Vitamin D enrichment of the food supply to reduce risk of chronic disease

The majority of our circulating levels of vitamin D (25OH D) originate from skin synthesis upon exposure to adequate sunlight. Skin synthesis of vitamin D is absent in winter or through other factors, making adequate dietary intake of vitamin D critical for at risk groups. Vitamin D has many functions beyond its role in calcium regulation and bone health, and it is now recognized that chronic disease risk is greater when vitamin D status is low as indicated by low serum 25OHD. Naturally occurring vitamin D3 in foods is limited to fatty ocean fish, as liver and eggs with their high cholesterol content are impractical to recommend. In the US, a variety of food categories beyond fluid milk may lawfully be fortified with vitamin D; however, this fortification is optional and not often done. Mandatory listing of vitamin D content on food labels may stimulate more optional fortification. Current research efforts explore the potential for plant foods to increase vitamin D2 intakes. We are studying fresh mushrooms which synthesize D2 from ergosterol after brief exposure to UVB light. Baker's yeast is another plant source of vitamin D2. The feasibility of fortifying bread with light exposed vitamin D2- enhanced yeast is currently under study and is an example of how the food industry could better meet the challenge of developing new foods to improve vitamin D status of the population. While experts were concerned that the D3 and D2 forms were not equally potent, new research demonstrates there is little difference.