1,25-Dihydroxyvitamin D, the hormonally-active form of vitamin D has been shown to be an effective immunomodulator, leading to a cytokine profile that is less inflammatory(Reference Holick1). Vitamin D supplementation has been shown to significantly reduce serum concentrations of TNFα by 10% and significantly increase serum concentrations of IL-10 by 40%, albeit in patients with congestive heart failure(Reference Schleithoff, Zittermann and Berthold2). The effect of vitamin D supplementation on immune function in apparently-healthy individuals has not been investigated. Thus, the aim of the present study was to assess the effect of vitamin D supplementation on markers of immune function in a group of young adults.
A total of 236 apparently-healthy young males and females aged 20–40 years were recruited from Coleraine and Cork and randomly assigned to receive 5, 10 or 15 μg cholecalciferol/d or placebo for 22 weeks(Reference Cashman, Hill and Lucey3); 211 volunteers completed the study with >85% compliance (males 107; females 104). Vitamin D status (serum 25-hydroxyvitamin D, S-25(OH)D concentrations) and serum concentrations of the pro-inflammatory cytokine TNFα and anti-inflammatory cytokine IL-10 were assessed at baseline and post intervention using commercially-available ELISA kits.
One-way between-groups analysis of covariance (ANCOVA) was conducted to assess the effect of treatment on vitamin D status and markers of immune function, controlling for age, gender, BMI and baseline concentrations. Vitamin D supplementation significantly affected S-25(OH)D concentrations (as shown in Table) but did not have an effect on serum concentrations of TNFα or IL-10.
IQR, interquartile range.
a,b,c,d Means with unlike superscript letters were significantly different between groups (ANOVA; P<0.05). *Effect of treatment assessed by ANCOVA controlling for age, gender, BMI and baseline concentrations.
In conclusion, vitamin D supplementation had a significant effect on vitamin D status in a dose-responsive manner, but did not affect serum concentrations of TNFα or IL-10 in young adults. It has however, been suggested that circulating S-25(OH)D concentrations >100 nmol/l are required to optimise all vitamin D-dependent functions, levels higher than those observed in the present study, even after supplementation.
This work was supported by the UK Food Standards Agency.