8 Foods with highest concentration of quercetin

Many people dream of a longer and healthier life span. Living longer or increasing longevity can be achieved through practicing a healthy lifestyle and eating healthy foods.

Fruits and vegetables are important sources of natural compounds and substances shown in research studies to promote longevity. 

One of these substances includes antioxidants, compounds produced naturally in the body or sourced through the foods we eat and supplementation.  

One example of a naturally occurring antioxidant is glutathione. However, glutathione levels decrease, suggesting that the body does not efficiently produce this antioxidant during aging. Hence, it is essential to take supplements to replenish naturally-occurring antioxidants. 

 Antioxidants are vital since they scavenge free radicals, compounds that cause cellular damage and early aging when produced in high amounts. Free radicals are natural byproducts of metabolism in the body. 

There should be a balance between antioxidants and free radicals in the body. An imbalance between these two substances results in oxidative stress. To counter oxidative stress, increasing antioxidants through supplementation is one of the keys to a healthier and longer life. 

Quercetin is one of the powerful antioxidants that can be sourced outside the body. 

What is quercetin? 

Quercetin is a powerful antioxidant found in many fruits and vegetables. This antioxidant is present as a pigment in fruits, plants, and vegetables. Quercetin belongs to a group of antioxidants called flavonoids.

However, quercetin is not naturally produced in the human body and has to be taken as a supplement or eaten from fruits and vegetables rich in quercetin pigments. 

The antioxidant quercetin is well supported in research to have the potential to treat or manage the following: 

  • Alzheimer’s disease 
  • Cancer
  • Cardiovascular diseases 
  • Arthritis 
  • Type 2 diabetes

Due to its anti-inflammatory effects, it can potentially treat several neurodegenerative diseases, cardiovascular diseases, and long-term autoimmune disorders. 

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What fruits or vegetables are rich in quercetin? 

Now that we understand the significance of quercetin in promoting health, let’s dive into the world of quercetin-rich foods. These flavorful and nutrient-packed options not only tantalize your taste buds but also provide a substantial dose of this potent antioxidant.

1. Onions 

Onions come in yellow, red, and pink varieties and are rich in phytochemicals. These phytochemicals include phenolics, flavonoids, copaenes, carotenoids, vitamins, amino acids, and anthocyanins.

They are used to garnish and season food. Their aromatic flavors add to the taste of your everyday dish. However, an interesting fact about onions is that they are rich in quercetin, even higher than other fruits and vegetables containing quercetin. 

The total quercetin content of onion is about 300 mg/kg [1]. However, not all onion varieties have the same quercetin content. The yellow (chartreuse onion) varieties contain the highest levels of quercetin, followed by red and pink onions. The pink types contain the lowest amount of quercetin. 

Storage factors also affect the amount of quercetin found in the onions. Those stored in higher temperatures, such as 30 degrees Celsius, and those reserved for more extended periods tend to have lesser quantities of quercetin than fresh onions and those stored in colder temperatures. 

Interestingly, a study [2] also found that genetic factors play a role in the amount of quercetin in onions. Interbreeding of onions could be a potential answer in producing onions with high amounts of quercetin. 

Onions can be eaten raw or cooked with your favorite dish. Although the total levels of quercetin may change with cooking, the reduction of quercetin is not significant. 

2. Apples 

Apples are well known to be rich sources of phytochemicals, including quercetin. On average, an apple has approximately 4.4 mg of quercetin.

You can eat apples raw or cooked and still enjoy their quercetin. While cooking or heating can remove some quercetin, the amounts released are not significantly high. 

The common phrase, “an apple a day keeps the doctor away,” rings more true today with the wealth of information from research studies on apples. Apples are known to have protective effects against many diseases, including cancer [3].

Similar to onions, apples also have high levels of quercetin and are rich in other phytochemicals that can protect the body against many illnesses. 

3. Grapes 

Grapes, the main components of the Mediterranean diet, are composed of glucose and fructose, sugars, water, vitamins, minerals, and phytochemicals.

The Airen grape variety has been shown to contain the highest amount of quercetin [4]. However, eating grapes raw would best preserve the amount of quercetin in the fruit.

Processing food, such as turning it into juice, lowers the amount of quercetin and destabilizes the structure of this compound. Hence, the next time you want to reap the benefits of grapes, you can eat them raw. 

4. Berries

Berries are regarded as rich sources of phytochemicals, including the flavonoid quercetin. The good news is that eating berries raw increases quercetin’s bioavailability in the blood.

Eating 100 grams of berries daily can increase quercetin’s bioavailability by 50% [5]. This is high enough to reap the benefits of this vital antioxidant in the body. 

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5. Peppers

Peppers are used to garnish and season food. There are many varieties of peppers grown across the world.

Despite where they are cultivated and grown, all have high levels of quercetin. However, as with onions, not all bell peppers are equal. The red pepper contains the highest quercetin, followed by orange, yellow, and green peppers [6]. 

