PRKN and Parkinson disease: Although low-protein diets are known to aid levodopa control of PD symptoms by evening out variations in brain levodopa levels (a post-prandial surge in plasma branched-chain amino acids following a protein-rich meal competitively inhibits brain levodopa uptake), what is proposed here is that such diets might aid prevention or slow progression of PD by boosting striatal Parkin levels [269,270,271].