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Onion Calories
Low-calorie bulb vegetable with vitamin C and sulfur compounds
CALORIES
GI
POTASSIUM
FIBER
Onion Nutrition Facts
Selected: 100 g
40
KCAL / 100G
Carbs
9.3g
· 88%
Protein
1.1g
· 10%
Fat
0.1g
· 2%
Fiber
1.7g
Onion Vitamins & Minerals
Vitamins
Vitamin C
7.4mg · 8% DV
B6
0.12mg · 7% DV
Folate
19µg · 5% DV
B1
0.05mg · 4% DV
Minerals
Phosphorus
29mg · 4% DV
Potassium ⭐
146mg · 4% DV
Calcium
23mg · 2% DV
Magnesium
10mg · 2% DV
Onion Glycemic Index
GLYCEMIC INDEX
GLYCEMIC LOAD
Accounts for portion size — a more realistic measure than GI alone.
Is Onion Processed?
NOVA 1
Unprocessed
1. Unprocessed
2. Minimally Processed
3. Processed
4. Ultra-Processed
NOVA classifies foods into 4 groups by industrial processing. NOVA 1 (unprocessed) is the healthiest.
Does Onion Contain Allergens?
No known major allergens
Which Diets Is Onion Good For?
Vegan
✓ Suitable
Vegetarian
✓ Suitable
Gluten-Free
✓ Suitable
Dairy-Free
— Not suitable
Mediterranean
✓ Suitable
Paleo
✓ Suitable
Whole30
— Not suitable
DASH
— Not suitable
Keto
✓ Suitable
Low FODMAP
— Not suitable
Onion Fat Profile
SATURATED
0.04g
MONOUNSATURATED
0.01g
POLYUNSATURATED
0.02g
Foods Similar to Onion
Onion — Frequently Asked Questions
How should half an onion be stored after cutting?
Keep the cut onion in an airtight container in the refrigerator so its odor does not transfer to other foods. Use it within a few days for the best flavor and texture.
Why do onions make your eyes water, and how can you reduce it?
Cutting an onion releases volatile sulfur compounds that irritate the eyes. Chilling the onion first, using a sharp knife, and chopping in a well-ventilated area can help.
Does cooking onion destroy all of its nutritional value?
No. Cooking can reduce some heat-sensitive compounds, but much of the onion's fiber and many plant compounds remain. Brief sautéing is generally gentler than prolonged high-heat cooking.
Is raw or cooked onion easier to digest?
Cooked onion is softer and is often easier for many people to tolerate. Raw onion can trigger gas, bloating, or reflux symptoms in sensitive individuals.
Can onion be frozen?
Yes, chopped onion freezes well. It will become softer after thawing, so it is best used in soups, sauces, omelets, and cooked dishes rather than salads.
How can you reduce onion breath?
Brushing the teeth and tongue, drinking water, and eating parsley, mint, or plain yogurt may help reduce the odor. Some sulfur compounds are absorbed and later released through the breath, so the smell may not disappear immediately.
Why is onion often added to meat and bean dishes?
Onion adds sweetness, aroma, and savory depth, especially in slowly cooked dishes. It can make bean dishes more appealing, although people prone to gas may prefer smaller portions.
Do you need to add sugar to caramelize onions?
Usually not. Onions contain natural sugars that brown and develop sweetness when cooked slowly over low heat. Added sugar may speed browning but also makes burning more likely.
Can onion work as a natural antibiotic?
No. Onion contains beneficial plant compounds, but it does not replace antibiotics for bacterial infections. Symptoms of an infection should be assessed by a healthcare professional.
Should people with irritable bowel syndrome be cautious with onion?
Yes. Onion can worsen bloating, gas, and abdominal discomfort in some people because it is high in fermentable carbohydrates. Onion-infused oil can provide flavor without the onion solids for people following a low-FODMAP approach.
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Nutrition data compiled from USDA FoodData Central and scientific sources.