Vitamin D is essential for immune functioning, can increase life expectancy, and even reduce deaths from COVID-19. 

I heard that mushrooms contain Vitamin D, so I had to know - can eating mushrooms help keep me alive and healthy during this pandemic?

The "Sunshine" Vitamin

Known as the Sunshine Vitamin, Vitamin D is the only vitamin that humans can produce by our own skin when exposed to sunlight! In the summer, we store up a reserve of this essential vitamin in our fat to be used in the winter months.

I was shocked to learn that Vitamin D deficiency is linked to reduced life expectancy. But it’s no wonder, when you consider the multitude of ways it is needed to maintain good health.

We have Vitamin D receptors all over our bodies, including our bones, intestines, pancreas, and all immune system cells.  It is essential in the regulation of cell growth and metabolism, and for maintaining bone mineralization and growth.

Astoundingly, Vitamin D affects as many as 2,500 genes, influencing which ones are turned on and off during the course of your life. That’s 10% of all of your genes!

Home Grown King Oyster Mushroom Canada

Can Vitamin D Prevent Covid Deaths?

Vitamin D is also an essential player in your immune system, ramping it up to fight infection, and turning it down to prevent inflammation. Studies have shown that therapeutic doses of Vitamin D resulted in a 42% decrease in influenza infection, but can it ward off Covid19?

Groundbreaking research has shown that Vitamin D could play a vital role in preventing and minimizing the severity of Covid19, and in preventing deaths.

An analysis of eight independent research studies has shown that people with higher levels of Vitamin D were more likely to survive COVID-19 infection than those with lower levels. Researchers postulate that Vitamin D may inhibit the metabolic pathways that lead to a cytokine storm, protecting those infected with COVID-19 from acute respiratory distress and death.

The results are so compelling that 200 doctors from around the world have recently signed an Open Letter to governments, doctors, public health officials, and health care workers, urging them to immediately begin recommending higher doses of Vitamin D to combat COVID-19.

Topping Up Winter Lows

Since we can make our own Vitamin D, I never worried too much about supplements. Yet in Canada there isn’t enough winter sunlight to top up our reserves, and many people are deficient!

In fact Health Canada recommends taking a daily supplement of 600 IU Vitamin D daily to prevent disease, and up 4,000 IU daily if needed to boost levels. The goal is to maintain blood levels of 25(OH)D higher than 50 nmol/L, a measure used to monitor our levels of Vitamin D.

However, some studies are suggesting that we aim for 125nmol/L of 25(OH)D or higher to prevent infections such as COVID-19, and we might need to supplement as high as 6,000 to 10,000 IU per day to achieve this! Researchers extrapolated that zero deaths from COVID-19 might be obtained with blood levels exceeding 125nmol/L of 25(OH)D3. Zero deaths.

Consult your doctor before taking high doses of Vitamin D. While there have been some concerns about risks of arterial calcification with very high levels of Vitamin D, research shows that Vitamin K can minimize this risk.

Do Mushrooms Make Sunshine Vitamins?

Yes they can! Mushrooms produce Vitamin D much in the same way that humans do – through the “skin” on their gills and cap when exposed to sunlight! Mushrooms can contain significant amounts of Vitamin D2, particularly if they have been sundried.

In recent research Paul Stamets found that Shiitake mushrooms that were grown and dried indoors had only 110 IU of Vitamin D2 per 100g, but the same strain when dried in the sun soared to 21,400 IU of Vitamin D2. Wow!

Stamets’ research showed that, while all parts of the mushrooms did produce Vitamin D when exposed to sun, including the cap and the stem, the gills were the most effective producer of this important nutrient.

Stamets also found that exposure to sun could increase Vitamin D levels in previously dried mushrooms. In addition, many different mushroom varieties, including cremini, oyster, portabella, and white button mushrooms have also shown high levels of Vitamin D2 if exposed to UVB radiation.

Is Vit D2 from Mushrooms the Right Kind?

Renowned mycologist Paul Stamets totes mushrooms as an important source of Vitamin D, especially for vegans and vegetarians, but can we really get enough of the right kind of Vitamin D from mushrooms?

There are several different types of Vitamin D, but the two most biologically significant forms are Vitamin D2 and Vitamin D3. The only natural sources of vitamin D3 (Cholecalciferol) in the Canadian food supply are fatty fish and egg yolks, and much of our dietary supply is from fortified foods like milk.

By contrast, Vitamin D2 (Ergocalciferol) is found naturally in some mushrooms, plants and yeasts. Structurally these molecules are almost identical, and both kinds of Vitamin D are converted into calcidiol in your liver to be stored, and then converted to calcitriol in your kidneys to be used.

Most over-the-counter supplements in Canada contain vitamin D3, which is generally regarded as more effective at raising Vitamin D levels in the blood. The BC government has advised that Vitamin D3 is considered three times more effective at increasing Vitamin D in the blood, and has a longer lasting effect.

Many studies do show, however, that Vitamin D2 is an effective supplement for raising blood Vitamin D, and that in some cases can be preferable as a more affordable, and vegetarian alternative.

A German study compared 26 people who took a vitamin D2 supplement to 26 others ingesting vitamin D-enriched mushrooms four times per week for five weeks.  They consumed button mushrooms exposed to UV light that resulted in 20,000 IU/100 grams fresh weight.

