A balanced carbohydrate: protein diet in the management of Parkinson's disease.

Although restricting dietary protein is a proposed adjunct to treating Parkinson's disease (PD), the effect of carbohydrate consumption is unknown. We measured plasma levodopa and large neutral amino acid (LNAA) levels in nine PD patients treated with carbidopa/levodopa and different isocaloric meals containing high protein-low carbohydrate, low protein-high carbohydrate, and balanced 5:1 carbohydrate:protein mixtures. We found that levodopa levels increased significantly regardless of the type of diet, but that plasma LNAA levels varied less and motor performance was superior after the balanced diet than after the other two meals. We conclude that PD patients can consume nutritionally adequate meals and still maintain a stable plasma levodopa:LNAA ratio.