Mushroom Coffee Side Effects: What to Know

Written by Holly Xing

Mushroom coffee is coffee plus a few functional ingredients, so most of its side effects come from two places: the caffeine, and the specific mushrooms or herbs in the blend. Here's what's worth knowing, what's rare, and who should check with a doctor first.

Is mushroom coffee safe?

For most healthy adults, a cup or two a day is well tolerated. The questions to ask are how much caffeine you're getting, which mushrooms and herbs are in it, whether you take medication, and whether you're pregnant or nursing. A brand that lists every ingredient and amount makes this much easier to answer.

Caffeine side effects

Most mushroom coffees still contain real coffee. Too much caffeine can cause jitters, a racing heart, anxiety, upset stomach and poor sleep. Health Canada recommends no more than 400 mg a day for adults and 300 mg if pregnant or breastfeeding. The FDA also cites 400 mg for most adults, and in the US ACOG advises under 200 mg a day during pregnancy.

JostArriba has about 70 mg of naturally occurring caffeine per serving, so 1 to 3 servings is 70 to 210 mg. We also add 150 mg of L-theanine, which studies link with smoother alertness when paired with caffeine (Owen 2008). It's still caffeine: avoid it late in the day if it affects your sleep.

Digestion, reflux and allergies

Coffee can bother some stomachs. Some mushroom coffees also use ground whole mushroom or added fibers, which don't dissolve and can sit heavy. JostArriba uses fully soluble extracts, so there's no sludge in the cup. If you have reflux, start with half a packet, drink it with food, and talk to your doctor if symptoms persist. See acid reflux and JostArriba.

If you're allergic to mushrooms or molds, avoid mushroom coffee or ask your allergist first. Stop drinking it if you notice itching, rash, swelling or breathing trouble, and get medical help if symptoms are severe.

Reishi, ashwagandha and lion's mane

Reishi. Memorial Sloan Kettering lists nausea, insomnia, dry mouth, itching and dizziness as reported side effects, with rare reports of liver injury mostly linked to reishi powder. Talk to your provider if you take blood thinners or immunosuppressants (MSK).

Ashwagandha. The NIH says it appears well tolerated for up to about three months, with mild effects such as stomach upset, loose stools and drowsiness, plus reports of thyroid effects and rare liver injury (NIH ODS; LiverTox). JostArriba has 200 mg of KSM-66 per serving; the main KSM-66 trial used 600 mg a day for 60 days and reported it was well tolerated (Chandrasekhar 2012).

Lion's mane. No serious problems were reported in the main human trial, which used 3 g a day for 16 weeks (Mori 2009).

Who should skip it or ask first

  • Children and teens. JostArriba is formulated for adults.
  • Pregnant or nursing. Talk to your provider first.
  • Taking medication. Especially blood thinners, immunosuppressants or thyroid medication, or if you have a thyroid or liver condition.
  • Caffeine sensitive. Start with half a serving.
  • Before surgery. Tell your surgeon about any supplements you take, including reishi.

Will I get "high" or addicted? No. Lion's mane and reishi are not psychedelic. The caffeine can cause mild dependence in regular drinkers, so if you cut back suddenly you may get a headache for a day or two. Reducing gradually helps.

How to start

Begin with one serving in the morning, see how you feel for a week, and adjust. Choose a brand that lists every ingredient and dose, uses extracts rather than ground powder, and tests each batch for heavy metals and mold. JostArriba is third-party tested for pathogens, yeast, mold, mycotoxins and heavy metals. More answers are on our FAQ page.

Comparing brands? Read Best mushroom coffee for focus: an honest 2026 guide.

This article is for general information and isn't medical advice. Talk to your healthcare provider about your own situation.

These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Try the 8-serving trial pack