PH: Conceptualization, Data curation, Formal Analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writingoriginal draft, Writingreview and editing
Quick answer: L-carnitine is most plausible for people with a real carnitine deficit or a context where trials show bigger effects: older adults, people with overweight or obesity, some metabolic-health populations, dialysis patients under medical care, and athletes using it for recovery over weeks, not days
But of course, glutathione is not the only skin brightening ingredient on the market
Evidence boundary The largest Phase 2b trial used oral dosing for 24 weeks and did not show statistically significant weight loss versus placebo