What is the effect of dietary protein on levodopa in patients with Parkinson disease (PD)?

Updated: Aug 29, 2019
  • Author: Robert A Hauser, MD, MBA; Chief Editor: Selim R Benbadis, MD  more...
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Patients recently diagnosed with Parkinson disease are often confused regarding dietary protein, because they receive conflicting information.

Levodopa is absorbed via a large neutral amino acid active carrier system and therefore competes with dietary proteins for absorption; this effect is generally relatively small and is not clinically important for most patients, especially those with early or moderate disease. However, as the disease progresses and patients become more and more sensitive to maintaining relatively narrow therapeutic serum concentrations of levodopa, this effect can become clinically relevant. These patients usually have significant motor fluctuations. Some report that when they are "on" and they eat a meal including protein, they turn "off." Others find that if they eat a protein meal, their next levodopa dose does not kick in. These patients may benefit from a low protein or a protein redistributed diet.

In a low-protein diet, the total daily protein intake is spread more or less equally over the day. In a protein-redistributed diet, individuals only consume food very low in protein during the day and then eat a high-protein meal in the evening. Unfortunately, these diets are difficult to follow; dietary consultation may be beneficial for patients in whom such diets are considered.

For patients with early and moderate Parkinson disease, the considerations are quite different. As with patients with more advanced Parkinson disease, patients with early and moderate Parkinson disease will get the most complete and consistent absorption of levodopa by taking their levodopa doses a half hour or more before meals or 1 hour or more after meals. However, most patients with early or moderate disease will not notice a difference in clinical benefit, whether they take their levodopa with meals or apart from meals.

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