Shiitake

What it is

Shiitake (Lentinula edodes) comes from East Asia and has been eaten there for centuries. Today it is cultivated worldwide on wood or substrate and in Europe is a perfectly ordinary edible mushroom, fresh, dried or as powder. In the German guidelines for edible mushrooms it is on the list of customary species.

For the health question, what matters is which product is meant. The whole mushroom and its powder are foods. Lentinan is an active substance purified from it that is injected as a medicine in Japan. In addition there are extracts from the mushroom’s network of threads, the mycelium: LEM, Lentinex and AHCC. These products are chemically different, and their study results cannot simply be transferred to shiitake capsules.

Even with capsules made from the mushroom itself, a close look is worthwhile. The German Cancer Information Service (Krebsinformationsdienst) points out that the exact composition of such supplements is usually not known and that contamination cannot be ruled out in imported products. Products that state whether fruiting body or mycelium was processed and how much beta-glucan they contain make sense.

How it is supposed to work

The main candidate is lentinan, a beta-glucan with a branched structure. Immune cells recognize such sugar chains from fungal cell walls via receptors such as dectin-1 and are thereby put on standby. This is well described in cell and animal experiments. When eaten, lentinan does not reach the blood unchanged, so the effect would have to work via immune cells in the gut.

The second candidate is eritadenine, a purine derivative. Dried shiitake contain 300 to 650 mg of it per 100 g, and some is lost during cooking. In animal experiments, eritadenine lowers cholesterol and triglycerides, and does so differently from statins: it alters the lipid metabolism genes of the liver and promotes the uptake of LDL. Shiitake also provides fiber, ergothioneine and vitamin D precursors.

What users are looking for

Most people use shiitake for the immune system, often in autumn and winter, some for cholesterol or as an accompaniment to cancer therapy. Many report that they catch colds less often or feel more robust since they have been eating shiitake regularly or taking a powder. These are personal accounts. They fit the laboratory findings, but a controlled study with infections as an endpoint does not yet exist.

What the studies show

The shiitake immune study

52 healthy men and women aged 21 to 41 ate 5 or 10 g of dried shiitake per day for four weeks. Immune cells in the blood, antibodies in saliva and inflammation values were measured. After four weeks, the immune cells were more active, sIgA was higher and CRP lower. Both groups ate shiitake; there was no placebo group.

The lentinan analysis in gastric cancer

Japanese researchers analyzed the data of 650 patients from five randomized trials individually. All received chemotherapy, half of them additionally lentinan. With lentinan, overall survival was significantly longer, hazard ratio 0.80, without contradictions between the studies. This concerns injected lentinan under medical supervision, not mushroom powder.

The cholesterol study with shiitake extract

52 people with slightly elevated cholesterol took 10.4 g per day of a beta-glucan-rich shiitake mixture, equivalent to 3.5 g of mushroom beta-glucan, or placebo for eight weeks. Cholesterol and blood lipids did not change, nor did the inflammation markers. The gut flora changed, and the product was well tolerated.

Where the data stop

The immune values from the shiitake study are laboratory findings, not protection against infection. Whether shiitake protects against colds has not been studied, and the study lacked a control group. Lentinan swallowed as a capsule in a small amount changed only the number of B cells in 42 healthy older adults, nothing else. The survival data in gastric cancer come from injected lentinan and cannot be transferred to food supplements. A shiitake mycelium extract did not help in prostate cancer, and across all cancer types a meta-analysis of 22 studies with 1,723 patients showed better response but no established survival benefit.

On cholesterol the picture is contradictory. The frequently cited reductions come from a seven-day study from the 1970s and from animal experiments. The modern controlled experiment with 3.5 g of shiitake beta-glucan found no effect, the bar study only on triglycerides. AHCC, an extract from shiitake mycelium, has a notable phase II study on HPV infections with 50 women. However, it consists mainly of alpha-glucan and is a product in its own right, not shiitake powder. In a study with 45 colorectal cancer patients, the mycelium extract LEM missed its main goal for nerve damage after chemotherapy; only the higher dose showed a trend. I found no human data on longevity endpoints.

Status, approval and legal

Shiitake is an ordinary food in the EU. According to the EU Novel Food Catalogue, the fruiting body and its aqueous extract powder are not considered novel, and powders and capsules made from them may be sold as food supplements. Dried mycelium powder, by contrast, is considered a novel food without authorization. Since 2011, only one specific mycelium extract has been authorized, at no more than 2.5 ml per day in food supplements. Unlike reishi, Cordyceps sinensis and Coriolus, the expert commission of the German authorities BVL and BfArM has not classified shiitake as a medicine. Lentinan is approved as a medicine in Japan, not in Germany. There is no authorized EU health claim for shiitake, and it is not on the WADA Prohibited List 2026.

Safety

As an edible mushroom, shiitake is unproblematic for most people. The best-known risk is shiitake dermatitis: an itchy, streak-like rash resembling whiplash marks, typically around 48 hours after eating raw or undercooked mushrooms. French poison control centers documented 59 cases from 2014 to 2019; the duration increased with the amount eaten, and all healed without after-effects. The BfR points out that the rash can also occur after cooked mushrooms, and sunlight can make it worse. In a small study with 4 g of shiitake powder daily, 5 of 10 healthy people developed eosinophilia, partly with abdominal complaints, which disappeared after stopping. Large, slippery pieces swallowed unchewed can cause intestinal obstruction. Interactions with medicines have not been systematically studied. Anyone who has already reacted with a rash should avoid shiitake. There are no official maximum amounts for shiitake powder.

Sources

• Dai et al., J Am Coll Nutr 2015 – shiitake consumption and immune markers
• Oba et al., Anticancer Res 2009 – lentinan in advanced gastric cancer
• Sohn et al., Integr Cancer Ther 2026 – meta-analysis of shiitake extracts in cancer
• Morales et al., Eur J Nutr 2021 – shiitake beta-glucan in elevated cholesterol
• Gaullier et al., Int J Med Mushrooms 2011 – oral lentinan in older adults
• Boels et al., Clin Toxicol 2022 – shiitake dermatitis at French poison control centers
• Levy et al., J Allergy Clin Immunol 1998 – eosinophilia after shiitake powder
• Lindequist, J Fungi 2024 – shiitake as a multi-substance mixture, lentinan and eritadenine
• BfR 2004 – health risk of shiitake mushrooms
• Implementing Decision 2011/73/EU – shiitake mycelium extract as a novel food ingredient