Lion's mane: what the evidence shows for memory and mood, side effects and how to choose a supplement

What is lion’s mane?

Lion’s mane (Hericium erinaceus) is an edible mushroom that looks like a white ball of hanging spines. In Japan it’s called yamabushitake. It’s eaten across East Asia and used in traditional medicine there.

Researchers are interested in three groups of compounds in it:

• polysaccharides, including beta-glucans;
• hericenones, found in the fruiting body;
• erinacines, found mainly in the mycelium, the mushroom’s root-like network.

In cell and animal studies these compounds increased proteins that support the growth of nerve cells. That’s where the “brain mushroom” reputation comes from. But mouse studies don’t tell you what will happen in people. Lion’s mane is not a proven nootropic: it’s a food mushroom with a small set of human trials.

Lion’s mane benefits: what human trials show

Memorial Sloan Kettering (MSK), a US cancer centre, describes the human data as limited. These are the main trials:

Lion’s mane for memory

The clearest results came from older people with mild memory problems. But the Japanese trial had 15 people per group, and its lead author worked for a mushroom-growing company. The Taiwanese trial was run with staff from the company that makes the mycelium extract.

A 2025 systematic review pooled scores on the MMSE (a short test of memory and attention) from two studies. On average they rose by 1.17 points, on a scale with a maximum of 30.

Mood and stress

In a 2010 Japanese study, 30 women ate biscuits containing lion’s mane powder for 4 weeks. Their depression and anxiety scores fell compared with the start. In the 2023 UK trial, lower stress in young adults was only a trend, not statistically significant. In fact, word recall improved more in the placebo group by the end. The authors say plainly that the sample was small and the findings are tentative.

What this adds up to:

• every trial is small: the Japanese, UK and US ones had 24–41 participants;
• they used different products: mushroom powder, biscuits, a special mycelium extract;
• in the Japanese trial the effect faded within a month of stopping;
• in young healthy people there’s little sign of benefit.

No health claim for lion’s mane has been authorised in the UK or EU. For other options, see our brain and memory section.

Fruiting body or mycelium on grain?

This is the most important choice. iHerb sells both, and the label often says what’s inside only in small print.

• Fruiting body is the mushroom itself. Its powder was used in the Japanese memory and mood studies.
• Mycelium on grain (often labelled myceliated oats or mycelial biomass) is grown on oats or rice and ground up together with the grain.
• Erinacine A-enriched mycelium extract is a special product with a higher erinacine content. It has been tested in only one trial.

Why mycelium on grain is harder to judge: an analysis of supplements made from chaga, another medicinal mushroom, found mycelium-on-grain products were rich in starch that the mushroom itself doesn’t contain. A company that sells fruiting-body supplements carried out the study. But the logic holds: the grain doesn’t disappear from the finished powder.

Extract or powder?

Powder is simply the dried, ground mushroom. An extract is made by simmering the raw material in hot water, sometimes with an alcohol step as well. A ratio such as “8:1” means 8 kg of mushroom made 1 kg of extract.

Hot water is good at drawing out polysaccharides, which is why extracts often state their beta-glucan content. That’s a useful line: without it, you can’t check what you’re getting. We found no human trials comparing powder with extract.

How much lion’s mane to take

There’s no official dose. Trials are the best guide:

Practical tips:

1. Start low, for example 1 g a day, and increase after a week if you feel fine.
2. Take it with food to reduce the chance of stomach discomfort.
3. Judge the result after 8–12 weeks. In the Japanese trial the difference from placebo appeared at week 8.
4. If nothing has changed after 3 months, stop: there’s no point paying for more.

The same plan step by step, with the signs that mean you should stop at once:

Lion’s mane side effects and who should avoid it

In trials lion’s mane was generally well tolerated, and in the Japanese study blood tests showed no harm. The 2025 systematic review lists possible side effects:

• stomach discomfort and nausea;
• headache;
• skin rash and other allergic reactions.

In the Taiwanese trial four people dropped out because of stomach discomfort, nausea and rash.

The most serious reported case is acute respiratory distress syndrome in a 63-year-old man in Japan. He had been taking a lion’s mane extract, and a lymphocyte test showed a strong reaction to that extract. He recovered after steroid treatment on a ventilator. It’s a single case, but it shows that an allergic reaction to the mushroom is possible.

Don’t take lion’s mane if:

• you’re allergic to mushrooms;
• you’re pregnant or breastfeeding: we found no safety studies for these times;
• it’s for a child.

Talk to your GP or pharmacist first if you have asthma or another allergic condition, take regular medicines or have a long-term illness. MSK doesn’t list drug interactions, but research is limited. A cough, breathlessness, a rash or itching while taking it are reasons to stop and seek medical advice.

Other ways to support your memory

If your memory has clearly got worse, see your GP rather than buying supplements. There are many possible causes, including a lack of vitamin B12, which a blood test can pick up.

If you simply want to look after your brain, start with the basics:

• 7–9 hours of sleep on a regular schedule;
• regular physical activity;
• oily fish in your diet; if you eat little, read how to choose fish oil;
• a check of your diet with our vitamin check.

For another popular memory supplement, see our article on ginkgo biloba.

How to choose a lion’s mane supplement on iHerb

1. Look for “fruiting body” on the label. If it says “mycelium”, check whether it was grown on grain.
2. Check how many milligrams of mushroom are in a serving and compare with trial doses of 1.8–3 g a day.
3. Prefer products that state beta-glucan content rather than only “polysaccharides”.
4. Choose a single-ingredient product rather than a “nootropic blend”.
5. Look for independent quality testing (USP, NSF or similar seals).
6. Work out the cost per gram of mushroom per day, not per bottle. Our guide to supplement labels explains how to read the panel.