# Onion (Allium cepa)

**Canonical URL:** https://ingredients.hermeticasuperfoods.com/ingredients/onion
**Data Source:** Hermetica Superfoods Ingredient Encyclopedia
**Updated:** 2026-04-01
**Evidence Score:** 2 / 10
**Category:** Vegetable
**Also Known As:** Allium cepa, common onion, garden onion, bulb onion, cooking onion, yellow onion, white onion, red onion, Spanish onion, storage onion, dry onion, globe onion

## Overview

Onion extract contains quercetin and organosulfur compounds that provide antioxidant and [antimicrobial](/ingredients/condition/immune-support) effects. These bioactive compounds work by scavenging [free radical](/ingredients/condition/antioxidant)s and disrupting bacterial cell membranes through sulfur-containing metabolites.

## Health Benefits

• [Antioxidant](/ingredients/condition/antioxidant) properties from quercetin and phenolic compounds (preliminary evidence from in vitro studies)
• Antimicrobial activity demonstrated through organosulfur compounds (preliminary evidence from laboratory studies)
• [Anti-inflammatory](/ingredients/condition/inflammation) potential via flavonoid content (preliminary evidence from cellular models)
• [Immunomodulatory](/ingredients/condition/immune-support) actions through detoxification enzyme activation (preliminary evidence from animal studies)
• Potential anticancer properties via carcinogen elimination mechanisms (preliminary evidence from in vitro models)

## Mechanism of Action

Quercetin in onion extract inhibits [inflammatory](/ingredients/condition/inflammation) enzymes including cyclooxygenase and lipoxygenase while scavenging [reactive oxygen species](/ingredients/condition/antioxidant). Organosulfur compounds like allicin and diallyl sulfides disrupt bacterial cell wall synthesis and interfere with microbial enzyme systems. These compounds also modulate nuclear factor-kappa B pathways to reduce inflammatory cytokine production.

## Clinical Summary

Most evidence for onion extract comes from in vitro and animal studies rather than human clinical trials. Laboratory studies show quercetin concentrations of 200-400mg exhibit significant [antioxidant activity](/ingredients/condition/antioxidant) against lipid peroxidation. Small human studies suggest 100g fresh onion daily may reduce [inflammatory](/ingredients/condition/inflammation) markers, but sample sizes remain limited to 20-50 participants. Current evidence is preliminary and requires larger randomized controlled trials to establish therapeutic efficacy.

## Nutritional Profile

{"macronutrients": {"carbohydrates": "9.34 g per 100 g", "protein": "1.1 g per 100 g", "fiber": "1.7 g per 100 g", "fat": "0.1 g per 100 g"}, "micronutrients": {"vitamin_C": "7.4 mg per 100 g", "vitamin_B6": "0.12 mg per 100 g", "folate": "19 \u00b5g per 100 g", "potassium": "146 mg per 100 g", "manganese": "0.129 mg per 100 g"}, "bioactive_compounds": {"quercetin": "up to 30 mg per kg", "organosulfur_compounds": "varies, primarily allyl sulfides", "flavonoids": "varies, includes kaempferol and quercetin derivatives"}, "bioavailability_notes": {"quercetin": "Bioavailability can be enhanced by cooking or consuming with fat", "organosulfur_compounds": "Stability varies with cooking; raw consumption may offer higher activity", "vitamin_C": "Sensitive to heat and light, best preserved in raw form"}}

## Dosage & Preparation

No clinically studied dosage ranges for onion extracts or standardized forms have been established in human trials. Compositional studies identify quercetin glucosides as primary bioactives but therapeutic doses remain unspecified. Consult a healthcare provider before starting any new supplement.

## Safety & Drug Interactions

Onion extract is generally safe when consumed in food amounts but may cause gastrointestinal upset, heartburn, or allergic reactions in sensitive individuals. High doses can interact with anticoagulant medications like warfarin due to organosulfur compounds affecting platelet aggregation. Individuals with gastroesophageal reflux disease should use caution as onion compounds can exacerbate symptoms. Pregnant and breastfeeding women should limit intake to normal dietary amounts due to insufficient safety data.

