Several aspects of modern life can impair immune system functioning (excessive sugar intake, poor sleep, chronically elevated stress levels—you get the image), making it tougher to stay healthy. Identifying our immune-sapping triggers, and adapting our lifestyle accordingly is a great start.

Still, no one’s perfect—so, we often reach for supplements like vitamin D and vitamin C for extra immune strength. But there’s another less popular nutrient gaining attention for its immune-benefiting potential: Quercetin. 

We’ve most likely ingested this bioactive plant compound before in the form of onions, apples,  or tea, but increasing research indicates it might be worth supplementing. Here, we break down the advantages of Quercetin, how to get more in your diet, and whether supplementing is correct for you. 

Immune-Supporting Antioxidant

Health Benefits of Quercetin

Like any nutrient, Quercetin isn’t a wonder drug for immunity or health in isolation. But the body of existing studies on Quercetin is encouraging [1]. 

Here are a few specific ways Quercetin may improve health:

1. It can reduce the risk of viruses, from colds to herpes.

Quercetin may help prevent and treat a wide range of viral infections, including URTIs (upper respiratory tract infections) such as the flu and the common cold.

In one research paper published in the JCERC (Journal of Clinical & Experimental Cardiology), supplementation with 1,000 milligrams (mg) quercetin per day minimized the incidence of upper respiratory tract infections after a period of intense exercise—3 hours of cycling, three days in a row, during winter. 

2.  It can possibly help with seasonal allergies.

Quercetin’s immediately noticeable and most apparent benefit is the prevention of histamine-mediated allergic symptoms.

More studies are required in humans, but clinical trials—including one published in the journal Molecules—show that Quercetin can help combat conditional allergic rhinitis.

How exactly? It seems to help prevent mast cells’ overactivation, which secretes histamine—an inflammatory chemical that’s involved in allergy symptoms like sneezing and itching. Vitamin C can enhance the Quercetin’s allergy-combating potential [2]. 

3. It can help minimize chronic inflammation.

Free radicals in our body promote inflammation, but antioxidants help neutralize and scavenge free radicals. So it makes sense that a flavonoid antioxidant  (Quercetin) would have anti-inflammatory properties [3]. 

4. It can ward off dementia and boost cognitive function.

Alzheimer’s, Dementia, and other neurodegenerative diseases can be exacerbated by oxidative stress due to an overabundance of free radicals in the body. 

Not only does Quercetin have antioxidant effects that counteract these effects, but it aids the development of fresh mitochondria, the energy-revving “powerhouse” of cells (mitochondrial biogenesis) in the brain for improved cognition [4]. 

5. It is believed to have properties that minimize the risk of cancer.

Umpteen flavonoid antioxidants, not just Quercetin, have shown anti-cancer properties, which is one reason eating loads of colorful veggies and fruits is so beneficial for you. But Quercetin, particularly, has been shown to inhibit cancer cell growth and multiplication or proliferation.

6. It may support heart and cardiovascular health in multiple key ways.

Quercetin’s heart benefits go beyond and above its ability to battle inflammation. Here are a few more reasons it can support your heart:

Individuals who consume diets high in flavonoid antioxidants tend to have lower cholesterol levels.

Oxidative stress may wreak havoc on fatty structures in our body. Clinical trials indicate that Quercetin helps prevent LDL cholesterol (the “bad” kind of cholesterol) from oxidizing into an even more fatal form.

One research in the AHA (American Heart Association) Journal found that 500 mg of Quercetin per day remarkably decreased systolic and diastolic blood pressure, especially among people with diabetes.

Foods high in Quercetin.

Before we delve into supplementing information, you should know that Quercetin is found in tons of delicious, healthy,  plant-based foods (often in the outer layer or peel). While upping your intake of quercetin-dense foods may not treat the conditions mentioned above, it will support overall health.

• red onion 
• red apples
• capers (most concentrated source!)
• berries
• shallots
• scallions
• grapes
• tomatoes
• broccoli
• Brussels sprouts
• kale
• citrus fruits
• cabbage
• nuts (almonds and pistachios)
• asparagus (cooked has slightly more)
• bell peppers (green and yellow)
• black tea
• green tea
• elderberry tea
• buckwheat 

Safety and Side Effects

Quercetin is present in numerous veggies and fruits and is safe to take. As a supplement, it appears to be usually safe with little to no side effects. In a few instances, taking in excess of 1,000 mg of Quercetin per day can cause mild symptoms like stomach aches, headaches, or tingling sensations.

When taken in the food, Quercetin is safe for breastfeeding and pregnant women. However, research on the safety of quercetin supplements for breastfeeding and pregnant women is lacking, so you should avoid taking Quercetin if you’re nursing or pregnant.

As with any supplement, consult your medical practitioner before taking Quercetin, as it can interact with some medicines, including blood pressure medications and antibiotics.

Bottom line

Quercetin is one of those nutrients that’s excellent for overall wellness—as it supports immunity and has anti-inflammatory perks—and it may be specifically advantageous for individuals struggling with seasonal allergies. Food sources are abundant (think veggies, fruits, nuts, teas) and contain various other nutrients.

Still, to help prevent or manage a specific ailment, supplementation at doses of 500 to 1,000 mg is typically necessary. Just remember, as, with all supplements, it’s essential to check in with your physician first if you have concerns or questions. 

Remember: When it comes to supporting overall immunity, Quercetin should be just one component of your regimen(nothing works in isolation, after all).

To provide your immune system an additional boost, get 7 to 9 hours of sleep a night, consume immune-boosting foods, consider additional expert-backed supplements for immune health, manage stress, or stay active, any existing health conditions you may have.