Hi, Z. Your friend might want to read up on eating protein with Parkinson's disease or talk to the patient's dietitian or doctor. Protein is essential to life, so you can't stop eating it altogether. From what I read, patients can take the medication 30 to 60 minutes before eating and the med can do its job without interference from protein.
Also, plants have much less protein than meats, fish, dairy and eggs, so eating bread and pasta should not be a problem.