2. White Button Mushroom
The trick of the champignon cellars beneath Paris — ergosterol → vitamin D₂ in the glow of a UV lamp.
White Button Mushroom in 1 minute
What does it provide? Mushroom β-glucans (β-(1→3)/(1→6)), chitin/chitin-glucan complex, ergosterol (converts to vitamin D₂ under UV light), ergothioneine (a rare, dietary antioxidant amino acid), small amounts of protein, and B vitamins (especially B2 — riboflavin, B3 — niacin, B5 — pantothenic acid).
How much? Fresh/sautéed: 80–100 g/meal. Hess 2018 human RCT used 84 g/day (≈ 1 cup) for 10 days. The UV-treated form dramatically increases D₂ content.
When to avoid? IBS-mannitol sensitivity (fresh mushroom); raw in large quantities (agaritine — a natural hydrazine compound, weakly mutagenic in vitro; largely degrades with cooking); mushroom allergy; canned with brine (lower in FODMAPs for sensitive individuals but may contain preservatives).
The European cradle of button mushroom cultivation is 17th-century France: according to accounts, Louis XIV's famous head gardener Jean-Baptiste de La Quintinie first experimented with it in the dark greenhouses of Versailles's Potager du Roi, where they began growing the button mushroom alongside overflowing melons. In 1707, Joseph Pitton de Tournefort wrote a separate dissertation for the Académie des Sciences in what was the first known scientific cultivation description. The 18th–19th century Parisian breakthrough was the discovery of the city's vast underground catacombs and abandoned quarries as "champignon" cellars: the constant 12–14 °C temperature and 90% humidity proved ideal — hence the world-famous "champignon de Paris" name.
By the mid-19th century, mushrooms were being produced by the ton in the Parisian catacombs across some 300 km of tunnels, and city kitchens received fresh produce daily by cart. In 1893, at the Pasteur Institute, Constantin and Matruchot developed the controlled, sterile "spawn" (mushroom seed) production process, which eliminated random contamination — this turning point shaped 20th-century industrial cultivation. A fun fact: the American birthplace of mushroom cultivation is Kennett Square, Pennsylvania, where in the 1880s Eberhardt William Swayne began growing the French hardy button mushroom strain — today the town supplies more than half of the US mushroom crop and proudly bears the name "Mushroom Capital of the World." The button mushroom is today the world's most widely consumed cultivated mushroom.
Scientific Background
The white button mushroom (Agaricus bisporus) bioactive matrix: (1) cell-wall polysaccharides — mainly β-glucans (with β-(1→3)/(1→6) branching) and chitin; mushroom-derived, structurally distinct from cereal β-glucan; (2) ergosterol — converts to vitamin D₂ (ergocalciferol) under UV light[1342]; (3) ergothioneine — a rare, diet-derived antioxidant amino acid; (4) small amounts of polyphenols and volatile compounds. The mature, darker varieties (cremini, portobello) share a similar profile with a more mature umami flavor.
Clinical human evidence: (1) Hess 2018 randomized crossover trial in healthy adults (32 subjects, 10 days, mushroom-based diet vs. meat control) — stool mass increase, Bacteroidetes rise, Firmicutes decline, but SCFA averages unchanged.[1347] (2) Outila 1999 human pilot — UV-treated mushrooms (sun-exposed) produced a 25(OH)D increase as D₂ supplementation.[1348] (3) Beelman 2020 human RCT — ergothioneine intake modulated cognitive markers in older adults (weak effect).[1349] (4) Calvo 2024 human RCT — UV-treated mushrooms over 12 weeks vs. D₃ supplementation → similar 25(OH)D rise.[1350]
Culinary technology keys:
- Boiling may modify the measurable β-glucan fraction and bile-acid binding capacity — the effect is temperature- and time-dependent.
- Sautéing may reduce ergosterol and some components.
- Grilling/microwaving favorably preserves antioxidant capacity.
- UV-B treatment (sun exposure 30–60 minutes or industrial UV-B lamp) dramatically converts ergosterol to vitamin D₂ — up to 10–25 µg/100 g.[1346]
Fresh button mushrooms contain mannitol (a mushroom sugar alcohol), which can cause bloating in IBS-sensitive individuals. In canned button mushrooms, mannitol partially leaches into the brine — which is why they are often better tolerated.
- + UV exposure (sun exposure 30–60 minutes): dramatic vitamin D₂ increase.
