Vegetables
Onion
Fructans and quercetin, a flavonoid studied for its antioxidant properties.
Nutrition facts
Serving: 1/2 onion (80 g)
| Nutrient | Per serving | % DV |
|---|---|---|
| Calories | 32 kcal | |
| Protein | 0.9 g | |
| Carbs | 7.4 g | |
| Fibre | 1.4 g | 5 % |
| Sugars | 3.4 g | 3 % |
| Fat | 0.1 g | 0 % |
| Saturated fat | 0 g | 0 % |
| Sodium | 3 mg | 0 % |
Values per serving, calculated from the USDA FoodData Central (SR Legacy).
What the label does not say
- Onion is rich in fructans, fermentable carbohydrates that the fibre figure does not fully count; that is why it ranks among the foods highest in FODMAPs, even in small amounts.
- It is one of the main dietary sources of quercetin (a flavonol), concentrated in the outer layers of the bulb and more abundant in yellow and red onions than in white ones (Price and Rhodes, 1997); the table does not show it.
Preparation
Its quercetin holds up fairly well to heat: sautéed or roasted, onion keeps most of it; boiled, some moves into the water, which a soup keeps (Crozier et al., 1997). Removing the outer layers removes a good share of it.
To mention to a professional
- On a low-FODMAP diet supervised by a professional, onion (and garlic) is among the first foods removed because of its fructans; onion-infused oil contains none, as fructans are not oil-soluble.
Sources
- Onions, raw
- USDA FoodData Central, SR Legacy
- Monash University, FODMAP database
- Price and Rhodes, 1997 (onion flavonols by variety and layer)
- Crozier et al., 1997 (quercetin and cooking)
Educational information: it does not replace the advice of a health professional, especially if you take medication, are pregnant or are breastfeeding.