The amazing ability of shiitake mushrooms to accumulate Vitamin D
There is a certain satisfaction in putting food by, a simple task that one never truly appreciates until the deep and dark days of winter, when through stored food one can reconnect to the vibrancy life takes on in the summer months. It feels deeply human to sense the comfort a stored harvest brings.
Our farm shelves are stocked with canned soups, tomatoes, salsa, and the freezer jammed full of lamb, pawpaw pulp, and berries. And perhaps most abundant of all are the jars of mushrooms from the season, both specimens of lions mane, oyster, and shiitake we grew this year, as well as hunks of wild-harvested chaga and dried reishi, waiting for hot winter tea brews on the wood stove to awaken their potent medicinal compounds.
While the stored harvest brings a sense of security and abundance, in many cases processing foods means a drop in nutritional or medicinal value. As we dehydrate, can, and freeze, we can do our best to preserve the potential of food, but inevitably some of the value with fresh and live foods is lost. Curiously, with mushrooms, one could argue that dried product is not nutritionally inferior compared to the fresh, but simply different.
Vitamin D is hard to find in food, yet it plays a critical role in overall health. Specifically, the vitamin is converted in the liver and kidneys and in its active form supports maintaining blood levels of phosphorus and calcium while also promoting bone mineralization and absorption of calcium. It is also linked to supporting a healthy immune system and regulation of cell differentiation and growth. Common sources of vitamin D include sunlight, oil-rich fish, and some dairy products, through many are fortified with D. Fortified foods provide most of the vitamin D in the American diet. Almost all of the U.S. milk supply is voluntarily fortified with 100 IU/cup.
Deficiency in Vitamin D is linked to rickets in children and osteomalacia in adults. Those at risk for deficiency include infants who are exclusively breast fed, seniors, and people with limited sun exposure.[i] Vitamin D deficiency is a very common occurrence among cancer patients.[ii] There are varying perspectives on the relationship of depression and vitamin D, a topic that needs more investigation.[iii]
Vitamin D & Mushrooms
Despite popular assumption that mushroom want to be grown in dark, dank caves underground, they actually need light to fully develop fruiting bodies. Mushrooms starved of the necessary UV light frequencies will appear shrunken or pale in color. Even more remarkable is that mushrooms can actually synthesize Vitamin D when exposed to UV light, whether natural or synthetic. Vitamin D is actually not really a vitamin, it’s a hormone that the sun stimulates organisms (i.e. your body and mushrooms) to produce.
One study from Penn State[iv] looked at the use of pulsed UV light to increase vitamin D content in button, crimini, oyster, and shiitake. The results of this study demonstrated that, "after a very short exposure time of about 1 sec (system generates 3 pulses per second) the Vitamin D2 content of these mushroom varieties can be increased from very little to upwards of 800% DV/serving."
Paul Stamets further explored this relationship and also compared synthetic UV with natural sunlight.[v] While UV lamps result in more overall Vitamin D conversation in mushrooms, natural light, as he notes, is "a convenient source…whereas setting up a UVB light chamber is not." Natural sunlight still results more than a 400% increase in D; Stamets found that sun dried shiitake went from 100 IU/100 grams to nearly 46,000 IU/100 grams. This rate is plenty for normal consumption, as recommendations from the Institute of Medicine encourage a dose of 600 IU per day for people up to age 70, and 800 IU for those over 70.[vi]
With winter coming, sunlight is at a premium. In many parts of the US, especially the northeast, its impossible to naturally produce vitamin D from the sun during winter because the sun does not get high enough in the sky for ultraviolet B (UVB) rays to penetrate earth’s atmosphere. This phenonemom is known as the “Vitamin D” Winter.[vii] People living higher than the latitude of 37 degrees are at a greater risk of developing a deficiency, which essentially equates to half of the continental US.[viii]
During this time, we rely on the stores of vitamin D in our system to meet this need. Vitamin D can last in fat tissue for approximately two months, and when consumed via supplement (including mushrooms) circulates in the blood for about 24 hours, According to a 2010 journal article published by Pediatric Nephrology[ix]. Another study, published in a 2008 issue of The American Journal of Clinical Nutrition[x], found that patients given a single dose of 100,000 international units of cholecalciferol, a form of vitamin D, had elevated levels of calcidiol in their blood for 84 days on average. This suggests that vitamin D can stay in the blood longer than 84 days, though the exact maximum length of time is not known.
Is reasonable, then, to calculate that one might be able to enjoy the Vitamin D from sunlight for a few months into winter, but as we enter the new year, our bodies are starved for more. During this time, the consumption of just 1 oz of mushrooms could potentially feed us with 12,880 IU, or 21 days worth of Vitamin D.
