Mushroom coffee side effects: mostly the kind you want
Steady energy with no jitters and no crash. A clear head. A calmer baseline. A gut that is fed instead of prodded. That is what people report after they switch to a mushroom coffee built on 3,000mg of fruiting body mushrooms a serving. The one honest adjustment is caffeine, and it is explained below.
Choose your FungkiFungki, rated 4.9 by verified buyers. Fungki Coffee, rated 5.0. Made in Canada. Certified B Corporation.
The side effects people actually report
- Steady energy, no jitters, no crash. Cordyceps, 1,000mg a serving in Fungki, supports the energy your cells make rather than energy you borrow. Fungki Coffee keeps 44mg of low-acid caffeine for the lift, with Reishi and Siberian ginseng to keep it level.
- A clear head and sharper focus. Lion's Mane, 1,000mg a serving in both, supports the signalling your brain uses to stay switched on. The word that comes up most in our focus reviews is sharp.
- Calm and grounded, still switched on. Reishi, 1,000mg a serving in both, supports a balanced stress response. Customers call it grounded, and they mean grounded at work, not sleepy.
- A gut that is fed, not prodded. Fungki is built on organic roasted chicory root, a prebiotic fibre that feeds the good bacteria. Fungki Coffee is low-acid cold brew, so the morning coffee sits well.
- The morning you look forward to. Ritual is the most common theme in our reviews. Both taste like coffee, dissolve with a stir, and replace the habit without asking you to give it up.
The mushrooms in the bag, and what each one does
Lion's Mane
1,000mg · Fruiting body · in Fungki and Fungki Coffee
Focus and a clear head. Supports nerve growth factor signalling, the maintenance work your brain does on its own cells.
Reishi
1,000mg · Fruiting body · in Fungki and Fungki Coffee
The calm baseline. Supports a balanced stress response, so the lift arrives without the spike.
Cordyceps
1,000mg · Fruiting body · in Fungki
Stamina without stimulants. Supports the energy your cells make, which is why Fungki needs no caffeine at all.
Fungki only
The prebiotic we put in on purpose
Fungki's roasted base is organic chicory root, the richest food source of inulin, a prebiotic fibre that feeds the beneficial bacteria in your gut. Regular coffee gives your gut acid and under a gram of fibre. Fungki gives it a meal. It is why people who want gut support choose Fungki, why the reviews call it gentle on the stomach, and why it tastes rich and roasted with no coffee in it.
Fungki Coffee takes the other road: a low-acid cold brew and decaf base with no added fibre, oil or grain, for the person who wants the coffee itself, minus the acid and most of the caffeine.
Choose Fungki
The one honest adjustment: caffeine
A regular 8 oz coffee carries about 95mg of caffeine. Fungki Coffee carries 44mg, and Fungki carries none. If you are leaving a full-strength habit, your body notices. Caffeine blocks adenosine, the signal that tells you that you are tired, and for a few days that signal comes through at full strength. That is the flat afternoon or the headache some people describe in the first week. It is the caffeine leaving, not the mushrooms arriving.
In the research it starts within a day, peaks on the second day, and is gone within nine. Keep the ritual, drink water, and give the mushrooms the month they deserve. And if regular coffee left you wired and tense, the change works in your favour from the first serving: Fungki Coffee at 44mg takes most of that away, and Fungki takes all of it.
No jitters, no crash. I feel focused, clear-headed, and somehow lighter, like my body and mind are in sync.
Maria, verified review of Fungki Coffee on rainbo.com
It is not the mushrooms. It is what was added to them.
When a mushroom coffee sits badly, the ingredient list on the back of the bag usually explains it. Many brands add prebiotic fibres such as inulin, acacia or tapioca. Some add MCT oil and coconut milk powder for creaminess. Some are made from mycelium, the root-like part of the fungus, grown on oats or sorghum, so grain starch ends up in the powder. Each of those is a common reason for an unhappy stomach, especially before breakfast, and none of them is in a Rainbo bag.
Fungki Coffee contains none of them. The ingredient list is low-acid cold brew coffee, decaf coffee, Lion's Mane and Reishi fruiting body extracts, Siberian ginseng root and Himalayan salt. No added fibre, no oil, no grain, and a low-acid base that sits well where regular coffee does not.
Fungki has no coffee in it at all, and its base is organic roasted chicory root, a prebiotic fibre that feeds the gut rather than prodding it. Want the coffee itself, low-acid and lighter on caffeine? Fungki Coffee. Want to leave coffee behind and feed your gut while you are at it? Fungki.
