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In-vitro evidence suggests that the lipid component of foods alters vitamin D absorption. This single-blinded, cross-over postprandial study examined the effect of changing the lipid component of a 20 mg vitamin D 3 fortified dairy drink on postprandial 25(OH)D concentrations. Participants consumed one dairy drink per visit: a non-lipid, a pre-formed oleic acid micelle, an olive oil and a fish oil dairy drink. There was a significant time à drink à baseline status effect on 25(OH)D concentrations (p ¼ 0.039). There were no time à drink, time or drink effects on 25(OH)D in vitamin D sufficient participants (>50nmol/L). However, there was an effect of time on changes in 25(OH)D concentrations after the olive oil dairy drink (p ¼ 0.034) in vitamin D insufficient participants (<50nmol/L). There were no effects after the other diary drinks. Olive oil may improve vitamin D absorption from fortified foods. Further research is needed to examine the practical implications of changing the lipid component of fortified foods.

Vitamin D intakes and status are low in many countries due to seasonal UVB exposure variation and the fact that few foods are naturally vitamin D rich. Data modelling studies show that vitamin D intakes increase with food fortification, and countries with mandatory fortification policies have higher vitamin D intakes and status compared to countries without. While many foods can be vitamin D fortified, vitamin D bioavailability differs depending on fortification methods, food structure and composition. Randomised controlled trials (RCT) report that vitamin D2 bioavailability varies between foods, whereas vitamin D3 is bioavailable from many foods. In vitro studies suggest that altering the lipid composition of fortified foods increases vitamin D3 absorption. Olive oil increased vitamin D3 absorption during in vitro digestion compared to other dietary oils. Additionally, when vitamin D3 was incorporated into micelles formed from in vitro digestion of olive oil, more vitamin D3 was absorbed compared to other dietary oils. However, in a human postprandial study, a preformed vitamin D3 micelle dairy drink did not increase vitamin D3 absorption, and a vitamin D3 olive dairy drink increased vitamin D3 absorption in vitamin D insufficient participants only. Action is urgently needed to improve vitamin D intakes and status worldwide. Food fortification improves vitamin D intakes; however, fortification strategies unique to each country are needed. This review will synthesise the literature describing data modelling and intervention trials that assess the safety and efficacy of vitamin D fortification strategies, and those manipulating food composition to alter vitamin D bioavailability from fortified foods. Additionally, RCT examining the impact of vitamin D fortification strategies on vitamin D intakes and status over time are reviewed.

Food fortification improves vitamin D intakes but is not yet mandated in many countries. Combining vitamin D with different dietary lipids altered vitamin D absorption in in-vitro and postprandial studies. This randomised, placebo-controlled trial examined the effect of the lipid composition of a vitamin D fortified dairy drink on change in 25-hydroxyvitamin D (25(OH)D) concentrations. Sixty-three healthy adults aged 50+ years were randomised to one of the following for 4 weeks: vitamin D fortified olive oil dairy drink, vitamin D fortified coconut oil dairy drink, vitamin D supplement or placebo control dairy drink. All vitamin D groups received 20µg of vitamin D3 daily. Serum was collected at baseline and post-intervention to measure 25(OH)D concentrations and biomarkers of metabolic health. Repeated measures general linear model analysis of covariance (RM GLM ANCOVA) compared changes over time. There was a significant time*treatment interaction effect on 25(OH)D concentrations for those classified as vitamin D insufficient (p<0.001) and sufficient at baseline (p=0.004). 25(OH)D concentrations increased significantly for all insufficient participants receiving vitamin D3 in any form. However, for vitamin D sufficient participants at baseline, 25(OH)D concentrations only increased significantly with the coconut oil dairy drink and supplement. There was no effect of vitamin D on biomarkers of metabolic health. Vitamin D fortification of lipid-containing foods may be used in lieu of supplementation when supplement adherence is low or for individuals with dysphagia. These results are important given the recent recommendation to increase vitamin D intakes to 15-20µg for older adults in Ireland.

AbstractIntroductionData modelling studies confirm a role for food fortification to improve vitamin D intakes and status. However, there is very little research reporting the bioavailability of vitamin D from foods to inform food fortification strategies. There is some evidence to suggest that the lipid component of foods impacts vitamin D uptake in cells; however, no studies have examined the absorption kinetics of vitamin D from different lipid delivery systems in humans. The aim of this research is to compare changes in serum vitamin D concentrations using different vitamin D emulsions as delivery systems.MethodsA single blind, controlled, 4-way crossover postprandial study was conducted. Participants consumed 4 different 20μg vitamin D enriched emulsion drinks (olive oil emulsion, fish oil emulsion, mixed micelle emulsion and a non-fat control drink) with a low-fat breakfast on 4 occasions separated by a 1-week washout. Serum 25-hydroxyvitamin D (25(OH)D3) concentrations and cardiometabolic risk markers were measured at baseline and 2, 4, 6 and 8 hours after consuming the drink. Statistical analysis was performed in IBM SPSS Statistics, Version 24 (SPSS Inc. Chicago, IL, USA). Repeated measures ANOVA was performed to assess the effects of the 4 treatments.ResultsSix males and six females aged between 22 and 65 years completed the study. All participants were healthy with a mean BMI of 24.7 ± 4.1kg/m2 for males and 25.1 ± 4.5kg/m2 for females. Each 100 ml drink contained 106 kcal, 4 g fat, 11.9 g carbohydrate and 5.5 g protein, apart from the control which contained 70kcal and 0 g fat. The breakfast contained 321 kcal, 0.7 g fat, 66 g carbohydrate and 10.3 g protein. There was an increase in 25(OH)D3 concentrations over the 8-hour assessment period following consumption of all 4 drinks. Two-way repeated measures ANOVA showed a significant drink*time interaction. No participants experienced any negative side effects after consuming any of the drinks.DiscussionThe absorption kinetics of vitamin D is different depending on the lipid delivery system. This is the first human study demonstrating the bioavailability of vitamin D3 from various emulsions including a novel mixed micelle emulsion. All emulsions were palatable, effective and safe to consume.