Onion: The Superfood for Blood and Artery Health — Allicin & Quercetin Benefits and the Best Ways to Eat It

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 Onions are among the most common vegetables in our diet — yet when eaten correctly, they can be a true superfood for blood and cardiovascular health.

Let’s explore what makes onions so powerful: their key compounds, their effects on the body, and whether raw or cooked onions are better for you.

A fresh onion cut in half, showing its inner layers and texture.
A fresh onion cut in half, showing its inner layers and texture.


1. What’s Inside an Onion?

Onions are far more than just a sweet, aromatic vegetable. They are packed with bioactive compounds that protect your blood and arteries — including allicin, quercetin, sulfur compounds, flavonoids, and vitamin C.

1) Allicin

This sulfur-based compound forms when onions are cut or crushed, activating enzymes that release their sharp aroma (and your tears!).

Key Benefits:

  • Powerful antibacterial, anti-inflammatory, and antioxidant properties

  • Helps reduce inflammation in blood vessels and improves circulation by thinning the blood

Pro Tip:
After cutting onions, let them sit in the open air for 5–10 minutes before eating. This allows allicin to fully develop.

2) Quercetin

A potent flavonoid antioxidant abundant in onions.

Key Benefits:

  • Protects blood vessel walls from damage

  • Prevents oxidation of LDL (“bad”) cholesterol

  • Supports blood pressure regulation and helps prevent arteriosclerosis (hardening of arteries)

Most of the quercetin is found in the onion skin, but the bulb also contains a meaningful amount.

3) Sulfur Compounds

These are responsible for onion’s pungent flavor and aroma.

Key Benefits:

  • Prevent platelet aggregation (blood stickiness)

  • Enhance smooth blood flow and reduce the risk of clots

2. The Amazing Health Benefits of Eating Onions

  1. Improves Blood Circulation and Regulates Blood Pressure
    Quercetin dilates blood vessels, while allicin and sulfur compounds thin the blood, helping maintain stable pressure.

  2. Lowers Cholesterol Levels
    Onions decrease LDL (“bad”) cholesterol while maintaining or raising HDL (“good”) cholesterol, lowering arteriosclerosis risk.

  3. Powerful Antioxidant and Anti-Inflammatory Effects
    Neutralizes free radicals and reduces chronic inflammation in blood vessels — slowing vascular aging.

  4. Boosts Immunity
    The combination of allicin and vitamin C strengthens your immune defense against bacteria and viruses.

An infographic illustrating how onion nutrients affect blood and blood vessels.
An infographic illustrating how onion nutrients affect blood and blood vessels.


3. Raw vs. Cooked Onions — Which Is Better?

Raw Onions

Best for blood and vascular health, since allicin and sulfur compounds remain intact.
However, raw onions may be harder to digest — eat them with meals or in moderate amounts.

Cooked Onions

Heat can destroy some antioxidants and active compounds.
To retain nutrients, add onions at the end of cooking rather than early in the process.

In short:
Choose raw onions for maximum health benefits, or lightly cooked onions for easier digestion and richer flavor.

4. How to Maximize Onion Health Benefits

1) Recommended Daily Amount: ½ to 1 Onion

About 100–200 g per day (half to one medium onion) is ideal. Consistency is key.

2) Let It Rest After Cutting

Allow sliced onions to sit for 5–10 minutes before eating. This activates the enzyme reaction that maximizes allicin formation.

3) Add at the End When Cooking

When stir-frying or simmering, toss onions in during the final stage to minimize heat damage to antioxidants.

4) Don’t Throw Away the Peel — It’s Quercetin-Rich!

Onion skins contain dozens of times more quercetin than the flesh.

Try boiling clean onion skins to make onion peel tea or add them to broth for extra nutrients.

Why it works:

  • Heat stability: Quercetin is relatively heat-resistant, unlike allicin.

  • Extraction: Hot water releases quercetin trapped in the skin’s fibers.

  • Absorption: Boiling helps convert quercetin into a more absorbable form (aglycone).

Drinking onion peel tea is one of the most effective and natural ways to boost quercetin intake.

5. The Bottom Line

Keeping your blood and arteries healthy is essential for long-term wellness.
And the humble onion — affordable and easy to find — is one of the best foods to help.

When eaten correctly and consistently, onions can aid in blood pressure control, improved circulation, cholesterol balance, and artery protection.
True health starts with simple, everyday choices — like adding an onion to your plate.

Related Posts

References

  • National Institutes of Health (NIH): Quercetin and Cardiovascular Health

  • Journal of Nutrition: Effects of Onion Intake on Blood Pressure and Cholesterol

  • Journal of the Korean Society of Food Science: Studies on Onion’s Bioactive Compounds

  • Korean Dietetic Association: Functional Food Ingredient Data

※ Some of the images in this post were created using AI image generation tools from Miricanvas, ChatGPT, Google Gemini, and Wrtn.

Disclaimer

This article is for informational purposes only and does not substitute for professional medical advice.
Consult your doctor or nutritionist for personalized guidance.

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