Does Mushroom Coffee Break a Fast?
Does Mushroom Coffee Break a Fast? Here's the Math
By Chris Rea, COO of Mariko Grove · August 2026
Updated August 26, 2026
Short answer: black mushroom coffee is very low in calories, in the same range as a plain black cup of regular coffee. That's arithmetic, not a health claim, and it's the honest place to start before anyone tells you what fasting is supposed to do for you.
The real question underneath "does mushroom coffee break a fast" usually isn't about the mushrooms at all. It's about calories, and about which fasting rule you're following. This post walks through what's actually in a serving, what happens when you start adding milk or sugar, and why two people can ask the exact same question and get two different honest answers depending on the fasting approach they're using.
What's Actually in a Cup
Before the math means anything, here's what a serving of Mariko Grove mushroom coffee actually contains, straight from the label.
- Ground Mushroom Coffee: a 1 tablespoon (10g) serving contains ground Arabica coffee, 500mg Lion's Mane mushroom, and 500mg Chaga mushroom.
- Instant Mushroom Coffee: a 1 teaspoon (3g) serving contains instant coffee, 150mg Lion's Mane mushroom, and 150mg Chaga mushroom.
Both formats use the same short ingredient list: coffee and mushroom, nothing else. No sugar, no sweeteners, no flavoring, no grain fillers, no gums, and no oils added. That matters for this particular question, because it means a black cup of either one is compositionally close to a black cup of regular coffee, with a small amount of mushroom powder added on top.
The Calorie Math: Black Coffee and Black Mushroom Coffee
Mariko Grove doesn't publish an exact calorie count for either product, so we're not going to invent one here. What we can do is show you the honest range, using published figures for plain coffee and for other unsweetened mushroom coffees, and explain why our own cup would reasonably sit in that same range.
Plain black coffee is close to calorie-free. An 8 fl oz cup contains fewer than 3 calories, according to Healthline's review of intermittent fasting and coffee, and USDA FoodData Central puts brewed coffee at roughly 1 calorie per 100 grams. Coffee is about 98 to 99 percent water once it's brewed; there just isn't much left to carry calories.
Unsweetened mushroom coffee tends to land a little higher than plain black coffee, but still low. Third-party nutrition trackers list one widely sold instant mushroom coffee, also just instant coffee and mushroom extract with nothing else added, at about 10 calories per 2.5-gram packet. Another popular blend lists about 15 calories per 6-gram serving, though that formula also includes added MCT oil, which raises the number compared to a coffee-and-mushroom-only blend. Mariko Grove's ingredient list has no added oils, so a black cup of either of our blends would be expected to sit toward the lower end of that published range, in the same neighborhood as a plain cup of coffee rather than meaningfully above it.
The mushroom powder itself is a tiny part of that math. A gram of Lion's Mane or Chaga powder carries only a few calories, and a serving of our ground blend contains 1 full gram of mushroom (500mg plus 500mg) in a 10-gram scoop; the instant blend contains 300mg (150mg plus 150mg) in a 3-gram scoop. Neither amount is large enough to meaningfully change the arithmetic on its own.
The Real Variable Is What You Add
This is where the actual calorie total gets decided, and it has nothing to do with mushrooms. It's the same variable for regular coffee, instant coffee, and mushroom coffee alike: what you pour into the cup after it's brewed.
| Addition | Typical amount | Approx. calories |
|---|---|---|
| Black, no additions | 8 fl oz | Under 5 |
| Splash of whole milk | 1 tbsp | ~9 |
| Half-and-half | 1 tbsp | ~20 |
| Non-dairy powdered or liquid creamer | 1 tbsp | ~20 to 35 |
| Heavy cream | 1 tbsp | ~50 |
| Granulated sugar | 1 tsp | ~16 |
| Flavored syrup | 1 tbsp (about 2 pumps) | ~40 |
Figures are approximate, drawn from USDA FoodData Central values for common dairy and sweetener amounts and from published café nutrition information for flavored syrups. This table applies to any coffee, mushroom or otherwise; the cup itself isn't the variable, the add-ins are.
Read that table plainly: a splash of milk barely moves the number, a full serving of cream or sugar adds up fast, and stacking two or three additions together can turn a 5-calorie cup into a 60 or 80-calorie one. If you're weighing whether mushroom coffee fits your fast, the honest question isn't "does it have mushrooms in it," it's "what did I put in the cup."
It Depends on Why You're Fasting
Here's the part most articles skip past: there isn't one universal rule for what breaks a fast, because "fasting" isn't one single practice. Different approaches draw the line in different places, and both are legitimate on their own terms.
Strict zero-calorie approaches treat any caloric intake, even a few calories, as ending the fasting window by definition. This is common in lab-ordered fasting before bloodwork, where many labs instruct water only and put coffee, black or otherwise, on the do-not-drink list, not because of a health claim but because the point is a clean baseline sample. Some religious and personal fasting practices use this same strict definition.