Sun dried mushrooms are one of the more readily available forms of Vitamin D that we can easily cultivate in the forests of the United States. Stamet’s measurements further indicate that the Vitamin D in sun-exposed mushrooms lasts up to a year. Stocking up on sun-dried shiitake
In the end, we can currently piece together this story, drawing from studies that look at Vitamin D, mushroom accumulation, and the effects of Vitamin D supplements in the body. (see references below) More research is needed to better understand this process. But one thing is clear, Vitamin D is rare in foods and a critical part of our diet, and UVB-exposed mushrooms like shiitake can offer a significant quantity of D naturally.
How we dry
Our farm is part of a growing agricultural sector producing log-grown mushrooms. While we also grow oysters and some others indoors, it is out in the woods where we marvel in the process where inoculated logs utilize the natural conditions of the forest to grow and produce mushrooms. Log-grown mushrooms offer this advantage over their indoor counterparts; once logs are inoculated they require no energy inputs other than human labor to manage. Indoor cultivation requires constant monitoring and often inputs to regulate ideal temperature and humidity patterns.
It’s with this natural, low-energy production system that we first learned about solar dehydration. It’s remarkable simple – mushrooms are place “gills up” on stainless screens with holes in them and the covered with a screen to keep them sanitary. We then leave them in sunlight for at least 5 hours, where the sun dries them out while engaging the vitamin D conversion in the caps.
Other benefits of this product include an intensification of the shiitake flavor, known as “umami” [xi], which in Japanese means a, "pleasant savory taste." For many years, there were only four tastes widely recognized to be detected by the human tongue; sweet, sour, salty, bitter. This fifth flavor has become all the rage in recent years by chefs, fueled by a renaissance in the good food movement.
All types of mushrooms contain gluatmates[xii], the compounds which produce this flavor, but shiitake are notable as having especially high concentrations of these amino acids. Another compound, known as nucleotides[xiii], are also highly present in shiitake and the two together produce a powerful version of the flavor.
Using dried shittake
Wellspring Forest Farm sells both sun-dried shiitake and sun-dried shiitake powder, both of which are easy to use in a wide variety of recipes.
For the dried mushroom caps, simple rehydrate for 20 – 30 minutes in water (or even red wine) and then dice and add to noodle dishes, stir-fry, or any recipe calling for mushrooms. You can also add directly to soups, as they will rehydrate in the pot!
The dried power can be used base for a soup or as a breading agent for meats or vegetable tempura batter.
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[i] "Vitamin D Deficiency: Symptoms, Causes, and Health Risks." WebMD. Ed. Elaine Magee. WebMD. Web. 20 Nov. 2015.
[ii] "Vitamin D Deficiency Common in Cancer Patients." ScienceDaily. American Society for Radiation Oncology, 3 Oct. 2011. Web. 20 Nov. 2015.
[iii] Penckofer, Sue, Joanne Kouba, Mary Byrn, and Carol Ferrans. "Vitamin D and Depression: Where Is All the Sunshine?" Issues in Mental Health Nursing. U.S. National Library of Medicine. Web. 20 Nov. 2015. <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2908269/>.
[iv] Beelman, R.B. and Kalaras, M.D. (2008). Vitamin D2 Enrichment In Fresh Mushrooms Using Pulsed UV Light
[v] Stamets, Paul. "Place Mushrooms in Sunlight to Get Your Vitamin D." Fungi.com. 6 Aug. 2012. Web. 20 Nov. 2015. <http://www.fungi.com/blog/items/place-mushrooms-in-sunlight-to-get-your-vitamin-d.html>
[vi] "Vitamin D." Health Professional Fact Sheet. National Institute of Health, 11 Nov. 2004. Web. 20 Nov. 2015. <https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/>.
[vii] Tavera-Mendoza, Luz E., and John H. White. "Cell defenses and the sunshine vitamin." Scientific American 297.5 (2007): 62-72.
[viii] Johnson, Lana R. "Vitamin D insufficiency due to insufficient exposure to sunlight and related pathology." Student Pulse 2.12 (2010).
[ix] Shroff, Rukshana, Craig Knott, and Lesley Rees. "The virtues of vitamin D—but how much is too much?." Pediatric Nephrology 25.9 (2010): 1607-1620.
[x] Holick, Michael F., and Tai C. Chen. "Vitamin D deficiency: a worldwide problem with health consequences." The American journal of clinical nutrition 87.4 (2008): 1080S-1086S.
[xi] Kristin, Ohlson. "Umami: The Secret Flavor." Experience Life Magazine, 1 May 2012. Web. 20 Nov. 2015. <https://experiencelife.com/article/umami-the-secret-flavor/>.
[xii] Kurihara, Kenzo. "Glutamate: from discovery as a food flavor to role as a basic taste (umami)." The American journal of clinical nutrition 90.3 (2009): 719S-722S.
[xiii] Sugahara, T., et al. "Contents of 5'-nucleotides and free amino acids in different varieties of dried Shiitake mushroom (Lentinus edodes Sing.)." Journal (1975).