Low-protein diet boosts treatment.

In patients with Parkinson's disease, the brain's dopamine-secreting neurons inexorably die off. The most common treatment to combat the tremors, slowness, and rigidity in these patients is a dopamine precursor called levodopa. But the drug's effects can decrease over time, causing a person to cycle between "on" periods of low symptoms and "off" periods of high, often-debilitating, symptoms.

A research team in Italy reports that lowering the protein content in a patient's diet can improve levodopa therapy and reduce off periods.

Researchers know that protein affects the movement of levodopa into the brain: Too little protein results in too much medication too fast, causing involuntary, jerking muscle movements. Too much protein results in too little levodopa acting against tremors and other Parkinson's symptoms.

Ioannis Ugo Isaias of the Institut Clinici di Perfezionamento in Milan and his colleagues compared the effects of a low-animal-protein diet and a more typical, balanced diet in 18 Parkinson's patients. The volunteers followed one diet for 2 months and then the other diet for 2 months. During both phases of the study, patients recorded the lengths of their on and off periods as well as the dosages of levodopa required to quell their symptoms.

While eating the low-protein diet, all 18 patients recorded fewer off periods and averaged about 100 fewer minutes of off time per day than while on the balanced diet. Twelve patients reported no change in levodopa dosage while on the low-protein diet, but six patients required an average of 9 percent less levodopa in their midday dose while eating less protein. The researchers reported their findings on Feb. 23 at the World Parkinson Congress in Washington, D.C.

Though "more studies are needed" to confirm the value of eating less protein, the results suggest that "instead of [just looking for] new drugs, we can use the ones we have more effectively," says Isaias.--C.G.