Usually when people talk about getting all of the essential vitamins and nutrients, they simply advise you to eat more veggies! And while vegetables are potent with micronutrients, adding more greens to your diet won’t do you any good when it comes to this particular fat-soluble micronutrient: vitamin D.
The only vegetable that contains the all-important vitamin D is irradiated mushrooms (and they really aren’t even a vegetable, but a fungus). “Mushrooms produce vitamin D2 by converting ergosterol in their membranes via a photochemical reaction in the same way that UV from the sun converts cholesterol to vitamin D3,” says Robert Bruce Beelman, Ph.D., an expert on the effects of UV light on mushrooms.
Mushrooms contain a different type of D than what’s formed as a result of sun exposure in our bodies (or what we consume from fatty fish or eggs). When hit with adequate and sustained UV light, mushrooms produce D2, while our bodies produce D3. Vitamin D2 usually comes from plant sources like mushrooms and D3 from animal sources like salmon.
Another cool thing about mushrooms is that you can expose them to more UV light to increase the amount of D2 in them. Beelman used pulsed light emitted from a Xenon lamp on mushrooms in his research, but even placing your shrooms outdoors will do the trick to boost their D supply, according to famous mycologist Paul Stamets.
The only other plants containing vitamin D are algae and phytoplankton, which actually contain D3 rather than D2. Though often put in the “sea vegetables” category, algae isn’t actually a vegetable. Nonetheless, this marine botanical provides a potent—and highly sustainable—source of plant-based D3.*
While our bodies can still use D2 (ergocalciferol), a large body of science underscores its inferiority to vitamin D3 (cholecalciferol). Indeed, D3 is far superior for human consumption based on its bioactivity, stability, and bioefficacy.*
Case in point: You would have to eat a lot of D2-rich mushrooms daily, approximately seven cups, to consume about 5,000 I.U. (i.e., the amount to achieve vitamin D sufficiency in normal-weight adults). But since vitamin D2 is two to three times less effective than vitamin D3, you actually need 14 to 21 cups of mushrooms. Who’s ready for that fungi challenge?