Author – Phoebe Chan – BSc (Hons) Nutrition and Human Health
Quercetin naturally occurs in lots of plants, fruits, and vegetables in different forms (1). It belongs to the flavonoid family of phytonutrients – colourful plant compounds that help protect plants from environmental stress. Flavonoids are widely researched for their potential health benefits, and quercetin is one of the most abundant flavonoids found in the human diet (2).
It is also known for its powerful antioxidant properties, helping to combat free radicals and reducing oxidative stress in the body. Research has also suggested that quercetin may support cardiovascular health by lowering blood pressure and cholesterol levels, while promoting healthy blood vessel function (3).
This blog explores some of the best natural food sources of quercetin and shares simple ways to increase your intake through everyday foods.
15 Foods Rich in Quercetin
1. Red Onions
All onions contain quercetin; but due to their pigment, red onions have the highest flavonoid content, including quercetin. The cooking method used for onions can reduce the content, so it is important to hold back on boiling and frying to get the maximum flavonoid intake from these pungent vegetables. Red onions can be easily incorporated into stir fry’s, salads or sandwiches.
2. Apples
Apples contain four different phytochemicals along with the beneficial fibre, known as pectin. To get the benefits of quercetin, eat your apples unpeeled (3). They contain around 5 mg per 100 g, which is roughly half an apple. This is a popular source of quercetin and highly accessible too (4).
3. Berries
Blueberries are an excellent source of quercetin as they contain 17 different phytochemicals including resveratrol (3). Moreover, any type of deeply coloured berry or cherry will contain quercetin. They all contain vitamins, minerals, fibre and other protective antioxidants and phytonutrients. Frozen berries, like wild blueberries or dark sweet cherries, are also a great source of quercetin and are available all year round (5). They can easily be mixed into smoothies and breakfasts.
4. Kale
Kale contains 8 mg of quercetin per 100 g (about a cup). It is a great leafy green that supports cell health. In addition, kale is a great source of the carotenoid’s lutein and zeaxanthin, which are concentrated in the retina and support healthy vision (4). Besides quercetin, it is also a rich source of vitamin A, vitamin C and fibre (3). This works well in salads in smoothies.
5. Capers
These are tiny, green flower buds and are a staple in Mediterranean cooking. In North America, capers are primarily enjoyed in Italian dishes, like chicken piccata or rice dishes.
Raw capers offer around 234 mg of quercetin per 100 mg and preserved capers in brine offer 173 mg of quercetin. Their salty, pickle-like taste lends flavour to salads, grain bowls, dressings and roasted vegetables. They are also delicious scattered onto meats, poultry or fish (5).
6. Red Grapes
Grapes have gotten much attention as a source of resveratrol, a powerful polyphenol antioxidant. They are also a great source of quercetin.
All grapes contain some quercetin; however, the darker red and purple varieties typically contain more than green grapes. It is also important to look for organic grapes and grape juices as the cleanest and healthiest source of quercetin, resveratrol and other nutrients (5).
7. Broccoli
Broccoli and other cruciferous vegetables are a rich source of vitamins and minerals in addition to healthy cell promoting compounds such as sulforaphane and indole-3-carbinol (4).
Along with quercetin, broccoli is also rich in vitamin K and vitamin C. Furthermore, it contains another flavonoid, kaempferol, that offers potent antioxidant capabilities. A one-cup serving also provides 5g of fibre (3). It is best to steam broccoli lightly to preserve nutrients.
8. Green Tea
Green tea offers 2.63 mg of quercetin per 100ml. It also provides high amounts of polyphenol called EGCG which helps maintain cholesterol and glucose levels already within the normal range, supports brain and nerve health, and provides cellular health support (4). This is a good alternative to a regular cup of tea or black coffee.
9. Tomatoes
All tomatoes are a good source of quercetin; however cherry tomatoes are the best as they have the highest ratio of skin to flesh (3). In addition, one study showed that organically-grown tomatoes offered up to 79% more quercetin than conventionally-grown tomatoes.
If you’re thinking about increasing your quercetin intake, opt for organic or home-grown tomatoes for salads, sandwiches, sauces, soups and salsas (5).
10. Asparagus
Like other green vegetables, asparagus is high in antioxidants. These include vitamin E, vitamin C and glutathione, as well as various flavonoids and polyphenols.
It is especially high in the flavonoid’s quercetin, isorhamnetin, and kaempferol (6). Asparagus pairs well with many dishes and can be roasted or grilled for flavour.
11. Spinach
Another leafy green vegetable that uses quercetin as a natural antioxidant and protective pigment. It has a slightly bitter taste and is often used in salads, smoothies or soups (7).
