The Role of Vitamin C in Selected Autoimmune and Immune-Mediated Diseases: Exploring Potential Therapeutic Benefits

Autoimmune diseases are characterized by immune response dysregulation against self-components, leading to chronic inflammation and tissue damage. Vitamin C (VitC), a water-soluble vitamin with established functions in antioxidant defence and collagen synthesis, has also been of interest based on its potential immunomodulatory effects. This review discusses the role of VitC in the course and progression of (A) autoimmune diseases (multiple sclerosis, rheumatoid arthritis, Sjögren's disease, type 1 diabetes, Hashimoto's thyroiditis, pernicious anaemia, antiphospholipid syndrome), (B) other immune-mediated diseases (Crohn's disease, periodontitis), and (C) Alzheimer's disease, a neurodegenerative disorder with autoimmune features. Results from clinical, observational, and experimental trials show that VitC deficiency is common in many of these diseases and may contribute to increased oxidative stress and immune disequilibrium. Supplementation has been associated with improved antioxidant levels, control of inflammatory mediators, and, in some cases, clinical outcomes like disease activity decrease or symptom load. Although findings vary across conditions and few large, randomized trials are available, the overall evidence indicates that maintaining good VitC status can be useful in maintaining immune homeostasis and reducing inflammation. VitC should be viewed as an adjunct to be employed safely, perhaps and ideally within larger treatment regimens, but not in place of effective therapies. Further research, including large-scale clinical trials, will be required to determine more clearly optimal dosing, timing of treatment, and patient population most likely to benefit. By integration of current knowledge, this review recognizes both promise in VitC for treatment of autoimmune/immune-mediated disease and promise in its potential use within future treatment regimens.