Importance: Despite the widespread use of nutritional supplements and dietary interventions for treating hair loss, the safety and effectiveness of available products remain unclear. Objective: To evaluate and compile the findings of all dietary and nutritional interventions for treatment of hair loss among individuals without a known baseline nutritional deficiency. Evidence Review: The MEDLINE, Embase, and CINAHL databases were searched from inception through October 20, 2021, to identify articles written in English with original findings from investigations of dietary and nutritional interventions in individuals with alopecia or hair loss without a known baseline nutritional deficiency. Quality was assessed with Oxford Centre for Evidence Based Medicine criteria. Outcomes of interest were disease course, both objectively and subjectively measured. Data were evaluated from January 3 to 11, 2022. Findings: The database searches yielded 6347 citations to which 11 articles from reference lists were added. Of this total, 30 articles were included: 17 randomized clinical trials (RCTs), 11 clinical studies (non-RCT), and 2 case series studies. No diet-based interventional studies met inclusion criteria. Studies of nutritional interventions with the highest-quality evidence showed the potential benefit of Viviscal, Nourkrin, Nutrafol, Lamdapil, Pantogar, capsaicin and isoflavone, omegas 3 and 6 with antioxidants, apple nutraceutical, total glucosides of paeony and compound glycyrrhizin tablets, zinc, tocotrienol, and pumpkin seed oil. Kimchi and cheonggukjang, vitamin D3, and Forti5 had low-quality evidence for disease course improvement. Adverse effects were rare and mild for all the therapies evaluated. Conclusions and Relevance: The findings of this systematic review should be interpreted in the context of each study's design; however, this work suggests a potential role for nutritional supplements in the treatment of hair loss. Physicians should engage in shared decision-making by covering the potential risks and benefits of these treatments with patients experiencing hair loss. Future research should focus on larger RCTs with active comparators.