Boost Your Vitamin D This Winter—With Mushrooms!

Chanterelle mushrooms soaking in the sun

As the colder months approach, maintaining adequate vitamin D levels becomes essential to support our immune system, reduce inflammation, and promote healthy cell growth, neuromuscular function, and bone health. Vitamin D insufficiency, as defined by the World Health Organization, is a serum 25(OH)D level below 20 ng/ml. However, many experts now differentiate between deficiency (below 20 ng/ml) and insufficiency (below 30 ng/ml). Either way, it’s important to ensure your vitamin D levels aren’t running low.

Interestingly, humans are uniquely equipped to produce vitamin D naturally through skin exposure to sunlight. But factors like latitude and genetics significantly impact how much vitamin D we can synthesize. For example, living above 37° latitude—like in the San Francisco Bay Area (37.7° North) or my hometown in the Dolomites (46° North)—means we’re too far north to produce enough vitamin D from sunlight, especially during winter.

Thankfully, there are other ways to boost your vitamin D—starting with your diet. In addition to fatty fish, egg yolks, and liver, mushrooms can be an incredible source of this essential nutrient. Even better, there’s a simple way to supercharge their vitamin D levels at home!

Here’s the trick: Expose mushrooms to sunlight, with their “gills” (undersides) facing up, for at least an hour before cooking. This exposure can dramatically increase their vitamin D content. Unlike many other vitamins, vitamin D remains stable through cooking and drying, so you won’t lose the benefit when preparing your mushrooms.

In fact, research has shown that exposing indoor-grown mushrooms like shiitake, reishi, and maitake to sunlight for 6–8 hours can skyrocket their vitamin D levels. For instance, vitamin D levels in shiitake mushrooms increased from 134 IU to an astonishing 46,000 IU after sunlight exposure (Stamets, 2005)!

Beyond boosting your vitamin D, mushrooms are a fantastic addition to your diet for their diversity and health benefits. Incorporating a variety of mushroom types is a great way to add to your weekly goal of eating 30 different vegetables, fruits, herbs, and spices.

So, whether you forage for mushrooms this weekend or pick some up at your local farmer’s market, try giving them a sunbath before adding them to your meals. Mushrooms pair beautifully with garlic and fresh herbs, making them a delicious side dish. They’re also perfect in stews, pasta sauces, or risottos, where their umami flavor shines.

How do you enjoy your mushrooms best? Let me know—and enjoy the health boost!

Reference:

Stamets, P. (2005). Notes on nutritional properties of culinary–medicinal mushrooms. International Journal of Medicinal Mushrooms, 7(1), 103–110. Retrieved 12/4/2024 from: https://www.researchgate.net/profile/Paul-Stamets/publication/240299749_Notes_on_Nutritional_Properties_of_Culinary-Medicinal_Mushrooms/links/542978260cf2e4ce940ee37c/Notes-on-Nutritional-Properties-of-Culinary-Medicinal-Mushrooms.pdf