Clinical Evaluation of Vitamin A Supplementation on Disease Development, Progression and Treatment of Multiple Sclerosis: Current Evidence and Future Perspectives

Vitamin A constitutes an essential nutrient with important actions in immunological responses and the Central Nervous System (CNS). Neuroimmunological functions of vitamin A are mediated through its active metabolite, Retinoic Acid (RA). RA contributes to the regeneration and plasticity of the CNS, exerting also a key role in enhancing tolerance and reducing inflammatory responses by regulating T- and B- cells, as well dendritic cells’ populations. Several important studies have documented low plasma vitamin A levels in patients suffering from Multiple Sclerosis (MS). Vitamin A deficiency also leads to dysregulation of immune tolerance and pathogenic immune cell production in MS. In view of the above, the present review aims to critically summarize and discuss the currently available clinical studies, focusing on the potential beneficial effects of vitamin A on controlling MS pathophysiology. Cochrane Register of Controlled Trials (CENTRAL), BioMed Central, and MEDLINE databases database was thoroughly searched, using relative keywords, in order to identify clinical trials published in English. According to the existing clinical studies, the role of vitamin A in MS could be dual: it may decrease inflammation, while, at the same time, it may increase autoimmunity tolerance, also contributing to brain protection of MS patients. However, it must be stated that, at the present time, there is no clear clinical indication for using vitamin A as a complimentary treatment for MS. Further clinical trials with vitamin A supplementation as a potential cotreatment agent or as an add-on option are strongly recommended.