L-Ergothioneine, a mushroom-derived nutrient sold as a dietary supplement for longevity, is absorbed through its own dedicated carrier and kept for weeks. The most consistent human signal is a modest improvement in self-rated sleep quality, seen mainly in small company-funded trials. Memory effects are mixed; heart and survival links rest on blood levels, not supplement trials. Safety appears favorable at studied amounts; benefits remain plausible but unproven. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Plasma or whole-blood ergothioneine | No established target; track change from the individual's own baseline | Confirms uptake |
| Hemoglobin | Women 12.0–15.5 g/dL; men 13.5–17.5 g/dL | Safety check |
| Serum creatinine and eGFR | Creatinine 0.6–1.3 mg/dL; for eGFR, no established target, track change from own baseline | Safety check; kidney function governs retention |
| ALT and AST | ALT 7–56 U/L; AST 8–48 U/L | Safety check |
Cadence: Baseline, then blood count, kidney and liver tests at about 3–4 months and every 6–12 months while supplementation continues; sleep and memory ratings at 4 weeks, 16 weeks, then every 6 months