Boost Your Immunity with These Quercetin-Rich Foods

Along with the cozy comforts of winter, such as hot cocoa, warm socks, and crackling fires, come the inevitable challenges of stuffy noses, colds, and flu. Fortunately, there are numerous ways to strengthen our immune systems through daily habits—such as regular exercise, getting enough rest, and fueling our bodies with nourishing foods. One key player in this process is quercetin, a plant compound found in many familiar foods, helping to enhance your immune system, fight off illnesses, and support your overall well-being.

When evaluating the healthiness of food, many people focus on its macronutrient (carbs, fats, and proteins) and micronutrient (vitamins and minerals) profiles. However, for plant-based foods, their health-boosting properties extend beyond just these nutrients, thanks to plant compounds—known as phytochemicals, phenolic compounds, polyphenols, or phytonutrients. Scientists have identified over 8,000 such compounds, each offering its own distinct health benefits. These compounds are categorized into different groups and subclasses, and quercetin belongs to the flavonol subclass of the flavonoid family, being one of the most researched. Let's explore why.

Health Benefits of Quercetin

All phytonutrients, including quercetin, are powerful antioxidants that help reduce inflammation and protect the body from harmful free radicals. These unstable atoms can cause considerable damage to healthy cells, potentially leading to cell death or illness. They are behind various health issues, ranging from wrinkles to serious conditions like heart disease and cancer.

However, quercetin's antioxidant benefits are just the beginning of its potential. Research reveals that quercetin boasts impressive antibacterial, antiviral, antimicrobial, and wound-healing effects, significantly strengthening the immune system. Additionally, studies suggest that quercetin helps protect against type 2 diabetes, arthritis, and heart disease. Further studies have even shown that it has neuroprotective effects throughout our lives, from safeguarding against neurological disorders in children to protecting against Alzheimer's disease in adults.

One of quercetin’s most remarkable therapeutic qualities is its ability to combat cancer. Studies have shown that quercetin affects cancer in various ways, including reducing cell viability, preventing cell proliferation, promoting cancer cell death, and ensuring proper disposal of dead cancer cells. Additionally, it interferes with the metabolic processes that nourish cancer cells and disrupts the energy production system within them (the mitochondria, for those of you into biology), ultimately destroying the cells.

Given all of these impressive benefits, you might be wondering how to incorporate more quercetin into your diet. Fortunately, it’s found in a wide array of fruits and vegetables you’re likely already familiar with, and it’s one of the most common flavonols in the Western diet.

Here are some top sources of quercetin to help you get started on your journey to a stronger immune system.

Healthy Food Sources of Quercetin

1. Red Onions

All onions contain some quercetin, but red onions are particularly rich in this powerful phytonutrient, with around 45 mg of quercetin in a small onion. Onions also offer other beneficial plant compounds, such as kaempferol, which is known for its strong anti-inflammatory effects. Plus, they’re a versatile ingredient for a variety of dishes—think eggs, soups, stir fry, nachos, sandwiches—the possibilities are endless.

2. Apples

Apples are not just packed with fiber and immune-boosting vitamin C, but they’re also a great source of quercetin. An average-sized apple gives you 4 mg closer to your daily quercetin target. A lot of these nutrients are found in the skin, so to maximize their benefits, try to keep the peel on when you eat them.

3. Buckwheat

Don’t be misled by the word “wheat” in its name: this flavorful whole grain is naturally gluten-free and packed with essential nutrients. Loaded with B vitamins such as thiamin, niacin, folate, riboflavin, and B6, buckwheat helps sustain your energy levels throughout the day. Additionally, it’s a fantastic source of quercetin, with one cup providing 36 mg of this valuable nutrient.

4. Capers

We all recognize and enjoy capers as a tangy addition to many Italian recipes, but do you know what they actually are? These flavorful, salty morsels come from the unripe green buds of the caper bush, and despite their bold flavor, they’re often overlooked for their nutritional benefits. Capers are rich in essential minerals like calcium and iron, as well as a variety of plant compounds, including quercetin. Just a quarter-cup of capers offers a remarkable 122 mg of quercetin.

5. Green Tea

For your daily intake of plant compounds, don’t forget to check your tea collection. Green tea is not only rich in quercetin, but it also boasts a high amount of epigallocatechin-3-gallate (EGCG), a phytonutrient that has long been attributed to green tea’s medicinal properties, helping regulate cholesterol and blood sugar levels. Additionally, each 12-ounce serving provides 15 mg of quercetin.

6. Kale

As if we needed another reason to eat kale, this celebrated superfood also delivers a solid dose of quercetin, providing 23 mg in just one cup of raw kale. Beyond quercetin, kale is a powerhouse of nutrition, supplying vitamin K for blood clotting, vitamin C to support immune function, and vitamin A for promoting eye health.

7. Blueberries

Blueberries make the ideal addition to smoothies and a delicious topping for pancakes. Their vibrant color is just a hint of the many health benefits they offer. These antioxidant-rich berries are loaded with quercetin and anthocyanins, offering up to 14 mg of quercetin per cup. Additionally, they’re a great source of fiber, potassium, and manganese, all of which contribute to strong bones and healthy blood pressure.

8. Broccoli

Broccoli, a member of the cruciferous vegetable family, is known for providing more protein than many other vegetables, making it an excellent green choice for plant-based meals. Additionally, it’s rich in quercetin, with just a small bowl of raw broccoli delivering 14 mg of this powerful plant compound.

9. Pistachios

Pistachios, often underrated, are not just a tasty snack, but a powerhouse of nutrients to support overall health. These green nuts are packed with a range of beneficial phytochemicals like beta carotene, lutein, zeaxanthin, anthocyanins, and, of course, quercetin. A single cup of pistachios can provide up to 5 mg of quercetin, so be sure to grab some the next time you're shopping for nuts.