at the University of Washington in Seattle.
"While there was some suggestion that tomatoes might also be associated with a reduced risk of Parkinson's, it was not clear," Searles Nielsen said.
Peppers' good-for-neuron powers were much "clearer in people who had never used tobacco regularly," Searles Nielsen added. Exposure to nicotine from tobacco use "is likely going to overshadow what people would get in their diet," she explained.
While the study findings are promising, Searles Nielsen stressed that they show an association and not necessarily a cause and effect.
"While it is certainly intriguing to think that eating peppers may protect against Parkinson's disease, we have to consider that there are other explanations," she said. "With further research, hopefully that can be learned."
Dr. Michael Okun, national medical director for the National Parkinson Foundation, who was not involved in the study, called the findings "interesting," but cautioned that that they are far from conclusive.
"It is not clear from this study that family members at risk (those with a family history of Parkinson's) should rush out and start eating red peppers," Okun said. "Much work will need to be done to understand the mechanism and to establish potential benefits in the Parkinson's 'at risk' population."
Still, it can't hurt to include peppers in your diet, Searles Nielsen said. "If you happen to like peppers, fine," she added. Just don’t overdo it. "Keep in mind that too much of a good thing may not be a good thing," Searles Nielsen said.
The study is published May 9 in the journal Annals of Neurology.
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