Tropical fruits linked to parkinsonism.

In the tropics, unusual illnesses resembling Parkinson's disease have baffled researchers for decades. One ailment, called Guam syndrome, causes neurological problems on that Pacific island. Scientists have suspected that eating a local food, such as a sago palm, might cause the condition, but the link hasn't been proved. To confuse matters, the disease has abated in recent years, perhaps because Western foods have replaced traditional fare.

Although Guam syndrome remains a mystery, a study in the July 24 LANCET from the Caribbean island of Guadeloupe suggests that three commonly eaten tropical fruits--soursop, custard apple, and pomme cannelle--and teas made from these plants may cause other Parkinson's-like diseases.

These conditions, called atypical Parkinson's and progressive supranuclear palsy (PSP), can mimic the muscle rigidity, tremors, slowness of movement, and poor balance of classical Parkinson's. They are more difficult to treat, however, because they don't respond to the drug levodopa, the best weapon against Parkinson's disease.

Unlike the classical disease, atypical Parkinson's and PSP affect both sides of the body equally. Moreover, they can cause incontinence, posture problems, slurred speech, and loss of eyelid control. Neurologist Dominique Caparros-Lefebvre noticed these symptoms in elderly patients while working at the Centre Hospitalier Universitaire des Antilles et de la Guyane in Guadeloupe. The observation prompted her to investigate what these patients had been eating.

Many patients mentioned the three fruits or tea made from them. All three belong to Annonaceae, a family of plants that harbor benzyltetrahydroisoquinoline alkaloids. Studies in animals indicate that these compounds are neurotoxins.

Caparros-Lefebvre examined 87 people, average age 65, who had been diagnosed with parkinsonism and compared their eating and drinking habits with those of 65 healthy adults.

Only 22 of the patients had classical Parkinson's disease; the other three-fourths of the group had atypical Parkinson's or PSP. Among European and North American patients, these proportions are reversed, says study coauthor Alexis Elbaz of Salpetriere Hospital in Paris.

Of 31 patients with PSP, a mild paralysis that causes trunk and neck rigidity, 29 had eaten the fruits and 26 had drunk the teas regularly for at least 2 years. Of 34 patients who had atypical Parkinson's, all had eaten the fruits regularly and 28 had consistently drunk the teas.

In contrast, only 13 of 22 people with classical Parkinson's disease had eaten the fruits regularly and only 4 had drunk the teas. Similarly, among the 65 healthy participants, only 39 ate the fruits and 28 drank the teas.

When patients were asked to stop consuming the fruits and tea, many saw their conditions stabilize. Symptoms even abated in a few patients.

"This is extremely interesting," says neurologist Herman J. Weinreb of New York University. "It's another piece of evidence that parkinsonism is related to toxins in the environment."

Although many people eat these fruits, the neurological problems don't usually start until people are in their 60s, says Caparros-Lefebvre.

Younger people might more efficiently metabolize and excrete any neurotoxins present in these foods, says Paul A. Rosenberg, a neurologist at Children's Hospital and Harvard Medical School in Boston. Or it might simply take a long time for the body to ingest enough toxins to accumulate dangerous concentrations, Elbaz says. Also, the number of brain cells declines with age, leaving older people more vulnerable to neurotoxins.

The study authors caution that their work is preliminary and so it's too early to suggest that people change their diet. Another study is planned that will account for other lifestyle variables, Caparros-Lefebvre says.