Print Friendly, PDF & Email

The health benefits of Quercetin have been recognized for as long as 3,500 years. The people of antiquity put great value on the Quercetin-rich pomegranate juice as an elixir of good health. Nowadays, Quercetin supplements can be purchased at very little expense and can provide enormous benefits to those wanting to heal or optimize their health.

In this post, we will explore the science to reveal the full range of benefits that Quercetin offers, before hinting at the best ways in which you can get extra Quercetin into your diet and supplement regime.

Quercetin Snapshot

I personally don’t take quercetin because it has poor absorption. I’ve tried doses as high as 2000mg and don’t notice anything.

Most of the studies brought down here are done in animals in various conditions.  Also, it’s important to note that all of the benefits below are dependent on quercetin being absorbed, so many of these benefits may not translate to people.


  • Anti-inflammatory
  • Protects against a wide range of health conditions


  • Bioavailability is not good
  • May alter thyroid function
  • Inhibits COMT

What is Quercetin?

Quercetin belongs to a group of plant pigments, called flavonoids, that give many vegetables and fruits their color. Quercetin is the most widely consumed flavonoid in the human diet (R).

Like all flavonoids, Quercetin demonstrates antioxidant defense by scavenging free radicals and inhibiting oxidation of various molecules. In doing so, Quercetin protects against the negative effects of free radicals, such as cell membrane damage, DNA alterations and cell death (R, R1)

By protecting the body against the damage wrought by these free radicals, Quercetin can protect against a wide range of health conditions that we will now explore.

Benefits of Quercetin

1) Quercetin Protects the Brain

Quercetin is a powerful antioxidant that may protect brain cells from oxidative stress (R).

Quercetin protects the brain from toxicity associated with D-galactose. This protection is associated with Quercetin’s ability to increase superoxide dismutase (SOD) activity and decrease levels of malondialdehyde (MDA) (R).

Flavonoids, including Quercetin, inhibit the pro-inflammatory molecules that are associated with many progressive brain disorders. These include Alzheimer’s disease, viral and bacterial meningitis, AIDS dementia complex, and stroke (R).

Quercetin reverses cognitive deficits in aged and lipopolysaccharide-intoxicated mice (R).

Neuroleptics, used in the treatment of schizophrenia and other brain-related disorders, are often associated with side effects involving movement disorders, similar to Parkinson’s. In mice, pretreatment with Quercetin reduces the side effects of neuroleptic medications (R).

2) Quercetin Might Heal Leaky Gut

Research has found that chronic stress can cause mast cells in the gut to become unstable; a process that leads to increased permeability of the gut wall (leaky gut) (R, R1).

Quercetin stabilizes these mast cells, thereby preventing and healing leaky gut (R, R1).

Quercetin has also been shown to tighten the junctions between the cells in the gut. In doing so it helps prevent unwanted food particles from entering the bloodstream (R).

Quercetin reverses leaky gut in rodents that are given a substance that induces colon damage (R).

3) Quercetin is Anti-inflammatory

Quercetin decreases pro-inflammatory cytokines which can lead to tissue damage in humans (R).

Quercetin inhibits the genetic expression of pro-inflammatory TNF-a (R).

One study found that men who took Quercetin experienced fewer symptoms of prostatitis – inflammation of the prostate (R).

Quercetin decreases the release of MCP-1IL-6, and IL-8, which are all pro-inflammatory (R).

Quercetin inhibits the formation of prostaglandins, key mediators in the inflammatory response (R).

4) Quercetin May Be Anti-Aging

In mice, Quercetin was found to increase exploratory behavior, spatial learning, and memory. These effects were related to Quercetin’s ability to enhance brain functions, limit oxidative stress and increase glutathione levels. The authors conclude that these findings suggest that Quercetin may work as a possible natural anti-aging supplement (R).

Quercetin was found to extend the lifespan and increase stress resistance of worms (R).

A second study confirmed that Quercetin increases the ability of worms to handle stress, both thermal and oxidative while increasing their average lifespan by 15% (R).

However, it is unclear how well these worm studies translate to mammals. A 2013 study found that Quercetin does not extend the lifespan of animals. More research is needed (R).

5) Quercetin May Prevent Cancer

Scientists have long considered Quercetin, and other flavonoids contained in fruits and vegetables, important in cancer prevention. People who eat more fruits and vegetables tend to have a lower risk of certain types of cancer (R).

In fact, smokers who consume lots of antioxidant-rich phenols have enhanced protection against cancer (R).

