How Many Calories Is in a Mushroom

Mushrooms are among the lowest-calorie foods you can eat. A single raw white mushroom (about 18–20g) contains roughly 4 to 5 calories. A full 100g portion of raw mushrooms, which might include 5 to 7 medium-sized ones, provides only 20 to 25 calories. This makes mushrooms one of the most calorie-light ingredients available, ideal for adding bulk and nutrition to meals without significantly increasing energy intake.

Cooked mushrooms are slightly more calorie-dense due to water loss during cooking, but even then, a 100g cooked portion typically contains 28 to 35 calories which is still extremely low compared to most vegetables or proteins.

Calories by Type and Preparation

Different types of mushrooms offer similar calorie counts with slight variation. White button, chestnut, portobello, and closed cup mushrooms all contain around 20–25 calories per 100g raw. Larger mushrooms like portobellos may appear heavier in calories simply due to size, but per gram, the values are nearly identical.

Exotic varieties such as shiitake, oyster, enoki, and king oyster mushrooms are also low in calories, typically in the 25–35 calorie range per 100g, depending on moisture and density. Dried mushrooms, however, are calorie-dense due to the absence of water, up to 200–300 calories per 100g dry, though a serving size is usually much smaller.

The biggest calorie jump comes from how mushrooms are cooked. Frying mushrooms in butter or oil can more than double their calorie count, as mushrooms act like sponges, soaking up fat quickly. A small handful sautéed in olive oil can go from 25 calories to over 100 calories with added fat alone.

Nutritional Breakdown

Mushrooms are incredibly low in calories but surprisingly high in nutrients. A 100g serving typically provides 2–3 grams of protein, less than 1 gram of fat, and 2–3 grams of carbohydrate, mostly from fibre and trace sugars. They’re rich in B vitamins, especially B2 (riboflavin) and niacin (B3), as well as selenium, potassium, copper, and small amounts of vitamin D, especially when exposed to sunlight or UV light.

Mushrooms also contain beta-glucans, a form of soluble fibre that supports immune health and may help regulate cholesterol and blood sugar levels.

Health Benefits of Mushrooms

Thanks to their high nutrient density and low energy content, mushrooms are a weight-loss friendly food that also supports broader health goals. They’re low in fat, high in antioxidants, and naturally gluten-free. Their umami flavour makes them a satisfying meat substitute or filler in meals, especially for people reducing animal products.

Mushrooms also support heart health, thanks to their fibre and potassium content, and have been studied for their potential anti-inflammatory and immune-boosting properties. Their role in gut health is emerging too, thanks to prebiotic compounds that feed beneficial gut bacteria.

Downsides and Considerations

Mushrooms are well tolerated by most people, but they can cause digestive discomfort in some due to their fibre and natural sugar alcohols like mannitol. Overeating large amounts may lead to bloating or gas, especially if not cooked well. Some wild mushrooms are toxic, so it's essential to only consume varieties that are farmed, labelled, or foraged with expert knowledge.

Another consideration is how they’re prepared. Mushrooms cooked in butter, cream, or oil-heavy sauces can become surprisingly calorie-rich, defeating the benefit of their naturally low energy content. Creamy mushroom soup, for example, may contain 200–300 calories per bowl, depending on the recipe.

Glycaemic Index of Mushrooms

Mushrooms have a very low glycaemic index, typically under 15, and an extremely low glycaemic load. This means they have little to no impact on blood sugar, making them ideal for diabetic diets or anyone managing insulin resistance. Because they’re low in carbohydrates, they fit easily into low-carb, keto, and whole food diets.

How Mushrooms Are Grown and Used

Mushrooms are grown in dark, damp environments and harvested year-round. Most commercial mushrooms, like white button and chestnut, are cultivated indoors on composted substrates. Exotic varieties are often grown on wood, straw, or specialised growing blocks.

In the kitchen, mushrooms can be grilled, roasted, sautéed, or eaten raw in salads. Their earthy flavour pairs well with garlic, herbs, and umami-rich ingredients like soy sauce or balsamic vinegar. They’re commonly used as meat extenders in dishes like burgers, stir-fries, and stews to lower calorie density without losing taste or texture.

Healthier Ways to Cook Mushrooms

To keep mushrooms low in calories, it’s best to roast or grill them without oil, or use a non-stick pan with a splash of water or stock. If using oil, measure it carefully even one tablespoon of olive oil adds 120 calories. Finishing mushrooms with lemon, herbs, or chilli can bring out flavour without extra fat.

Combining mushrooms with lean proteins or grains can help balance the meal without overpowering it. Their savoury profile also makes them a great swap for high-calorie meats in pasta dishes, risottos, or tacos.

Volume vs Weight: Why Mushrooms Can Be Misleading

Mushrooms shrink considerably when cooked, losing water and appearing much smaller on the plate. This shrinkage can lead people to eat more by volume than they realise, especially in dishes like stir-fries or fajitas. For example, 100g of raw mushrooms might look like a full bowl, but after cooking, it may appear as just a few spoonfuls even though the calorie count hasn't changed much. This makes raw vs cooked weight tracking important for anyone logging their food closely.

Portobello and Large Mushroom Varieties

Larger mushrooms like portobellos or flat caps can vary more in calorie count simply because of their size. A single grilled portobello can weigh 100–120g, putting it around 25–35 calories, even without oil. However, they’re often used as burger substitutes or stuffed with cheese or breadcrumbs, which can turn a 30-calorie mushroom into a 250–300 calorie meal element, especially once baked with fat.

Mushrooms in Restaurant Dishes

In restaurants, mushrooms are rarely served plain. They're often part of creamy starters, mixed grills, or risottos, where they're cooked in butter, oil, or cream. Even a small serving of garlic mushrooms at a pub can easily exceed 300 calories, mostly from the added fat. This is worth noting when encouraging readers to view mushrooms as low-calorie, they are, until something else is added.

Mushrooms and Weight Loss Science

There’s some interesting emerging research showing that replacing some or all meat with mushrooms in meals can support fat loss. One study found that using mushrooms as a partial meat substitute led to lower overall calorie intake, greater satiety, and comparable protein satisfaction. This makes mushrooms not just low in calories, but actively useful in reducing calorie density of meals without sacrificing flavour or satisfaction.

Summary

Mushrooms are extremely low in calories, with around 20–25 per 100g raw. Even cooked, they rarely exceed 35 calories unless prepared with added fats. They offer fibre, protein, B vitamins, and antioxidants in a compact, flavourful package. Their low glycaemic impact and ability to bulk out meals make them ideal for weight control and metabolic health. While preparation style can add hidden calories, mushrooms on their own are one of the most nutrient-rich, low-calorie ingredients available.