Button Mushroom Calories & Nutrition Calculator

Raw button mushrooms (Agaricus bisporus) contain 22 kcal per 100g, with 3.09g protein, 0.34g fat, and 3.26g carbohydrates. The macronutrient split by calories is approximately 56% protein, 14% fat, 30% carbohydrate — an unusually protein-dominant profile for a produce item. At 7.1 calories per gram of protein, button mushrooms rank among the most protein-efficient produce items — chicken breast is still more efficient at 5.4 kcal/g protein, but button mushrooms achieve this ratio from the plant kingdom at only 22 kcal total per 100g serving ^[1][2].

The protein in button mushrooms includes all essential amino acids, though leucine and lysine are the limiting amino acids at lower concentrations than animal protein. The total amino acid profile is considered nutritionally adequate for supplementary protein. Mushrooms are approximately 92% water by weight, which explains the low calorie density and why they shrink significantly during cooking ^[2][3].

For food journaling, 1 cup of sliced raw button mushrooms (70g) provides only 15 calories and 2.2g protein — making mushrooms one of the lowest-calorie foods you can add to any meal for bulk and satiety without meaningful calorie impact.

Button mushrooms provide 9.3mcg selenium per 100g raw (17% of the 55mcg Daily Value). This is noteworthy because selenium is predominantly found in animal proteins, Brazil nuts, and grains — button mushrooms are the only commonly consumed produce item with meaningful selenium content. A single cup (70g) delivers 6.5mcg (12% DV) ^[1][3].

For comparison: 1 large egg provides 15.4mcg selenium at 78 kcal, while 100g raw mushrooms provide 9.3mcg at 22 kcal. Per calorie, mushrooms deliver 0.42mcg selenium per kcal vs. eggs at 0.20mcg/kcal — more than double the efficiency. Cooking concentrates selenium further: boiled mushrooms reach 11.9mcg/100g (22% DV), and sautéed mushrooms approximately 14.0mcg/100g (25% DV) ^[1][2].

Selenium content in mushrooms varies with the selenium content of the growing substrate (compost). Commercially grown button mushrooms in selenium-enriched substrates can reach 20–30mcg per 100g. Standard USDA values reflect typical commercial growing conditions.

Button mushrooms are one of the richest produce sources of niacin (vitamin B3) at 3.607mg per 100g (23% of the 16mg DV). Per calorie, this translates to 0.16mg niacin per kcal — compared to chicken breast at 8.9mg/100g but 0.05mg/kcal, or tuna at 8.6mg/100g at 0.07mg/kcal. Mushrooms deliver niacin more efficiently per calorie than any common animal protein ^[1][2].

Cooking preserves niacin well because it is relatively heat-stable. Boiled mushrooms retain 4.46mg/100g (28% DV) and sautéed mushrooms approximately 5.4mg/100g (34% DV) — both higher per 100g than raw due to water loss concentrating the nutrient. Niacin is water-soluble, so some leaches into boiling water, but the concentration effect from water loss offsets this ^[2][3].

Beyond niacin, button mushrooms contain riboflavin (B2) at 0.40mg/100g (31% DV), pantothenic acid (B5) at 1.5mg/100g (30% DV), and modest amounts of thiamine, folate, and B6. The overall B-vitamin profile is exceptional for a produce item and rivals many grain products.

Raw button mushrooms contain 318mg potassium per 100g — just 11% less than the banana (358mg), which is commonly perceived as the standard potassium-rich food. But the calorie context changes the picture entirely: mushrooms deliver 14.5mg potassium per calorie, while bananas deliver 4.0mg per calorie. Per calorie, mushrooms provide 3.6x more potassium ^[1][2].

A practical cup-to-cup comparison: 1 cup sliced raw mushrooms (70g) provides 223mg potassium at 15 kcal, while 1 medium banana (118g) provides 422mg potassium at 105 kcal. The banana provides more total potassium, but the mushrooms do so at 14% of the calorie cost. For potassium-conscious food journaling on a calorie budget, mushrooms are the superior choice ^[1][3].

Cooking increases potassium concentration: boiled mushrooms reach 356mg/100g and sautéed mushrooms approximately 480mg/100g — making cooked mushrooms roughly equivalent to banana in absolute potassium while remaining dramatically lower in calories.

Cooking method dramatically affects button mushroom nutrition per 100g because of water loss. Raw mushrooms are 92% water; boiling and draining reduces water content, concentrating nutrients in the remaining mass. Key changes from raw to boiled per 100g: iron 0.50mg → 1.74mg (3.5x increase), selenium 9.3mcg → 11.9mcg (28% increase), niacin 3.6mg → 4.5mg (25% increase), fiber 1.0g → 2.2g (120% increase) ^[1][2].

The iron increase from 0.50mg to 1.74mg during boiling is the most dramatic cooking change. This occurs because mushroom tissue collapses and releases water while retaining mineral content. The non-heme iron in mushrooms is not lost to boiling water in significant quantities because it's bound to organic molecules within the cell structure ^[2][4].

Sautéing (dry heat, no oil) concentrates nutrients even further: selenium reaches approximately 14.0mcg/100g (25% DV), niacin 5.4mg/100g (34% DV), and potassium 480mg/100g. However, adding oil changes the calorie picture — 1 teaspoon of oil adds ~40 kcal to a 100g serving of sautéed mushrooms, nearly doubling the total calories. For accurate logging, always account for cooking fat.