In this article
- Which mushrooms count as medicinal
- What mushroom fiber is made of
- Medicinal mushrooms fiber, fresh and dried
- Extracts and the fiber they leave behind
- What the turkey tail trials found
- Mushroom fiber as a prebiotic
- Mushrooms next to other vegetable sides
- A week of mushrooms, counted out
- Getting the most fiber from medicinal species
- Swap one side dish this week
- Medicinal mushroom fiber questions
- Sources
3 grams a day. That’s the dose of PSK, a turkey tail mushroom extract, used in Japanese cancer trials summarized by the National Cancer Institute, and it has nothing to do with fiber.
That gap sums up the topic. Medicinal mushrooms fiber comes from eating the mushroom itself, where USDA measures 3 to 4.4 grams per 100 grams in fresh shiitake, maitake and lion’s mane, while the headline research mostly tests concentrated extracts.
Which mushrooms count as medicinal
The National Cancer Institute’s PDQ summary on medicinal mushrooms explains that these species have long been used in Asia. Japan and China have approved some of them as add ons to standard cancer treatment for more than 30 years.
The NCI covers turkey tail (Trametes versicolor) and reishi (Ganoderma lucidum) in the most depth, and also names maitake and shiitake. Several of these, along with lion’s mane, are everyday foods as well as supplement ingredients, which is where the fiber story gets interesting.
The NCI credits most of the immune effects to large polysaccharides called beta glucans. Some of those same molecules also count as dietary fiber when you eat the whole mushroom.
The NCI also points out that dietary supplements aren’t reviewed for effectiveness before they’re sold unless they make disease claims. That’s one more reason to look at what a product actually contains.
What mushroom fiber is made of
A 2023 review in the Journal of Fungi by Yu and colleagues breaks mushroom fiber into three main parts: chitin, the tough material in fungal cell walls; beta glucans; and hemicellulose, a plant like structural carbohydrate.
Most of it is insoluble. The review cites one analysis in which soluble fiber made up just 0.50 to 4.42% of the mushrooms tested, compared with 23.6 to 43.1% for insoluble fiber, and notes that beta glucans sit in both fractions but lean insoluble.
| Fiber type in mushrooms | Share reported in one analysis | Main components |
|---|---|---|
| Insoluble fiber | 23.6 to 43.1% | Chitin, beta glucans, hemicellulose |
| Soluble fiber | 0.50 to 4.42% | Smaller share of beta glucans and other polysaccharides |
So when you eat mushrooms, you’re mostly getting the insoluble kind, with only a small soluble share. That’s worth knowing if you’re choosing foods for a specific fiber type.
Medicinal mushrooms fiber, fresh and dried
USDA has measured fiber in several mushrooms that double as medicinal and culinary species. Here’s what the numbers look like fresh, next to the dried forms that turn up in supplements:
| Mushroom | Form | Fiber per 100 g |
|---|---|---|
| Reishi | Dried fruiting body | 64.2 g |
| Shiitake | Dried | 11.5 g |
| Lion’s mane | Raw | 4.38 g |
| Shiitake | Raw | 4.17 g |
| Maitake | Raw | 3.07 g |
| King oyster | Raw | 3.01 g |
| White button (culinary only) | Raw | 1.72 g |
The reishi figure comes from a 2024 analysis in Foods by Peng and colleagues, while the others are USDA FoodData Central values. Drying removes water, so dried mushrooms look far denser in fiber by weight.
In practice you eat much less dried mushroom. A 15 gram portion of dried shiitake gives about 1.7 grams of fiber, roughly what you’d get from 40 grams of fresh shiitake.
Reishi’s 64.2% looks remarkable on paper. But the reishi products studied in the NCI summary are extracts taken in measured doses, so very little of that fiber ever reaches a typical user.
Curious how mushroom fiber fits into your daily total? Our fiber calculator can show you the daily number you’re working toward.
Extracts and the fiber they leave behind
The medicinal research mostly uses extracts. The NCI describes PSK and PSP from turkey tail, and the reishi products Ganopoly and MAK, all designed to deliver specific compounds in measured doses.
