Mushroom Coffee Side Effects
What's common, what's rare, and who should skip it, sourced to case reports and government databases rather than brand FAQs.
Quick Summary
For most healthy adults the usual effects are caffeine and some gut upset. The rare, serious reports involve heavy chaga use and the kidneys, and reishi powder and the liver.
Side effects at a glance
| Feature | How common | Likely cause | Source |
|---|---|---|---|
| Jitters, insomnia, racing heart | Common if you are caffeine-sensitive | Caffeine | FDA |
| Bloating, gas, loose stools | Commonly reported | Added fiber or mushroom powder | Check the ingredient list |
| Oxalate kidney injury | Rare case reports | Chaga, high doses over months | Kikuchi 2014; Lee 2020; Kwon 2022 |
| Liver injury | Rare case reports | Reishi powder | LiverTox; Wanmuang 2007 |
| Heavy metals | Varies by product | Mushrooms take up metals from where they grow | Our heavy-metals review |
Caffeine is the effect most people feel
Mushroom coffee is still coffee. Some blends are lower per serving. Ryze, for example, is covered in our caffeine breakdown, which compares a serving with about 96 mg in 8 oz of brewed coffee. Two servings, or a regular coffee on top, still count toward the FDA’s 400 mg/day figure for healthy adults (FDA).
In pregnancy, the EFSA reference discussed on that caffeine page is 200 mg/day. See also how much caffeine is too much.
Stomach upset
Many blends add prebiotic fibers or powdered mushroom, so gas and bloating are common complaints, especially in the first week. Starting with half a serving is a sensible test. Check the label for inulin or chicory if you are sensitive to FODMAPs.
Chaga and oxalate
- Kikuchi 2014 (Japan): a 72-year-old woman took 4–5 teaspoons of chaga powder a day for 6 months, developed oxalate nephropathy, and needed hemodialysis.
- Lee 2020 (Korea): a 49-year-old man reached end-stage kidney disease after years of chaga powder. The remaining chaga measured 14.2 g oxalate per 100 g.
- Kwon 2022 (Korea): a 69-year-old man took 10–15 g/day of chaga powder plus 500 mg/day vitamin C for 3 months and developed acute kidney injury. Function recovered after dialysis and steroids.
Those doses are not a typical cup
The cases used far more chaga than a coffee blend is likely to contain. Most brands do not disclose milligrams per mushroom, so you cannot check. Skip chaga blends if you have kidney disease or a history of kidney stones, and ask a clinician first.
Reishi and the liver
LiverTox (NIH) says small trials of reishi showed no routine liver-enzyme changes. Isolated case reports describe liver injury that usually resolved after stopping (LiverTox). A 2007 report described fatal fulminant hepatitis after switching to reishi powder for 1–2 months. The patient was also taking other agents (Wanmuang 2007).
Stop and see a doctor for dark urine, yellowing skin or eyes, or pain in the upper right abdomen. Heavy metals are a separate issue: our lead and heavy-metals review.
Who should skip it or ask first
Who Might Like This
- ✓Healthy adults who stay inside their caffeine limit and choose brands that disclose mushroom amounts and publish metal testing.
Who Should Consider Alternatives
- ×Kidney disease or kidney stones, especially with chaga blends.
- ×Liver disease, especially with reishi blends.
- ×Blood thinners, diabetes medicines, or immunosuppressants. Interaction data are thin. Ask a pharmacist.
- ×Pregnancy and breastfeeding. Safety data on the extracts are lacking, and caffeine limits still apply.
- ×A known arrhythmia or strong caffeine sensitivity.
Our verdict
For most healthy adults, mushroom coffee’s main side effects match coffee’s, plus some gut upset. The serious risks in the literature are rare and tied to large, ongoing doses of chaga or reishi powder. See the best mushroom coffee for products that disclose amounts.
Sources
How we checked
Case details (ages, doses, outcomes) are the ones in the cited papers, checked against the Oct 26 spec and the papers’ public records. We did not add a rate for how often this happens, because the papers are case reports.
Ryze’s caffeine milligrams are not repeated here. They live on the caffeine guide, which can be updated on its own.
Frequently Asked Questions
Yes. Added fibers and mushroom powders commonly cause gas or bloating at first.
There is no evidence of harm for most people at normal amounts. Chaga is high in oxalate, and heavy long-term powder use has caused kidney injury in case reports.
Coffee itself and added fibers can both have that effect.
For most healthy adults, if you stay within caffeine limits. The case reports cluster around large daily amounts of chaga or reishi.
The caffeine can. Lower-caffeine blends still contain some.
The same categories: caffeine, gut upset, and whatever mushrooms are in the blend. See the RYZE review.
This is not medical advice. Case reports are not proof that a typical cup will cause the same injury. Stop and see a doctor for yellowing skin, dark urine, or a sudden drop in how much you urinate. Evident does not sell these products and uses no affiliate links.