Onions, cooked, no added fat
Common food
Photo: Wikipedia
Cooked onions are a soft, translucent, and deeply savory staple, their sharp raw bite transformed into a mellow, sweet, and umami-rich flavor through the Maillard reaction. Nutritionally, they are a low-calorie, high-fiber food that provides a notable dose of vitamin C and antioxidants like quercetin, even after cooking.
Calorie split: 10% protein · 88% carbs · 2% fat
↓ Full nutrition💚 Why it's loved
People adore cooked onions for their incredible ability to form the foundational flavor base (soffritto, mirepoix) of countless dishes, adding a deep, savory sweetness that enhances everything from soups to steaks. Their versatility allows them to be caramelized into a jam, fried into crispy rings, or simply sweated into a sauce.
⚠️ Watch-outs & how to enjoy it better
Cooked onions can cause digestive discomfort (gas, bloating) in some individuals due to their fermentable fibers (FODMAPs). For those monitoring blood sugar, their natural sugars (4.97g/100g) can contribute to a mild spike if eaten in large, isolated portions. To counteract, pair with protein or healthy fats to slow digestion, and use them as a flavorful component within a balanced meal rather than the main event.
Key benefits
- Excellent source of prebiotic fiber (2g per 100g) to feed gut bacteria.
- Rich in the antioxidant quercetin, which may have anti-inflammatory properties.
- Provides a good amount of immune-supporting vitamin C.
- Very low in fat and calories, adding volume and flavor to meals.
- Contains sulfur compounds that support cellular health.
🍽️ Popular dishes
🌍 Where it's eaten
💡 Did you know?
The chemical reaction that makes onions sweet and brown when cooked is the same Maillard reaction responsible for the flavor of seared steak, toasted bread, and roasted coffee.
Full nutrition (USDA data · scales with serving)
| Water | 86.9 g |
| Energy | 47.0 kcal |
| Protein | 1.3 g |
| Total lipid (fat) | 0.12 g |
| Carbohydrate, by difference | 11.0 g |
| Fiber, total dietary | 2.0 g |
| Total Sugars | 5.0 g |
| Calcium, Ca | 27.0 mg |
| Iron, Fe | 0.25 mg |
| Magnesium, Mg | 12.0 mg |
| Phosphorus, P | 34.0 mg |
| Potassium, K | 171 mg |
| Sodium, Na | 141 mg |
| Zinc, Zn | 0.20 mg |
| Copper, Cu | 0.05 mg |
| Selenium, Se | 0.60 ug |
| Vitamin C, total ascorbic acid | 7.4 mg |
| Thiamin | 0.05 mg |
| Riboflavin | 0.03 mg |
| Niacin | 0.13 mg |
| Vitamin B-6 | 0.13 mg |
| Folate, total | 19.0 ug |
| Folic acid | 0.00 ug |
| Folate, food | 19.0 ug |
| Folate, DFE | 19.0 ug |
| Choline, total | 7.2 mg |
| Vitamin B-12 | 0.00 ug |
| Vitamin B-12, added | 0.00 ug |
| Vitamin A, RAE | 0.00 ug |
| Retinol | 0.00 ug |
| Carotene, beta | 1.0 ug |
| Carotene, alpha | 0.00 ug |
| Cryptoxanthin, beta | 0.00 ug |
| Lycopene | 0.00 ug |
| Lutein + zeaxanthin | 4.0 ug |
| Vitamin E (alpha-tocopherol) | 0.02 mg |
| Vitamin E, added | 0.00 mg |
| Vitamin D (D2 + D3) | 0.00 ug |
| Vitamin K (phylloquinone) | 0.50 ug |
| Alcohol, ethyl | 0.00 g |
| Caffeine | 0.00 mg |
| Theobromine | 0.00 mg |
Fat & fatty acid profile (per 100g)
| Fatty acids, total saturated | 0.05 g |
| SFA 4:0 | 0.00 g |
| SFA 6:0 | 0.00 g |
| SFA 8:0 | 0.00 g |
| SFA 10:0 | 0.00 g |
| SFA 12:0 | 0.00 g |
| SFA 14:0 | 0.01 g |
| SFA 16:0 | 0.04 g |
| SFA 18:0 | 0.01 g |
| Fatty acids, total monounsaturated | 0.01 g |
| MUFA 16:1 | 0.00 g |
| MUFA 18:1 | 0.01 g |
| MUFA 20:1 | 0.00 g |
| MUFA 22:1 | 0.00 g |
| Fatty acids, total polyunsaturated | 0.02 g |
| PUFA 18:2 | 0.01 g |
| PUFA 18:3 | 0.01 g |
| PUFA 18:4 | 0.00 g |
| PUFA 20:4 | 0.00 g |
| PUFA 20:5 n-3 (EPA) | 0.00 g |
| PUFA 22:5 n-3 (DPA) | 0.00 g |
| PUFA 22:6 n-3 (DHA) | 0.00 g |
| Cholesterol | 0.00 mg |
Amino acid profile (per 100g)
Estimated from Onions, dehydrated flakes — USDA does not publish this profile for Onions.
| Tryptophan | 0.13 g |
| Threonine | 0.22 g |
| Isoleucine | 0.32 g |
| Leucine | 0.31 g |
| Lysine | 0.43 g |
| Methionine | 0.07 g |
| Cystine | 0.16 g |
| Phenylalanine | 0.23 g |
| Tyrosine | 0.22 g |
| Valine | 0.21 g |
| Arginine | 1.2 g |
| Histidine | 0.15 g |
| Alanine | 0.25 g |
| Aspartic acid | 0.49 g |
| Glutamic acid | 1.4 g |
| Glycine | 0.37 g |
| Proline | 0.28 g |
| Serine | 0.26 g |
FAQ
Why do onions turn brown and sweet when cooked?
This is due to the Maillard reaction and caramelization. The high heat breaks down the onion's natural sugars and amino acids, creating hundreds of new, complex flavor compounds that are savory, sweet, and nutty.
Is the nutritional value of an onion lost when cooked?
Some heat-sensitive nutrients like vitamin C decrease, but cooking actually makes other antioxidants, like quercetin, more bioavailable and easier for your body to absorb. The fiber and mineral content remain largely stable.
How can I reduce the digestive issues onions sometimes cause?
Cook onions thoroughly, as this breaks down some of the fermentable fibers. You can also try using the green tops (scallions) which are often better tolerated, or start with smaller portions to see your personal tolerance.
Nutrient density (calculated · NRF9.3)
Nutrient Rich Foods index: beneficial nutrients (protein, fiber, vitamins, minerals) minus saturated fat, added sugar & sodium, per 100 kcal.
NRF9.3 index — Fulgoni, Keast & Drewnowski, 2009. Computed from USDA nutrients.
Weight-loss friendliness (composite index)
Energy density 0.47 kcal/g · 11% calories from protein · 2.0 g fiber · 5.0 g sugar per 100 g.
Composite of energy density (Rolls et al., 1999), protein & fiber satiety, minus sugar. A calculated heuristic — ranks satiety-per-calorie, not a clinical measure.
Dietary load (calculated from USDA values)
Potential renal acid load. Positive = acid-forming, negative = alkaline-forming.
Sodium-to-potassium ratio: 0.82 (lower is better — aim for ≤ 1)
Sodium:potassium per WHO potassium guidance. Computed from USDA nutrients.