Mushrooms offer a unique plant-based source of vitamin D, a nutrient important for human health. While many associate vitamin D with animal products or sun exposure, mushrooms naturally produce this compound. Understanding how mushrooms synthesize vitamin D and how to enhance its content can provide a valuable dietary contribution, particularly for those seeking non-animal sources.
How Mushrooms Create Vitamin D
Mushrooms contain ergosterol, a precursor to vitamin D. When exposed to ultraviolet (UV) light, this ergosterol undergoes a photochemical reaction, converting into ergocalciferol, commonly known as vitamin D2. This process is similar to how human skin synthesizes vitamin D3 when exposed to sunlight. The UV light acts as a catalyst for this conversion.
The amount of vitamin D2 produced depends on factors like the intensity and duration of UV exposure, as well as the initial ergosterol content in the mushroom. While some wild mushrooms may contain small amounts of vitamin D2 from natural light exposure during growth, cultivated mushrooms typically have very low levels because they are often grown in dark environments. However, their rich ergosterol content means they have a high potential for vitamin D production post-harvest.
Increasing Vitamin D in Store-Bought Mushrooms
It is possible to significantly boost the vitamin D content of store-bought mushrooms at home through simple UV exposure. Begin by thinly slicing your mushrooms, such as white button, cremini, portobello, shiitake, or oyster varieties, to maximize the surface area exposed to light. Spreading them evenly on a tray, with the gills facing upward if possible, will allow for more efficient absorption of UV rays.
Place the tray in direct sunlight for 15 to 60 minutes, ideally during midday hours when the sun’s UV rays are strongest. Even shorter exposures, like 15 minutes, can lead to substantial increases in vitamin D2. Avoid leaving them for excessively long periods, such as more than two hours, as prolonged exposure can cause the vitamin D2 to break down. It is important that the mushrooms are in direct sunlight, as glass windows block most UV light and prevent this conversion.
Nutritional Role of Mushroom Vitamin D
Mushrooms primarily provide vitamin D2, which differs from vitamin D3 found in animal sources and produced by human skin. Both forms, D2 and D3, are absorbed and utilized by the body. Studies indicate that D2 from mushrooms is effective in raising and maintaining blood vitamin D levels.
A 70-gram serving of UV-exposed mushrooms can reliably provide a nutritionally meaningful amount of vitamin D2, often exceeding 100% of the Recommended Dietary Allowance (RDA) for many adults. For instance, a 100g serving can provide around 10 micrograms (400 IU) or even up to 30 micrograms (1200 IU) of vitamin D, depending on the exposure conditions. This makes UV-treated mushrooms a valuable dietary option, especially for individuals following plant-based diets, to help meet their daily vitamin D requirements.