Are Mushrooms Low FODMAP? Why Most Mushrooms Are High FODMAP

Most mushrooms are high FODMAP due to their high mannitol content. This includes the most popular varieties: button mushrooms, cremini (baby bella), portobello, shiitake, enoki, and porcini. Mannitol is a sugar alcohol (polyol) that mushrooms naturally produce in significant quantities, and it is poorly absorbed in the human gut. For people with IBS, eating high-FODMAP mushrooms can cause bloating, gas, abdominal pain, and diarrhea. The notable exception is oyster mushrooms, which are low FODMAP and safe to enjoy.

This is disappointing news for mushroom lovers, but understanding which varieties to avoid and which alternatives are available can help you navigate the low-FODMAP diet more confidently.

Why Are Mushrooms High in Mannitol?

Mannitol is a polyol — the “P” in FODMAP — and it is naturally abundant in most mushroom species. Fungi produce mannitol as an osmolyte, a compound that helps them regulate cellular water balance and protect against environmental stressors like drought and temperature changes. Mannitol can constitute 10-20% of the dry weight of some mushroom species, which is an exceptionally high concentration.

When you eat mushrooms containing mannitol, the mannitol passes through the small intestine largely unabsorbed because humans lack an efficient mechanism for absorbing sugar alcohols. Once in the large intestine, mannitol has a dual effect: it draws water into the bowel through osmosis (potentially causing diarrhea) and is fermented by gut bacteria (producing gas that causes bloating and distension).

The mannitol content varies by species, but most commonly consumed mushrooms exceed the FODMAP threshold at even moderate serving sizes.

FODMAP Breakdown: Mushrooms by Variety

Mushroom Type	Serving	FODMAP Level	FODMAP Type	Notes
Button/white mushroom	75g	High	Mannitol	Common cooking mushroom
Cremini (baby bella)	75g	High	Mannitol	Same species as button, more mature
Portobello	75g	High	Mannitol	Same species as button, fully mature
Shiitake	75g (2 fresh)	High	Mannitol	Also high when dried
Enoki	75g	High	Mannitol, Fructans	Double FODMAP concern
Porcini	75g	High	Mannitol	Popular in Italian cuisine
Chanterelle	75g	High	Mannitol	Limited testing data
Oyster mushroom	75g (1 cup)	Low	Trace mannitol	The safe exception
Canned champignon	75g (drained)	Low	Reduced mannitol	Canning leaches mannitol into liquid

The Oyster Mushroom Exception

Oyster mushrooms (Pleurotus ostreatus) are the standout exception in the mushroom world. Monash University has tested oyster mushrooms and confirmed they are low FODMAP at a 75g serving (about 1 cup). Their mannitol content is significantly lower than other mushroom varieties.

Oyster mushrooms have a delicate, slightly sweet flavor and a tender texture that works well in stir-fries, soups, and pasta dishes. They are increasingly available in regular supermarkets and are commonly found in Asian grocery stores.

How to use oyster mushrooms:

• Tear into strips and pan-fry in garlic-infused oil until golden and crispy at the edges
• Add to stir-fries with bell peppers, carrots, and tofu over rice
• Roast at high heat (220C/425F) with olive oil and thyme for concentrated flavor
• Add to ramen or noodle soups
• Use as a meat substitute — large oyster mushrooms can be shredded to create a pulled-pork-like texture

If you miss mushrooms on the low-FODMAP diet, oyster mushrooms are your best friend.

What About Canned Mushrooms?

Interestingly, canned champignon (button) mushrooms test as low FODMAP at 75g when drained. The canning process involves storing the mushrooms in water for an extended period, and mannitol — being water-soluble — leaches out of the mushroom tissue into the surrounding liquid.

Important: This only applies to the drained mushrooms. Do not drink or cook with the canning liquid, as it now contains the mannitol that leached out of the mushrooms.

Canned mushrooms have a softer texture and milder flavor than fresh, so they work best in dishes where mushrooms are cooked into a sauce, soup, or casserole rather than featured prominently. They are a reasonable option for adding mushroom flavor to pasta sauces and stews.

How to Get Mushroom Flavor Without the FODMAPs

If mushrooms are a major part of your cooking and you miss them, here are some strategies for replicating that savory, umami depth.

Soy sauce and tamari: Rich in umami, low FODMAP at 2 tablespoons. Adds the deep, savory quality that mushrooms provide.

