The efficacy of different vitamin D supplementation delivery methods on serum 25(OH)D: A randomised double-blind placebo trial.

The use of vitamin D supplementation has increased due to greater recognition of widespread deficiency. There has been little research on the effectiveness of different delivery methods and therefore the aim of was to test the efficacy of different delivery methods on serum 25(OH)D. Using a randomised repeated measures double-blind placebo design (registered under ClinicalTrials.gov Identifier no. NCT03463642), changes in serum 25(OH)D over a 4-week period using a capillary spot method were monitored. 62 female participants blindly chose a number related to a supplementation delivery method: pill placebo, pill, oral liquid, oral liquid placebo, Skin oil application (SOA) placebo, SOA plus vitamin D 3 suspension, or SOA plus vitamin D 3 suspension with essential oil enhancer; active vitamin D supplements contained 100,000IU. Participants took their allocated supplements over a 24-hr period with serum 25(OH)D retested 4 weeks later. Liquid chromatography-tandem mass spectrometry method was applied to dried blood spot samples by an independent laboratory. ANCOVA reported a significant difference between the groups (F 1,6 = 146.68; p < 0.001, eta² = 0.51). Separate analysis within the delivery methods (pill, SOA, oral liquid) indicated significant differences between the active and placebo supplementation groups (p < 0.01). Post hoc analysis of absolute changes indicated vit D pill and SOA + vit D + essential oil had significant increases (p < 0.05) in serum 25(OH)D compared to all other interventions with no significant difference between them. In human participants vitamin D oral pill has the greatest effect on serum 25(OH)D levels. Skin oil application delivery of vitamin D using a penetrator enhancer has also been shown to be an effective method of delivery. [ABSTRACT FROM AUTHOR]