Quercetin - Benefits, Dosage, Supplements & More


What is Quercetin

Quercetin is a natural chemical that is found in some plants and has been shown to have a wide range of health benefits. Quercetin is a flavonoid, a group of plant metabolites thought to provide health benefits through cell signalling pathways and antioxidant effects. Flavonoids are polyphenolic molecules containing 15 carbon atoms and are soluble in water. The body doesn’t make quercetin, so you have to get it from plants or in a quercetin supplement. The best food sources of quercetin include; onions, citrus fruits green leafy vegetables, such as broccoli, seeds, olive oil, red grapes.

A single serving of onions is considered to be one medium onion, which contains approximately 50 milligrams (mg) of quercetin. But most people tend to not eat a whole onion in one sitting so you’re probably not getting quite that much quercetin when you eat onions.

Even with all these natural sources of quercetin, it’s estimated that most people following a typical Western diet only get 0 to 30mg of Quercetin a day. That’s not a lot, considering research shows that some of quercetin’s health benefits are reached at supplemental intake levels of 500 to 1,000 mg per day.

It’s also available as a dietary supplement in powder and capsule form.

People take a Quercetin supplement for several health benefits such as;

  1. Preventing Infection
  2. Boost immunity
  3. Reduce inflammation
  4. Combat allergies
  5. Aid exercise performance
  6. Maintain general health

Science-based Benefit Benefits of quercetin

Quercetin is a safe natural anti-oxidant and anti-inflammatory polyphenolic compound that found in various natural sources include onion, red grapes, honey and citrus fruits. It was shown that quercetin has the ability to chelate zinc ions and act as zinc ionophore. Therefore, quercetin could have antiviral activity against many RNA viruses. It has unique biological properties that may improve mental/physical performance and reduce infection risk. These properties form the basis for potential benefits to overall health and disease resistance, including anti-carcinogenic, anti-inflammatory, antiviral, antioxidant, and psychostimulant activities. They also have the ability to inhibit lipid peroxidation, platelet aggregation and capillary permeability, and to stimulate mitochondrial biogenesis.

What does quercetin do in the body?

It can protect the body from free radicals – according to a 2008 study by Maastricht University, Netherlands, quercetin acts as a powerful antioxidant, helping to protect cells from damage by free radicals: unstable molecules that can age the body and may lead to serious health conditions.

It can reduce inflammation – a 2016 Malysian study reported that quercetin hinders the action of inflammatory enzymes that would otherwise activate the immune system and cause inflammation.8 Indeed, an earlier study, published in 2012 by Iran’s Isfahan University of Medical Sciences, found that giving healthy male athletes a combination of quercetin and vitamin C for eight weeks reduced blood test markers for inflammation in the body.

Nootropic – It may also drop inflammation in the brain which improves signalling to the rest of the body. When the brain becomes inflamed, it becomes less efficient and therefore Quercetin can act as a nootropic.

It may help reduce blood pressure – a meta-analysis of seven trials carried out by the USA’s University of Alabama in 2016 reported that taking 500mg or more of quercetin a day significantly reduced blood pressure levels. How this happens is still not fully understood but one theory is that quercetin may act on cells that control blood vessel contraction and dilation, improving blood flow.

It may act as a natural antihistamine – quercetin stimulates the immune system and restricts the release of histamine in the body, relieving allergy symptoms in conditions like hay fever, according to a 2016 study published in Molecules.

It could have anti-bacterial and anti-viral properties – a 2017 study in Microbiology Research found the phytonutrient could prevent the replication of bacteria, including E. Coli. In addition, a 2014 review by the University of Michigan, USA, suggested quercetin also blocked several respiratory viruses from replicating inside the body, including the common cold and flu.

It can help regulate blood sugar – according to a 2019 review of studies, published in Phytotherapy Research, taking 500mg or more of quercetin daily for at least eight weeks reduced blood glucose levels in people with metabolic syndrome, who have an increased risk of developing heart disease, stroke and diabetes.

Research studies done on Quercetin

May have anticancer effects.

Because quercetin has antioxidant properties, it may have cancer-fighting properties.

