Usually, when people talk about getting all the essential vitamins and nutrients, they just advise you to eat more vegetables! And while vegetables are powerful with micronutrients, adding more greens to your diet will not help you when it comes to this particular fat-soluble micronutrient: vitamin D.
The only vegetables that contain the extremely important vitamin D are irradiated mushrooms (and they really are not even vegetables, but fungi). “Mushrooms produce vitamin D2 by converting ergosterol into their membranes by a photochemical reaction in the same way that UV from the sun converts cholesterol to vitamin D3,” said Robert Bruce Bielman, Ph.D., an expert on the effects of UV light on fungi.
Mushrooms contain a different type of D than that formed as a result of sun exposure in our bodies (or what we consume from oily fish or eggs). When hit with adequate and prolonged UV light, fungi produce D2, while our bodies produce D3. Vitamin D2 usually comes from plant sources such as mushrooms and D3 from animal sources such as salmon.
Another great thing about mushrooms is that you can expose them to more UV light to increase the amount of D2 in them. Bellman used pulsed light emitted by a xenon lamp on mushrooms in his study, but even placing mushrooms outdoors will do the job of increasing their supply of D, according to renowned mycologist Paul Stamets.
The only other plants that contain vitamin D are algae and phytoplankton, which actually contain D3, not D2. Although often classified as “sea vegetables”, algae are not actually vegetables. However, this marine botanical product provides a powerful – and extremely sustainable – source of plant-based D3. *
Although our bodies can still use D2 (ergocalciferol), much of the science emphasizes its lower level than vitamin D3 (cholecalciferol). In fact, D3 is much better for human consumption based on its bioactivity, stability and bioefficiency. *
Example: You will have to eat a lot from D2-rich mushrooms daily, approximately seven cups to consume about 5000 IU (ie the amount to achieve enough vitamin D in normal weight adults). But because vitamin D2 is two to three times less effective than vitamin D3, you actually need 14 to 21 cups of mushrooms. Who is ready for this fungal challenge?