From 2014 says the jury is not in

[MBAnderson]

maybe somebody has something more recent or more authoritative?

" ... although there has been ongoing debate regarding the effect of L-dopa on neurons in PD patients. Some believe that treatment of PD patients with L-dopa potentially promotes neurodegeneration owing to the production of free radicals secondary to dopamine catabolism [31, 32], while others have found a potential neuroprotective effect in animal models [33, 34].

The ELLDOPA study was designed to try to determine whether L-dopa is toxic and accelerates the progression of PD [35]. Patients receiving L-dopa had less clinical deterioration from baseline than did placebo patients, suggesting a protective, rather than a toxic, effect. However, SPECT studies performed as part of this clinical trial demonstrated that patients who received L-dopa had an increased rate of decline in uptake of striatal β-CIT (a dopamine transporter ligand) compared with placebo, suggestive of a toxic, rather than a protective, effect. Therefore, the ELLDOPA study did not resolve the issue of whether or not L-dopa is toxic in PD [36]. Given the very robust beneficial effects of L-dopa for motor symptoms, the discrepant decline in imaging markers may be better explained by the artifactual effects on the ligands assessed (see below). The clinical effects of L-dopa are being studied currently in a delayed-start design (LEAP study) being conducted in the Netherlands (R. de Bie, personal communication) ... "

ncbi.nlm.nih.gov/pmc/articl...