Using food fortification to improve vitamin D bioaccessibility and intakes

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.