Onion: 40-Calorie Allium Packed with Quercetin, Prebiotic Fiber & Sulfur Flavor
100 g raw onion gives 40 kcal, 7 mg vitamin C and prebiotic fructans that feed gut bacteria while adding depth to almost every cuisine.
What Is an Onion?
Onion (*Allium cepa*) is a bulb in the allium family. Layers store **fructans** and sulfur compounds that release their signature aroma when cut.
Common Varieties & Uses
- **Yellow/Brown**: everyday cooking, long storage
- **White**: milder, great in salsa
- **Red/Purple**: crisp raw in salads, pickles
- **Sweet (Vidalia, Walla Walla)**: high sugar, ideal for rings
Nutrition per 100 g (raw)
|Calories|Protein|Fat|Carbs|Fiber|Vit C|Potassium|
|---|---|---|---|---|---|---|
|40 kcal|1.1 g|0.1 g|9.3 g|1.7 g|7 mg (8 %)|146 mg (3 %)|
Science-Backed Benefits
- **Quercetin & sulfur** act as antioxidants
- **Fructan fiber** = prebiotic fuel for bifidobacteria
- Low calorie bulk aids weight management
Drawbacks
- High FODMAP → bloating in IBS
- Tear-inducing gas (syn-propanethial-S-oxide)
- Raw onion breath—balance with parsley or cook thoroughly
Prep & Tear-Free Tips
- Chill bulb 20 min or cut under vent to reduce tears
- Slice root last (highest irritant concentration)
- Save peels for vegetable stock—extra quercetin
Cooking Techniques
- **Sauté** 5 min for base of soups & curries
- **Slow-caramelize** 45 min for sweet jam
- **Quick-pickle** in vinegar 30 min for tacos
- Roast wedges 200 °C, 25 min for mellow sweetness
Flavour Pairings
- Garlic, thyme, cumin
- Beef, lentils, chickpeas
- Balsamic, apple cider vinegar
Buying & Storage
- Choose dry papery skins, no soft spots
- Store whole bulbs **cool, dark, ventilated** → 4–6 weeks
- Cut onion in airtight box, fridge 5 days (keep away from apples)
- 1. Onion