Over 20 to 22 years of follow-up, 805 people developed Parkinson's disease -- 438 men and 367 women.
When researchers compared those who ate the most flavonoids with those who ate the least, they found that only men saw a statistically significant benefit, lowering their risk of Parkinson's by 40 percent.
Gao said it wasn't clear why only men benefited from the extra flavonoid intake, but he noted that other studies have also found differences between men and women. Gao said it's not clear if there's a biological mechanism causing these differences, or another factor.
But, when the researchers looked at the dietary compounds individually, it was clear that berries could benefit both men and women, lowering the risk of Parkinson's disease by about 25 percent for those who had at least two servings of berries a week.
Gao said that anthocyanins protect the cells from oxidative damage and they also have an anti-inflammatory effect, which may be how berries help to reduce Parkinson's risk.
The study findings should be interpreted cautiously because the participants were mostly white professionals, and the results might not apply to other ethnic groups. Also, recollections of dietary intake may be faulty, and it's possible that other properties of fruits and vegetables might have influenced the results, the authors said.
Dr. Michael Okun, medical director of the National Parkinson Foundation, said, "It is exciting to see research emerging about modifiable dietary issues that may affect the risk of getting diseases such as Parkinson's."
But, he added, it's important for people to realize that this research isn't applicable to people who already have the disease.
He also said it will be important to confirm these findings in other studies and learn the mechanism of how berries and other flavonoids appear to offer some protection against Parkinson's disease.
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