Quercetin lowers TNF-a and, therefore, lowers the risk of cancer; TNF-a encourages the growth and spreading of most tumor cells. In fact, mice with TNF-a deficiency are resistant to skin cancer (R).

This fits in with other studies demonstrating the anti-cancer properties of flavonoids that lower TNF-a (R).

Frequent intake of Quercetin-rich foods leads to a lower risk of developing lung cancer. The association was even stronger among subjects who smoked more than 20 cigarettes daily (R)

Quercetin slows tumor growth in leukemia cell studies (R)

Quercetin stops fast reproducing cancer cells when they are in an early, non-productive phase of the cell replication cycle. This freezes tumor growth and also initiates mitochondrial pathways of apoptosis (cell death) (R, R1).

Quercetin causes apoptosis (cell death) of human colon cancer cells by inhibiting the NF-κB pathway (R).

It has been shown that Quercetin induces the death of leukemia cells in by inhibiting Cox-2 expression and regulating the expression of biological processes involves in apoptosis (cell death) (R).

Quercetin enhances the efficacy of conventional chemotherapeutic drugs, like doxorubicin (R).

Some researchers have concluded that Quercetin may be a useful treatment for rare cancers that are resistant to conventional drugs (R).

One study found that Quercetin caused toxicity in leukemic and breast cancer cells but had no effect on normal, healthy cells (R).

Giving Quercetin to mice with leukemia led to a 5-fold increase in the lifespan compared to that of untreated controls (R).

6) Quercetin Reduces the Histamine Response

Quercetin has been shown to control the release of histamine, leukotrienes, and prostaglandins (R).

Quercetin suppresses H1R (Histamine H1 Receptor) gene expression (by suppressing of Protein-Kinase C-δ activation) (R).

I recommend a Quercetin supplement to a lot of my clients who have histamine issues, especially if they are TH2-dominant.

7) Quercetin is Antibacterial

Quercetin exerts antibacterial activity against various types of Staphylococcus infections, including antibiotic-resistant S. aureus (MRSA) (R).

One study showed that Quercetin increases the susceptibility of MRSA to other antibacterial compounds (R, R1)

Quercetin shows antibacterial activity against the H. Pylori infection (R)

Quercetin inhibits the growth of a wide range of oral bacteria. Therefore, it may be a useful treatment for dental cavities, gum infections and oral mucosa infectious diseases (R).

The antibacterial properties of Quercetin are at least partially attributed to its ability to inhibit DNA gyrase – an important enzyme involved in DNA unfolding (R).

Quercetin offers an effective alternative to the immediate dangers of antibiotic usage and the possibility of a global antibiotic resistance (R).

8) Quercetin Limits, and Protects Against, Obesity

In mice, Quercetin supplementation reduced body weight by nearly 40% and suppressed the expression of fat cell metabolism and inflammation-related cytokines (R).

By modulating AMPK and MAPK pathways, Quercetin inhibits the formation of fat cells and trigger existing fat cells to self-destruct (R).

In mice, dietary Quercetin reduced body weight gain caused by a high-fat diet and improved insulin sensitivity and glucose intolerance in mice (R).

Quercetin-treated mice showed enhanced GLUT4 translocation and AKT signaling in fat tissues, suggesting Quercetin increases glucose uptake in fat tissues (R).

Quercetin inhibits fat accumulation and obesity-induced inflammation in cell studies (R).

In rats, Quercetin reduces obesity-induced skeletal muscle wasting by inhibiting inflammatory receptors and their signaling pathway (R).

High dose Quercetin administration reduced blood glucose levels, improved blood lipids and reduced high blood pressure in obese rats (R).

9) Quercetin May Prevents and Treat Diabetes

Mice fed on a Quercetin-rich diet for seven weeks showed a reduction in blood glucose levels and blood glycated hemoglobin without any changes in insulin. This was possibly due to the inhibition of small intestine maltase activity (R).

Rats with type-1 diabetes, who were given Quercetin (10-15 mg/kg body weight) for 10 days, showed significantly lowered blood sugar levels (R).

Quercetin added to the diet of diabetic mice led to the recovery of cell proliferation (R).

In genetically obese rats, Quercetin supplementation improved insulin resistance (R).

Quercetin’s inhibitory effect on glucose uptake may be due to its action on the glucose transporter GLUT4 (R).

Quercetin alters the ERK1/2 pathway, which plays an important role in the regulation of glucose-induced insulin secretion (R, R1).

One cell study analyzed the effects of ten compounds present in berries on glucose uptake. Two forms of Quercetin (Quercetin-3- O-glycoside and Quercetin aglycone) were the most potent compounds for regulating glucose uptake via the AMPK pathway (R, R1).

