Surely you’ve heard cow’s milk is a good source of vitamin D. However, many people don’t realize vitamin D is not naturally found in dairy products. Instead, it is fortified and added for nutritional benefit.
About 1 billion people globally have low vitamin D levels, which is an important nutrient for bone health, muscle function, nerves, and the immune system.1 Many non-dairy milks are also fortified with vitamin D (as well as calcium, vitamin B12, and other nutrients) and can be a great source in your diet. Exposing your skin to the sun is effective as well, but can be difficult for many people during a large portion of the year. Fortunately we have a solution to help meet your vitamin D needs: mushrooms! 
When mushrooms are exposed to ultraviolet light (such as the sun or a UV lamp), they generate vitamin D. Mushrooms have a compound in their cell walls called ergosterol. When exposed to UV light, the ergosterol goes through a series of processes that transforms it into ergocalciferol, another name for vitamin D2.2 (Vitamin D3, also called cholecalciferol, is a different form that is produced by animals.)
Unfortunately, many mushrooms found in grocery stores are grown in the dark and have minimal, if any, UV light exposure prior to arriving at the store. However, you can take interventions after purchasing to promote vitamin D production.
The Recommended Dietary Allowance for adults (aged 19-70) is 15 mcg/day.3 Some wild mushroom varieties have nearly 60 mcg per 100 g serving, while button mushrooms most commonly found in a grocery store have as little as 1 mcg per 100 g.4 (Note: 100 g is approximately 3 button mushrooms, or 1 small portabella mushroom.)
However, exposing these mushrooms to the sun can drastically change that. There are two methods to further increase the production: cutting and flipping. Slicing mushrooms increases the surface area that is exposed to the sun, therefore allowing more vitamin D production. In one study in Germany, sliced button mushrooms exposed to sunlight for 15 minutes reached 17.5 mcg/100 g and as high as 32.5 mcg/100 g after 60 minutes in the sun. Flipping them over and exposing the gills can also boost the vitamin D content; the gills can generate up to 4 times as much vitamin D compared to the cap in all varieties.5
There is limited evidence on the vitamin D content when the mushrooms are cooked. The available studies showed at least 62-88% retention after adjusting for water loss in cooking.6 So if you prefer to cook your mushrooms, you can still reap the benefits.
Eating just one serving of sun-exposed mushrooms daily will provide a significant amount of your vitamin D needs, if not meet them entirely.
There are many varieties of mushrooms (experts estimate 14,000 edible varieties!), both available in traditional grocery stores as well as specialty or farmers’ markets. Many varieties have become popular among health aficionados for their reported benefits.
Some studies suggest reduced anxiety, improved immunity, and improved blood sugar management from various mushroom species. While the data is limited at this time, there are few potential side effects to incorporating mushrooms into your diet. Mushrooms are also high in antioxidants, which can help reduce inflammation and oxidative stress.7
Some of our favorite varieties of mushrooms to cook with include Shiitake, Chanterelle, Oyster, Enoki, and Porcini.
Our advice: mushrooms are a nutrient powerhouse and a delicious way to get vitamin D. But remember, you should never rely on one food to be the sole source of a nutrient in your diet. Aim for a variety of plants to get the most health benefits from your dairy-free and plant-based diet.
Even with the healthiest diet, you should always talk to your healthcare provider about testing your vitamin D levels and making appropriate interventions if necessary.
Ready to head to the kitchen? Check out some of our favorite ways to cook mushrooms with the recipes below. Find dozens more on our Recipes Page.
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