High serum concentration of the acute phase protein fibrinogen is associated with tissue inflammation and is an independent risk factor for cardiovascular disease (CVD). Low vitamin D status is associated with an increased risk of CVD and the active form of the vitamin, 1,25-dihydroxyvitamin D3, is a potent immunomodulator. Furthermore, vitamin D supplementation has been shown to reduce serum concentrations of inflammatory markers such as C-reactive protein in vitamin D deficient individuals. The aim of this study was to assess the effect of vitamin D supplementation on serum fibrinogen concentrations in a group of apparently healthy adults aged ≥64 years recruited in Cork and Coleraine.
A total of 202 individuals (males, n=81; females, n=121) were randomly assigned to receive either 5, 10 or 15 μg vitamin D3/d or placebo for 22 weeks. Serum vitamin D status (25-hydroyvitamin D (25(OH)D)) and fibrinogen concentrations were measured at baseline and post intervention using commercially available ELISA kits.
Vitamin D status did not significantly correlate with serum fibrinogen concentrations at baseline or post intervention. One-way analysis of covariance (adjusted for age, sex, centre, body mass index and baseline concentrations) revealed that while vitamin D supplementation significantly increased vitamin D status, it did not alter fibrinogen concentrations.
25(OH)D, 25-hydroxyvitamin D.
* Values are median (IQR).
† Effect of treatment assessed on log transformed data by ANCOVA. Different superscript letters denote significant differences between treatment groups (ANOVA).
In conclusion, vitamin D supplementation had a significant dose-response effect on vitamin D status, but did not affect serum concentrations of the inflammatory marker fibrinogen in healthy older adults. These findings concur with previous research in vitamin D deficient adults. However, it has been suggested that 25(OH)D concentrations >100 nmol/l may be required for modulation of immune responses; concentrations higher than those observed in the current study, even after vitamin D supplementation.
This work was supported by the UK Food Standards Agency.