By inhibiting the NF-kb pathway, Quercetin may block the production of toxins involved in the development of tissue injuries often seen in diabetic subjects (R).

10) Quercetin Reduces Symptoms of Arthritis

There are reports of people with Rheumatoid Arthritis who had fewer symptoms when they switched from a typical Western diet (meat heavy) to one with lots of berries, fruits, vegetables, nuts, roots, seeds, and sprouts containing Quercetin and other antioxidants (R).

A cell study found that Quercetin inhibited neutrophil activation and synoviocyte proliferation – two key factors in the development and proliferation of arthritis (R).

As discussed above, Quercetin inhibits inflammatory cytokines, MMP-9 and TNF-a. This might explain why Quercetin, at 750mg per day, takes just 2-3 days to ease arthritic pain and inflammation (R).

Quercetin has a key advantage over conventional arthritis drugs (such as methotrexate and paclitaxel) in that it doesn’t cause serious systemic toxicity (R).

11) Quercetin is Good For Your Heart

Daily doses of Quercetin reduces systolic blood pressure (R).

Quercetin-rich supplementation from onion peel extract improved blood lipid profiles, glucose, and blood pressure – all of which are important factors in heart health (R).

Regular Quercetin supplementation provides beneficial effects on blood lipid behavior, especially in cigarette smokers who are exposed to a high degree of oxidative stress and are particularly susceptible to the development of coronary heart disease (R)

Lastly, a study found that 500mg of Quercetin per day significantly reduced HDL cholesterol (R).

12) Quercetin May Reduce Allergies

Lactose, eggs, peanuts, fish, wheat, shellfish, tree nuts, and soy can all trigger an immunoglobulin E (IgE) allergic response (R).

Quercetin is a potent suppressor of IgE allergic responses and, therefore, should be used as an alternative medicine to treat IgE-mediated food allergies (R).

Mast cells, which are activated during an allergic response, promote inflammation by releasing molecules such as histamine, leukotrienes, cytokines chemokines, and neutral proteases. Quercetin inhibits human mast cell activation by controlling the amount of calcium that enters each cell (R).

The histamine H1 receptor (H1R) gene is up-regulated in patients with allergic hay fever.  The level of H1R expression correlates with the severity of allergic symptoms. Quercetin inhibits the up-regulation of histamine H1 receptor (R).

13) Quercetin Enhances the Immune System

Clinical trials have shown that Quercetin reduces susceptibility to viral illnesses (R).

Because they stretch their bodies to exhaustion so frequently, endurance athletes are more susceptible to getting sick than normal people. One study showed taking 1000 milligrams of Quercetin a day protected cyclists from developing exercise-induced respiratory infections following heavy training (R).

14) Quercetin May Improve Athletic Endurance

Quercetin improves human endurance exercise capacity (VO2 max and performance) (R, R1).

In just seven days, Quercetin supplementation (500mg taken twice per day) increased endurance without exercise training (R).

15) Quercetin Reduces Blood Pressure

Quercetin decreases blood pressure and reduces the severity of hypertension (R)

Quercetin improves the function of endothelial cells and vascular smooth muscle, which are responsible for governing blood pressure (R).

16) Quercetin May Protect the Liver

Treatment with Quercetin, prior to receiving toxic amounts of ethanol, protected the liver of rats against oxidative stress by neutralizing the products of lipid peroxidation and increasing the production of the antioxidant Glutathione (R, R1).

Quercetin limited the cytotoxicity and oxidative stress that would otherwise occur in the livers of rats that were given a diet rich in aflatoxin (R).

Quercetin can mitigate acetaminophen-induced liver toxicity by reducing reactive oxygen and nitrogen species (R).

Rats with diet-induced liver damage that were then given Quercetin showed decreased levels of liver damage enzymes, lipoperoxidation, DNA damage and a lower degree of overall inflammatory processes (R).

Quercetin protects against obesity-induced fatty liver disease by stimulating mitochondrial oxidative metabolism in the liver (R).

17) Quercetin May Protect the Kidneys

Quercetin reduces damage done to the kidneys of rats that are administered toxic substances, such as chemotherapy drugs (R).

A compound called Fe-NTA induces significant oxidative stress in the kidneys. Quercetin substantially reduces kidney dysfunction and structural changes while restoring depleted kidney antioxidant enzymes (R).

18) Quercetin is Good for Circulation

Quercetin improves the health of your blood vessels by increasing the products of nitric oxide and reducing endothelin-1 concentrations (R).

