Controlled-protein dietary regimens for Parkinson's disease.

Continuous levodopa replacement still is the most efficacious treatment for patients with Parkinson's disease. Unfortunately, the neutral aromatic amino acids contained in dietary proteins may compete with this drug for intestinal absorption and transport across the blood-brain barrier, thus limiting its efficacy and being responsible for the occurrence of motor fluctuations. Current guidelines recommend low-protein dietary regimens with protein redistribution, as shifting protein intake to the evening has proved to ameliorate the response to levodopa. However, adherence to this dietary regimen does not seem to be satisfactory and response is variable. Recent studies have shown that low-protein products designed for chronic renal failure patients are safe, tasty, well-tolerated and useful in improving both adherence to low-protein dietary regimens and levodopa-related motor fluctuations. However, there still is the need to define the selection criteria for the patients who may benefit the most from adherence to this regimen.