An extract taken at a few grams a day can’t supply much fiber, even if some beta glucans come along. And the NCI notes that supplement ingredients can vary from lot to lot, so two bottles with the same name may not match.
For fiber, the whole mushroom wins. A cup of cooked mushrooms, per the Dietary Guidelines food source list, gives 3.4 grams of fiber for 44 calories, more than any capsule routine could.
Weighing mushroom capsules against fiber supplements or whole food options? Our comparison charts lay out the popular choices so you can see what each delivers.
What the turkey tail trials found
Turkey tail has the strongest human data of any medicinal mushroom in the NCI summary, all of it using the PSK extract alongside standard cancer treatment:
| Study | Participants | Reported result |
|---|---|---|
| Gastric cancer trial, Japan | 262 randomized | 5 year disease free survival 70.7% vs 59.4% |
| Gastric cancer meta analysis | 8 trials, 8,009 patients | Overall survival hazard ratio 0.88 |
| Japanese multicenter trial | 751 patients | 5 year overall survival 67.9% vs 61.8%, not statistically significant |
| Colorectal cancer meta analysis | 3 trials, 1,094 patients | 5 year survival 79.0% vs 72.2% |
The NCI reports that PSK was usually taken at 3 grams a day and that few adverse events were reported. It also stresses that the FDA has not approved medicinal mushrooms as a cancer treatment.
The multicenter result narrowly missed statistical significance overall. In a subgroup with a granulocyte to lymphocyte ratio of 2.0 or higher, a blood marker of immune balance, survival was 68.7% vs 55.4%.
None of this tells you anything about fiber. The effects are tied to a purified extract, not to a serving of mushrooms on your plate.
Mushroom fiber as a prebiotic
A prebiotic is a food component your gut bacteria ferment for their own benefit and yours. The Yu review reports that mushroom fiber can shift gut bacteria toward beneficial groups and raise short chain fatty acids, compounds bacteria produce when they ferment fiber.
Most of that evidence comes from lab fermentation and animal studies. In one lab model, fiber from the shaggy ink cap mushroom raised Bifidobacterium and boosted propionic and butyric acid production.
Another lab study fermenting white button mushroom fiber found more acetic and propionic acid. The review also describes fiber from Poria cocos improving high blood sugar in mice and king oyster fiber lowering fasting blood glucose in obese rats, along with lab findings on cholesterol and constipation relief. Human trials using mushroom fiber itself are still scarce, so treat these as early signals.
If you’re building more fiber into your meals for steadier digestion, our gut health guides walk you through it one meal at a time.
Mushrooms next to other vegetable sides
Mushrooms are usually eaten as a vegetable side, so that’s the fairest comparison. Here’s how a cup of cooked mushrooms stacks up, using the Dietary Guidelines list:
| Cooked vegetable, 1 cup | Fiber | Calories |
|---|---|---|
| Broccoli | 5.2 g | 54 |
| Cauliflower | 4.9 g | 34 |
| Carrots | 4.8 g | 54 |
| Kale | 4.7 g | 43 |
| Green beans | 4.0 g | 44 |
| Mushrooms | 3.4 g | 44 |
| Asparagus | 2.9 g | 32 |
Mushrooms land toward the lower end of this group but still bring a respectable amount. Their real advantage is versatility: they slip into eggs, sauces, soups and grain bowls where broccoli or kale would feel out of place.
Combining them is even better. A stir fry with a cup each of cooked mushrooms and broccoli gives about 8.6 grams of fiber for under 100 calories, close to a third of the Daily Value.
A week of mushrooms, counted out
Say you cook a cup of mushrooms three times this week: sautéed shiitake and maitake with dinner on Monday, mushrooms folded into an omelet on Wednesday, and a mushroom and lentil soup on Friday.
At about 3.4 grams per cooked cup, that’s roughly 10 grams of fiber across the week from mushrooms alone. Add half a cup of lentils to the soup and Friday’s bowl gains another 7.8 grams.