19) Quercetin Might Improve Your Sex-life

Oxidative stress is a primary cause of erectile dysfunction (inability to get or maintain an erection). Quercetin treats erectile dysfunction by reducing levels of oxidative stress in diabetic mice (R).

20) Quercetin is an Asthma Treatment

Quercetin relaxes smooth muscle that lines the airways and, therefore, may provide therapeutic relief of asthma symptoms and decrease reliance on conventional, short-term asthma treatments (R).

21) Quercetin May Protects Your Eyes

Quercetin reduces the risk of cataracts by acting on a number of pathways that play important roles in eye lens function (e.g. oxidative stress, non-enzymatic glycation, and epithelial cell signaling) (R).

Retinal cells are found at the back of your eye and act as light receptors, playing an important role in setting the color, resolution, and brightness of your vision. Quercetin has a protective effect on retinal cells (R).

Aldose reductase (AR) is an enzyme that can accumulate in the lenses of people with consistently high blood sugar, such as diabetics, and cause significant eye problems. Quercetin can limit the negative consequences of high AR on eyes (R).

In animals, Quercetin enhances lens clarity (R).

Finally, The National Eye Institute found that Quercetin behaves as a powerful antioxidant and prevents inflammation in eye tissues (R).

22) Quercetin May Protect Against Radiation

Quercetin mitigates the damage done to the skin of rodents that are exposed to X-ray radiation, which would otherwise induce skin fibrosis (R).

23) Quercetin Works with Resveratrol to Increase Its Effects

The combination of quercetin and resveratrol, a compound/polyphenol from grapes, can also have more health benefits. For example, they combine their effects together to inhibit colon cancer and increase cancer cell death (apoptosis) in human cell culture (R).

In rats, this combination also significantly reduced fat tissue. In contrast, resveratrol or quercetin alone did not have any effect on the fat tissue. The combination of resveratrol and quercetin is synergistic (R).

Future Studies

As mentioned, Quercetin lowers TNF-a. High TNF-a levels are associated with the following diseases: Crohn’s, Alzheimer’s, Rheumatoid Arthritis, Psoriasis, and Ankylosing Spondylitis. Antibodies raised against TNF-α are now commercially available under prescription and are proving beneficial for many patients.

Because of the impact of Quercetin on TNF-a, it is likely that further studies will emerge showing that Quercetin is beneficial for a whole range of health conditions.


Quercetin is a safe, natural supplement that you can use as a primary therapy or in conjunction with conventional methods (R).

However, there have been a small number of reports indicating that Quercetin can act as a thyroid disruptor. Thus, you should think carefully when considering its supplemental and therapeutic application in those with existing thyroid irregularities (R).

Quercetin Has Toxic Effects on Neurons

While quercetin has antioxidant effects, not enough is known about its effects on healthy cells. In rat nerve cells, quercetin treatment for 24 hours can cause cell death (R).

The nerve cells died in a concentration-dependent manner. This means that more cells died when the concentration of quercetin was higher. Additionally, the cells died in an equal manner of apoptosis (programmed cell death) and necrosis (death due to injury or disease) (R).

The results of this study indicate that more caution is required when using quercetin for treating health problems (R).

Quercetin Increases Homocysteine Levels

Homocysteine is a product of protein metabolism. High concentrations of homocysteine are associated with strokes and heart attacks. In human liver cancer cell culture, quercetin significantly increased homocysteine concentration (R).

This increase in homocysteine outside of the cells (extracellular) may be related to increased methylation. Thus, people should be more cautious when using quercetin supplements (R).

Dietary Sources of Quercetin

Screen Shot 2016-07-25 at 19.41.09

Quercetin is found in a large number of foods. How the food was grown and transported will impact the concentrations of Quercetin (R).

You can enhance the absorbability of Quercetin by combining it with glucose. Thus, sugary fruit like apples and blueberries are probably a good bet for a natural Quercetin source (R).

Buy Quercetin Supplements

FDA Compliance

The information on this website has not been evaluated by the Food & Drug Administration or any other medical body. We do not aim to diagnose, treat, cure or prevent any illness or disease. Information is shared for educational purposes only. You must consult your doctor before acting on any content on this website, especially if you are pregnant, nursing, taking medication, or have a medical condition.


1 Star2 Stars3 Stars4 Stars5 Stars (34 votes, average: 4.53 out of 5)

Why did you dislike this article?



  • leah taba

    sino author?

