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Reishi is one of the mushrooms our naturopaths get asked about most. These are the questions they ask in store before you take it home.

A good fit if

• Immune support is your reason for buying, and you want a single species
• You're comfortable with evidence that measures blood markers rather than sick days
• You want the Latin name and a beta-glucan figure on the label
• You'd like the triterpenes too, so you're choosing a dual extract

Check with us first if

• You're having, or have had, cancer treatment. Cochrane found no evidence to support reishi as a first-line cancer treatment, and a review of case reports in people with cancer found mushroom products were the ones most often involved in severe reactions. Talk to your treating team first.
• You take a medicine that affects your immune system, including after a transplant. We haven't found a human interaction study for reishi, so we won't guess either way.
• You take warfarin or another blood thinner. Australia's required warfarin warning applies to maitake, not reishi, and we won't stretch it. Bring the pack in anyway.
• You're pregnant or breastfeeding. No trial of these mushrooms included pregnant or breastfeeding women, and Australia's permitted ingredients list sets no warning either way. That isn't the same as evidence that it's safe.
• It's for a child. There's no safety guidance for reishi in children.

• Hot-water extract. Best known for: The water-soluble beta-glucan part. Absorption: Ratios such as 8:1 concentrate the fibre; this is the type used in immune-marker trials. Typical use: The usual choice when immune support is your reason.
• Dual extract (water plus alcohol). Best known for: Beta-glucans plus the bitter triterpenes particular to reishi. Absorption: The alcohol step adds the part that hot water leaves behind. Typical use: When you want both parts in one product.
• Whole dried powder. Best known for: The ground mushroom itself, not concentrated. Absorption: There's no concentration step, so you get whatever the mushroom contained. Typical use: Ask for a beta-glucan figure first.
• Spore oil. Best known for: The oily part of cracked spores, a different product altogether. Absorption: One trial, and it didn't state its dose. Typical use: Not interchangeable with a reishi powder or extract.

Reference values. There's no Nutrient Reference Value for reishi. It's a fungus, not an essential nutrient, so the NHMRC doesn't set one.

Typical supplemental range. Most reishi trials we've reviewed used 1 to 3 g a day. The Cochrane review pooled trials at 1.4 to 3 g a day for 12 to 16 weeks, and the trial in older women used 2,000 mg a day of dry extract for 8 weeks. Australian products often give around 1 to 2 g a day of extract. These figures are for context, not a recommendation, and extracts vary a lot in strength, so read the label and follow its directions.

Upper level. None is set. Australia's permitted ingredients list (Schedule 1) has no daily dose cap for Ganoderma lucidum. That doesn't mean there's no limit, only that the rules don't set one, and one small trial found symptoms got worse at a higher dose in a specific group of men.

Worth knowing. If you're comparing two tubs, compare the beta-glucan percentage rather than the milligrams. A bigger amount of a weaker extract doesn't give you more. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Reishi itself: not eaten as food; taken as a powder or extract
• Shiitake, oyster and enoki: culinary sources of the same (1,3)(1,6)-beta-D-glucan fibre

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• A known mushroom or mould allergy. Allergy was the main cause in the severe cases across 92 case reports in people with cancer, and those cases mostly involved mushroom products.
• Cancer. Cochrane found there wasn't enough evidence to justify Ganoderma lucidum as a first-line cancer treatment, and study quality was generally poor. Check with your treating team.
• Higher doses, for some people. In 29 men with Gulf War Illness, symptoms were worse than with placebo at the higher reishi dose (p=0.012).
• Side effects overall. In Cochrane's pooled trials, people taking reishi were 1.67 times as likely to report a side effect as those on placebo (95% CI 0.86 to 3.24), and none were serious.
• Pregnancy and breastfeeding. None of the trials we hold included pregnant or breastfeeding women, and Schedule 1 has no pregnancy warning for Ganoderma lucidum.
• Children. Safety in children hasn't been established for reishi.
• Immunosuppressants, transplant medicines and blood thinners. There are no human interaction studies, so we can't say either way.
• If you take prescription medicines, check with your doctor, pharmacist or one of our naturopaths before you start.