Grilled Portobello Mushroom
Quick answer
A medium portion of Grilled Portobello Mushroom (100 g) contains 28 kcal, with 2.4 g of net carbohydrates and 2.5 g of protein.
- Carbs4.2 g55.3%
- Protein2.5 g32.9%
- Fat0.4 g11.8%
- Fibre1.8 g
Percentages of total energy (calories)
How many calories are in a portobello mushroom?
Portobello is the "big brother" of the brown mushroom, and one is the size of the palm of your hand. There are only 28 calories per 100 g grilled, and a large mushroom (about 100 g) has about the same. So you can eat two and feel you have had a "steak" for less than 60 calories.
Do mushrooms raise blood sugar?
No. They have about 2.4 g of available carbohydrate per 100 g, so the glycemic index does not apply. That makes them a friend of weight-loss and keto diets and of anyone watching their blood sugar.
Why is it called a "mushroom steak"?
Because its texture is meaty and dense, and its taste has a rich flavour called umami, the same flavour you sense in meat and cheese. So many vegetarians use it instead of meat in burgers.
But watch out: it has little protein (2.5 g per 100 g), so it replaces meat in taste and texture, not in protein.
How to cook it smartly
- You can grill it or bake it in the oven with a spoon of olive oil, garlic and thyme. Mushrooms soak up oil like a sponge, so don't add more.
- You can stuff it with cottage cheese and parsley and bake it in the oven.
- Use it as a burger "bun" instead of bread: two portobellos with the meat or cheese in the middle.
Lighter alternatives
- Instead of a burger bun (about 61): two grilled portobellos.
- Instead of fries on the side: grilled portobello slices.
Nutrition facts
| Nutrient | Per 100 g | Per typical portion (100 g) |
|---|---|---|
| Calories | 28 kcal | 28 kcal |
| Protein | 2.5 g | 2.5 g |
| Carbohydrate | 4.2 g | 4.2 g |
| Available carbohydrate | 2.4 g | 2.4 g |
| Sugar | not available | — |
| Fat | 0.4 g | 0.4 g |
| Dietary fibre | 1.8 g | 1.8 g |
| Glycemic index | Not applicable | |
| Glycemic load | Not applicable | |
| Insulin index | not tested | |
The typical portion is approximate, for comparison purposes.
Comparison & smarter alternatives
It has 28 kcal per 100 g, ranking 33 of 74 in Vegetables (lowest first).
Frequently asked questions
How many calories are in a portobello mushroom?
About 28 calories per 100 g grilled, and a large mushroom has about the same.
Do mushrooms raise blood sugar?
No, they have very little carbohydrate.
Is portobello suitable for keto and weight loss?
Definitely; it is low in calories and almost free of starch. But watch how much oil you use when grilling.
Can mushrooms replace meat?
In taste and texture yes, but not in protein. So add another protein source to the meal.
Read also
References & Scientific Sources
- The glycemic index does not apply because this food has less than 5 g of available carbohydrate per 100 g, and a GI test requires 25 to 50 g of available carbohydrate, per: ISO 26642:2010. Food products — Determination of the glycaemic index (GI) and recommendation for food classification. International Organization for Standardization; 2010. www.iso.org/standard/43633.html
- Definition of available carbohydrate and glycemic load: FAO/WHO. Carbohydrates in human nutrition: report of a joint FAO/WHO expert consultation. FAO Food and Nutrition Paper 66. Rome; 1998. www.fao.org/4/w8079e/w8079e00.htm
Medically reviewed by Dr. Wassim Habib | Founder, WiBo Health · 31 October 2026
Disclaimer: This guidance is for nutritional lifestyle orientation and does not constitute a diagnostic medical device under EU Regulation MDR 2017/745.