February 15, 2011 — Regular consumption of flavonoids, especially anthocyanins found mainly in berries, may help protect against Parkinson's disease (PD), according to new observational results using data on men and women in the Health Professional Follow-Up Study and the Nurses' Health Study.
The relationship however, was only significant among men. The findings were released February 13 ahead of presentation in April at the American Academy of Neurology 63rd Annual Meeting in Honolulu, Hawaii.
|Dr. Xiang Gao|
"Some animal studies suggest a potential protective effect of flavonoids and berries on PD," Xiang Gao, MD, PhD, of the Harvard School of Public Health and Brigham and Women's Hospital, Boston, Massachusetts, told Medscape Medical News.
Until now, however, there have been no prospective human studies on this topic, he noted. "Our study is the first one to look at whether intakes of flavonoid and flavonoid-rich foods are associated with future risk of developing PD.
"Although it's too early to say that eating berries can reduce PD risk, benefits of berries have been reported in several previous studies, for example, lowering risk of hypertension," Dr. Gao concluded. "So it is good, at least no harm, if we can have 2 to 3 cups of berries a week."
The researchers analyzed more than 2 decades worth of follow-up data on 49,281 men in the Health Professional Follow-Up Study and 80,336 women in the Nurses' Health Study. They had detailed information on intake of total flavonoids and their subclasses, including anthocyanins. Their analysis focused on 5 major sources of flavonoid-rich foods, including tea, berry fruits, apples, red wine, and oranges/orange juice.
During follow-up, a total of 805 subjects developed PD. In men, after adjusting for multiple confounders, those in the top quintile of flavonoid consumption were about 40% less likely to develop PD relative to those in the bottom quintile of consumption.
"For men, the updated relative risk of the highest vs lowest total flavonoid intake is 0.6 (95% confidence interval, 0.43 – 0.83)," Dr. Gao told Medscape Medical News.
In women, there was no relationship between overall flavonoid consumption and developing PD. "Honestly," said Dr. Gao, "we don't have an answer for this observed gender difference at this time. Clearly, more studies are needed to explore this."
Honestly, we don't have an answer for this observed gender difference at this time. Clearly, more studies are needed to explore this.
In pooled analyses looking at different subclasses of flavonoids, intakes of anthocyanins and anthocyanin-rich foods, such as berries and apples, were significantly associated with lower risk for PD in men and women (P for trend < .05 for both).
Why anthocyanins? "We don't know the exact mechanisms at this time; however, it is established that anthocyanins can cross blood brain barrier," Dr. Gao said.
He also noted that animal studies have shown that consumption of anthocyanin-rich foods, such as blueberries or strawberries, increase dopamine release, alleviating oxidative stress and suppressing neuroinflammation in the brain.
Antioxidants in PD is an area of "keen interest," Connie Marras, MD, PhD, of Toronto Western Hospital Movement Disorders Centre and University of Toronto, Ontario, Canada, who was not involved in the study, noted in an interview with Medscape Medical News. "Some people feel that oxidative stress may contribute to the pathology to Parkinson's disease in one way or another, and we are continuing to pursue trials of antioxidants — coenzyme Q10, for example."
This new study provides a "very interesting finding that needs to be pursued," she added. "But it's an observational study, so we really don't know if this 'signal' is really related to a causal association between the flavonoid intake and Parkinson's disease or are these types of foods indicative of a lifestyle that protects against Parkinson's disease."
Dr Gao agrees that "more studies are needed to examine potential neuroprotective effects of anthocyanins and other flavonoids."
The study was supported by the National Institutes of Health. The researchers and Marras have disclosed no relevant financial relationships.
American Academy of Neurology 63rd Annual Meeting: Abstract 3697.
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Cite this: Diet Rich in Flavonoids May Guard Against Parkinson's Disease - Medscape - Feb 15, 2011.