Vegetable

Onions

Health
ScoreA

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).

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Why Onions scores 83

Nutrient density26

Protein quality7

Fiber content9

Healthy fats5

Bioactive compounds14

Glycemic impact8

Top nutrients

% Daily Value per ½ cup (85 g)

Vitamin C 7.0%Vitamin B6 6.0%Manganese 4.8%Folate 4.1%Copper 3.7%

Nutrition

per_100g

Calories

1.1g

Protein

9.3g

Carbs

0.1g

Fat

1.7g

Fiber

Health benefits

Cardiovascular protection through reduced inflammation and blood pressure modulation

moderate evidence

Quercetin and organosulfur compounds inhibit inflammatory pathways and improve endothelial function, while chromium and inulin support healthy cholesterol and triglyceride levels

Improved glycemic control and insulin sensitivity

moderate evidence

Inulin acts as prebiotic fiber slowing glucose absorption, while quercetin enhances insulin secretion and may improve pancreatic beta-cell function

Enhanced bone density and reduced osteoporosis risk

moderate evidence

Organosulfur compounds may inhibit osteoclast-mediated bone resorption and promote osteoblast activity, particularly beneficial in postmenopausal women

Prebiotic-driven gut microbiota health and increased short-chain fatty acid production

strong evidence

Inulin fermentation by beneficial bacteria increases butyrate production, strengthening intestinal barrier function and reducing systemic inflammation

Antioxidant and anti-cancer potential through quercetin and organosulfur compounds

emerging evidence

Quercetin scavenges free radicals and modulates apoptotic pathways; organosulfur compounds induce phase I/II detoxification enzymes

Pairs well 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

Practical tips

·Best timing: 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.
·Consume onions raw or lightly cooked to preserve heat-sensitive organosulfur compounds; cooking beyond 20 minutes significantly reduces thiosulfate concentrations
·Store whole onions in cool, dark, well-ventilated conditions (50-70°F) to extend shelf life up to 2-3 months without refrigeration; avoid plastic bags which trap moisture
·Slice or chop onions 10-15 minutes before consumption or cooking to allow enzymatic activation of organosulfur compounds; let sit at room temperature to maximize conversion
·Prioritize red and yellow onions over white varieties, which contain 2-3x higher quercetin and polyphenol concentrations for equivalent intake