WEDNESDAY, April 2, 2003 (HealthDayNews) -- Consuming lots of fruits and fruit juices appears to increase the risk of Parkinson's disease, a new study suggests.
But people shouldn't cut back on their consumption of fruit, the researchers add.
The culprit may be pesticides, plant-borne toxins or herbicides, not the fruit itself, says researcher Andrew Grandinetti, an epidemiologist at the Pacific Biomedical Research Center at the University of Hawaii at Manoa.
He will present the findings April 3 at the American Academy of Neurology's annual meeting in Honolulu.
"I really want to stress that fruit intake is a very important part of health in general," says Grandinetti, who adds that fruit consumption has been linked with cancer prevention. "I suspect [the increased risk] might be a marker of pesticide exposure."
There was no increased risk, he notes, for those with a high Vitamin C intake from diet and supplements.
Parkinson's disease is a progressive disorder of the central nervous system that produces symptoms such as body tremors, slowness of movement, stiffness of limbs and balance problems.
About 2 percent of the population will develop Parkinson's in their lifetime, according to Mayo Clinic estimates. Parkinson's results from a progressive degeneration of the brain, with a loss of neurons that produce dopamine.
Medication to restore dopamine levels is commonly given, but as the disease progresses, the disabilities accumulate, experts say.
Grandinetti's team evaluated more than 8,000 study subjects from 1965 on, noting the incidence of Parkinson's disease over 34 years of observation and taking into account dietary habits. Increased fruit and fruit juice intake boosted the risk of getting the disease.
The increased risk varied, depending on the measurement used.
The team used two measurements, a 24-hour diet recall and a food frequency questionnaire, to determine fruit and fruit juice consumption. If subjects reported more than three servings a day on the 24-hour recall measure, they had a 70 percent increased risk of Parkinson's after adjusting for other variables such as bowel movement frequency (the more regular, the less risk).
On the food frequency questionnaire, if they had one or more servings of fruit a day, the risk of Parkinson's increased by 55 percent after other variables were taken into account.
The study began looking at data in 1965, Grandinetti notes, when "pesticides were more persistent than the ones currently used."
Dr. Honglei Chen, a Parkinson's expert and research associate at the Harvard School of Public Health, says the new study's findings reflect those of earlier research.
"There is little doubt that environmental factors, though still to be identified, play important roles in late-onset Parkinson's disease," she says.
Besides pesticides, living in rural areas and neurotoxins have been implicated in the development of Parkinson's disease, Chen says, but more research is needed.
"Given the potential beneficial effects of fruits and vegetables on other major chronic diseases, people should continue to view fruits and vegetables as a healthy component in their diets," Chen says.
Grandinetti agrees. "Eating fruit is a healthful thing." However, "it's probably a good idea to wash fruit pretty thoroughly."
In other Parkinson's developments reported at the American Academy of Neurology meeting, researchers said on April 1 that a new cell therapy product called Spheramine shows promise.
Six patients followed for 24 months on the therapy had a 41 percent improvement in their motor function, even while off other Parkinson's drugs.
The cell therapy works, the researchers say, by enhancing levels of the neurotransmitter dopamine in the brain, which is lacking in Parkinson's patients.
Studies of the cell therapy are continuing.
More information
To learn more about Parkinson's disease, visit the Mayo Clinic and Mount Sinai School of Medicine.