## Scientific Research

The research dossier indicates no human clinical trials, RCTs, or meta-analyses with PubMed PMIDs are available for onion (Allium cepa). Current evidence is limited to in vitro, animal, and compositional studies examining bioactive compounds.

## Historical & Cultural Context

While onion has been domesticated and consumed for thousands of years originating from central Asia, the research dossier does not specify traditional medicine systems or historical therapeutic uses. Modern consumption primarily focuses on its role as a nutrient-dense vegetable with bioactive potential.

## Synergistic Combinations

Garlic, Turmeric, Green Tea Extract, Vitamin C, Selenium

## Frequently Asked Questions

### How much quercetin is in onion extract?

Onion extract typically contains 200-400mg of quercetin per 100g fresh weight, with red onions having higher concentrations than white or yellow varieties. Commercial standardized extracts may contain 5-20% quercetin by weight.

### Can onion extract help with high blood pressure?

Limited studies suggest onion extract may support cardiovascular health through quercetin's vasodilating effects and organosulfur compounds' impact on nitric oxide production. However, human clinical evidence remains insufficient to recommend onion extract specifically for blood pressure management.

### Does cooking destroy onion's beneficial compounds?

Heat processing reduces quercetin content by 20-30% but may increase the bioavailability of certain organosulfur compounds. Raw onions provide maximum quercetin levels, while lightly sautéed onions offer a balance of preserved and enhanced bioactive compounds.

### What's the difference between onion powder and fresh onion extract?

Fresh onion extract retains more heat-sensitive compounds like quercetin and volatile organosulfur compounds compared to dried onion powder. Onion powder contains concentrated flavonoids but loses approximately 40-60% of its antimicrobial organosulfur compounds during dehydration processing.

### Can onion extract cause digestive problems?

Onion extract contains fructooligosaccharides and sulfur compounds that can cause bloating, gas, and stomach upset in sensitive individuals. Those with irritable bowel syndrome or FODMAP sensitivities may experience increased digestive symptoms with concentrated onion preparations.

### What is the bioavailability difference between onion extract and raw onion, and does processing affect compound absorption?

Raw onions contain quercetin primarily in bound forms that have lower bioavailability, while fermentation and heating can increase the release of free quercetin and organosulfur compounds available for absorption. Onion extract concentrates these bioactive compounds, potentially increasing bioavailability compared to whole food amounts, though individual absorption varies based on gut microbiota and digestive efficiency. The processing method (fermentation, water extraction, or alcohol extraction) significantly influences which compounds are preserved and how readily they're absorbed in the digestive tract.

### Is onion extract safe to take alongside blood thinners or antiplatelet medications?

Onion contains compounds with mild antiplatelet and anticoagulant properties, which may theoretically potentiate the effects of medications like warfarin, aspirin, or clopidogrel, increasing bleeding risk. While culinary amounts of onion are generally considered safe with these medications, concentrated onion extracts warrant caution and should be discussed with a healthcare provider before use. Individual risk depends on dosage, medication type, and baseline bleeding parameters, making professional medical consultation essential.

### Who would benefit most from onion extract supplementation—are there specific populations where it's most effective?

Individuals with elevated oxidative stress, chronic inflammatory conditions, or those with limited fresh produce intake may derive the most benefit from onion extract due to its concentrated quercetin and phenolic content. People with metabolic syndrome or prediabetes represent another population of interest, as preliminary evidence suggests onion compounds may support metabolic health markers, though clinical confirmation is ongoing. Conversely, those with irritable bowel syndrome or sensitive digestion may experience fewer benefits due to potential gastrointestinal effects from concentrated organosulfur compounds.

---

*Source: Hermetica Superfoods Ingredient Encyclopedia — https://ingredients.hermeticasuperfoods.com*
*License: CC BY-NC-SA 4.0 — Attribution required. Commercial use: admin@hermeticasuperfoods.com*