Practical application of a low-protein diet for Parkinson's disease.

Thirty-eight patients with Parkinson's disease were treated with a protein-restricted diet in addition to their usual drug regime. Patients who had failed to obtain a significant response to levodopa previously did not benefit. Sixty percent of those with fluctuations in response to levodopa improved, primarily obtaining an increase in the ratio of "on" to "off" hours. Benefit was always noted within a week of diet initiation. The diet was well tolerated with a low incidence of side effects, which could usually be reversed by a reduction in levodopa dosage. A low-protein diet is a simple adjunct to levodopa therapy that can be readily instituted on an outpatient basis. It may improve even those patients with fluctuations who have failed to obtain optimal benefit from all forms of manipulation of the dosage schedule of levodopa or the addition of newer ancillary medications.