12. Hot Peppers
Both yellow and green hot peppers are high in quercetin with about 51 mg and 15 mg of quercetin per 100 g of peppers respectively. However, you may want to use in moderation depending on your spice tolerance (8).
13. Herbs (Dill & Cilantro)
Dill and cilantro are some of the best sources of quercetin. They contain 55 mg and 53 mg per 100 g of the herbs respectively. Adding herbs to a recipe is a great way to add flavour and increase your quercetin intake (8).
14. Shallots
Shallots, which taste like mild onion and garlic combined, can be used for creating delicious sauces and dressings. In addition to quercetin, shallots provide vitamins, minerals, various antioxidants and a healthy amount of immune-supportive organosulfur compounds (5).
15. Buckwheat
Buckwheat offers up to 36 mg of quercetin per 100 g. Not only is buckwheat a good way to increase your quercetin intake, but it’s a great substitute for wheat if you are gluten free. Buckwheat works great as a base in bowls of mixed foods such as a stir fry or porridge (4).
Factors that Affect Quercetin Content
Food preparation and storage can affect quercetin concentrations. For example, fried and boiled foods tend to contain lower levels of quercetin. Boiling causes the greatest decrease by degrading the quercetin, which leaches out into the boiling water.
Quercetin content also depends on how foods are stored. For example, onions can lose 25% to 33% of their quercetin content in the first 12 days of storage, but suffer minimal loss after that.
Finally, growing conditions also influence quercetin levels. Flavanol concentrations are generally higher in plants exposed to greater amounts of ultraviolet-B rays. Plants grown in the UK have been found to have lower flavanol levels than those grown in South Africa, due to the UK’s greater use of greenhouses, which block the ultraviolet-B rays (9).
Conclusion
Quercetin is a naturally occurring flavonoid found in many fruits, plants and vegetables. It is known for its powerful antioxidant properties, which may help reduce oxidative stress in the body.
Foods high in quercetin include: apples, red onions, berries, kale, capers, spinach and hot peppers among others. Adding quercetin rich foods to your diet does not need to be complicated. Simple choice like these can naturally increase your intake, whilst supporting a balanced, nutrient-rich eating pattern.
FAQ’s (Frequently Asked Questions)
What foods are highest in quercetin?
Some of the richest natural sources of quercetin include apples, red onions, capers, kale, berries, spinach, broccoli, grapes, cherries, and hot peppers.
Can cooking reduce quercetin content in foods?
Some cooking methods may reduce quercetin levels, especially prolonged boiling. Light steaming or eating certain foods raw can help preserve more of their natural quercetin content.
Is quercetin found only in fruits and vegetables?
No. Quercetin can also be found in herbs, teas, and some grains. Foods such as capers, dill, green tea, and buckwheat also contain quercetin.
References
- https://futureyouhealth.com/blogs/knowledge-centre/what-is-quercetin
- https://www.cytoplan.co.uk/ask-the-expert/what-is-quercetin-and-how-can-it-support-my-health?utm_medium=cpc&utm_source=google&utm_campaign=fallback_22322625504_x&gad_source=1&gad_campaignid=22329103811&gbraid=0AAAAAD7jWi3m98K2IMAqznlKDV7WIPXD3&gclid=CjwKCAjw5ZXQBhBdEiwAI5XVWVxstRHUDbm33T_dCfjnAFMGv7bK2hlhfMIGxJhydAnsuR8lzUjyLhoCui0QAvD_BwE
- https://www.webmd.com/diet/foods-high-in-quercetin
- https://www.lifeextension.com/wellness/antioxidants/quercetin-foods?srsltid=AfmBOopMTsCHZvvBV_xxx3ayvb-kwqIMwmofCVdmlPi8yjPi7vIFqKcU
- https://www.gaiaherbs.com/blogs/seeds-of-knowledge/where-can-i-find-quercetin-foods?srsltid=AfmBOorsOpqaFqb4dDBur9zocZ02aXSRXF325mqMMsPqurBZmrgbeZma
- https://www.healthline.com/nutrition/asparagus-benefits#antioxidants
- https://www.seekinghealth.com/blogs/education/top-ten-foods-high-in-quercetin-and-how-to-prepare-them?srsltid=AfmBOooBqvaGjk8tWU32btarZLvCDTaDBoRGz-zsk83dhJzLJ_TSydMC
- https://healco.com/blogs/news/top-10-foods-high-in-quercetin-that-you-should-eat-daily?srsltid=AfmBOooQz6GXSk94xLDqW8mR9Z2BPIJZd5_X8RjLuQyupYBHEnZ3oFuG
- https://www.todaysdietitian.com/quercetin-in-the-spotlight/