Antioxidants are known to scavenge free radicals in the body. The green pepper has the lowest scavenging activity of the four varieties of peppers. However, this is similar to the other peppers, suggesting that you can eat any type of pepper to get the benefits of quercetin

6. Kale

Kale, often hailed as a nutritional superstar, also boasts a significant quercetin content, making it a fantastic addition to your diet. This leafy green vegetable contains vitamins, minerals, and antioxidants that contribute to your overall well-being. 

Known for its impressive quercetin content, kale is one of the top sources of this antioxidant among leafy greens, with approximately 7-9 milligrams of quercetin per 100 grams of raw kale.

Beyond quercetin, kale is a nutritional powerhouse, providing essential nutrients like vitamin K, vitamin C, vitamin A, and fiber. It’s also low in calories, making it a weight-conscious choice.

Consuming kale can help reduce inflammation, support heart health, and boost your immune system, thanks to its quercetin content. Additionally, kale is associated with improved digestion and better skin health.

7. Broccoli

Broccoli is well known to be rich in phytochemicals, including different types of flavonoids. This vegetable is also high in quercetin. However, cooking broccoli can reduce the amounts of quercetin in the vegetable [7]. 

The quercetin in broccoli contributes to its anti-inflammatory properties, making it beneficial for reducing the risk of chronic diseases. Broccoli consumption is also associated with improved heart health and digestive regularity.

Broccoli contains a notable amount of quercetin, with approximately 2-3 milligrams per 100 grams of raw broccoli. While it may not have the highest quercetin levels among vegetables, it’s still a valuable source.

To retain the maximum quercetin content, it’s best to lightly steam or sauté broccoli. Overcooking may lead to some nutrient loss, so aim for a tender-crisp texture.

8. Tea

Tea, in particular green tea, is rich in phytochemicals and flavonoids such as quercetin. A cup (about 100 ml) of green tea contains at least 2.49 milligrams of quercetin.

Apart from quercetin, it is a rich source of vitamins and epigallocatechin-3-gallate, another powerful antioxidant. Supplementation with green tea extracts can boost the level of quercetin in your body [8]. 

tea

What are the health effects of quercetin?

Supplementation with quercetin is one way of boosting the levels of this powerful antioxidant and flavonoid in your body.

Currently, quercetin supplements are available as pills or capsules. A daily dose of 500 mg of quercetin is found to be safe and effective in treating or managing various illnesses, including type 2 diabetes. 

Although quercetin supplements are generally safe, individuals taking these supplements still report a few side effects. Some of these side effects include the following: 

  • Stomach aches 
  • Headaches 

When planning to take quercetin supplements, it is best to take lower doses. A dose of 1000 mg daily can increase the risk of kidney damage where quercetin is excreted.

Pregnant women and older patients are also advised not to take quercetin since there are few studies examining quercetin’s long-term safety or toxicity on these individuals. 

Longevity, or a long and healthy lifespan, is within reach today through supplementing powerful antioxidants such as quercetin. 

Always seek advice from your doctor when taking supplements for quercetin. You can choose to eat foods rich in quercetin or take supplements where you are assured that appropriate levels of quercetin are available in the blood and absorbed in the body. 

Conclusion

Quercetin is a remarkable flavonoid antioxidant in various foods that offers many health benefits. We’ve explored eight quercetin-rich foods, and these foods not only provide a potent dose of quercetin but also offer a wide range of vitamins, minerals, and other essential nutrients.

Incorporating these quercetin-rich foods into your daily diet can be a delicious and nutritious way to support your health. However, it’s essential to remember that a balanced diet, rich in various fruits, vegetables, and other nutrient-dense foods, is key to overall health.

While quercetin is a valuable component, it should be part of a holistic approach to nutrition and wellness. Experiment with different recipes, mix and match these foods, and discover delicious ways to enhance your well-being.

FAQs

Which food is highest in quercetin?

Red onions have the highest concentration of quercetin among common foods, making them an excellent choice to increase your quercetin intake.

What is the most effective form of quercetin?

Quercetin supplements in capsule or tablet form are often considered the most effective way to ensure a consistent and concentrated dose of quercetin, but it’s essential to follow recommended dosages.

Which plant has the most quercetin?

Among plants, buckwheat stands out as one of the highest natural sources of quercetin, making it a valuable addition to a quercetin-rich diet.

Is ginger high in quercetin?

While ginger does contain quercetin, it’s not among the top sources, so it’s not considered particularly high in quercetin compared to other foods like onions or apples.

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[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4486465/ 
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5562462/ 
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC442131/ 
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8306294/ 
[5] https://pubmed.ncbi.nlm.nih.gov/16800769/ 
[6] https://pubmed.ncbi.nlm.nih.gov/17995862/ 
[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6407093/ 
[8] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5537887/ 

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