Supplement analysis backed by scientific evidence · PT

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Moderate evidenceImmunity

Shiitake Extract

Whole shiitake mushrooms and their beta-glucan lentinan have measurable immune effects in humans — including a survival benefit as injected lentinan alongside gastric cancer chemotherapy — but that drug is not the capsule on the shelf. Oral supplement evidence is thin and rests largely on one small dietary trial.

What the science says

  • Injectable lentinan extends survival in advanced gastric cancer Moderate evidence

    An individual-patient meta-analysis of 5 randomized trials (n=650) of intravenous lentinan added to chemotherapy for unresectable or recurrent gastric cancer found a significant overall survival advantage (hazard ratio approximately 0.80). Lentinan is an approved injectable adjunct in Japan; this evidence says nothing about swallowing a shiitake capsule, since injected purified beta-glucan and oral extract are different exposures entirely.

  • Eating whole shiitake shifts immune markers Limited evidence

    In a 4-week randomized dietary trial, 52 healthy adults aged 21-41 ate 5 g or 10 g dried shiitake daily; both groups showed increased circulating gamma-delta T cells and NK-T cells, higher secretory IgA, and reduced CRP. It was a single small unblinded study measuring biomarkers, not infections, so it demonstrates immune modulation without demonstrating clinical benefit.

  • Cholesterol lowering by eritadenine Limited evidence

    Shiitake contains eritadenine, which lowers plasma cholesterol robustly in rodents by altering phospholipid methylation. Human data are essentially limited to small, dated, uncontrolled reports; no modern RCT establishes a lipid effect at edible or supplemental doses.

  • Mycelium versus fruiting body products Limited evidence

    Many US 'shiitake extract' capsules are grain-grown mycelium biomass, where much of the mass is residual starch from the substrate rather than fungal beta-glucan. Independent analyses of mushroom supplements repeatedly find beta-glucan content far below label implication, and alpha-glucan (starch) counted as 'polysaccharides'. Look for stated beta-glucan percentage and fruiting-body sourcing before assuming a product resembles anything studied.

Dosage & safety

Studied doseThe dietary trial used 5-10 g/day of dried shiitake (about 50-100 g fresh). Oral supplement labels typically give 500-1,500 mg/day of extract, a dose with no direct efficacy evidence. Lentinan in oncology is given intravenously at 1-2 mg once or twice weekly under medical supervision and is not comparable to any oral product.
SafetyWell tolerated as a food. The distinctive adverse effect is shiitake dermatitis — a whip-like linear flagellate rash caused by lentinan in raw or undercooked mushrooms, appearing 24-48 hours after ingestion and resolving over 1-3 weeks; thorough cooking largely prevents it. Occupational spore exposure causes hypersensitivity pneumonitis in mushroom workers. Rare reports of eosinophilia and photosensitivity with concentrated extracts. Because beta-glucans stimulate immune signaling, caution is reasonable in autoimmune disease and in transplant recipients on immunosuppressants; discuss with an oncologist before combining with cancer treatment. Not banned in sport.

Scientific references

Where to buy

Swanson Vitamins, Shiitake Mushroom Extract, 500 mg, 120 Capsules

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