Onion
The kitchen's living medicine cabinet: rich in quercetin and organic sulphur compounds, which support insulin sensitivity and heart health, with a very low glycemic index (15).
Glycemic index
Glycemic load
Calories
Protein
💡 Smart Nutritional Guidance
Consumption advice
The basis of cooking and an everyday salad ingredient; its fibre supports healthy gut bacteria and helps keep blood sugar steady in the long run.
Best preparation methods
Eat it raw in salads to get the full benefit of quercetin, or sauté it lightly in olive oil, and avoid frying it until it burns.
Important Nutritional Note
For people with diabetes or insulin resistance, it is always recommended to consider the total glycemic load (GL) of the meal rather than relying on the glycemic index alone.
Nutrition facts
| Nutrient | Per 100 g | Per typical portion (50 g) |
|---|---|---|
| Calories | 40 kcal | 20 kcal |
| Protein | 1.1 g | 0.6 g |
| Carbohydrate | 9.3 g | 4.7 g |
| Available carbohydrate | 7.6 g | 3.8 g |
| Fat | 0.1 g | 0.1 g |
| Dietary fibre | 1.7 g | 0.8 g |
The typical portion is approximate, for comparison purposes.
Comparison & smarter alternatives
Among the foods in Vegetables with a glycemic index (7), it ranks 3 (lowest first).
Smart alternatives from the same family:
Frequently asked questions
Is Onion good for weight loss?
Yes. Onion is very low in calories (40 kcal per 100 g), so you can eat a generous amount to add volume and fullness to a meal without many calories.
How does Onion affect blood sugar?
Its glycemic index is 15 (Low), a clinically reviewed estimate rather than a laboratory measurement. A typical 50 g portion has a glycemic load of 0.6 (Low), so the effect of this portion on blood sugar is limited.
What is the nutritional value of a typical portion of Onion?
A typical 50 g portion of Onion provides about 20 kcal, 0.6 g protein, 4.7 g carbohydrate, 0.1 g fat and 0.8 g fibre.
Reviewed by the WiBo Health medical team · Last reviewed 13 October 2026
Disclaimer: This guidance is for nutritional lifestyle orientation and does not constitute a diagnostic medical device under EU Regulation MDR 2017/745.