Lion's Mane (Hericium erinaceus) is the functional mushroom with the most distinctive chemistry — and, unusually for this category, several placebo-controlled human trials behind it.
The compounds, which are genuinely unusual
Lion's Mane contains two families of compounds not found together anywhere else: hericenones, concentrated in the fruiting body, and erinacines, in the mycelium.
Both have been studied for their effect on nerve growth factor (NGF) — a protein involved in the growth, maintenance and survival of neurons. What makes erinacines particularly interesting is their size: they are small enough to cross the blood-brain barrier, which the overwhelming majority of molecules cannot. Most compounds marketed for cognition never reach the brain at all. These do.
That is a real, specific mechanism, and it is why Lion's Mane has attracted more serious research attention than most mushrooms.
The trial in mild cognitive impairment
Mori and colleagues (2009), in Phytotherapy Research, randomised 30 Japanese adults aged 50 to 80 with mild cognitive impairment to Lion's Mane or placebo — around 3g a day of dried powder for 16 weeks.
Scores on a cognitive function scale improved significantly in the Lion's Mane group and did not improve on placebo. Side effects were limited to mild abdominal discomfort, with liver function markers staying in normal range throughout.
The most telling detail is what happened afterwards. When researchers followed up after participants stopped taking it, the improvement receded. An effect that appears with a supplement and fades when it is withdrawn is exactly the pattern you would expect if the supplement caused it — that washout is stronger evidence than the improvement alone.
The trials in healthy adults
The obvious question is whether any of this applies to people without cognitive impairment. Two more recent studies looked at exactly that.
A 2023 randomised, double-blind, placebo-controlled study in Nutrients gave 41 healthy adults aged 18 to 45 1.8g of Lion's Mane. After a single dose, participants were significantly quicker on the Stroop task — a standard measure of processing speed and cognitive interference — at 60 minutes post-dose (p=0.005). After 28 days of supplementation, the study observed a trend toward reduced subjective stress.
A further double-blind randomised placebo-controlled study, published in Frontiers in Nutrition, examined acute effects of a standardised extract on cognition and mood in healthy younger adults, adding to the same picture.
A single dose producing a measurable, statistically significant change in processing speed in healthy young people is a notable result. It suggests something is happening acutely, not only over months in clinical populations.
Where the evidence stands
Three placebo-controlled trials, in two different populations, pointing the same direction, with a plausible mechanism underneath — that is a stronger position than most ingredients in the wellness aisle can claim.
The fair caveat is scale: these are studies of 30 and 41 people, and larger replication would settle the question properly. A 2025 systematic review in Frontiers in Nutrition gathering the evidence on Hericium erinaceus as a supplement reflects growing research interest in doing exactly that.
This is also exactly why no supplement brand is allowed to tell you what these ingredients do. Claims about botanicals sit unassessed in GB law rather than rejected — a distinction we have written about in why no brand can legally tell you what its ingredients do.
What to look for in a product
- Dose matters. The trials used 1.8g to 3g a day. Many products provide considerably less.
- Fruiting body or mycelium? Hericenones come from the fruiting body, erinacines from the mycelium — different compounds, both of interest.
- What does "10:1" mean? Ten kilos of raw material produced one kilo of extract. Useful shorthand, but it says nothing about which compounds concentrated.
- Has it been tested? Mushrooms bioaccumulate from their substrate. Ask for the results.
Sources
- Mori K, Inatomi S, Ouchi K, Azumi Y, Tuchida T. Improving effects of the mushroom Yamabushitake (Hericium erinaceus) on mild cognitive impairment: a double-blind placebo-controlled clinical trial. Phytotherapy Research, 2009; 23(3):367–372. PubMed 18844328.
- The Acute and Chronic Effects of Lion's Mane Mushroom Supplementation on Cognitive Function, Stress and Mood in Young Adults: A Double-Blind, Parallel Groups, Pilot Study. Nutrients, 2023; 15(22):4842. PubMed Central, PMC10675414.
- Acute effects of a standardised extract of Hericium erinaceus on cognition and mood in healthy younger adults: a double-blind randomised placebo-controlled study. Frontiers in Nutrition, 2025. PubMed Central, PMC12018234.
- Benefits, side effects, and uses of Hericium erinaceus as a supplement: a systematic review. Frontiers in Nutrition, 2025.