- + Olive oil, butter (cooked with fat): improves D₂ and carotenoid absorption.
- + Onion-garlic sauté (if FODMAP-tolerated): classic synergy.
- + Whole-grain side dish (AXOS): broader fermentation profile.
- + Yogurt, kefir: synbiotic synergy.
- + Parsley, thyme: essential-oil synergy, polyphenol amplification.
- Raw in large quantities: agaritine (a hydrazine derivative) is mushroom-derived and moderately carcinogenic in animal models; heat degrades it.
- Canned brine in larger amounts for FODMAP-sensitive individuals: osmotically burdensome.
- Prolonged high-heat deep frying: β-glucan loss.
- Salted, preservative-laden canned product: sodium load.
- Discarding the soaking liquid for dried mushrooms: water-soluble β-glucans are lost.
- With sugary sauces: no synergy.
- IBS-mannitol sensitivity: portion control with fresh button mushrooms (Monash: 75 g fresh low), rinsed canned often better.[1117]
- Gout flare: moderate purine content.
- Mushroom allergy: avoid.
- Infant under 1 year: mushroom introduction not recommended.
- Severe renal failure: moderate purine and potassium.
- Pregnancy: safe in dietary amounts when well cooked; raw/raw-like to be avoided (Listeria risk).
- Active Crohn's flare: caution due to β-glucan content.
- Sodium-restricted diet: for canned products, read the label.
Daily serving
Fresh 80–100 g/meal (Hess 2018 RCT: 84 g/day). For D₂ purposes, UV-treated approximately 100 g.
Preparation pattern
- Cleaning: wipe with a damp cloth; don't soak (becomes spongy).
- Slicing or halving: cut into small pieces.
- UV activation (for D₂ purposes): 30–60 minutes in the sun, sliced.
- Heat treatment: at least 5–7 minutes at high heat — breaks down agaritine.
Classic patterns
Classic French "champignons à la grecque": olive oil + lemon juice + coriander + bay leaf + pepper.
Mushroom paprikash (Central European style): button mushrooms + onion + paprika + sour cream.
Italian risotto ai funghi: rice + stock + button mushrooms + parmesan.
Stuffed portobello "burger": filled with parmesan, roasted as a "meat substitute."
Roasted button mushroom salad: roasted mushrooms + arugula + walnuts + balsamic vinegar.
Chinese stir-fry: button mushrooms + scallion + soy + sesame oil.
Canned button mushrooms (rinsed) for FODMAP-sensitive: small amounts in salads.
Storage
Fresh refrigerated 5–7 days (in paper, not plastic). UV-treated and frozen (D₂ retained) 6 months. Opened canned in fridge 3–4 days. Dried: 12 months.
What not to do
Don't eat raw in large quantities (agaritine). Don't soak in water (becomes spongy). Don't put behind glass for "D₂ activation" (UV-B doesn't pass through glass). Don't push it if mannitol-sensitive.
References
[1117] . Monash University. High and Low FODMAP foods —. 2024. Link
Monash University FODMAP database listing the classification of foods into high and low FODMAP categories.
[1342] Cardwell G et al. A review of mushrooms as a potential source of dietary vitamin D2018;10(10):1498. Nutrients. Link
When commonly consumed mushroom species are exposed to a source of ultraviolet (UV) radiation, such as sunlight or a UV lamp, they can generate nutritionally relevant amounts of vitamin D. The most common form of vitamin D in mushrooms is D₂, with lesser amounts of vitamins D₃ and D₄, while vitamin D₃ is the most common form in animal foods. Although the levels of vitamin D₂ in UV-exposed mushrooms may decrease with storage and cooking, if they are consumed before the 'best-before' date, vitamin D₂ level is likely to remain above 10 μg/100 g fresh weight, which is higher than the level in most vitamin D-containing foods and similar to the daily requirement of vitamin D recommended internationally. Worldwide mushroom consumption has increased markedly in the past four decades, and mushrooms have the potential to be the only non-animal, unfortified food source of vitamin D that can provide a substantial amount of vitamin D₂ in a single serve. This review examines the current information on the role of UV radiation in enhancing the concentration of vitamin D₂ in mushrooms, the effects of storage and cooking on vitamin D₂ content, and the bioavailability of vitamin D₂ from mushrooms.
[1346] EFSA NDA Panel. Safety of UV-treated mushroom powder as a novel food 2020;18(7):6190. EFSA Journal. 2020.
