[Diet therapy in Parkinson disease].

The significance of restrictions on protein for patients with Parkinson's disease is reviewed. Large neutral amino acids and levodopa share the same saturated carrier system through the blood-brain-barrier. Fluctuating patients are sensitive to a decreased supply of levodopa from the blood, and clinical studies show that an increased concentration of large neutral amino acids in the blood decreases mobility and reduces "on-time". A reduction of protein intake to 0.75-0.8 g/kg body weight/day has been recommended. A protein redistribution diet implying that less than 10% of the daily protein is taken in daytime and the rest in the evening, gives best results. However, in the elderly, protein restrictions may lead to a lasting negative nitrogen balance, and even in younger patients the supply of certain minerals and vitamins may become too low or marginally adequate. The diet must therefore be used with caution.