Which onion is more anti-inflammatory?

November 2, 2025 •

3 min read

According to a 2021 review, red onion peel extract ameliorated oxidative stress in rat liver and kidney, showing potent anti-inflammatory effects. This highlights how onion variety can significantly impact its anti-inflammatory properties, a key factor when considering which onion is more anti-inflammatory for dietary purposes.

Quick Summary

Comparing onion varieties reveals significant differences in anti-inflammatory compounds, with red onions generally offering superior benefits due to higher flavonoid content. Cooking methods also impact nutrient retention.

Key Points

Red Onions are Top for Potency: Red onions contain the highest levels of both quercetin and anthocyanins, two powerful anti-inflammatory and antioxidant compounds.
Yellow Onions are a Strong Contender: While generally containing fewer anthocyanins than red varieties, yellow onions are also a rich source of anti-inflammatory quercetin and beneficial sulfur compounds.
Cook with Care: Eating onions raw, especially red ones, is the best way to retain their heat-sensitive anti-inflammatory flavonoids. Boiling can cause significant nutrient loss.
Don't Overpeel: The highest concentration of quercetin is found in the outer layers and inedible dry skin of onions, so peel as little as possible to maximize benefits.
Variety is Key: For comprehensive nutritional benefits, including different anti-inflammatory compounds, incorporating various types of onions into your diet is recommended.
Cooking Methods Matter: While eating raw is ideal, light sautéing and microwaving are better at preserving quercetin compared to methods like deep frying or boiling.

Comparing anti-inflammatory compounds in different onion varieties

When evaluating which onion is more anti-inflammatory, it's important to look at their key bioactive compounds: quercetin and anthocyanins. All onions contain quercetin, a flavonoid with proven anti-inflammatory effects, but the concentration varies by type. Red onions, for instance, are particularly rich in anthocyanins, the pigments that give them their vibrant color. These compounds work together to combat oxidative stress and inflammation in the body.

The powerful role of quercetin

Quercetin is a powerful antioxidant that has been extensively studied for its ability to neutralize free radicals and reduce inflammatory markers. Research indicates that quercetin helps inhibit inflammation-causing substances like leukotrienes and prostaglandins, which are involved in conditions such as rheumatoid arthritis and osteoarthritis. Yellow onions and shallots are good sources of quercetin, but the concentration is highest in the outer layers and dry, inedible skins of yellow and red varieties. In fact, some studies show specific red onion cultivars have notably higher concentrations than yellow ones.

The advantage of red onions: anthocyanins

The deep red-purple color of red onions comes from anthocyanins, a specific class of flavonoids with strong antioxidant and anti-inflammatory properties. Due to their higher anthocyanin content, red onions generally exhibit superior overall antioxidant and anti-inflammatory activity compared to white varieties. These compounds help protect cells from damage and support the immune system. While white onions also offer benefits, they contain significantly fewer anthocyanins.

The impact of cooking on anti-inflammatory benefits

How you prepare your onions can significantly affect their anti-inflammatory properties. The bioactive compounds, particularly quercetin, are sensitive to heat and can leach out into water during cooking.

Raw preparation: Eating onions raw, such as in salads or salsas, is one of the best ways to maximize their anti-inflammatory benefits, especially for red onions with their high anthocyanin content.
Steaming and Microwaving: Studies have shown that some cooking methods, like microwaving and steaming, may increase or preserve the content of certain sulfur compounds, while causing minimal flavonoid loss compared to boiling.
Frying: Frying can lead to the greatest loss of flavonoids, making it the least optimal choice for retaining the onion's anti-inflammatory properties.
Light cooking: Lightly cooking onions, like a quick sauté, has been shown to not significantly affect quercetin intake.

Comparison of onion varieties for anti-inflammatory properties


Feature	Red Onion	Yellow Onion	White Onion
Key Anti-Inflammatory Compounds	High in quercetin and anthocyanins.	High in quercetin and sulfur compounds.	Rich in sulfur compounds, but lower in quercetin.
Antioxidant Levels	Generally the highest, particularly in anthocyanins, which protect cells.	Rich in quercetin, contributing strong antioxidant activity.	Contains antioxidants but at lower levels than red and yellow varieties.
Best for Anti-Inflammatory Diet	Excellent when consumed raw to preserve anthocyanins and quercetin.	A good all-purpose option; best for preserving quercetin is to avoid boiling.	Offers benefits, but other varieties are better for targeting specific anti-inflammatory compounds.
Flavor Profile	Mildly sweet and pungent, often used raw in salads.	Strong, sulfurous flavor that mellows and sweetens when cooked.	Mild and sweet, suitable for salsas and many cooked dishes.

The crucial role of quercetin in inflammation reduction

Quercetin, present in all onion types but concentrated in red and yellow varieties, works by inhibiting inflammatory pathways in the body. Studies on human cell lines and animal models have shown its ability to reduce pro-inflammatory cytokines like TNF-α, IL-6, and IL-1β. It also inhibits enzymes involved in the inflammatory cascade, such as COX and LOX pathways, which are the same pathways targeted by many non-steroidal anti-inflammatory drugs (NSAIDs). Furthermore, research suggests that quercetin can help alleviate inflammation in various conditions, including colitis and asthma, by modulating signaling pathways involved in the immune response.

Conclusion

For those specifically seeking the strongest anti-inflammatory benefits, red onions are the superior choice due to their high concentration of both quercetin and the potent antioxidant anthocyanins. To maximize the anti-inflammatory compounds, it is best to consume red onions raw, perhaps sliced thinly in salads or sandwiches. However, yellow and white onions also contribute valuable anti-inflammatory effects through their quercetin and organosulfur compounds, especially when prepared to minimize nutrient loss. Ultimately, incorporating a variety of onions into your diet ensures a wide range of beneficial compounds that support overall health and combat inflammation.

An extensive review on the effects of Allium cepa (onion) can be found in the Journal of Pharmacopuncture.

Frequently Asked Questions

Red onions contain high amounts of quercetin and anthocyanins, both of which have anti-inflammatory properties. Anthocyanins give red onions their color and contribute significantly to their antioxidant activity.

To maximize the anti-inflammatory benefits from flavonoids like quercetin, it is generally best to eat onions raw. Cooking, especially boiling, can cause these heat-sensitive compounds to leach out or degrade.

Yes, white onions possess anti-inflammatory properties, but they contain lower levels of flavonoids like quercetin compared to red and yellow varieties. They do, however, contain beneficial sulfur compounds that also contribute to health benefits.

Quercetin is a powerful flavonoid antioxidant that fights inflammation by neutralizing free radicals and inhibiting inflammatory pathways in the body. It suppresses the production of pro-inflammatory cytokines and enzymes.

Yes, the color can be an indicator of the antioxidant profile. Red onions get their color from anthocyanins, which are potent antioxidants, making them particularly effective against inflammation. Darker colors often signify a higher concentration of certain compounds.

Yes, you should avoid over-peeling. The outermost layers and dry papery skin of onions have the highest concentration of beneficial flavonoids like quercetin, so peeling minimally helps preserve these compounds.

Yes, shallots are a type of onion that also possess anti-inflammatory compounds. Like red and yellow onions, they contain quercetin and offer significant health benefits, including supporting heart health and immunity.