Vitamin D: dietary requirements and food fortification as a means of helping achieve adequate vitamin D status.

Vitamin D deficiency is evident in many parts of the globe, even in the sunnier regions, for a variety of reasons. Such deficiency contributes to risk of metabolic bone disease as well as potentially other non-skeletal chronic diseases in both early-life and later-life, and thus strategies for its prevention are of major public health importance. Dietary Reference Intervals (called Dietary Reference Intakes (DRI) and Dietary Reference Values (DRVs) in North America and Europe, respectively) for vitamin D have a key role in protecting against vitamin D deficiency in the population, and these have been re-evaluated in recent years on both sides of the Atlantic. The current DRI and DRVs for vitamin D and their basis will be overviewed in this review as well as some limitations that existed within the evidence-base and which contribute some degree of uncertainty to these new requirement estimates for vitamin D. The review will also compare current population intake estimates for children and adults in North America and Europe against the estimated average requirement (EAR) for vitamin D, as a benchmark of nutritional adequacy. While vitamin D supplementation has been suggested as a method of bridging the gap between current vitamin D intakes and new recommendations, the level of usage of vitamin D supplements in many countries as well as the vitamin D content of available supplements in these countries, appears to be low. The fortification of food with vitamin D has been suggested as a strategy for increasing intake with potentially the widest reach and impact in the population. The present review will highlight the need to re-evaluate current food fortification practices as well as consider new additional food-based approaches, such as biofortification of food with vitamin D, as a means of collectively tackling the low intakes of vitamin D within populations and the consequent high prevalence of low vitamin D status that are observed. This article is part of a Special Issue entitled '17th Vitamin D Workshop'.