Calories in Portobello Mushroom

About Portobello Mushroom Nutrition

Portobello mushrooms are simply mature white button mushrooms — the same species, Agaricus bisporus, left to grow large and open until the cap broadens and deepens in flavor. Their meaty, dense texture and savory taste make them a favorite low-calorie stand-in for meat, yet a portobello has just 22 calories per 100g — roughly 18 calories in a single large cap. They deliver 3.2g protein, 3.4g carbs, only 0.3g fat, and almost no sodium per 100g, along with B vitamins, potassium, selenium, and copper. Grilled whole as a 'burger' or 'steak,' a portobello cap is one of the most filling foods you can eat for so few calories.

With 22 calories per 100 grams, Portobello Mushroom provides 3.2g of protein,3.4g of carbohydrates, and 0.3g of fat.

Macronutrient Breakdown

• Protein: 3.2g - 58% of calories
• Carbohydrates: 3.4g - 62% of calories (including 1g fiber)
• Fat: 0.3g - 12% of calories

Health Benefits of Portobello Mushroom

• Extremely low in calories (22/100g, ~18 per cap) yet large and filling — an ideal meat substitute for weight management
• Naturally fat-free and very low in sodium, supporting heart-healthy and low-sodium eating patterns
• Provide B vitamins (riboflavin, niacin, pantothenic acid) that help convert food into energy
• Good source of potassium and selenium, minerals important for blood pressure and antioxidant defense
• Contain beta-glucan and ergothioneine, compounds studied for immune support and cellular protection
• Mushrooms exposed to UV light supply vitamin D, one of the few plant-based dietary sources

How to Eat Portobello Mushroom

Portobellos are best cooked, which concentrates their flavor and softens the meaty caps. The cap itself stays low in calories (~18 each) — what raises a 'portobello burger' is the oil, bun, and cheese, so brush lightly with oil and grill or roast rather than frying. Remove the stem and dark gills if you prefer a milder taste and cleaner presentation. Use whole caps as burger or steak substitutes, slice them into stir-fries, fajitas, and pasta, or stuff and bake them with vegetables and a little cheese. Marinating in balsamic, garlic, and herbs before grilling adds big flavor for almost no extra calories.

Selection and Storage

Choose firm, dry portobellos with intact caps and no sliminess, dark wet spots, or strong odor; the gills underneath should look fresh rather than mushy. Store them unwashed in a paper bag in the refrigerator (not a sealed plastic bag, which traps moisture and speeds spoilage) and use within about five days. Wipe caps clean with a damp cloth or rinse briefly just before cooking — mushrooms absorb water quickly, which can make them steam instead of sear.

Dietary Considerations

Portobello mushrooms are naturally vegan, vegetarian, gluten-free, fat-free, and very low in sodium. With only about 2.4g net carbs per cap they fit easily into low-calorie, low-carb, keto, and Mediterranean eating patterns, and their meaty bulk makes them a popular plant-based main. They are widely used as a beef substitute in burgers and 'steaks.' As with all mushrooms, cook them thoroughly and introduce them gradually if you are not used to eating much fiber.

Related Foods & Further Reading

Portobellos belong to the same family as the everyday white button mushroom and cremini — all the same species at different ages — so they're worth comparing when you want more flavor or a meatier bite. For a more intense, umami-rich option, shiitake mushrooms bring deeper savory notes and studied immune-supporting beta-glucans. To round out a low-calorie plate, pair grilled portobellos with broccoli and onions, which add fiber and flavor for very few extra calories.