The European Journal of Internal Medicine has just published the results of a randomized and controlled clinical trial evaluating the effect of L-arginine combined with liposomal vitamin C when given to people with chronic obstructive pulmonary disease (COPD). Previous research has suggested that L-arginine metabolism is disturbed among people with COPD, with less L-arginine available for nitric oxide synthase (NOS) activity (and less nitric oxide production), and more funneled into arginase or incorporated into proteins, generating multiple inhibitors of NOS, such as asymmetric dimethylarginine (ADMA). This decrease in nitric oxide availability underlies the endothelial dysfunction observed among people with COPD, contributing to an increase in reactive oxygen species, as well as symptoms such as reduced exercise performance and a worsening in disease severity.
One hundred fifty people were enrolled, with roughly half receiving 1.66 g L-arginine and 500 mg liposomal vitamin C, twice daily, vs a matching placebo for 4 weeks. The primary outcome of the study was the variation in the CRQ-SA (Chronic Respiratory Questionnaire self-administered) score, a measure of health-related quality of life, with multiple functional secondary outcomes. After 4 weeks, significant improvements were observed with the active supplement in CRQ-SA scores, especially the subdomain of dyspnea, and other assessments of patient-reported symptoms or other activities of daily living (London Chest Activity of Daily Living Scale, etc.). No significant changes in lung function or exercise performance were observed, but an improvement in dyspnea perception occurred independently. Men were more likely to benefit than women, as well as people with poorer CRQ scores at baseline. Notably, this same combination/dose of L-arginine and vitamin C was associated with improved symptoms in a survey of people with Long-COVID symptoms.