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 D 2 bioavailability varies between foods, whereas vitamin D 3 is bioavailable from many foods. In vitro studies suggest that altering the lipid composition of fortified foods increases vitamin D 3 absorption. Olive oil increased vitamin D 3 absorption during in vitro digestion compared to other dietary oils. Additionally, when vitamin D 3 was incorporated into micelles formed from in vitro digestion of olive oil, more vitamin D 3 was absorbed compared to other dietary oils. However, in a human postprandial study, a preformed vitamin D 3 micelle dairy drink did not increase vitamin D 3 absorption, and a vitamin D 3 olive dairy drink increased vitamin D 3 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.