Proportioned Carbohydrate

SUMMARY The entry of Levodopa into the brain is limited by competition with large neutral amino acids (LNAA). A strict low protein diet improves motor fluctuations but might lead to protein malnutrition. Because insulin secretion lowers plasma LNAA, a stable dietary ratio of carbohydrate:protein might be as effective as protein restriction. This double blind crossover study compared the effects of three proportioned diets: (A) a 7:1 carbohydrate: protein ratio; (B) a 30:1 carbohydrate: protein ratio; and (C) a 1:1.5 carbohydrate:protein ratio, on motor fluctuations, plasma LNAA and levodopa in 12 Parkinson patients. After random assignments to each diet, patients were observed for 11 hours. Serum levodopa and LNAA levels and motor component of the UPDRS were measured hourly. The 7:1 and high carbohydrate diets were both effective at stabilizing plasma LNAA levels. Mean hourly sum of LNAA was significantly different on each of the diets, being highest on the high protein diet and lowest on the high carbohydrate diet. There was a significant correlation between plasma LNAA and amount of “off” time, and a significant inverse correlation between plasma LNAA and amount of time “on with dyskinesias.” A fixed dietary carbohydrate:protein ratio stabilizes plasma LNAA levels and may optimize response to levodopa without the risk of malnutrition.