The Hidden Kingdom

Beneath every forest floor runs a hidden network. Fine, thread-like fungal strands, called mycelium, weave through the soil, linking the roots of trees and carrying water, nutrients and even chemical signals between them. What we call a mushroom is only the fruit of this vast underground organism. For thousands of years, healers in China, Japan, Siberia and beyond have prized certain mushrooms as some of the most powerful medicines in nature. Science is now discovering why. (See The Green Prescription.)

A kingdom of their own

Fungi are neither plants nor animals. They belong to a kingdom of their own, and are, surprisingly, more closely related to us than to plants. They can't make energy from sunlight, so like us, they must find their food, and like us, they must defend themselves against bacteria, viruses and other threats. Many of the compounds they have evolved for their own protection turn out to support ours too.

In the 1990s, the Canadian forest ecologist Suzanne Simard showed that trees could pass carbon to one another through these fungal networks, a discovery that gave rise to the idea of the "wood wide web".¹ Fungi are the great connectors of the natural world.

What makes mushrooms medicinal

Beta-glucans are complex sugars in the walls of fungal cells. The immune system recognises them, and they appear to "train" it, helping it respond more effectively to threats while staying in balance. Immunologists describe them as immunomodulators: they help to regulate immunity rather than simply boosting it.
Triterpenes, found especially in reishi and chaga, are bitter compounds studied for calming, anti-inflammatory and liver-protecting effects. (See Bitter Is Better.)
Ergothioneine is a powerful antioxidant that mushrooms make in abundance. The body has a dedicated transporter to absorb it, which suggests it matters to us.
Unique compounds such as the hericenones and erinacines of lion's mane, and cordycepin from cordyceps, each with their own actions.

Like herbs, mushrooms work through many compounds acting together. (See The Inner Life of Plants.)

What we call a mushroom is only the fruit of a vast underground organism.

Everyday mushrooms

You don't need exotic extracts to enjoy the benefits of mushrooms. Culinary mushrooms are nourishing foods in their own right.

In a study in Singapore, older adults who ate more than two portions of mushrooms a week had a lower risk of mild cognitive impairment, the stage that often comes before dementia.²
In a large American study, people who ate mushrooms had a lower risk of depression.³
In a four-week trial, healthy young adults who ate cooked shiitake mushrooms every day showed better-functioning immune cells and lower markers of inflammation.⁴

The sunshine trick

Mushrooms contain a substance called ergosterol, which turns into vitamin D when they are exposed to UV light, just as our skin does.⁵ Place sliced mushrooms gill-side up on a sunny windowsill or outdoors for 30 to 60 minutes before cooking to boost their vitamin D. It's a useful trick in the UK, where vitamin D is hard to come by in winter. (See Living by the Sun.)

The medicinal mushrooms

Reishi: the mushroom of immortality

Reishi (Ganoderma lucidum), known in China as lingzhi, has been revered for more than 2,000 years. It is a calming adaptogen, traditionally used to "nourish the spirit", support deep sleep and strengthen the body's resilience to stress. Its beta-glucans support immunity, while its bitter triterpenes have been studied for calming, liver-protecting and anti-inflammatory effects.⁶ It is woody and bitter, so it's taken as a long-simmered tea or an extract rather than eaten. Best in the evening.

Lion's mane: the mushroom for the mind

Lion's mane (Hericium erinaceus) looks like a shaggy white waterfall of icicles. It contains two families of compounds, hericenones in the mushroom itself and erinacines in its mycelium, which stimulate the production of nerve growth factor, a protein that helps nerve cells grow and repair, in laboratory studies.⁷ In a small Japanese trial, older adults with mild cognitive impairment who took lion's mane for 16 weeks scored better on tests of thinking and memory than those taking a placebo, although the benefits faded after they stopped.⁸ It is also delicious, with a texture like crab or lobster when sautéed in butter. (See Where Body Care Meets Mind.)

Turkey tail: an immune ally

Turkey tail (Trametes versicolor) grows in colourful, fan-shaped layers on fallen wood across Britain. It is one of the best-researched medicinal mushrooms. In Japan, an extract called PSK has been used alongside conventional cancer treatment since the 1970s, and a review of studies found that turkey tail extracts, used alongside conventional treatment, were linked with improved survival in several cancers.⁹ In a small American trial in women who had completed breast cancer treatment, turkey tail helped their immune systems recover.¹⁰ It is always a complement to medical care, never a replacement, and should only be used during cancer treatment with the oncology team's agreement.

Cordyceps: energy and stamina

Cordyceps has been used in Tibetan and Chinese medicine for energy, stamina, lung health and vitality. The wild form is rare and very expensive, so most products today use cultivated Cordyceps militaris. In one trial, people taking it for three weeks had better tolerance to high-intensity exercise and could keep going for longer.¹¹ It is energising, so best taken in the morning.

Chaga: the king of the birch

Chaga (Inonotus obliquus) grows as a dark, crusty, charcoal-like mass on birch trees in cold northern forests. It has long been brewed as a tea in Siberia and Scandinavia, and is very rich in antioxidants. Chaga is high in oxalates, and there are reports of kidney damage in people who took large amounts for long periods,¹² so enjoy it in moderation, and avoid it if you have kidney problems or kidney stones. Much wild chaga is now over-harvested, so choose sustainable sources.

Shiitake and maitake: food as medicine

Shiitake (Lentinula edodes) and maitake (Grifola frondosa), or "hen of the woods", are delicious culinary mushrooms with genuine medicinal value, rich in beta-glucans. Always cook shiitake well: eating it raw or undercooked can cause an unusual itchy, whip-like rash in some people. (See Food as Medicine.)