Compare that with a daily medicinal mushroom capsule. Across seven days it’s unlikely to add even a few grams, because the dose is measured for compounds, not fiber.
Looking for more ways to cook with mushrooms, beans and grains? Our recipe eBooks have plenty of easy, fiber rich ideas.
Getting the most fiber from medicinal species
- Buy shiitake, maitake and lion’s mane fresh when you can, and cook them as part of a meal.
- Keep dried shiitake in the pantry; soak them in warm water, slice and add them to soups and stir fries, along with the soaking liquid for flavor.
- Treat reishi and turkey tail as supplement ingredients, not as a meaningful fiber source.
- Check Supplement Facts panels for a fiber line before assuming a mushroom product counts toward your daily total.
- Pair mushrooms with beans, whole grains or berries to reach a meaningful fiber total.
Swap one side dish this week
Pick one dinner this week and replace a white rice or pasta side with a cup of sautéed shiitake or maitake. Using the Dietary Guidelines figure for cooked mushrooms, the mushrooms alone bring about 3.4 grams of fiber for around 44 calories.
Do it twice a week and you’ve added close to 7 grams without buying a single supplement. That’s the most reliable way medicinal mushrooms add fiber to your diet.
Medicinal mushroom fiber questions
Do medicinal mushrooms have fiber?
Yes, when you eat the mushroom itself. USDA measures about 3 to 4.4 grams of fiber per 100 grams in raw shiitake, maitake and lion’s mane, and dried reishi is about 64% fiber by weight.
Is mushroom fiber soluble or insoluble?
Mostly insoluble. One analysis cited in a 2023 review found insoluble fiber at 23.6 to 43.1% of mushroom content, compared with 0.50 to 4.42% for soluble fiber.
Do mushroom supplements count toward daily fiber?
Usually not much. Extracts are dosed in grams for specific compounds, so check the Supplement Facts panel for a fiber line before counting it.
Are mushrooms a prebiotic?
Possibly. Mushroom fiber raised beneficial bacteria and short chain fatty acids in lab and animal studies, but human trials using mushroom fiber are still limited.
Which mushroom has the most fiber?
Among fresh mushrooms USDA has measured, lion’s mane leads at 4.38 grams per 100 grams, just ahead of shiitake at 4.17 grams. Dried forms are much denser because the water is gone.
Does turkey tail have fiber benefits?
Turkey tail’s research is about the PSK extract, not fiber. In NCI summarized trials, PSK at about 3 grams a day was paired with cancer treatment.
How many mushrooms should I eat for fiber?
A cup of cooked mushrooms gives about 3.4 grams of fiber, or 12% of the 28 gram Daily Value. Two or three cups a week adds up while you build the rest of your fiber from beans, grains and fruit.
Sources
- U.S. Department of Agriculture, Agricultural Research Service. “Mushroom, lion’s mane (1999626); shiitake (1999628); white button (1999629); maitake (2003602); king oyster (2003599); Mushrooms, shiitake, dried (168436).” FoodData Central. 2019 to 2026. fdc.nal.usda.gov
- PDQ Integrative, Alternative, and Complementary Therapies Editorial Board. “Medicinal Mushrooms (PDQ), Health Professional Version.” National Cancer Institute. 2024. www.cancer.gov
- Yu C, Dong Q, Chen M, et al. “The Effect of Mushroom Dietary Fiber on the Gut Microbiota and Related Health Benefits: A Review.” Journal of Fungi. 2023. www.mdpi.com
- Peng G, Xiong C, Zeng X, Jin Y, Huang W. “Exploring Nutrient Profiles, Phytochemical Composition, and the Antiproliferative Activity of Ganoderma lucidum and Ganoderma leucocontextum: A Comprehensive Comparative Study.” Foods. 2024. mdpi-res.com
- U.S. Department of Agriculture and U.S. Department of Health and Human Services. “Food Sources of Dietary Fiber.” Dietary Guidelines for Americans, 2020 to 2025. dietaryguidelines.gov
- U.S. Food and Drug Administration. “Daily Value on the Nutrition and Supplement Facts Labels.” 2024. www.fda.gov
