How might we maximize the therapeutic efficiency of levodopa? Parkinson’s disease is a disease of dopamine deficiency in the brain. You can’t just have people take dopamine, because it can’t pass through the blood-brain barrier. But you can give people a dopamine precursor called levodopa, or L-dopa, which can get up into the brain and be turned into dopamine. However, with prolonged treatment, the patients start to show a reduced response to levodopa. After five years of levodopa treatment, the benefits start wearing off before the next dose, or don’t completely contain symptoms in a substantial proportion of patients, and represents a major source of disability and significantly impairs quality of life. Therefore, maximizing the therapeutic efficiency of levodopa is an important goal, and that’s where protein-restricted diets come in. Wait, what does protein have to do with Parkinson’s?…