Mushroom Coffee Side Effects: What to Know, Ingredient by Ingredient
3 min read By Mataye
In brief
Mushroom coffee side effects, ingredient by ingredient: caffeine, stomach upset, chaga and kidneys, reishi and liver, erythritol, and who should avoid it.
Mushroom coffee side effects are mostly caffeine effects: jitters, a faster heartbeat and poor sleep if you drink it late. The mushrooms can also cause mild stomach upset and may interact with some medicines. Here is the full list, ingredient by ingredient, with the studies, and who should avoid it.
Side effects at a glance
| Ingredient | Possible effects | At what dose |
|---|---|---|
| Caffeine (45 mg per Mataye serving) | Jitters, palpitations, poor sleep | Depends on sensitivity; EFSA finds up to 400 mg a day safe for healthy adults; near bedtime it can shorten sleep |
| Lion's mane | Stomach upset, nausea, skin rash | Dose not established (Memorial Sloan Kettering) |
| Reishi | Nausea, insomnia, bleeding risk; a few cases of liver injury | Dose not established (Memorial Sloan Kettering) |
| Chaga | Kidney damage from oxalate | One case at 10 to 15 g a day for 3 months (Kwon 2022); one after long-term use (Lee 2020) |
| Erythritol | Laxative effect; open question on platelets | Laxative above 0.5 g/kg a day (EFSA 2023); platelet effect seen after a 30 g dose (Witkowski 2024) |
Caffeine effects
One serving of Mataye contains 45 mg of caffeine, about half a mug of instant coffee (around 100 mg, NHS). EFSA says up to 400 mg a day, spread through the day, raises no safety concerns for healthy adults, and caffeine close to bedtime can shorten sleep. For example, three servings of Mataye come to 135 mg, well under that limit, but count your tea and other coffees too. More in mushroom coffee and caffeine.
Stomach upset
Mild digestive discomfort and nausea have been reported with lion's mane and reishi (Memorial Sloan Kettering). If coffee upsets your stomach, start with half a serving in milk.
Chaga and the kidneys
Chaga can be very high in oxalate. Two Korean case reports show what very high doses can do. A 69-year-old man who took 10 to 15 g of chaga powder a day for three months developed acute kidney injury with oxalate deposits; his kidneys recovered after treatment (Kwon et al., 2022). A 49-year-old man who had taken chaga powder long-term reached end-stage kidney disease; the chaga he used contained 14.2 g of oxalate per 100 g (Lee et al., 2020).
These are single case reports. In the first, the man took 10 to 15 g of chaga a day, about 14 to 21 times the 700 mg in one Mataye serving, or 5 to 7 times the 2.1 g in three servings; he also took 500 mg of vitamin C a day. In the second, the damage followed long-term use. If you have kidney disease or kidney stones, ask your doctor first. See our chaga guide.
Reishi and the liver
A few cases of liver injury have been reported, notably with reishi powder (Memorial Sloan Kettering). Avoid it if you have a liver condition, unless your doctor agrees. See reishi benefits and safety.
Erythritol
Erythritol, the sweetener in Mataye, can be laxative in large amounts. In 2023 EFSA set an acceptable daily intake of 0.5 g per kg of body weight, which is 35 g for a 70 kg adult. A Mataye serving has far less: the serving is 6 g, of which 3.5 g is mushroom. Recent studies have also raised heart questions, covered in erythritol: what the research says.
Medicine interactions
- Blood thinners: reishi can increase bleeding risk (Memorial Sloan Kettering).
- Diabetes or blood pressure medicine: ask your doctor; evidence on mushroom effects here is limited.
- Immunosuppressants: ask your doctor.
If you take regular medicine, ask your pharmacist.
Who should avoid mushroom coffee
- Children, because it contains caffeine.
- Pregnant or breastfeeding women, unless their doctor agrees. The NHS limit in pregnancy is 200 mg of caffeine a day.
- Anyone allergic to mushrooms.
- People with liver or kidney disease, or on the medicines above, without medical advice.
Read next: mushroom coffee benefits, what mushroom coffee is and Mataye Mushroom Coffee, and how to make mushroom coffee.
Read next: how to choose a mushroom coffee, coffee during Ramadan.
Sources
- Kwon O et al. (2022). Chaga mushroom-induced oxalate nephropathy that clinically manifested as nephrotic syndrome: a case report. Medicine (Baltimore) 101(10):e28997. PubMed 35451393
- Lee S et al. (2020). Development of end stage renal disease after long-term ingestion of Chaga mushroom: case report and review of literature. Journal of Korean Medical Science 35(19):e122. PubMed 32419395
- EFSA Panel on Food Additives and Flavourings (2023). Re-evaluation of erythritol (E 968) as a food additive. EFSA Journal 21(12):e8430. PubMed 38125972
- Witkowski M et al. (2024). Ingestion of the non-nutritive sweetener erythritol, but not glucose, enhances platelet reactivity and thrombosis potential in healthy volunteers. Arteriosclerosis, Thrombosis, and Vascular Biology 44(9):2136-2141. PubMed 39114916
- Memorial Sloan Kettering Cancer Center, About Herbs: lion's mane, reishi
- EFSA, Caffeine; NHS, Foods to avoid in pregnancy
