Objective: To study the effect of dietary protein on levodopa effectiveness in Parkinson disease (PD) patients.

Background: Levodopa transport across the blood brain barrier is modulated by large neutral amino acids and thereby dietary protein has been suggested to interfere with levodopa effectiveness. Due to this PD patients are commonly advised to dose levodopa on an empty stomach. In a retrospective study of over 1000 patients, Virmani et al. [1] suggested that protein interaction with levodopa occurred in <15% of PD patients who had earlier disease onset and positive family history of PD.

Methods: Here we prospectively assessed the interaction between protein diets and levodopa causing motor symptom fluctuations in patients with PD. After IRB approval, subjects filled a questionnaire detailing their motor symptoms, medications used, presence and severity of motor fluctuations, and effect of dietary protein on levodopa effectiveness. Motor fluctuations due to protein interaction with levodopa were defined as leading to (i) longer time to levodopa effectiveness, (ii) reduced benefit or duration of benefit, (iii) dose failures or (iv) earlier wearing off from a previously effective dose. Statistical analysis was performed using SPSS 22 (IBM).

Results: 44 patients participated to date, with average motor onset at 60.5±12.3 years and disease duration of 8.4±6.6 years. 25% on levodopa reported motor fluctuation with high protein meals. These patients trended towards being younger at motor onset (55.9±12.9 vs 62.0±9.5; p=0.11), had started levodopa at an earlier age (57±10.2 vs 66±7.3; p<0.01), and were on equivalent maximum daily levodopa doses (857±382 vs 890±190 mg/day; p=0.78) for similar duration (2.9±5.4 vs 4.3±3.6 years; p=0.39). A higher percentage reported lifetime dopamine agonist use (82% vs 30%; p<0.05) and were also concurrently on a dopamine agonist with levodopa (50% vs 10%; p<0.05). Percent reporting family members with PD were equivalent (36% vs 39%; p=0.86).

Conclusions: In our cohort, 25% of patients with PD on levodopa reported protein interaction with levodopa and were possibly younger at disease onset, had started levodopa at an earlier age and a higher fraction had been on, and were concurrently on dopamine agonists. This suggests that counseling patients to dose levodopa on an empty stomach may not be warranted early in the disease.

References: 1.            Virmani T, Tazan S, Mazzoni P, Ford B, Greene PE. Motor fluctuations due to interaction between dietary protein and levodopa in Parkinson’s disease. J Clin Mov Disord 2016;3:8.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/interaction-of-dietary-protein-with-levodopa-in-parkinson-disease/