A sulfur compound obtained mainly from mushrooms and actively stored by the body. Blood levels fall with age, and lower levels track with poorer heart and brain health and greater frailty. Safety looks clean at the modest doses studied, but the benefits are still mostly based on association rather than proof — real potential paired with genuine uncertainty. (Full Review)

Protocol

Standard Dose

5–30 mg daily

5 mg approximates a mushroom-rich diet; 25–30 mg reflects research doses

Timing & Frequency

Once daily, with food

Any consistent time; long retention makes split or multiple daily doses unnecessary

Source

Supplement or food-first

Oyster, king oyster, and shiitake mushrooms are the richest sources; tempeh provides less

Time to effect

Health Benefits

Months

Any benefits accrue gradually over months, not as an acute effect

Blood & Tissue Levels

Days to weeks

Levels rise with consistent intake and accumulate steadily

Acute Effect

None

Not a compound with a felt short-term effect

Benefits

Medium: Cardiovascular health and lower mortality risk; antioxidant and anti-inflammatory cytoprotection

Low: Cognitive function and neuroprotection; frailty and healthy-aging resilience

Speculative: Skin health and photoprotection; metabolic and liver health; general healthspan and longevity extension

Contraindications

Pregnancy and breastfeeding

Advanced chronic kidney disease (eGFR <30 mL/min/1.73 m²)

Known hypersensitivity to the product or its excipients

Key Interactions

OCTN1-substrate and -inhibitor drugs (substrates: gabapentin, metformin, oxaliplatin; inhibitors: verapamil, quinidine, ipratropium)

Risk & Side Effects

Low: Mild, transient gastrointestinal symptoms

Speculative: Theoretical pro-oxidant activity; uncertain long-term and high-dose safety; facilitated uptake in inflamed or tumor tissue; insufficient data in pregnancy and lactation

Monitoring

Marker	Target	Why
Whole-blood ergothioneine	Higher-normal (no consensus range)	Direct measure of ergothioneine status and loading
hs-CRP	<1.0 mg/L	Tracks systemic inflammation
eGFR	>90 mL/min/1.73 m²	Confirms normal clearance; flags kidney disease that alters handling
ALT	<25 U/L	General safety check of liver function
CBC	Within reference range	Baseline safety of red cells, white cells, and platelets

Cadence: Baseline before starting, then safety labs at ~3 months and every 6–12 months; more frequent with kidney disease or interacting medications

Qualitative Assessment

Cognitive clarity and memory (subjective day-to-day sharpness)
Energy and sense of resilience or recovery from stress
Skin quality and tone
General well-being over months rather than days

L-Ergothioneine for Health & Longevity

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment