Raw white button mushrooms come in at around 22 calories per 100 grams, which makes them one of the lowest-calorie vegetables around, since most of their weight is water.
Why is mushroom's calorie count so low?
About 90 percent of a button mushroom is water; what's left is a small amount of protein, very little fat and a low amount of carbohydrate. That composition makes mushrooms both low in calories and filling — they take up space on the plate without adding much energy.
A single medium mushroom, around 18 grams, carries less than 4 calories on its own; even a handful barely registers in a calorie count.
How does cooking method change the calorie count?
Even though raw mushrooms are low in calories, how they're cooked can shift that number a lot. Mushrooms sautéed in butter or plenty of olive oil soak up a surprising amount of fat thanks to their spongy structure, so a portion of sautéed mushrooms can carry several times the calories of the raw version.
Mushrooms boiled in water or steamed keep a calorie count close to the raw version as long as no fat is added, which makes this method a better fit for anyone tracking calories.
What other nutrients do mushrooms provide?
Despite being low in calories, mushrooms are a good source of B vitamins and potassium, and their small protein content makes a modest contribution in plant-based diets. Some mushrooms exposed to sunlight or UV light can also contain vitamin D, though the amount varies by species and growing conditions.
Their fibre content also makes digestion easier; combined with their low calorie count, this is part of why mushrooms show up so often on diet-friendly food lists.
What should you keep in mind when counting calories?
When counting a mushroom dish's calories, it's not just the mushroom itself that matters but whatever oil, butter or sauce it's cooked with; many people underestimate a meal's total calories by pairing a low-calorie vegetable with a high-calorie sauce. That's why it's worth noting the cooking method alongside the portion size.
The calorie difference between mushroom varieties on the shelf (button, oyster, king oyster) is usually small too; they share a similar water and nutrient balance, so which one you pick doesn't change the calorie count much.
Are dried mushrooms different from fresh ones?
Since dried mushrooms have lost their water, they carry a much denser calorie count for the same weight than fresh mushrooms, so a recipe using dried mushrooms shouldn't be compared directly with fresh ones by weight. Once dried mushrooms are soaked back closer to their original volume, their calorie count drops back close to the fresh version, since what's really happened is the water has been added back.
Canned mushrooms show a similar quirk; the brine usually carries a small amount of salt that doesn't affect calories much, though the salt content is worth noting separately.
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This content is for information only and is not a substitute for medical advice. Consult your doctor before making any decision about your health.