Shiitake

What shiitake is

Shiitake is Lentinula edodes (Berk.) Pegler, family Omphalotaceae, an accepted species name in the GBIF taxonomy database.[3] Some older papers use the name Lentinus edodes; the same mushroom is meant.[2] The part eaten and studied is the fruiting body (the cap and stem). Memorial Sloan Kettering describes it as native to East Asia and grown worldwide, and says fresh and dried forms are commonly used in East Asian cooking.[4]

Shiitake is a food first. The research below involves several different things that should not be mixed up: whole dried mushroom, mycelial extracts, a rice bran fermented with the fungus, and purified lentinan.

Traditional use

Shiitake has long been eaten and used as a health food in East Asia. A review of lentinan says shiitake has been used to improve general health for thousands of years in Asia.[5] This is traditional use, not proof of effect. A tradition says nothing about whether a specific extract works.

What research shows

Memorial Sloan Kettering also notes that most lentinan studies used injections, and that it is uncertain whether eating shiitake has similar effects.[4] One trial found a shiitake extract alone was not an effective treatment for prostate cancer.[4]

For more on the compound, see shiitake, lentinan and immune research and PSK, PSP and lentinan: medicines versus supplements.

Lentinan is a medicine in some countries

Lentinan has been approved in Japan as a biological response modifier for treating gastric cancer.[10] Lentinan injection is described as a clinically approved drug in several Asian countries.[5] A prescribed injection given alongside chemotherapy is a different thing from a shiitake capsule or a meal, and results do not transfer between them.

Lab data and chemistry

Everything above is about effects in people. This section is different: it lists what laboratories have found in the mushroom, and what they measured. A compound being present does not show a health effect.

Food versus supplement. The nutrition numbers below describe shiitake eaten as food. Supplements (powders, extracts, mycelium grown on grain) are a different material, and their contents can differ a lot from the fruiting body. Lentinan, for example, is studied mainly as a purified injection, not as a capsule.[17] See fruiting body versus mycelium and mycelium grown on grain.

What the laboratory literature reports in shiitake

The Wikidata/LOTUS database lists 53 compounds reported in Lentinula edodes (Wikidata item Q320999).[12] A listing means "found in at least one study of this species", not "present in every product". The file we used does not carry the paper behind each statement, so we cite the Wikidata and ChEBI records. This is a selection of the compounds most relevant to what shiitake is known for.

Two things matter here. Eritadenine was found in shiitake and is studied for cholesterol: in rats it lowered cholesterol, and one mouse study used it as a positive control.[13] The effect has not been confirmed in people; Memorial Sloan Kettering says there is no clinical proof that shiitake lowers cholesterol.[4] Ergothioneine, an antioxidant amino acid that people get from food, is not in the LOTUS list we used, but it was measured in shiitake by the studies below.

Measured values

USDA FoodData Central values are per 100 g edible portion, public domain.[11] They are food-composition averages, not label claims for any product.

Notes on the table: the cooked-with-salt record (SR Legacy 170097) has the same values as cooked without salt in the file. Dried shiitake is concentrated because the water is gone (9.5 g water per 100 g against 89.7 g raw), so compare it with a dry-weight portion, not a fresh one. Energy is shown in the unit the record uses (kJ for raw, cooked and stir-fried; kcal for dried), so do not compare those cells directly. SR Legacy records are older USDA data (2018 release); two newer Foundation Foods records (FDC 1750346 and 1999628, shiitake) give similar raw values, for example 243 mg potassium and 4.17 g fibre per 100 g (FDC 1999628).[11]

The two fresh ergothioneine values disagree: USDA reports about five times more than the Canadian survey. The studies used different samples and methods, and the survey did not say whether its figures are per wet or dry weight, so we show both and do not pick one.[11][14]

For vitamin D2, USDA lists only a small amount in ordinary shiitake. The 3.9 ug in the dried record is a dried-food figure, and the SR record does not say whether the mushrooms were dried in sun. Mushrooms exposed to UV light or sunshine make far more vitamin D2 from ergosterol (the UVC experiment above is an extreme laboratory case, not a food). We did not find a USDA shiitake record that lists UV-exposed and unexposed shiitake side by side. See mushrooms and vitamin D.

What the numbers do and do not mean

• Values vary with strain, growing substrate, harvest time, drying and cooking. One survey reported higher ergothioneine in dried than in fresh shiitake and also higher after frying or autoclaving; the authors suggest heat may release it from cells, which is a hypothesis, not a tested result.[14]
• A compound found in a mushroom does not show that eating it, or taking a supplement, has a health effect. The cholesterol link for eritadenine rests on animal work.[13][4]
• A food portion and a supplement are very different. The numbers above describe fruiting bodies eaten as food; powders and extracts can contain more, less or different material.
• "Beta-glucan" on a label depends on the test used. Tests that count total sugar chains can include starch-like alpha-glucans from the grain in mycelium-on-grain products, so a high number may not be lentinan-type beta-glucan. See beta-glucans versus polysaccharides.
• Lentinan, the purified compound, is a beta-1,3-glucan used as an injected medicine in Japan and China.[17] Eating shiitake is not the same exposure.