General calorie-threshold practices, common in popular intermittent fasting routines built around a daily eating window, often use a rule of thumb that beverages under roughly 50 calories don't count against the fast. It's a widely repeated number. It's also, according to Healthline, a number with "no scientific evidence" behind the specific threshold: "Many popular health and media outlets claim that you won't break your fast as long as you stay under 50 to 75 calories during each fasting window." It's a popular convention people repeat, not an established rule.
Neither approach is more correct than the other; they're answering different questions. A black cup of mushroom coffee, at a few calories, would clear the general threshold approach easily and would still count as breaking a strict zero-calorie fast, exactly the same way a black cup of regular coffee would. We're not going to tell you which definition to use. That call belongs to whoever set the rules for your particular fast.
Instant vs Ground: Any Difference Here?
Not meaningfully. Both formats share the same ingredient philosophy: coffee and mushroom, no sugar, no fillers, no added oils. The ground blend carries a slightly larger mushroom amount per serving (500mg Lion's Mane plus 500mg Chaga in a 10g scoop, versus 150mg plus 150mg in a 3g scoop of instant), but that difference is measured in milligrams, not calories, and neither serving includes anything that would meaningfully change the arithmetic. If you're deciding between the two for reasons beyond fasting, our beginner's guide and brewing guide cover the practical differences in taste, prep, and format.
The Honest Close
We make coffee, not fasting protocols. We can tell you what's in the bag and the jar, and we can point you to the published numbers for plain coffee and for comparable unsweetened mushroom coffees. What we can't do is tell you whether that fits your fast, because that depends on rules we didn't write.
If you're doing mushroom coffee intermittent fasting as part of a program, an app, a doctor's guidance, or a religious practice, follow whoever is actually guiding that fast. Show them the ingredient list on our ground mushroom coffee or instant mushroom coffee product pages: coffee, Lion's Mane, Chaga, and nothing else. That's the label. Let it inform the decision, not us.
Frequently Asked Questions
Does mushroom coffee break a fast?
Black mushroom coffee is very low in calories, in the same range as plain black coffee, generally a few calories per cup. Whether that counts as "breaking" your fast depends entirely on which fasting approach you're following: strict zero-calorie approaches count any calories at all, while general calorie-threshold practices commonly treat anything under about 50 calories as negligible. We don't set that rule; whoever guides your fast does.
Does black mushroom coffee have calories?
Yes, a small amount, similar to plain black coffee. Mariko Grove doesn't publish an exact calorie count, but our ingredients are just coffee and mushroom powder with no sugar, fillers, or added oils, and published figures for comparable unsweetened mushroom coffees run roughly 5 to 15 calories per serving.
Do the mushroom extracts themselves add calories?
A small amount, but not much. A serving of our ground blend contains 1 gram total of Lion's Mane and Chaga powder (500mg each); the instant blend contains 300mg total (150mg each). Mushroom powder in those small gram amounts carries only a few calories, so it's a minor contributor to the total, not the main variable.
What if I add milk or sugar to my mushroom coffee while fasting?
That's what actually changes the calorie count. A splash of milk adds roughly 9 calories per tablespoon, cream runs closer to 50, and sugar adds about 16 calories per teaspoon. Stack a few of those together and you can move well past a general 50-calorie threshold and well past what any strict zero-calorie approach allows. If you want to keep a cup as close to calorie-free as possible, drink it black. For ratios and methods if you're blending mushroom coffee with your regular coffee, see our guide to mixing mushroom coffee with regular coffee.
Does instant mushroom coffee differ from ground when it comes to fasting?
Not meaningfully. Both are just coffee and mushroom powder with nothing added, so the calorie math is essentially the same for a black cup of either one. The ground blend has a larger mushroom amount per serving, but the difference is measured in milligrams, not calories.
The Bottom Line
Does mushroom coffee break a fast? Black, it's a low-calorie cup, in the same range as plain black coffee, so it clears a general calorie-threshold approach easily and would still end a strict zero-calorie fast, exactly like regular black coffee would. What you add to the cup matters far more than what's in the blend. And which rule applies to you is a question for whoever set the rules, not for us.
Curious what else is in the cup? Our beginner's guide to mushroom coffee covers the basics, and our brewing guide walks through prep for both formats.
And when your eating window opens, make the first cup count. Browse the mushroom coffee collection and pick the format that fits your morning, ground or instant.
About the Author
Chris Rea is the COO of Mariko Grove, overseeing operations, sourcing, and shipping logistics. He ensures every batch of mushroom coffee is handled with care from warehouse to doorstep.
Disclaimer: This article is provided for informational purposes only. It is not fasting, medical, or nutritional advice, and it does not endorse any particular fasting approach. If you're fasting for medical, religious, or personal reasons, follow the guidance of whoever oversees that specific practice, your doctor, a registered dietitian, a faith leader, or a program you've chosen, rather than a coffee company's blog post. Statements regarding mushroom coffee products have not been evaluated by the U.S. Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.