Group · Vegetables
Onion
The onion is an essential bulb vegetable in our kitchens, used for thousands of years to flavour and lift countless dishes. Yellow, red, white or spring, it comes in many varieties with flavours ranging from mild to sharp. With only 34.6 kcal per 100 g, around 6.2 g of carbohydrate, 1.3 g of protein and 1.4 g of fibre, the onion has a light nutritional profile that makes it a great ally in a balanced diet. Rich in water and aromatic sulphur compounds, it brings flavour and character to your dishes without adding many calories. Raw or cooked, it is one of the most versatile foods you can keep in your kitchen.
Macronutrient breakdown
Nutrition table per 100 g
| Calories | 35 kcal |
| Kilojoules | 146 kJ |
| Protein | 1,3 g |
| Carbohydrate | 6,2 g |
| Fat | 0,2 g |
| Fibre | 1,4 g |
Micronutrients per 100 g
All measured nutrients, ranked by share of the daily reference intake.
- Potassium220 mg11 %
- Copper0,08 mg8 %
- Vitamin B60,09 mg6 %
- Phosphorus44 mg6 %
- Manganese0,12 mg6 %
- Calcium29,2 mg4 %
- Magnesium13 mg3 %
- Vitamin C2,1 mg3 %
- Vitamin B9dietary folate equivalents21 µg
See the other 7 nutrients
- Vitamin B50,13 mg2 %
- Zinc0,19 mg2 %
- Iron0,21 mg2 %
- Iodine1 µg1 %
- Vitamin K10,4 µg1 %
- Vitamin A2,08 µg0 %
- Vitamin E0,02 mg0 %
Anses Ciqual 2025. Source: Anses, 2025, Ciqual food composition table
Tips
The onion can be cooked in a thousand ways and is often the aromatic base of a dish. Thinly sliced, it livens up salads, sandwiches and tartares. Softened gently in a pan, it develops a sweet, caramelised flavour that is ideal for tarts, soups and sauces. To limit added calories, sweat it with a little stock rather than too much fat.
How should you eat onion? Half to one medium onion is plenty to flavour a dish for two people. Here are a few useful pointers:
- Yellow onion: versatile, perfect for simmering and caramelising.
- Red onion: mild and colourful, ideal raw in salads.
- White onion and spring onion: more delicate, to eat raw or grill quickly.
As for nutrients, the onion provides vitamin C, fibre and the sulphur compounds responsible for its characteristic smell, as well as flavonoids (especially in red varieties). Its glycaemic index is moderate and its calorie density is low, which makes it a useful vegetable if you are trying to lose weight or move to a balanced diet. You can combine it with other tasty vegetables such as tomato or leek, its cousin in the allium family, to make bases for soups or colourful sautés.
To best preserve its benefits and aromas, gentle cooking is recommended: it avoids burning the sugars and keeps some of the heat-sensitive compounds. You will find the onion among many other foods in the vegetables family, to include regularly in your meals.
Tip for active people: the onion is not a source of energy in itself, but it enriches recovery dishes based on starchy foods and protein after exercise without unnecessary calories. It lifts the taste of a vegetable sauté or an omelette without relying on salt or fatty sauces, which helps keep a meal tasty and light.
Points to watch: raw onion can be hard to digest for some people, so start with small amounts. Be wary too of preparations such as fried onions or tarts rich in butter, which push up the calorie intake. Store your onions somewhere dry, dark and airy, away from potatoes, to stop them sprouting too quickly.
