Vitamin D status in humans worldwide presents itself as one the most important factors in human health.
The classic bone diseases associated with vitamin D deficiency, rickets and osteomalacia, are still prevalent among certain subpopulations. In addition, modern research has found a putative link between vitamin D status and the risk of a host of diseases including various cancers, heart disease, stroke, diabetes, multiple sclerosis and rheumatoid arthritis, among others. Compounding the issue is the fact that in modern society, individuals spend less time exposed to sunlight due to various factors. Sunlight exposure is the main source of vitamin D, which is produced from the conversion of 7-dehydrocholesterol in the epidermis through UV irradiation. As such, the use of vitamin supplements and foods containing vitamin D are an important source. However, the number of foods that are sources of vitamin D is limited and more sources are needed.Mushrooms are an abundant source of ergosterol, which is the precursor to vitamin D2. Mushrooms have been shown to contain small amounts of vitamin D2 when grown in the wild. Furthermore, the vitamin D2 content of cultivated mushrooms has been shown to increase with exposure to artificial UV light. The use of conventional continuous UV systems has been shown to take on the order of minutes to hours of exposure to increase the vitamin D2 levels to a significant level.
In fresh shiitake mushrooms, ergosterol concentrations are highest in the gills, followed by the cap and stalk, with the gills having twice the concentration of ergosterol as the cap.
When fresh button mushrooms are deliberately exposed to midday sunlight for 15–120 min, they generate significant amounts of vitamin D2, usually in excess of 10 μg/100 g FW.So eat more mushrooms that have been exposed to the sun.