Nervous System - Parkinson's Disease

A low protein diet (<0.8 g/kg/day) is not recommended for individuals on levodopa. If an individual insists on trialing a low protein diet, they should be monitored by a neurologist for levodopa related side-effects (e.g. nausea, dyskinesia, hallucinations), counselled by a dietitian to optimize nutrient content, and be advised to discontinue the diet after one to two weeks if no improvement is noted. 

A protein-redistribution diet may improve motor function in individuals with Parkinson's disease (PD) who respond to levodopa therapy, although the clinical trials assessing this link are of low methodological quality. A protein-redistribution diet is not recommended in those who do not respond to levodopa therapy due to controversial results and the absence of scientific rationale for its use. Individuals tend to find a protein-redistribution diet less acceptable beyond the short term (>1 month). This diet should be discontinued if individuals do not respond or if they experience adverse effects (e.g. severe dyskinesia, weight loss).

Country-specific Guidelines
International
The 2018 Movement Disorders Society guidelines for the management of motor and non-motor symptoms in PD do not mention protein or its potential interaction with levodopa.

 

The 2018 ESPEN guidelines for clinical nutrition in neurology recommend that people with PD who are taking levodopa should take their medication at least 30 minutes before eating, and those who experience motor fluctuations despite levodopa therapy can trial a protein-redistribution diet.

Canada
The 2019 Canadian guideline for Parkinson disease recommends that people with PD should avoid limiting the overall amount of protein in their diet. However, the authors recommend that practitioners should discuss a protein redistribution diet with clients who are taking levodopa.

United Kingdom
The 2017 National Institute of Clinical Excellence (NICE) guidelines recommend that health care practitioners advise people with PD against protein restriction and discuss a protein redistribution diet if an individual takes levodopa and experiences fluctuations in motor symptom control.

Early studies examining the effect of protein on levodopa showed a potential improvement in medication efficacy with a low protein diet, but advancements in therapy (e.g. controlled release tablets, surgical intervention) have made low protein diets relevant to fewer people with PD. A 2010 systematic review found there was not enough evidence to support the use of a low protein diet (<0.8 g/kg/day).

 

The same 2010 review found that on average, protein redistribution diets resulted in improved motor function in people who responded to levodopa, although the acceptability of the diet decreased over the long term (i.e. >1 month). The most frequently reported complications of the diet included severe dyskinesias (due to reduced levodopa dose), weight loss and hunger before the evening meal. Occasional complications included psychiatric disorders and hallucinations (due to levodopa overdose).

A 2017 narrative review noted two large observational studies. One study found that the prevalence of protein-levodopa interaction in those taking levodopa was about 12.4%. The other study suggested that a protein-restricted diet may improve motor function in some people taking levodopa, and that those eating more than 10 g protein/day above the RDA may need a higher levodopa dosage than those eating less protein.

Protein-redistribution diets (providing ≥0.8 g/kg/day protein) consist of shifting protein intake to the evening meal only. Very little protein is eaten at breakfast and lunch (relying predominantly on fruit and vegetables) and unlimited quantities (including second helpings) of protein-rich foods are eaten at the evening meal. People following a protein redistribution diet should aim to meet the protein RDA for their body size. See country-specific Dietary Reference Values. 

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