Read the back of the bag
What a typical mushroom coffee carries, next to what ours carry. The first column describes the category, read from brand labels and pages; no brand is named because the label is the point.
| A typical mushroom coffee | Fungki Coffee | Fungki | |
|---|---|---|---|
| Caffeine per serving | 35 to 95mg, by brand | 44mg, low-acid | None |
| Prebiotic fibre | Sometimes: inulin, acacia or tapioca, often unlabelled | None: a low-acid coffee base | Organic chicory root, on purpose |
| MCT oil or coconut milk powder | Some products add both | None | None |
| Grain in the powder | Some products are mycelium grown on oats or sorghum | None | None |
| Part of the mushroom used | Varies, and often not printed | Fruiting body, dual extracted | Fruiting body, dual extracted |
| Extract ratio printed | Rarely | 8:1 Lion's Mane, 16:1 Reishi | 8:1 Lion's Mane, 16:1 Reishi, 8:1 Cordyceps |
| Made in Canada | Varies | Yes | Yes |
Rainbo figures are from the labels, the live product pages and the Health Canada licence record, read the day this page was written. The category column comes from brand labels and pages read on 2026-09-03.
Three numbers from the label
3,000mg
of fruiting body mushrooms a serving, dried-mushroom equivalent
Fungki and Fungki Coffee labels
30
servings a bag, two teaspoons each
both labels
44mg / 0mg
caffeine a serving, Fungki Coffee and Fungki
Fungki Coffee label and Health Canada licence; Fungki label
Fungki or Fungki Coffee?
Both carry 3,000mg of fruiting body mushrooms a serving. Both are made in Canada. Both come with the same 30-day satisfaction guarantee and 25% off with free shipping on subscription. The only question is caffeine.
25% off
Leave caffeine behind, keep the ritual
Fungki. Caffeine-free, so there is nothing to crash from. Lion's Mane, Reishi and Cordyceps, 1,000mg each, on a roasted chicory root base that tastes like coffee. 30 servings.
$36.00 USD on subscription, or $48.00 one time
$1.20 a serving on subscription, $1.60 one time
Rich and roasted: chicory, mesquite, Ceylon cinnamon, vanilla
Prebiotic fibre for the gut, zero caffeine for the evening
Subscription saves 25% and ships free, delivered every 30, 60 or 90 days. Cancel any time. A one-time bag is $48.00 USD plus shipping.
Choose Fungki30-day satisfaction guarantee. Cancel any time.
25% off
Keep your coffee, lose the crash
Fungki Coffee. Low-acid cold brew and decaf with 44mg of caffeine, less than half a regular coffee. Lion's Mane and Reishi, a 3,000mg dried-mushroom equivalent, with Siberian ginseng. No added fibre, oil or grain. 30 servings.
$36.00 USD on subscription, or $48.00 one time
$1.20 a serving on subscription, $1.60 one time
Tastes like coffee, because it is coffee
The lift with no jitters and no crash, the most repeated line in its reviews
Subscription saves 25% and ships free, delivered every 30, 60 or 90 days. Cancel any time. A one-time bag is $48.00 USD plus shipping.
Choose Fungki Coffee30-day satisfaction guarantee. Cancel any time.
What people who switched report
I love supporting Canadian products!
I love supporting Canadian products and it is delicious! It taste like coffee and without the upset stomach.
Shawn K., Fungki Coffee
Verified Buyer
Love love love
I love love love the taste! I’ve tried 2 other mushroom drinks - one just didn’t mix in properly and stayed grainy and one gave me stomach aches. Fungki didn’t do any of those things! I look forward to my mushroom “coffee” every morning and it’s genuinely a ritual for me now
Saniya S., Fungki
Verified Buyer
Jitter-free and tasty!!
I’m verrrry sensitive to caffeine but genuinely love the taste of coffee, so I was hesitant to try this (even knowing it’s low-caffeine). But I trust Rainbo, so I gave it a shot and I’m so glad I did. No impending doom or shakes, just a subtle boost of energy and lazer focus (this is a huge win for me!!).
Haleigh R., Fungki Coffee
Verified Buyer
Grounded and less insane
I was drinking way too much coffee and now I have this and I feel so much more grounded and less insane.
MJ, Fungki
Verified Buyer
I LOVE This Coffee
I LOVE this coffee! It gives me a gentle, steady boost without the full-throttle caffeine jitters. The flavor is smooth, and it's become an important part of my morning ritual.
Vicki P., Fungki Coffee
Verified Buyer
Great Afternoon Coffee Alternative
Great afternoon coffee alternative. Without the problems sleeping later!!!
Jenn C., Fungki
Verified Buyer
What to expect
- Day 1. Two teaspoons, hot water, stir. It tastes like coffee. Fungki Coffee is coffee; Fungki is roasted chicory, mesquite and Ceylon cinnamon.
- Week 1. If you dropped caffeine, the adjustment settles. Keep the ritual, drink water, and let the mushrooms do their work.
- Week 4. Your next bag arrives before you run out. In our 2025 customer survey, 83% of daily takers who noticed a benefit had been consistent for 30 days or more (n=36). Give it the month.
SATISFACTION GUARANTEE
Try the whole bag. Then decide.