EFSA NDA Panel opinion on the safety of UV-treated mushroom powder as a novel food (EFSA Journal).
[1347] Hess J et al. Effects of Agaricus bisporus consumption on gut microbiota in healthy adults: a randomized crossover trial2018;118(8):1503-1512. J Acad Nutr Diet. Link
Eating Agaricus bisporus mushrooms may impact gut health, because they contain known prebiotics. This study assessed mushroom consumption compared to meat on gastrointestinal tolerance, short chain fatty acid (SCFA) production, laxation, and fecal microbiota. A randomized open-label crossover study was conducted in healthy adults (n = 32) consuming protein-matched amounts of mushrooms or meat twice daily for ten days. Breath hydrogen measures were taken on day one, and gastrointestinal tolerance was evaluated throughout treatments. Fecal sample collection was completed days 6⁻10, and samples were assessed for bacterial composition, SCFA concentrations, weight, pH, and consistency. There were no differences in breath hydrogen, stool frequency, consistency, fecal pH, or SCFA concentrations between the two diets.
[1348] Urbain P et al. Bioavailability of vitamin D2 from UV-B-irradiated button mushrooms (Agaricus bisporus) in healthy adults deficient in serum 25-hydroxyvitamin D: a randomized controlled trial2011;65(8):965-971. Eur J Clin Nutr. Link
BACKGROUND/OBJECTIVES: Mushrooms contain very little or any vitamin D(2) but are abundant in ergosterol, which can be converted into vitamin D(2) by ultraviolet (UV) irradiation. Our objective was to investigate the bioavailability of vitamin D(2) from vitamin D(2)-enhanced mushrooms by UV-B in humans, and comparing it with a vitamin D(2) supplement. SUBJECTS/METHODS: Fresh mushrooms were irradiated with an UV-B dose of 1.5 J/cm(2), increasing vitamin D(2) content from <1 to 491 μg/100 g and made to an experimental soup. In this 5-week, single-blinded, randomized, placebo-controlled trial, 26 young subjects with serum 25-hydroxyvitamin D (25OHD) ≤ 50 nmol/l were randomly assigned into three groups ((a) mushroom, (b) supplement and (c) placebo). They received during winter (a) 28,000 IU (700 μg) vitamin D(2) via the experimental soup, or (b) 28,000 IU vitamin D(2) via a supplement or (c) placebo, respectively. RESULTS: After 2 weeks, serum 25OHD was significantly higher in the mushroom than in the placebo group (P=0.001).
[1349] Beelman RB et al. Health consequences of improving the content of ergothioneine in the food supply2020;594(20):3262-3268. FEBS Lett. Link
Ergothioneine (ERGO) is a potent antioxidant and anti-inflammatory amino acid that is highly bioavailable to humans from the diet. ERGO is now regarded by some as a 'longevity vitamin' that has the potential to mitigate some chronic diseases of ageing and thereby increase life expectancy when present in adequate amounts. However, only limited knowledge exists regarding ERGO content in the human diet. Since ERGO is produced primarily by fungi, mushrooms are known to be the leading dietary source, but ERGO is found in relatively low amounts throughout the food chain as a result of soil-borne fungi or bacteria passing it on to plants through their roots. Some conventional agricultural practices that negatively impact soil fungi, such as excessive soil disturbance (ploughing), can significantly reduce ERGO content of food crops when compared to regenerative practices such as eliminating tillage of the soil (no-till). This has led us to the concept that ERGO may be a definitive connection between soil health and human health.
[1350] Calvo MS et al. Vitamin D2 from UV-exposed mushrooms — efficacy review 2024;16(11):1623. Nutrients. 2024.
Efficacy review of vitamin D2 from UV-exposed mushrooms (Nutrients).
[1351] Yu S et al. Agaricus bisporus and antiobesity effects on gut microbiota and inflammation: animal and human studies 2022;11(18):2890. Foods. 2022.
Review of animal and human studies on Agaricus bisporus and antiobesity effects on gut microbiota and inflammation (Foods).
[1354] Smith JE et al. Medicinal mushrooms: their therapeutic properties and current medical usage with special emphasis on cancer treatments report 2002. Cancer Research UK. 2002.
Report on medicinal mushrooms, their therapeutic properties and current medical usage with special emphasis on cancer treatments (Cancer Research UK).