Quercetin: What It Is, What It’s Used For, Benefits and How to Take It

Alfredo Valdés 8 min. of reading Antioxidants Leave a comment

Quercetin is a natural flavonoid found in numerous plant-based foods, particularly fruits, vegetables and certain herbal infusions. It is known for its antioxidant properties and its involvement in various biological processes that have attracted scientific interest.

But what is quercetin used for? What are its main benefits, and how can we incorporate it into our diet?

Here’s everything you need to know about this plant compound.

What Is Quercetin?

Quercetin, also known as quercetol, is a natural compound belonging to the flavonoid family, specifically the flavonol group.

Flavonoids are plant substances involved in various functions, including pigmentation and protection against certain environmental factors.

Quercetin occurs naturally in foods such as onions, apples, capers, grapes and tea.

Its main characteristic is its antioxidant activity, although other properties related to inflammatory responses and various physiological processes are also being investigated.

What Is Quercetin Used For? Properties and Benefits

Quercetin has been the subject of numerous scientific studies due to its various biological activities. Some of the most extensively researched properties of quercetin include the following.

1. Antioxidant Properties

One of the best-known characteristics of quercetin is its ability to interact with free radicals.

These compounds are naturally produced during cellular metabolism, although excessive accumulation can contribute to oxidative stress.

Quercetin has demonstrated antioxidant activity in experimental studies, which is why researchers are investigating its potential involvement in mechanisms related to cellular protection.

2. Anti-inflammatory Activity

Quercetin has also attracted interest because of its interaction with different mechanisms involved in inflammatory responses. Some experimental research has observed that it may modulate certain cellular signalling pathways and mediators associated with inflammation.

3. Quercetin and Cardiovascular Health

Another area of research focuses on its potential relationship with vascular function and certain cardiovascular parameters. Some clinical trials have investigated its effects on blood pressure and other indicators associated with circulatory health.

However, the results depend on factors such as dosage, intervention duration and the characteristics of the participants.

4. Quercetin and Allergies

One of the most interesting areas of research involving this flavonoid concerns mast cells, which are involved in the release of histamine.

Histamine plays a role in various bodily responses, including allergic reactions. In experimental studies, quercetin has shown the ability to influence certain mechanisms associated with histamine release.

5. Quercetin and Physical Exercise

Intense exercise can temporarily increase certain markers of oxidative stress and inflammation as part of the body’s normal adaptations to training.

For this reason, quercetin has also been investigated in the field of sports nutrition.

Some studies have evaluated its relationship with recovery, immune response and physical performance, although the available results are mixed.

Which Foods Contain the Most Quercetin?

Quercetin is found in numerous plant-based foods, making a varied diet a simple way to incorporate it into your daily nutrition.

Some of the most notable quercetin-rich foods include:

Food	Characteristics
Capers	Among the most concentrated dietary sources of quercetin.
Red and yellow onions	Notable for their flavonol content.
Apples	Quercetin is particularly concentrated in the skin.
Red berries	Blueberries, cherries and other berries provide various polyphenols.
Grapes	Contain quercetin and other phenolic compounds.
Green and black tea	Provide different flavonoids, including quercetin.

The amount of quercetin may vary depending on the plant variety, growing conditions, storage and food preparation methods.

Tip: Eating a variety of fruits and vegetables, including some with their skins when appropriate, helps incorporate different types of polyphenols into your everyday diet.

Quercetin in Food Supplements

In addition to occurring naturally in foods, quercetin is also marketed as an ingredient in food supplements, usually in capsules or tablets.

These products provide defined amounts of quercetin, generally higher than those obtained from a typical serving of food.

One aspect being investigated in supplement formulations is bioavailability, meaning the proportion of a compound that can be absorbed and reach the bloodstream.

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Quercetin with Vitamin C: Why Are They Combined?

Quercetin and vitamin C are two compounds that have been studied together for their antioxidant properties.

Vitamin C contributes to the protection of cells from oxidative stress, a function recognised by the European Food Safety Authority (EFSA).

Their combination is being investigated due to potential interactions between the two compounds.

How to Take Quercetin and What Is the Recommended Dosage?

There is no universally established daily dose of quercetin for the general population, although doses between 500 and 1,000 mg per day are frequently used, depending on the intended purpose.

When taking food supplements, it is advisable to follow the manufacturer’s instructions and not exceed the recommended daily dose.

When Is the Best Time to Take Quercetin?

Quercetin can be taken with a meal, particularly to make it easier to incorporate into a daily routine or to improve digestive tolerance.

There is insufficient evidence to establish that taking it at a particular time of day generally produces better results.

Contraindications and Possible Side Effects of Quercetin

Quercetin naturally present in foods is part of a normal diet. However, consuming it in the form of concentrated supplements requires certain precautions.

In some circumstances, digestive discomfort, headaches or other adverse reactions may occur. It is also important to consider the following:

Pregnancy and breastfeeding: There is insufficient information regarding the safety of quercetin supplementation.
Medication: Quercetin may interact with certain medicines, so a healthcare professional should be consulted before taking it.
Kidney or liver conditions: Medical advice is recommended before using concentrated supplements.
Long-term use: Information regarding its long-term safety remains limited.

Frequently Asked Questions About Quercetin

What are the benefits of taking quercetin?
Quercetin is known for its antioxidant properties and its biological activity in various cellular processes. Its potential effects on inflammatory responses, cardiovascular function and the immune system are currently being investigated.
Can you take quercetin every day?
Quercetin is naturally consumed every day through foods such as onions, apples and capers. When it comes to food supplements, consumption should follow the manufacturer’s instructions.
How long does quercetin take to work?
There is no established timeframe for observing effects from quercetin supplementation. Absorption begins after ingestion, but this does not mean that noticeable benefits occur immediately.
The results investigated depend on the dosage, formulation and duration of consumption.
Is it better to take quercetin alone or with vitamin C?
Both substances exhibit antioxidant activity, although they act through different mechanisms. Vitamin C contributes to protecting cells from oxidative stress, while quercetin has demonstrated antioxidant properties in experimental studies.
Which food is highest in quercetin?
Capers are among the foods with the highest concentrations of quercetin. Red and yellow onions, apples with their skins, grapes and certain berries are also notable sources. Their content may vary depending on the variety, growing conditions and food processing methods.

Conclusion: Is It Worth Adding Quercetin to Your Diet?

Quercetin is one of the most extensively studied plant flavonoids due to its antioxidant properties and interactions with various cellular processes.

Although research into its potential benefits continues to advance, it is important to distinguish experimental findings from effects demonstrated in humans.

Including quercetin-rich foods such as onions, apples, berries and capers is a simple way to increase the variety of plant compounds in your diet.

Food supplements, meanwhile, allow specific amounts of quercetin to be consumed, provided that usage recommendations and relevant precautions are followed.

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