If it is not what you hoped, return it within 30 days of delivery for a full refund of the purchase price, less shipping. Email info@rainbo.com with your order number and we will sort it out.
The questions people ask before they switch
Is mushroom coffee safe to drink every day?
For most healthy adults a daily serving of a mushroom coffee made from fruiting body extracts is an ordinary part of the day, and the good effects people report come from taking it daily. Both Fungki and Fungki Coffee print every ingredient and its extract ratio, so you and your practitioner can read exactly what is in the bag. If you are pregnant or breastfeeding, on medication, or have ever reacted to a mushroom, ask your practitioner before you start.
How long does the switch take?
If you are dropping caffeine, the adjustment starts within a day, peaks around the second day, and is gone within nine. Most people describe three or four flat days, then the steady version of their morning. Fungki Coffee at 44mg makes the drop smaller and the adjustment shorter. Keep the ritual and give the mushrooms the month.
Does mushroom coffee break a fast?
Fungki Coffee is coffee, mushroom extracts, ginseng root and salt, with no sugar, oil or milk powder, so on its own it is close to a black coffee. Fungki carries chicory root and mesquite, which bring a few calories and the prebiotic fibre. If your fast has a strict rule, drink either one with your first meal.
Can I drink it at night?
Fungki, yes. It has no caffeine at all, and a warm serving after dinner is how many people use it. Fungki Coffee carries 44mg, less than half a regular coffee, so think of it as a small coffee in the evening and time it the way you would time one.
Is Fungki Coffee decaf?
No. It is a blend of low-acid cold brew and decaf, which is how it lands at 44mg of caffeine a serving instead of the 95mg or so in a regular coffee: enough for the lift, not enough for the jitters. If you want zero caffeine, Fungki has none.
Which one if my stomach is sensitive?
Both were built for it. Fungki Coffee is a low-acid cold brew and decaf base with no added fibre, oil or grain, so it sits well where regular coffee does not. Fungki has no coffee in it at all, and its organic chicory root is a prebiotic fibre that feeds the gut, which is what many people with a sensitive stomach come to it for. Either way the mushrooms are fruiting body extracts with no grain in the powder.
What does 3,000mg actually mean on the bag?
It is a dried-mushroom equivalent. Fungki Coffee holds about 283mg of concentrated fruiting body extract per two teaspoon serving, at 8:1 for Lion's Mane and 16:1 for Reishi, which stands in for 3,000mg of dried mushroom. Fungki works the same way with three mushrooms at 1,000mg each. We print the ratios so the number has a basis.
The side effects you want
Steady energy, a clear head, a calmer baseline, a gut that is fed. Pick your Fungki and it ships with 25% off and free shipping on subscription.
Choose your Fungki30-day satisfaction guarantee. Cancel any time.
References
- Juliano LM, Griffiths RR. A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features. Psychopharmacology, 2004. https://pubmed.ncbi.nlm.nih.gov/15448977/ Read 2026-09-17
- Fredholm BB, Battig K, Holmen J, Nehlig A, Zvartau EE. Actions of caffeine in the brain with special reference to factors that contribute to its widespread use. Pharmacological Reviews, 1999. https://pubmed.ncbi.nlm.nih.gov/10049999/ Read 2026-09-17
- Bonnema AL, Kolberg LW, Thomas W, Slavin JL. Gastrointestinal tolerance of chicory inulin products. Journal of the American Dietetic Association, 2010. https://pubmed.ncbi.nlm.nih.gov/20497775/ Read 2026-09-17
- US Department of Agriculture, FoodData Central entry 171890. Coffee prepared from grounds with tap water: 40mg caffeine per 100g. https://fdc.nal.usda.gov/food-details/171890/nutrients Read 2026-09-17
- La Monica MB and colleagues. Lion's Mane, 1g single dose, double-blind placebo-controlled crossover trial in healthy adults: working memory and reaction time. Nutrients, 2023. https://pubmed.ncbi.nlm.nih.gov/38140277/ Read 2026-09-17
- Mitra S and colleagues. Reishi at 500mg and 1,000mg daily for 30 days, double-blind randomized trial: physical work capacity and vitality. International Journal of Medicinal Mushrooms, 2024. https://pubmed.ncbi.nlm.nih.gov/39241163/ Read 2026-09-17
- Chen S and colleagues. Cordyceps at about 1,000mg daily for 12 weeks in healthy adults 50 to 75: exercise performance. Journal of Alternative and Complementary Medicine, 2010. https://pubmed.ncbi.nlm.nih.gov/20804368/ Read 2026-09-17
- Health Canada, Licensed Natural Health Products Database. Fungki Coffee licence record: Lion's Mane 188mg of an 8:1 extract, Reishi 95mg of a 16:1 extract, eleuthero root 90mg of a 10:1 extract, caffeine 44.3mg per two teaspoon serving. https://health-products.canada.ca/lnhpd-bdpsnh/index-eng.jsp Read 2026-09-17
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.