How to use medicinal mushrooms

In cooking. Shiitake, maitake, oyster and lion's mane are wonderful in soups, stir-fries, risottos and broths. Dried shiitake make a deeply savoury stock.
As a tea or decoction. Woody mushrooms, such as reishi, chaga and turkey tail, are traditionally simmered gently for one to two hours, or longer, to draw out their compounds. A slice of ginger or a cinnamon stick softens reishi's bitterness.
As an extract. Hot-water extraction draws out beta-glucans; alcohol extraction draws out triterpenes. A dual extract uses both, to capture the whole mushroom.
As a powder stirred into coffee, hot chocolate, porridge, smoothies or soups.
Timing. Lion's mane and cordyceps suit the morning; reishi suits the evening.
Patience. Medicinal mushrooms tend to work gently and gradually, over weeks rather than days.

Choosing a good-quality product

Quality varies enormously, so it pays to read the label carefully:

Fruiting body or mycelium? Many cheaper products are made from mycelium grown on grain, such as rice or oats, and may contain a great deal of leftover grain starch. Look for products made from the mushroom's fruiting body, or that clearly state how much of the product is mushroom.
Look for beta-glucan content stated on the label, ideally tested by an independent laboratory. Be wary of products that only list "polysaccharides", which can include starch.
Check the extraction. Whole-mushroom powders are poorly digested; hot-water or dual extracts are more concentrated and better absorbed.
Choose organic and buy from reputable suppliers, as mushrooms readily absorb heavy metals and pollutants from where they grow.

Using mushrooms safely

Never eat wild mushrooms unless they have been identified by an expert. Some of Britain's most deadly mushrooms, such as the death cap, look harmless.
Reishi, chaga and some other mushrooms may thin the blood or lower blood pressure or blood sugar. Take care if you take blood thinners, blood pressure or diabetes medicines, and stop two weeks before surgery. (See When Plants Meet Pills.)
Because they act on the immune system, check with your doctor if you have an autoimmune condition, have had an organ transplant, or take medicines that suppress the immune system.
If you have cancer, use medicinal mushrooms only with the knowledge of your oncology team, alongside, never instead of, your treatment.
Avoid medicinal doses in pregnancy and breastfeeding unless advised by a practitioner.

As with herbs, the right mushrooms depend on your constitution and your whole picture, so it's best to seek a practitioner's guidance rather than self-prescribe. (See The Architecture of Balance.)

In short

Mushrooms are the fruit of vast underground fungal networks, and have been used as medicine for thousands of years.
Their beta-glucans help to regulate the immune system, alongside triterpenes, ergothioneine and other unique compounds.
Culinary mushrooms are nourishing foods, linked with better brain health, mood and immunity.
Reishi calms, lion's mane supports the mind, turkey tail supports immunity, and cordyceps builds energy.
Choose fruiting-body or dual extracts with tested beta-glucans, never eat unidentified wild mushrooms, and check for interactions.

At Rootwise, medicinal mushrooms are among our most valued allies, especially for people whose immunity, energy or resilience has been worn down. Gentle, deep-acting and remarkably versatile, they remind us how much healing the natural world still holds.

References

Simard SW et al. Net transfer of carbon between ectomycorrhizal tree species in the field. Nature, 1997.
Feng L et al. The association between mushroom consumption and mild cognitive impairment: a community-based cross-sectional study in Singapore. Journal of Alzheimer's Disease, 2019.
Ba DM et al. Mushroom intake and depression: a population-based study using data from the US National Health and Nutrition Examination Survey (NHANES), 2005–2016. Journal of Affective Disorders, 2021.
Dai X et al. Consuming Lentinula edodes (shiitake) mushrooms daily improves human immunity: a randomized dietary intervention in healthy young adults. Journal of the American College of Nutrition, 2015.
Cardwell G et al. A review of mushrooms as a potential source of dietary vitamin D. Nutrients, 2018.
Wachtel-Galor S et al. Ganoderma lucidum (Lingzhi or Reishi): a medicinal mushroom. In: Benzie IFF, Wachtel-Galor S (eds). Herbal Medicine: Biomolecular and Clinical Aspects, 2nd edition. CRC Press, 2011.
Kawagishi H et al. Erinacines A, B and C, strong stimulators of nerve growth factor (NGF)-synthesis, from the mycelia of Hericium erinaceum. Tetrahedron Letters, 1994.
Mori K et al. Improving effects of the mushroom Yamabushitake (Hericium erinaceus) on mild cognitive impairment: a double-blind placebo-controlled clinical trial. Phytotherapy Research, 2009.
Eliza WLY et al. Efficacy of Yun Zhi (Coriolus versicolor) on survival in cancer patients: systematic review and meta-analysis. Recent Patents on Inflammation & Allergy Drug Discovery, 2012.
Torkelson CJ et al. Phase 1 clinical trial of Trametes versicolor in women with breast cancer. ISRN Oncology, 2012.
Hirsch KR et al. Cordyceps militaris improves tolerance to high-intensity exercise after acute and chronic supplementation. Journal of Dietary Supplements, 2017.
Kikuchi Y et al. Chaga mushroom-induced oxalate nephropathy. Clinical Nephrology, 2014.

This article is for general information and isn't a substitute for personal medical advice. Never eat a wild mushroom unless it has been identified by an expert. If you take medicines, have a health condition, are pregnant or breastfeeding, speak to a qualified practitioner before using medicinal mushrooms.