Exploring the link between water-soluble vitamins and aging-associated immune system status

Background Aging is associated with numerous physiological changes that contribute to immunosenescence and inflammaging, resulting in a decline in immune defense and an increased susceptibility to infections. Older adults are at risk of inadequate dietary intake and suboptimal supply of micronutrients, including water-soluble vitamins, even those generally considered sufficient in the overall population. These deficiencies may have relevant but often underrecognized consequences for immune function in the elderly. Objective This review article aims to provide a well-defined overview and comprehensive assessment of the immunomodulatory properties of water-soluble vitamins in individuals aged 65 and older, with a particular focus on vitamins B1, B2, B3, B5, B6, B7, B9, B12 and C. Methods We reviewed and discussed available human-, animal- and in vitro studies examining the relationship between water-soluble vitamin status and immune parameters in older adults. In addition, we summarized, compared and graphically illustrated Recommended Dietary Allowances, Nutrient Reference Values and Tolerable Upper Intake Levels for the investigated vitamins across different reference systems. Conclusion Aging and insufficient plasma levels of water-soluble vitamins are both associated with immune decline and chronic inflammation. Adequate dietary intake and supplementation of vitamins B1–B12 and vitamin C may help counteract these aging-related immune alterations by supporting immune cell metabolism and reducing susceptibility to infections. Further human studies, and randomized controlled trials in particular, are required to better define the role of water-soluble vitamins in maintaining immune function during aging.