Vitamin B12 deficiency among asymptomatic healthy infants: its impact on the immune system.

AIM The immunomodulatory effects of vitamin B12 deficiency in children have not yet been established in the literature. In the current study, the effects of vitamin B12 on the immune system in asymptomatic and otherwise healthy infants have been studied. METHODS The study was conducted at Marmara University, "well-child" outpatient clinic. Vitamin B12 level was measured in a cohort of 611 healthy term infants, followed regularly for at least 6 months. Immunoglobulin measurements, lymphocyte subset analysis, cytokine production analysis, lymphocyte proliferation assays and evaluation of lymphocyte apoptosis were performed in a subset of 60 infants. RESULTS In this cohort, one out of three babies displayed vitamin B12 deficiency. The percentage of CD4+CD25+ regulatory T cells (Tregs) was lower in vitamin B12 deficient babies than in controls. Although the percentage of Tregs increased after treatment, the change was not significant. There was no difference of cytokine levels between vitamin B12 deficient and control groups. However, proinflammatory cytokines were reduced after treatment. No significant difference was observed for immunoglobulins, early apoptosis and lymphocyte proliferation. CONCLUSION Vitamin B12 deficiency is an underestimated health problem among the developing countries. The clinical consequences of the decreased percentage of Tregs associated with vitamin B12 deficiency, and reduction of proinflammatory cytokines after vitamin supplementation needs to be further studied, especially in terms of emerging allergies, autoimmune disorders and anti-inflammatory effects.