Astraeus hygrometricus

What is Astraeus hygrometricus?

Astraeus hygrometricus is a wild fungus called the barometer earthstar. Its tough outer skin splits into star-like arms. The arms open in damp air and curl shut when dry.

Young, unopened fruit bodies look like small round balls. In parts of India, Nepal, Thailand and Laos these are picked, cooked and eaten. They are sold in local markets in the rainy season and also used in folk medicine.

Here is the honest verdict on the evidence. There are no good human trials of this fungus as a medicine. Almost all the research sits in test tubes and in mice.

That it has been used for a long time tells you people valued it. It does not tell you the remedy works, and it does not tell you it is safe. We say that once here, and the rest of this page sticks to what is known.

The main real-world risk is not the fungus itself. It is picking the wrong one. Several round, earth-coloured fungi look alike when young, and some of those are poisonous.

How does Astraeus hygrometricus work?

No one has shown how this fungus acts in the human body, because the human studies have not been done.

Lab work points to two groups of compounds. In test tubes, sugar chains from the fungus (polysaccharides) mop up reactive molecules linked to cell damage. In mouse immune cells, some of these sugars switch on cells that engulf germs.

A triterpene from the fungus, called astrakurkurone, has been tested against the parasite that causes leishmaniasis. In test tubes and in mice it slowed the parasite. Whether it does anything in a person is not known.

Other lab tests report that extracts slow some bacteria and some tumour cell lines in a dish. Cell and mouse results often fail to repeat in people. Treat them as leads, not as findings about you.

There is also no good data on how much of these compounds you absorb from a cooked meal. Eating the fungus and taking a concentrated lab extract are not the same thing.

What forms does Astraeus hygrometricus come in?

Most people who use it meet it as food, not as a product.

Common forms:

Fresh young fruit bodies, sold in Asian village and roadside markets during the monsoon. These are cooked, usually in curries or soups.

Dried whole fungus, kept for later cooking.

Dried powder, used in some folk practice.

Spore dust from mature fruit bodies, which was traditionally dusted on wounds.

Research extracts, made with water or alcohol. These are lab materials, not retail goods.

There is no widely sold, tested supplement of this fungus in Europe, the UK or North America. Where mushroom blends list it, strength and purity are rarely checked. Wild-picked fungi are also not inspected for the heavy metals they can draw from soil.

Where it comes from:

Records describe this fungus as a seasonal food and a folk remedy across South and Southeast Asia.

Tribal communities in eastern India, including Santal groups, gathered the young balls after the first rains. They were eaten and also given for stomach complaints and weakness.

In parts of China and India, the dry spore dust of earthstars and puffballs was dusted on cuts and nosebleeds to stop bleeding. Some writers also list it for sore throats and skin sores.

In Thailand and Laos it was and still is chiefly a prized seasonal food, sold by weight in markets.

These accounts describe past practice. They are not a recommendation that you treat yourself with it.

What does Astraeus hygrometricus help with?

• Eaten as a seasonal food: This is the use with the firmest footing. Young fruit bodies are cooked and eaten widely in India, Nepal, Thailand and Laos. They supply protein, fibre and minerals like other edible mushrooms. Eating it is a food choice, not a treatment.
• Folk use for stomach upset: Tradition used it for indigestion and loose stools. No human trial has tested this. There is no evidence it settles a stomach, and poorly cooked or old fungi can upset one instead.
• Folk use as a wound dressing to slow bleeding: Dry spore dust from earthstars and puffballs was dusted on cuts in folk practice. The dust may act as a simple physical barrier. No trial supports it, and packing unsterile spore dust into a wound risks infection. Use a clean dressing instead.
• Folk use as a general tonic for weakness: It was given to build strength after illness. This claim has never been tested in people. Any benefit may simply be that of a protein-rich meal.
• Marketed claims about immune support: Some mushroom products borrow this claim from beta-glucan research. Mouse and cell studies show immune cells reacting to fungal sugars. No human study shows that eating this fungus changes how often you get ill.
• Marketed claims about antioxidant effects: Extracts score well on test-tube antioxidant assays. Those assays measure chemistry in a dish. They do not show a health benefit in people, and no human trial has looked for one.

Which foods are rich in Astraeus hygrometricus?

The fungus is itself the food. It is gathered wild after monsoon rains and is not farmed on any scale. There is no common food that contains it as an ingredient.

What are the side effects of Astraeus hygrometricus?

• Stomach ache, wind or loose stools, especially if undercooked
• Nausea or vomiting from old or spoiled fruit bodies
• Allergic reactions, including rash, itching or swelling
• Breathing irritation from inhaling clouds of spore dust
• Wound infection if raw spore dust is packed into a cut
• Severe poisoning if a toxic look-alike is eaten by mistake

Good to know:

In people who eat it as a cooked food, trouble seems uncommon. Most reports are mild stomach upset.

The serious risk is a mix-up at picking, not the fungus itself. Young earthballs (Scleroderma) and button-stage Amanita can look like round brown balls too. Amanita poisoning can damage the liver and can kill.

There is also no safety data at all on concentrated extracts in people.

How much Astraeus hygrometricus should you take?

• Recommended daily: No established dose exists, so this page gives none as a remedy. No health authority has set an intake, and no trial has tested one. Where it is sold, it is sold as a food by weight, like any market mushroom. Any amount you see on a blended mushroom powder label is the maker's choice, not a tested figure. If you are thinking of it as a medicine, speak to a doctor or a pharmacist first.
• Best time of day: Timing has not been studied and is unlikely to matter. As a food it is eaten at meals, like any other mushroom.
• With or without food: It is normally cooked and eaten as part of a meal. Cook it thoroughly, as you would any wild mushroom. Raw or old fungi are more likely to upset your stomach.
• Time to effect: Be prepared for it to do nothing you can feel. No human study has measured any effect, so no timescale can be given honestly. As a food, it behaves like a meal. Any claimed tonic effect rests on tradition alone.
• How long to take it: No safe or useful length of use has been studied. Traditional use was seasonal, following the rains, rather than daily all year. There is no data on taking concentrated extracts for weeks or months. Long runs of any unstandardised wild fungus product are not well founded.