Plant Oils as Potential Sources of Vitamin D
To combat vitamin D insufficiency in a population, reliable diet sources of vitamin D are required. The recommendations to consume more oily fish and the use of UVB treated yeast are already applied strategies to address vitamin D insufficiency. This study aimed to elucidate the suitability of plant oils as an alternative vitamin D source. Therefore, plant oils that are commonly used in human nutrition were first analyzed for their content of vitamin D precursors and metabolites. Second, selected oils were exposed to a short term UVB irradiation to stimulate the synthesis of vitamin D. Finally, to elucidate the efficacy of plant derived vitamin D to improve the vitamin D status, we fed UVB exposed wheat germ oil (WGO) for 4 weeks to mice and compared them with mice that received non exposed or vitamin D3 supplemented WGO. Sterol analysis revealed that the selected plant oils contained high amounts of not only ergosterol but also 7 dehydrocholesterol (7 DHC) with the highest concentrations found in WGO. Exposure to UVB irradiation resulted in a partial conversion of ergosterol and 7 DHC to vitamin D2 and D3 in these oils. Mice fed the UVB exposed WGO were able to improve their vitamin D status as shown by the rise in the plasma concentration of 25 hydroxyvitamin D [25(OH)D] and the liver content of vitamin D compared with mice fed the non exposed oil. However, the plasma concentration of 25(OH)D of mice fed the UVB treated oil did not reach the values observed in the group fed the D3 supplemented oil. It was striking that the intake of the UVB exposed oil resulted in distinct accumulation of vitamin D2 in the livers of these mice. In conclusion, plant oils, in particular WGO, contain considerable amounts of vitamin D precursors which can be converted to vitamin D via UVB exposure. However, the UVB exposed WGO was less effective to improve the 25(OH)D plasma concentration than a supplementation with vitamin D3.
Front. Nutr.