In a review of test-tube and animal studies, quercetin was found to suppress cell growth and induce cell death in prostate cancer cells https://www.spandidos-publications.com/or/33/6/2659

Other test-tube and animal studies observed that the compound had similar effects in liver, lung, breast, bladder, blood, colon, ovarian, lymphoid, and adrenal cancer cells. https://pubmed.ncbi.nlm.nih.gov/24223637/

Though these findings are promising, human studies are needed before quercetin can be recommended as an alternative treatment for cancer.

May lower your risk of chronic brain disorders

Research suggests that quercetin’s antioxidant properties may help protect against degenerative brain disorders, such as Alzheimer’s disease and dementia 

In one study, mice with Alzheimer’s disease received quercetin injections every 2 days for 3 months.

By the end of the study, the injections had reversed several markers of Alzheimer’s, and the mice performed much better on learning tests.

In another study, a quercetin-rich diet reduced markers of Alzheimer’s disease and improved brain function in mice at the early middle stage of the condition.

However, the diet had little to no effect on animals with middle-late stage Alzheimer’s.Coffee is a popular beverage that has been linked to a lower risk of Alzheimer’s disease. In fact, research shows that quercetin, not caffeine, is the primary compound in coffee that’s responsible for its potential protective effects against this illness.

Though these findings are promising, more research in humans is needed.

May reduce blood pressure

High blood pressure affects 1 in 3 American adults. It raises your risk of heart disease — the leading cause of death in the United States.

Research suggests that quercetin may help reduce blood pressure levels. In test-tube studies, the compound appeared to have a relaxing effect on blood vessels.

When mice with high blood pressure were given quercetin daily for 5 weeks, their systolic and diastolic blood pressure values (the upper and lower numbers) decreased by an average of 18% and 23%, respectively.

Similarly, a review of 9 human studies in 580 people found that taking more than 500 mg of quercetin in supplement form daily reduced systolic and diastolic blood pressure by an average of 5.8 mm Hg and 2.6 mm Hg, respectively.

Although these findings are promising, more human studies are needed to determine whether the compound could be an alternative therapy for high blood pressure levels.


How much quercetin is safe to take?

As mentioned previously, It’s highly unlikely that you will be able to get enough quercetin from your diet in order to feel the benefits you get from supplementation. A dose of 500-1000mg a day are considered safe.

Quercetin is found naturally in many plant-based foods, particularly in the outer layer or peel. We have listed some foods you can finds Quercetin in.


peppers — yellow and green

onions — red and white


asparagus — cooked



red apples

red grapes



red leaf lettuce

berries — all types, such as cranberries, blueberries, and raspberries

tea — green and black

Note that the amount of quercetin in foods may depend on the conditions in which the food was grown.

Don’t take quercetin if you are pregnant or breast-feeding as there isn’t enough evidence to show it’s safe. Quercetin can interact with certain medications, so speak to your GP before taking quercetin supplements.

Quercetin supplements

You can purchase quercetin as a dietary supplement online and from health food stores. It’s available in several forms, including capsules and powders.

Typical dosages range from 500–1,000 mg per day

On its own, quercetin has a low bioavailability, which means your body absorbs it poorly.

That’s why the supplements may include other compounds, such as vitamin C or digestive enzymes like bromelain, as they may increase absorption

Our Quercetin Complex supplement provides high-quality quercetin combined with the ideal blend of bromelain, bioflavonoids and vitamin C for antioxidant support.

Side-effects of quercetin?

Quercetin is considered safe to take for healthy people. However, it can have side- effects including: Headaches, nausea, numbness and tingling


Finally, quercetin is the most readily available dietary flavonoid. It’s been linked to improved exercise performance and reduced inflammation, blood pressure, and blood sugar levels. Plus, it may have brain-protective, anti-allergy, and anticancer properties.

The initial benefits seem promising and more human research is currently been carried out.

Quercetin is a flavonoid found in fruit and vegetables. It has a wide range of benefits, which people can get by supplementing alongside a balanced diet.

Although many studies have found many potential benefits of quercetin, many of these studies have been animal or in vitro studies.

Further research on humans is necessary to understand the benefits and side effects fully.

If people want to supplement their diet with quercetin, they should seek advice from a healthcare professional first.

Quercetin is available from our store.