The results showed similar levels of vitamin D were absorbed in the blood in both groups: those who ingested a supplement in pill form and those who put freshly cooked mushrooms in soup.

Other studies have also demonstrated that the Vitamin D2 found in mushrooms exposed to UV radiation is effective in raising blood levels of Vitamin D.

So while you might not want to rely on mushrooms as your sole source of the sunshine vitamin, adding them to your diet can boost to your Vitamin D levels!

Eat Your Sunshine Mushrooms

Although no official recommendations have yet been made, research on the protective effects of Vitamin D on COVID-19 are compelling enough to consider immediately upping our intake of Vitamin D.

Although we may still need over-the-counter Vitamin D supplements, mushrooms can be a vessel to deliver to us some of the many health benefits of the Sunshine Vitamin! As Dr. Kevin Cashman, summed up in the Journal of Nutrition;

“….UV light–exposed edible mushrooms are a novel, unappreciated, and unexploited food source offering a natural solution beyond traditional fortification to increase the vitamin D intake in the general population, particularly in those following vegetarian or vegan regimens.”

The best way to be sure to maximize the natural Vitamin D in mushrooms, is to grow and sun-dry them yourselves! – Luckily that’s easy to do!

Explore Grow Mushrooms Canada website for a wealth of articles and videos on mushroom growing.

5 Easy Steps to Boost Vitamin D in Your Mushrooms

  • Slice home-grown oyster, shiitake and other mushrooms and spread evenly on a tray.  Ideally face the gills upwards.  (You can also use store bought fresh or dried mushrooms.)
  • Put outdoors to soak up the sun’s rays for 2 days (longer may start to decrease the Vitamin D content).  Make sure to bring them in overnight to protect them from dew and hungry critters!
  • If necessary, use a dehydrator to finish drying the mushrooms until they are crispy.
  • Store your Vitamin D packed mushrooms in a glass jar or sealed container.
  • Rehydrate and cook into your favourite recipes.

Although supported by scientific research, the statements and products referred to throughout this site have not been evaluated by Health Canada. They are not intended to diagnose, treat, cure or prevent any disease. Individual results may vary. Seek the advice of a competent health care professional for your specific health concerns. If you have a medical condition or are pregnant please consult your primary health care provider before use. For those interested to delve deeper, we have included a list of some relevant studies below.

Effect of ultraviolet light–exposed mushrooms on vitamin D status: Liquid chromatography–tandem mass spectrometry reanalysis of biobanked sera from a randomized controlled trial and a systematic review plus meta-analysis.

Effects of postharvest pulsed UV light treatment of white button mushrooms (Agaricus bisporus) on vitamin D2 content and quality attributes

Bioavailability of vitamin D2 from irradiated mushrooms: an in vivo study

Photobiology of vitamin D in mushrooms and its bioavailability in humans

Notes on Nutritional Properties of Culinary-Medicinal Mushrooms (Paul Stamets)

Assessing the impact of a mushroom-derived food ingredient on vitamin D levels in healthy volunteers

Safety assessment of the post-harvest treatment of button mushrooms (Agaricus bisporus) using ultraviolet light

Vitamin D mushrooms: comparison of the composition of button mushrooms (Agaricus bisporus) treated postharvest with UVB light or sunlight

Vitamin D content of Maitake Mushrooms as per USDA 

Vitamin D2 formation from post-harvest UV-B treatment of mushrooms (Agaricus bisporus) and retention during storage

Bioavailability of vitamin D₂ from UV-B-irradiated button mushrooms in healthy adults deficient in serum 25-hydroxyvitamin D: a randomized controlled trial

About Vitamin D

Vitamin D levels advised: Dr John Campbell YouTube

Vitamin D 101 – A Detailed Beginner’s Guide

Vitamin D and Calcium: Updated Dietary Reference Intakes (Health Canada)

Vitamin D (National Institute of Health)

Vitamin D testing:

A new look at vitamin D challenges the current view of its benefits

Prevalence of Vitamin D Deficiency and Associated Risk Factors in the US Population (2011-2012)

Why is vitamin D so important?

Vitamin D status of Canadians as measured in the 2007 to 2009 Canadian Health Measures Survey

Optimal serum 25-hydroxyvitamin D levels for multiple health outcomes

Immunologic Effects of Vitamin D on Human Health and Disease

Time out: should vitamin D dosing be based on patient’s body mass index (BMI): a prospective controlled study

One hundred years after Vitamin D discovery: Is there clinical evidence for supplementation doses?

Vitamin D and Covid Implications

Dietary Supplements in the Time of COVID-19

COVID-19 Mortality Risk Correlates Inversely with Vitamin D3 Status, and a Mortality Rate Close to Zero Could Theoretically Be Achieved at 50 ng/mL 25(OH)D3: Results of a Systematic Review and Meta-Analysis

Therapeutic and prognostic role of vitamin D for COVID-19 infection: A systematic review and meta-analysis of 43 observational studies

Vitamin D and the Immune System (Summary of Research)

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The Key is to Keep Cold or Delay Shipping

Refrigeration will delay fruiting for a month or more, and a cold dark basement will slow them for 2-3 weeks.  A sticker on your parcel will alert the recipient to keep it cold.

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Consider also the option of a non-perishable gift, like booksmushroom hot chocolate, or a gift card so that your loved one can choose a living gift when timing is best for them.

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