Miso paste: Low FODMAP at 2 tablespoons (from soy, not barley). Provides complex umami flavor in soups, dressings, and glazes.

Oyster mushrooms: The one mushroom you can use freely at 75g per serving.

Canned mushrooms: Drained and used in moderation.

Roasted eggplant: Not a mushroom substitute per se, but roasted eggplant (low FODMAP at 75g) provides a similar meaty, savory quality in dishes.

Smoked paprika: Adds depth and complexity reminiscent of cooked mushrooms.

Nutritional yeast: Provides a savory, slightly cheesy umami flavor. Low FODMAP in typical serving sizes (2 tablespoons). Excellent sprinkled on pasta, quinoa, or roasted vegetables.

Does Cooking Reduce Mushroom FODMAPs?

No. Cooking does not reduce the mannitol content of mushrooms. Mannitol is thermally stable and does not break down with heat. Whether you eat mushrooms raw, sauteed, roasted, grilled, or boiled, the mannitol content remains the same.

The only preparation that meaningfully reduces mannitol is prolonged soaking or storage in water (as in the canning process), which allows mannitol to leach out. However, briefly rinsing fresh mushrooms before cooking does not remove enough mannitol to make a difference.

Dried mushrooms are worse, not better: Drying removes water while concentrating mannitol per gram. A small handful of dried shiitake mushrooms contains the same mannitol as a much larger portion of fresh shiitake, making dried mushrooms even more problematic.

Common Mistakes with Mushrooms on a Low-FODMAP Diet

Mistake 1: “I will just eat a small amount.” Even small amounts of high-mannitol mushrooms (1-2 button mushrooms) can be moderate FODMAP. During the elimination phase, it is best to avoid them entirely.

Mistake 2: Overlooking mushrooms in mixed dishes. Mushrooms are a common ingredient in pizzas, pasta sauces, stir-fries, soups, and pre-made meals. Always check ingredient lists.

Mistake 3: Assuming mushroom seasoning is safe. Mushroom powder, mushroom stock cubes, and mushroom-flavored seasonings concentrate mannitol and should be avoided during elimination.

Mistake 4: Confusing button, cremini, and portobello. These are actually all the same species (Agaricus bisporus) at different stages of maturity. They are all high FODMAP.

Scanning packaged foods and restaurant meals with FODMAPSnap can help catch hidden mushroom ingredients that might otherwise go unnoticed.

Mushrooms and Mannitol Reintroduction

During the FODMAP reintroduction phase, mushrooms are used to test the mannitol (polyol) challenge. Sweet potato is another food used for mannitol testing, but mushrooms are the more concentrated source.

A typical mushroom reintroduction schedule:

1. Day 1: 2-3 button mushrooms (about 20g)
2. Day 2: 4-5 button mushrooms (about 40g)
3. Day 3: 8-10 button mushrooms (about 75g)

Monitor symptoms for 24-48 hours after each test. Your results will tell you one of three things:

• Tolerated at all levels: You can include mushrooms freely in your personalized diet
• Tolerated at small amounts only: You can include small portions of mushrooms
• Not tolerated: Stick to oyster mushrooms and canned mushrooms

Many people find they can tolerate small amounts of mushrooms even if they react at higher doses. Knowing your personal threshold lets you make informed decisions about whether to include a few mushroom slices in a stir-fry or skip them entirely.

Key Takeaways

• Most mushrooms are high FODMAP due to naturally high mannitol content
• Oyster mushrooms are the key exception — low FODMAP at 75g
• Canned mushrooms (drained) are low FODMAP because mannitol leaches into the canning liquid
• Dried mushrooms are more concentrated and even higher in mannitol
• Cooking does not reduce mushroom FODMAP content
• Use soy sauce, miso, and nutritional yeast for umami without the mannitol
• During reintroduction, test your personal mannitol threshold

Related Reading

• Is Sweet Potato Low FODMAP? — Another food affected by mannitol
• Is Garlic Low FODMAP? — Like mushrooms, garlic is a common hidden ingredient
• Is Tofu Low FODMAP? — Pair tofu with oyster mushrooms for a plant-based meal
• Are Peppers Low FODMAP? — Safe vegetable to replace mushrooms in stir-fries

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This article is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional or registered dietitian before making significant changes to your diet, especially if you have IBS, SIBO, or other gastrointestinal conditions. FODMAP tolerance varies between individuals, and a supervised elimination and reintroduction process is recommended for best results.