Berries may offer sweet hope in reducing the risk of Parkinson's disease, Harvard researchers are reporting.
The Harvard School of Public Health examined the effect on Parkinson's disease of flavonoids, a dietary component found in citrus fruits, chocolate and berries. The study was released last Sunday, and will be presented at the American Academy of Neurology's 63rd Annual Meeting in Honolulu in April.
The exact reason people develop Parkinson's is not clear, though some genetic and environmental factors are thought to be responsible.
"The study opens up a whole area of potential future studies examining other types of environmental effects on Parkinson's," said Dr. Anna Hohler, a neurologist and professor of neurology at Boston University who was not involved with the study.
The study found that the top 20 percent of males who consumed the most flavonoids were 40 percent less likely to develop Parkinson's than the bottom 20 percent of men who consumed the least amount of flavonoids. In women, there was no correlation between overall flavonoid consumption and Parkinson's.
However, a subclass of flavonoid called anthocyanins, which are primarily found in berries, were associated with reduced risk of developing Parkinson's, said study author Dr. Xiang Gao, research scientist at Harvard.
"These components we found to have neuroprotective effects," he said. "Anthocyanins are a kind of pigment in food. For example, in a blackberry or a strawberry, when you see the different colors in these berries, that's because of anthocyanin."
The study examined 129,617 individuals - 49,281 men and 80,336 women. Participants were followed for 20 to 22 years, and were asked to periodically fill out questionnaires about their food consumption habits. During that period, 805 participants developed Parkinson's. When the study started, the average age of male participants was about 55, and the average age of female participants was about 51, Gao said.
Parkinson's is a neurodegenerative disorder that affects movement. Most people with the disease start to get symptoms in their sixties, though some people get it much earlier, Hohler said.
An estimated 60,000 Americans are diagnosed with Parkinson's disease each year, and as many as one million Americans live with Parkinson's, according to the Parkinson's Disease Foundation in New York.
The study did not track the consumption of all types of berries, but looked specifically at strawberries and blueberries.
"We asked about a number of different dietary items - how frequently they were eaten and the intake per month of each item," Gao said. "That means we could only list the most consumed foods."
Participant's questionnaires were then stored in a database where researchers could later revisit answers and calculate averages.
A strength of the study is the fact that people's eating habits were tracked before any of them had Parkinson's, Gao said.
"Otherwise, if you do a kind of study called a case-control study, in which you start with a group of people who already have Parkinson's disease and ask them to recall their dietary intake five years later, there may be some error," he said. "This way we reduce this kind of memory bias."
Gao said the link between flavonoid consumption on Parkinson's and gender could not be confirmed until further studies take place.
"Our study is the first prospective study in humans," he said. "So our observations need to be confirmed by other studies to see if there is a difference. And if the other studies find some sort of gender, the next step is to do some more studies to understand the mechanism."
The study raises further questions about the consumption of anthocyanin as well.
"Future research needs to find out in terms of quantity, how much do you need to consume to have a beneficial effect and in what period of time," Hohler said.
Although Gao agreed that more research must be done before any strong conclusions are made, he said there is certainly no harm in eating more berries.
"Although it's too early to recommend eating berries to reduce Parkinson's risk, think about the other beneficial effects of berries," he said. "If you only eat one cup of berries a month, maybe you can increase to another one."
Hohler plans to discuss the study with Parkinson's patients.
"When a study comes out like this, we say, 'There is one study so far which is interesting and may suggest that this might be somewhat neuroprotective,' but that further studies need to be done to clarify," she said. "Parkinson's patients are very eager to try things that might decrease their chance of developing [the disease]."