  • Connie

    Question: there are so many benefits to taking this- but the “cons” to taking this seem to be alarming as well. Also- you mention it Lowers HDL- don’t we want higher HDL?
    I’ve just started my son on this for allergies- but I’m not sure It’s a good idea now!! Any thoughts would be appreciated.

  • James Barclay

    Some things which need to be addressed: (1)Physicians have little or no training in nutrition unless disease processes are directly related. In such cases either elimination of offending foods, or in more usual cases pharmaceuticals are prescribed. (2)Aging, for the most part, is a natural process, It is not in and of itself a disease. And it should not be addressed in such a negative way which Americans view it. In many countries old age is revered as a sign of prolonged health and wisdom. In Japan it is viewed as a form of beauty and is revered. This Western mania can itself be viewed as a pathological syndrome. (3)These advertised purgatives, if used to excess, can be highly dangerous, A conservative and “natural” approach to systemic health, especially through a sensible regime of correct diet, rest , physical activity and mental/spiritual health maintenance, should be highly encouraged. (4) Megadosing can be highly poisonous and damaging as well wasteful and should be roundly avoided. Thank you

  • Stan Hingston

    Interesting you write that quercetin has anti-bacterial properties (point 37 above).
    WEb MD warns that quercetin may reduce the effectiveness of some bacterial anti-biotics and said nothing about it improving it. Did you run across anything in your research supporting this?

  • Michelle Dixon

    I am presently taking NatureThroid for Hashimoto’s and am interested in the possible issues concerning taking Quercetin with an existing Thyroid condition.

    1. Helen

      Hi Michelle, there aren’t any available studies on quercetin and its effects on people with thyroid conditions. You may want to read this study on how it affects thyroid function in rats.

  • Rob W

    Very nice article! I am considering using quercetin to try and treat my chronic prostatitis symptoms, but I have been reading the bioavailablity of the standard quercetin supplements is pretty poor. What are your opinions on Dihydroquercetin (AKA Taxifolin)? I have been reading it is much more potent and bio-available.

    BTW, it would be awesome if you could provide any info on treating chronic prostatitis. Its a really awful condition affecting many men that deserves a lot more attention.

    1. Ted S.

      Don’t know if this will help your prostatitis. It helped my BPH. I developed eye issues taking terazosin and flowmax (blurry vision and a gray spot like a shadow in my left eye.) My eye doctor scanned my eyes and found fluid build up in the center of my retina, which explains the gray spot. I searched for a natural solution to BPH and Dr. Michael Gregor mentioned to take 3 tablespoons of ground flax seed daily. Said it had the same therapeutic value as BPH meds. It worked for my. I have fewer night time bathroom visits and a stronger stream. Maybe it will help you. I thought prostatitis was a bacterial infection. I had to take antibiotics when I had that problem twice.

  • Doug

    This study appears to show that quercetin DECREASED serum homocysteine in rats fed high levels of methionine:

  • Pater Rolf Hermann Lingen

    “High HDL cholesterol levels linked to excessive mortality”
    That is today’s (30th Aug 2017) news. Source is the Herlev and Gentofte Hospital, Copenhagen.

  • Craig

    Found it very interesting reading & only thing negative is this Thyroid question? How safe is it over short term use compared to long term use?

  • Frankie

    Can you take the bio active form daily, or do you need to do a few weeks on and a few weeks off? If breaks are necessary, do you know the durations?


  • Teri

    I’m guessing it affects the thyroid by slowing it down some since we know kale and spinach are oxylates and affect the thyroid negatively. TSH may go up or thyroid meds may need to be tweaked.., all that said thyroid disease is also inflammatory like all autoimmune diseases..and the increased master cell response I’m having sent me here to research quercitin so I’m going to try it! And monitor..

  • Scott

    FYI: quercetin is not well absorbed and isoquercetin or ALPHA-GLYCOSYL ISOQUERCITRIN might be an improvement.

    Integrated therapeutics makes ALPHA-GLYCOSYL ISOQUERCITRIN supp.

  • Alba

    I’d also like to know how quercetin affects thyroid function.

  • Karen Jon

    Lowers HDL cholesterol? Isn’t that the good one?

  • Helena Edwards

    I am on synthroid and want to take Quercetin. Should I expect TSH to increase or decrease? and thus a need for dose adjustment? How long before Quercetin causes a change in the hormones . Should TSH be rechecked at 1 week or 1 month?

  • Barb

    How does it effect the Thyroid?

  • Joseph M. Cohen

    Interesting, I don’t notice that effect at high dosages.

  • Leave a Reply

    Your email address will not be published. Required fields are marked *

    This site uses Akismet to reduce spam. Learn how your comment data is processed.