scored 83/100
Onions are sulfur-containing bulb vegetables rich in quercetin and other polyphenols, providing anti-inflammatory and antioxidant benefits with minimal calories and carbohydrates (depending on variety).
6.5 g net carbs after fiber.
Representative amounts for this food, not measured for this item. Real content varies widely by variety, ripeness and storage.
These are the scored components, not a sum: the published score also reflects normalisation across the catalog, so the parts above will not add to 83.
Onions (Allium cepa) originated in Central Asia and have been cultivated for over 5,000 years across civilizations. They contain unique bioactive compounds including quercetin (a flavonoid), organosulfur compounds (thiosulfates, sulfoxides), and inulin (a prebiotic fiber). Red and yellow onions contain significantly higher polyphenol concentrations than white varieties. The sulfur compounds in onions are activated when cells are damaged—cutting, chopping, or cooking—making preparation method crucial for bioavailability. For longevity, onions support cardiovascular health through anti-inflammatory and lipid-modulating mechanisms, promote glycemic control via inulin and chromium content, and provide prebiotic fiber supporting gut microbiota diversity. Studies suggest regular onion consumption is associated with reduced cardiovascular disease risk and improved bone density, particularly in postmenopausal women. The quercetin in onions exhibits antioxidant and anti-cancer properties in vitro and animal models, though human evidence remains emerging. Onions are calorie-sparse but nutrient-dense, making them ideal for longevity-focused diets emphasizing whole-food density over volume.
Quercetin and organosulfur compounds inhibit inflammatory pathways and improve endothelial function, while chromium and inulin support healthy cholesterol and triglyceride levels
Inulin acts as prebiotic fiber slowing glucose absorption, while quercetin enhances insulin secretion and may improve pancreatic beta-cell function
Organosulfur compounds may inhibit osteoclast-mediated bone resorption and promote osteoblast activity, particularly beneficial in postmenopausal women
Inulin fermentation by beneficial bacteria increases butyrate production, strengthening intestinal barrier function and reducing systemic inflammation
Quercetin scavenges free radicals and modulates apoptotic pathways; organosulfur compounds induce phase I/II detoxification enzymes
Onions lack bioactive compounds requiring specific circadian timing. Consuming throughout the day optimizes cumulative prebiotic fiber intake and polyphenol exposure. Raw or lightly cooked preparations at any meal support consistent anti-inflammatory and metabolic benefits.
Fasting-compatible
Raw onions are compatible with fasting protocols; organosulfur compounds bioavailability is unaffected by fed/fasted state. Timing of intake relative to meals does not significantly alter quercetin or inulin efficacy.
Per 100 g of the default form. Bars show how much higher or lower onions is than the average across 137 peer foods in this category. Green means a favorable direction; amber means the opposite.
Onions is classified as a vegetable. Onions are sulfur-containing bulb vegetables rich in quercetin and other polyphenols, providing anti-inflammatory and antioxidant benefits with minimal calories and carbohydrates (depending on variety).
Onions scores 83/100 in Formulate, making it a great choice. Its strongest contributions come from Vitamin C, Vitamin B6, Manganese. The score blends nutrient density, fiber, healthy fats, protein quality, bioactive compounds, and glycemic impact.
Not particularly. A 85 g serving provides about 0.9 g of protein (~2% of the 50 g daily value).
Not really. A 85 g serving provides about 1.4 g of fiber (~5% of the 28 g daily value).
Sometimes — it depends on your daily carb budget. A 85 g serving has about 6.5 g of net carbs (7.9 g total minus 1.4 g fiber).
Best any time of day. Onions lack bioactive compounds requiring specific circadian timing. Consuming throughout the day optimizes cumulative prebiotic fiber intake and polyphenol exposure. Raw or lightly cooked preparations at any meal support consistent anti-inflammatory and metabolic benefits.
A typical serving is around 85 g (~34 kcal), based on the FDA's Reference Amount Customarily Consumed for this food category. There's no fixed daily target — most adults benefit from rotating onions alongside several other vegetable sources.
Onions pairs nicely with: Pair raw onions with tomatoes in salads because raw preparation maximizes organosulfur compound bioavailability, and tomato lycopene absorption is enhanced by dietary fat from olive oil dressing; Combine caramelized onions with garlic because both contain complementary organosulfur compounds that synergistically enhance anti-inflammatory effects; Pair onions with cruciferous vegetables (broccoli, cabbage) because both provide glucosinolates and organosulfur compounds that work through overlapping detoxification pathways; Combine onions with healthy fats (olive oil, avocado) because quercetin is fat-soluble, requiring dietary lipids for optimal absorption in the small intestine.