Group · Vegetables
Red onion
The red onion owes its colour to anthocyanins, the same pigments found in red fruits. Milder and sweeter than a yellow onion, it is often eaten raw, thinly sliced in salads.
In terms of nutrition facts, raw it provides 35 kcal per 100 g, with 5.63 g of carbohydrate, of which 5.2 g of sugars, 2.5 g of fibre and 1.31 g of protein. It provides 190 mg of potassium and 22 mg of calcium per 100 g.
Macronutrient breakdown
Nutrition table per 100 g
| Calories | 35 kcal |
| Kilojoules | 147 kJ |
| Protein | 1,4 g |
| Carbohydrate | 5,7 g |
| Fat | 0,4 g |
| Fibre | 2,5 g |
Micronutrients per 100 g
All measured nutrients, ranked by share of the daily reference intake.
- Potassium190 mg10 %
- Manganese0,12 mg6 %
- Vitamin C4,09 mg5 %
- Copper0,05 mg5 %
- Phosphorus29 mg4 %
- Vitamin B60,05 mg4 %
- Calcium22 mg3 %
- Vitamin B10,03 mg3 %
- Vitamin B9dietary folate equivalents10,9 µg
See the other 8 nutrients
- Vitamin B50,15 mg3 %
- Magnesium9 mg2 %
- Zinc0,21 mg2 %
- Iron0,19 mg1 %
- Vitamin B30,18 mg1 %
- Vitamin E0,12 mg1 %
- Omega-6 LA0,07 g1 %
- Vitamin A0,21 µg0 %
Anses Ciqual 2025. Source: Anses, 2025, Ciqual food composition table
Tips
It is not lower in calories than a yellow onion. It has 35 kcal against 39.2 for a fried white onion: the gap comes from the cooking, not the variety. Its mildness comes from a lower content of sulphur compounds, not from less sugar.
Its anthocyanins are what make it special. They are the same antioxidants as in red berries, absent from yellow and white onions. They break down in long cooking: raw, it keeps more.
Soak it to soften it further. Sliced, left for ten minutes in cold water with a little vinegar, then drained: it loses its bite without losing its crunch.
2.5 g of fibre, partly fructans. These are prebiotics, but also the reason onion is poorly tolerated with irritable bowel syndrome.
It keeps less well than yellow onion. Its higher water content makes it more fragile: two to three months somewhere dry and dark, against six months for a yellow one.
