Mushrooms are a rich source of natural vitamin D. Plant sterols are recognized as having positive health effects because they have been shown to decrease serum cholesterol levels and to play an important role in preventing colon cancer (Mattila et al 2002). Mushrooms contain a high amount of ergosterol, provitamin D2, which can be converted to vitamin D2 by ultraviolet (UV) irradiation. Because ergosterol is abundant in mushrooms, the best source of vitamin D is therefore sunlight. Vitamin D2 is derived by photo irradiation from its precursor ergosterol.
Ergosterol undergoes photolysis when exposed to UV light of wavelengths 280-320 nm, yielding a variety of photo irradiation products. The principal ones are provitamin D2, tachysterol, and lumisterol. Provitamin D2 undergoes spontaneous thermal rearrangement to vitamin D2. In the kingdoms Plantae and Animalia, ergosterol or vitamin D2 is almost absent. Therefore, the intake of vitamin D from food is mainly emphasized in both northern and southern latitudes. Eating vitamin D-enriched food makes calcium more available for children, the elderly, and postmenopausal women (Mau et al 1998).