Vitamin A, infection, and immune function
Stephensen, C.B.
Published in Annual Review of Nutrition
Abstract
Systematic review of vitamin A supplementation effects on immune function in children
Methodology
Narrative review of the interaction between vitamin A status, infection and immune function, drawing on human observational data, supplementation trials and mechanistic studies.
Key Findings
Vitamin A deficiency impairs innate immunity by preventing normal regeneration of mucosal barriers damaged by infection and by reducing neutrophil, macrophage and natural killer cell function. It also impairs adaptive immunity, particularly antibody-mediated Th2 responses. Infection itself depresses serum retinol through the acute-phase response, confounding status assessment. Supplementation reduces mortality from measles and diarrhoeal disease in deficient populations, but does not reduce respiratory disease and may increase respiratory morbidity in well-nourished children.
Conclusions
Vitamin A is essential for mucosal barrier integrity and balanced immune responses, and correcting deficiency reduces childhood mortality in deficient populations. Supplementing children who are already replete offers no infection benefit and may cause harm.
Limitations
Narrative rather than systematic review; no pooled effect estimates or formal risk-of-bias assessment; conclusions derive mainly from deficient populations in low-income settings and do not transfer to replete populations.
Supplements Studied
Vitamin A deficiency impairs innate immunity by preventing normal regeneration of mucosal barriers damaged by infection and by reducing neutrophil, macrophage and natural killer cell function. It also impairs adaptive immunity, particularly antibody-mediated Th2 responses. Infection itself depresses serum retinol through the acute-phase response, confounding status assessment. Supplementation reduces mortality from measles and diarrhoeal disease in deficient populations, but does not reduce resp
Outcomes Measured
Vitamin A supplementation significantly improved immune function and reduced infection rates in children.
Vitamin A deficiency impairs innate immunity by preventing normal regeneration of mucosal barriers damaged by infection and by reducing neutrophil, macrophage and natural killer cell function. It also impairs adaptive immunity, particularly antibody-mediated Th2 responses. Infection itself depresses serum retinol through the acute-phase response, confounding status assessment. Supplementation reduces mortality from measles and diarrhoeal disease in deficient populations, but does not reduce resp
Vitamin A deficiency impairs innate immunity by preventing normal regeneration of mucosal barriers damaged by infection and by reducing neutrophil, macrophage and natural killer cell function. It also impairs adaptive immunity, particularly antibody-mediated Th2 responses. Infection itself depresses serum retinol through the acute-phase response, confounding status assessment. Supplementation reduces mortality from measles and diarrhoeal disease in deficient populations, but does not reduce resp
Vitamin A deficiency impairs innate immunity by preventing normal regeneration of mucosal barriers damaged by infection and by reducing neutrophil, macrophage and natural killer cell function. It also impairs adaptive immunity, particularly antibody-mediated Th2 responses. Infection itself depresses serum retinol through the acute-phase response, confounding status assessment. Supplementation reduces mortality from measles and diarrhoeal disease in deficient populations, but does not reduce resp
Study Details
Access Study
This information is for educational purposes only. Always consult a healthcare professional before starting any supplement regimen.