Objective: To evaluate the lowest effective dose-response of folic acid on endothelial function in children with type 1 diabetes.
Study design: A randomized, double-blind, crossover, placebo-controlled trial was conducted in 20 children with type 1 diabetes (age range 10-18 years) after mandatory folate fortification in Australia. Each child received orally 4 interventions (1 per month)-3 folic acid doses (0.5, 2, and 5 mg) and 1 placebo dose--in random order. The primary outcome was 2-hour postintervention change in endothelial function measured with flow-mediated dilatation (FMD). Thirty-five children with type 1 diabetes from our folic acid interventional trial before folate fortification were used for comparison.
Results: All children completed the study. There were no differences in baseline FMD or folate status between the visits. Folic acid supplementation increased serum folate (P = .0001) and red cell folate (P < .0001), but none of the doses improved FMD (P = .96). Baseline serum folate and red cell folate levels and FMD and glyceryl trinitrate-mediated dilatation were significantly higher in these children compared with children from our trial before mandatory folate fortification (P = .0001, .0001, .014, and .04, respectively).
Conclusions: Folate status and vascular function have improved in children with type 1 diabetes since the introduction of mandatory folate fortification, but the beneficial endothelial effects of additional folic acid are no longer present.
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