Two reviews exist on vitamin D compounds in plants (Boland, 1986 Boland et al., 2003). Traditionally, only vitamin D 2 has been considered present in plants. The term vitamin D also includes vitamin D 2 that is produced in fungi and yeast by UVB-exposure of provitamin D 2 and small amounts can be found in plants contaminated with fungi. The occurrence of vitamin D 3 in algae suggests that vitamin D 3 may exist in the plant kingdom and vitamin D 3 has also been identified in several plant species as a surprise to many (Boland et al., 2003). Fish have the highest natural amount of vitamin D 3, which is expected to derive from a high content of vitamin D 3 in planktonic microalgae at the base of the food chain (Takeuchi et al., 1991 Sunita Rao and Raghuramulu, 1996a). The consequence of a low dietary intake and limited vitamin D derived from the sun is that the general populations fail to meet their vitamin D requirements (Brot et al., 2001 Bailey et al., 2010). Thereby, a dietary intake of vitamin D becomes essential, but very few food sources naturally contain vitamin D. Vitamin D 3 is synthesized in the skin by a photochemical conversion of provitamin D 3, but the necessary UVB rays (290–315 nm) are only emitted all year round in places that lie below a 35° latitude. As a result, there is a growing awareness about vitamin D as a requirement for optimal health. Thus, vitamin D insufficiency increases the risk of osteoporosis, but has also been linked to an increased risk of hypertension, autoimmune diseases, diabetes, and cancer (Hyppönen et al., 2001 Cantorna and Mahon, 2004 Holick, 2004 Lappe et al., 2007 Pittas et al., 2007 Kendrick et al., 2009). The main function of vitamin D is in maintenance and regulation of calcium levels in the body and vitamin D is, therefore, critically important for the development of a healthy skeleton. Finally, perspectives for a future production of vitamin D biofortified fruits, vegetables, and fish will be presented. It also addresses the occurrence of vitamin D and its hydroxylated metabolites in higher plants and in algae and discusses limitations and advantages of analytical methods used in studies of vitamin D and related compounds including recent advances in analytical technologies. This review summarizes the current knowledge on sterol biosynthesis leading to provitamin D. Small amounts can be found in plants contaminated with fungi and traditionally only vitamin D 2 has been considered present in plants. The term vitamin D also includes vitamin D 2 that is produced in fungi and yeasts by UVB-exposure of provitamin D 2. Microalgae contain both vitamin D 3 and provitamin D 3, which suggests that vitamin D 3 exist in the plant kingdom and vitamin D 3 has also been identified in several plant species as a surprise to many. Fish have the highest natural content of vitamin D expected to derive from an accumulation in the food chain originating from microalgae. Unfortunately, very few food sources naturally contain vitamin D and the general population as a results fail to meet the requirements. Vitamin D 3 is synthesized in the skin by a photochemical conversion of provitamin D 3, but the necessary rays are only emitted all year round in places that lie below a 35° latitude. Therefore, there is a growing awareness about vitamin D as a requirement for optimal health. The major function of vitamin D in vertebrates is maintenance of calcium homeostasis, but vitamin D insufficiency has also been linked to an increased risk of hypertension, autoimmune diseases, diabetes, and cancer.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |