10 Best Quercetin Supplements of 2023: Benefits, Dosage and Side Effects
There is a wide selection of quercetin supplement brands available on the market. However, it can be challenging to determine which one is the best option for you. Your individual needs and preferences may differ from others, so it's essential to have a set of purchasing criteria that aligns with your health goals.
Some factors to consider when selecting a quercetin supplement include the purity and potency of the product, the form in which it is available, the recommended dosage, and the reputation of the brand. For instance, if you have difficulty swallowing pills, you may prefer a liquid or powder form of the supplement, or if you prefer a specific brand, you may choose to stick with that.
It is essential to consult with your healthcare provider before starting any new supplement regimen. They can help you determine the appropriate dosage for your needs and ensure that it does not interfere with any existing medications or conditions.
Some factors to consider when selecting a quercetin supplement include the purity and potency of the product, the form in which it is available, the recommended dosage, and the reputation of the brand. For instance, if you have difficulty swallowing pills, you may prefer a liquid or powder form of the supplement, or if you prefer a specific brand, you may choose to stick with that.
It is essential to consult with your healthcare provider before starting any new supplement regimen. They can help you determine the appropriate dosage for your needs and ensure that it does not interfere with any existing medications or conditions.
Best Quercetin Supplements 2023
Where to buy quercetin supplements? Check out below the best quercetin supplements available online.
Evidence: A Randomised Controlled Trial of 152 outpatients with COVID-19 in Pakistan, 76 treated with quercetin phytosome, showed lower mortality, ICU admission, and hospitalization with treatment (International Journal of General Medicine, May 2021)
Vitamin D is essential to a healthy immune system as it initiates the adaptive immune response. Clinical trial data shows that Vitamin D supplementation is safe and protects against acute respiratory tract infection mortality whereas low levels of vitamin D are associated with higher risk for infection and mortality (bmj.com).
Quercetin has been shown to reduce inflammation in multiple studies. In this 8 week study (Javadi 2017) involving 50 women with rheumatoid arthritis, participants took 500mg of quercetin per day or a placebo. The quercetin group reported less early morning stiffness, morning pain, and after-activity pain.
Early studies on quercetin and inflammation are promising, although more large scale human studies need to be performed to verify these benefits.
There’s evidence that quercetin reduces allergy symptoms. Researchers believe quercetin’s anti-inflammatory effects may relieve allergy symptoms.
This study published in Molecules in 2016, for example, found that quercetin could be effective for treating the anaphylactic (allergic) reaction in someone with peanut allergies. A similar study from 2006 concluded that quercetin was a “safe, natural therapy that may be used as primary therapy or in conjunction with conventional methods” for blocking allergies.
It’s possible that quercetin has the same anti-allergy effect in humans, although more research needs to be done.
There’s also some evidence that quercetin has cancer-fighting properties. Researchers believe quercetin can fight cancer cells with its powerful antioxidant properties.
In 2015, researchers reviewed available test tube and animal studies on quercetin and prostate cancer. After reviewing available evidence, researchers found that quercetin suppressed cell growth and induced cell death in prostate cancer cells.
This study published in 2017 in Oncology Reports took things a step further, finding that quercetin induced cancer cell death in nine types of cancer, including prostate cancer, colon cancer, and breast caner.
Early research on the cancer-fighting benefits of quercetin is promising, although more research needs to be performed to verify these effects in humans.
Other evidence suggests quercetin lowers your risk of chronic brain disorders, including Alzheimer’s and dementia.
In this study published in Neuropharmacology in 2015, researchers gave quercetin to mice with Alzheimer’s, injecting them with quercetin every two days for three 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 a separate study published in 2018, researchers gave mice with Alzheimer’s a quercetin-rich diet. Researchers found the diet improved brain function in mice with early-middle stage Alzheimer’s, although it had no significant effect on middle-late stage Alzheimer’s.
You may have heard that coffee is linked to a reduced risk of Alzheimer’s. There’s certainly some research to back that claim up. However, research has suggested that quercetin (not caffeine) is the primary compound in coffee responsible for protective effects against Alzheimer’s.
Some people use quercetin to reduce blood pressure and improve other measurements of cardiovascular health. High blood pressure raises your risk of heart disease, which is the leading cause of death in the United States. Approximately 1 in 3 American adults have high blood pressure.
Research suggests that quercetin reduces blood pressure levels. In this study published in 2002, researchers found that quercetin exhibited vasodilator effects, widening blood vessels and reducing blood pressure.
Multiple studies on humans have suggested similar benefits. Researchers reviewed nine human studies involving 580 people. After reviewing available evidence, researchers found that taking more than 500 mg of quercetin supplement per day reduced systolic and diastolic blood pressure by 5.8mm Hg and 2.6 mm Hg, respectively. In other words, quercetin was shown to significantly improve blood pressure readings.
Some people take quercetin for its anti-aging effects. Antioxidants and anti-inflammatories – including quercetin – seem to have powerful anti-aging benefits. One study on young mice found that quercetin reduced mortality and extended lifespan. Another study from 2017 on human cells in test tubes found that quercetin reduced aging markers, with researchers concluding there was “anti-aging potential” for quercetin.
Others take quercetin supplements to improve endurance and exercise performance. This 2011 study reviewed 11 quercetin studies involving 254 human subjects and found that quercetin provided a statistically significant benefit in human endurance exercise capacity (VO2 max) and endurance exercise performance, although the effect “is between trivial and small”.
Finally, some diabetics take quercetin to help manage blood sugar. This study from 2019 found that taking 500mg of quercetin per day significantly reduced fasting plasma glucose (FPG) levels, suggesting that quercetin helped control fasting blood sugar. This study in 2019 found similar results, finding that quercetin lowered serum glucose levels at doses of 10, 25, and 50mg per kg.
Most supplements have a similar dosage, offering from 500mg to 1,200mg of quercetin per serving.
In some studies, researchers have given participants up to 5,000mg of quercetin per day with no reported side effects.
Quercetin has poor bioavailability. You might take a 1,200mg quercetin supplement, but your body only absorbs a small percentage of it. That’s why many quercetin supplements contain vitamin C or bromelain, as some evidence suggests they boost absorption.
There’s also some evidence that quercetin has a synergistic effect when combined with other flavonoid supplements. That’s why some quercetin supplements contain resveratrol, catechins, genistein, and other flavonoids.
There have been few reported side effects for quercetin supplements.
In some studies, large doses of quercetin (over 1,000mg) were linked with headaches, digestive issues, and tingling sensations. However, these symptoms were mild and uncommon.
Quercetin from food sources is safe for pregnant and breastfeeding women to take. However, there’s limited research on quercetin supplements in pregnant or breastfeeding women.
What are the best foods for quercetin?
A: Capers, peppers (yellow and green), onions (red and white), shallots, asparagus, cherries, tomatoes, red apples, red grapes, broccoli, kale, red leaf lettuce, cranberries, blueberries, raspberries, green tea, black tea, and coffee are all excellent foods for quercetin.
Quercetin Dihydrate vs Quercetin
1. Amazing Formulas - Quercetin 500 Mg (Best for Vegetarians)
Each Amazing Formulas Quercetin capsule contains 500 mg of quercetin dihydrate. Cost per capsule: $0.17. (120 vegetarian capsules per container).
Ratings: 4.7 out of 5 - More than 29,000 global ratings.
I've been sick twice in the past two months, one a mild cold, the other quite severe, DID NOT GET TESTED so can not attest to Covid 19. Anyway, once I got sick, I took 1000mg of Quercetin, combined with 200mg of Zinc Picolinate - ANECDOTAL EVIDENCE: I was free and clear of symptoms in the range of 6 to 10 hours, save for a lingering itch in my sinuses, which was gone after a good night sleep. Symptoms did not return in either case. This was ONE DOSE.
Our Take: If you are looking for best value in terms of quercetin suitable for vegetarians and vegans; and are taking it on a long term basis, this would be your choice.
2. Thorne Research Quercenase - Quercetin Phytosome Supplement with Bromelain
Quercenase is a combination of quercetin phytosome and bromelain. Quercetin phytosome is a new food-grade lecithin-based formulation of quercetin, was developed to overcome the low bioavailability hurdle of quercetin. Phytosome complexes are created by a patented process that binds a botanical extract to a phospholipid (phosphatidylcholine), which are key components of every cell membrane.
Each capsule contains 250 mg of quercetin phytosome and 100 mg of bromelain. Cost per capsule: $0.77.
Editor's Note: Most Quercetin Phytosome supplements consist of quercetin and sunflower lecithin in a 1:1 weight ratio along with about a fifth part of food-grade excipients. Therefore, 250 mg of quercetin phytosome will contain about 100 mg of quercetin.
BestReviews.com: A potent, science backed formulation by a brand known for quality that is made with the purest ingredients for maximum efficacy. However, it is relatively pricier than many similar products on the market.
Amazon Best Sellers: #43 Best Seller in Flavonoid Vitamin Supplements. 4.7 out of 5 overall rating with more than 200 customer reviews.
I have histamine intolerance and had spent many years taking prescription and OTC drugs. I wanted to get away from drugs and my functional medicine doctor recommended d-hist. It worked on my allergies but I would get migraines if I took it too often. I think it was the nettles. Anyway, I also didn't like that they used magnesium stearate. I bought this and it works just as well as my Claritin did. I get relief from runny nose and sneezing as well as itchy skin. I will sometimes add some extra bromelain but I am very happy. Thorne products are often more expensive but they use better ingredients and omit questionable ingredients that make production cheaper.
Our Take: If you are looking to buy from a reputable brand, this would be your choice.
3. Z-Stack Quercetin 500mg with Zinc, Vitamin C and Vitamin D3 - Best Immune Support Supplement
Where to buy Z-Stack: Z Stack Supplement
Note: To get 5% OFF, please use this coupon code: drfrancis
In an effort to make it easier for his patients, Dr Zelenko has developed an oral supplement that contains four key ingredients including quercetin (a zinc ionophore) in combination with zinc, vitamin C and vitamin D3. It’s referred to as 'Z-Stack Supplement'.
Each capsule contains 250 mg of quercetin, 15 mg of zinc, 2,500 IU of vitamin D3 and 400 mg of vitamin C. Cost per capsule: $0.83.
Z-Stack Vitamin cocktail provides key ingredients needed in order to help your body fight off this deadly invader. The Z-Stack Vitamins are Kosher certified, GMP certified and made in the USA.
Quercetin is a zinc ionophore. Meaning it transports zinc into the cells.
It is known that zinc will slow down the replication of coronavirus through inhibition of enzyme RNA dependent RNA polymerase (PubMed 2010). The COVID-19 virus is a single stranded RNA (RiboNucleicAcid) virus and requires the RNA polymerase to replicate.
Vitamin C and quercetin co-administration exerts a synergistic antiviral action due to overlapping antiviral and immunomodulatory properties and the capacity of ascorbate to recycle quercetin, increasing its efficacy.
Customer Review on ZStackLife:
My father and I have been taking Z Stack for 4 months. My wife has not. She came down with C-19. I still slept in the same bed with her and neither my father nor I got sick. She started the protocol and was fine in a few days. I'm sold on this product. - Feb 4, 2022
Related Evidence:
- What is the Zelenko protocol? The Zelenko COVID-19 Protocol was developed by Dr Vladimir Zelenko. A retrospective study analyzing Dr Zelenko's patient data was accepted for publication in the International Journal of Antimicrobial Agents after a rigorous peer review process. The study finds that early intervention and treatment of high-risk patients with COVID-19 resulted in significantly fewer hospitalizations and deaths. The treatment consisting of zinc, low-dose hydroxychloroquine (HCQ), and azithromycin, is also referred to as "The Zelenko Protocol." Dr Zelenko has since updated his protocols to incorporate new evidence.
4. MoxyVites Quercetin 500mg with Bromelain Supplement, Bioactive Phytosome Complex
Moxyvites quercetin complex is a combination of quercetin phytosome and bromelain. Regular quercetin has poor solubility and low oral absorption. Moxyvites' technology binds quercetin with a glucose bond & incorporation of phospholipids into standardized extracts improving the absorption and bioavailability by 20X. Their complex delivery system utilizes phytosome technology in which phytoconstituents react with phospholipids for better and improved bioavailability.
Each capsule contains 250 mg of quercetin phytosome and 80 mg of bromelain. Cost per capsule: $0.29.
Amazon Best Sellers: #31 Best Seller in Flavonoid Vitamin Supplements.
Reviews: 4.8 out of 5 overall rating with more than 380 customer reviews.
Our Take: If you are looking for best value in terms of quercetin phytosome with bromelain and are taking it on a long term basis, this would be your choice. Another value added ingredient this product has is curcumin, well known also for it's anti-inflammatory and anti-oxidant effects.
Evidence: A Randomised Controlled Trial of 152 outpatients with COVID-19 in Pakistan, 76 treated with quercetin phytosome, showed lower mortality, ICU admission, and hospitalization with treatment (International Journal of General Medicine, May 2021)
5. Vitaraw Quercetin, Zinc, Bromelain, Vitamin C, Vitamin D3
- Immunity Booster, Antioxidant & Anti Inflammatory
The Ultimate Immune Defense by Vita Raw
Quercetin carries anti-aging elements that promote blood sugar levels and stronger endurance while acting as an anti-inflammatory supplement. Bromelain is the principal ingredient that enhances the potency and absorption of Quercetin.
An all-in-one premium daily immune vitamin made with top quality nutrients at optimal doses. Stay healthy, happy, and energized with a powerhouse multi-vitamin that naturally strengthen your body's defense system.*
An Advanced Formulation Immune Booster For Adults*
Experience a robust antioxidant for cardiovascular and digestive health with VitaRaw's Quercetin + Bromelain + Stinging Nettle Root + Vitamin C with Zinc for adults. Fused with 50 mg of Zinc and 500mg of Vitamin C & Quercetin that reinforces immunity, strong bones, balanced energy levels, and proper growth of the body.*
*These statements have not been evaluated by the Food & Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.
- Gluten-Free & Gelatin-Free
- Vegan & Vegetarian Friendly
- Made With Non-GMO Ingredients
- Safe, Pure, High-Quality Supplements
Quercetin Bromelain with Stinging Nettle Root
- Healthy Digestion & Immune Function Support*
- Strong Antioxidant Properties To Protect The Body From Free Radicals**
- Added Bromelain for Maximum Absorption*
- Maintains General Health*
Dosage (per capsule) : Quercetin 250mg Supplement, Zinc 25mg, Vitamin C 250mg, Vitamin D3 63mg, Bromelain 75mg
Ratings : 4.6 out of 5 - more than 1,000 global ratings
I started taking this when I began feeling like a cold was coming on. My throat was really bothering me, I had a bad headache, and I was sneezing. Quite honestly, I thought it was something worse than I cold but I remained optimistic. I took the Quercetin immediately and I felt better in a couple days. From my experience, it seemed to prevent my symptoms from worsening. My back also feels a little better. I sit a lot so this supplement might be helping with the discomfort I normally have.
6. Forest Leaf Quercetin, Bromelain, Stinging Nettle, Vitamin C
Uniquely formulated using a blend of quercetin and bromelain, this supplement from ForestLeaf may help with sinus relief, allergies, cardiovascular and respiratory health.
Amazon Best Sellers: #3 Best Seller in Flavonoid Vitamin Supplements.
Ratings: 4.6 out of 5 - more than 6,000 global ratings
- Advanced Sinus and Allergy Supplement
- Natural Vegetable Capsules
- Non GMO, Dairy, Gluten, Egg and Nut Free
- Every pill contains stinging nettle leaf extract.
- All of its products and pills are tested for maximum absorption.
- 45 servings per bottle, 200mg of vitamin C per serving.
Ingredients: Vitamin C 200mg, Quercetin 500mg, Stinging Nettle Leaf 500mg, Bromelain 150mg, Vegetable Cellulose (capsule), Microcrystalline Cellulose, Magnesium Stearate and Silicon Dioxide
Review: I have year round allergies and lately what I had been taking wasn't working and my eyes were always running. It was extremely annoying and frustrating to be crying from one eye all day. I read the reviews and decided to try this. I've been taking them twice a day since March 1st and I stopped crying the first day. I love these natural pills. They work!!!!
7. Kappa Nutrition Immune C Plus
Kappa Nutrition ultrapure immunity boost defense formula features 12 ingredients, vitamin C non-acidic + Zinc + Vitamin D3 + Acerola + Ginger + Rutin + Bitter Orange + Rose Hips + Copper + Selenium + Quercetin + Echinacea, to help strengthen the body’s defenses to keep you protected year round with extra immunity support. Promotes antioxidant activity: Kappa Nutrition Immune C Plus has powerhouse antioxidant ingredients to help fight off free radicals that can damage cells and immune health
Kappa Nutrition capsules were expertly formulated with the best quality ingredients to support a healthy immune system. With this exclusive formula you can feel confident knowing you're getting a quality dietary supplement to keep you feeling great year-round
- 90 Capsules
- Contains Selenium, Copper, Acerola, Ginger, Rutin, Bitter Orange, Rose Hips, Echinacea, Immune C Plus, 12 in 1 Immune Support
MADE IN THE USA AND TESTED FOR PURITY AND SAFETY
Our High Potency Superior Absorption Immune C Plus Advanced Complex Capsules are manufactured right here in the USA. Immune C Plus Advanced Complex is Made with an easy to swallow vegan capsule form that helps boost healthy immune levels
HIGHLY BIOAVAILABLE FORM OF IMMUNE C Plus 12 IN 1 ADVANCED COMPLEX
Has minerals in chelating form that are able to greatly enhance the bioavailability of Ingredients making them highly absorbable.
PROMOTES IMMUNE HEALTH
Research showed that Immune C Plus Advanced Complex promotes and boost your immune system
Dosage (per capsule) : Quercetin 500mg, Vitamin C 500mg, Zinc 25mg, Vitamin D3 2500iu
Ratings : 4.7 out of 5 - more than 2,000 global ratings
Review: This is an amazing combo or vitamins needed to help fight against colds! High levels of vitamin ax + other vitamins that typically boost your bodies’ absorption of the vitamin C. Plus, one thing I like the most - only 2 capsules s make a dose - and they’re NOT horse pills! Amazing! Love this & I orally recommend!
8. Vimerson Health Quercetin Curcumin Bromelain (Best Quercetin with Curcumin)
About this item
- Vimerson Health's Turmeric Quercetin Bromelain supports muscle and joint health* and supports the immune system* with this perfectly combined daily multivitamin and mineral supplement; It also provides antioxidant support and balanced inflammatory response;* The antioxidant properties of this blend help the body in its ability to neutralize free radicals*; These cause oxidative stress which contributes to many imbalances in the body such as allergies.
- Match made in heaven: This superb concoction of plants, herbs, and nurtrients combine in perfect harmony to support each other, and enhance their benefits in the body; The antioxidant properties of this blend help to soak up free radicals; These cause oxidative stress which contributes to aging, therefore this blend helps slow down the signs of aging and heart health*; It is also known for relieving allergy symptoms *
- The combination of Quercetin and bromelain along with turmeric, provide a powerful immune support* and help balance the body’s inflammatory response*.
- Our promise to you: Each batch we produce is packed with love and real ingredients for real results*; Vimerson Health’s Turmeric Bromelain is formulated safely and gently with no dangerous extraction processes or harsh chemicals*; It is made NATURAL and contains zero soy, sugar, GMOs, gluten, and dairy; You're getting more goodness per capsule than anyone else*; Our Turmeric Bromelain provides you with the immune support you require to be happy*
- Vegan, gluten free, soy free, non-GMO: This, and all our products, are manufactured in the USA, meeting GMP standards; Here at Vimerson Health we select only the highest quality herbs, minerals and vitamins for optimal potency and efficacy; Our standards of testing surpass any others on the market, ensuring that only the best result is delivered to you; Our advanced formula is suitable for men, women and seniors, and is lovingly compacted in veggie easy-to-swallow capsules.
Ratings: 4.7 out of 5 - more than 2,800 global ratings
9. Dr Mercola Quercetin and Pterostilbene Advanced
- Combining two powerful antioxidants, Quercetin and Pterostilbene Advanced supports seasonal, heart and mitochondrial health as well as mental focus, brain and cognitive function, exercise performance and more.*
- The Quercetin Phytosome Complex in Dr Mercola formula offers 20 times the bioavailability of regular quercetin.*
- Quercetin and Pterostilbene Advanced also contains the active and more easily absorbable form of pterostilbene – trans-Pterostilbene – which is nature identical to blueberries.
*These statements have not been evaluated by the Food and Drug Administration.
These products are not intended to diagnose, treat, cure, or prevent any disease.
Amazon Ratings: 4.7 out of 5 - more than 300 ratings.
Related Products for Immune Support:
- Combining two powerful antioxidants, Quercetin and Pterostilbene Advanced supports seasonal, heart and mitochondrial health as well as mental focus, brain and cognitive function, exercise performance and more.*
- The Quercetin Phytosome Complex in Dr Mercola formula offers 20 times the bioavailability of regular quercetin.*
- Quercetin and Pterostilbene Advanced also contains the active and more easily absorbable form of pterostilbene – trans-Pterostilbene – which is nature identical to blueberries.
These products are not intended to diagnose, treat, cure, or prevent any disease.
Amazon Ratings: 4.7 out of 5 - more than 300 ratings.
Related Products for Immune Support:
10. Doctor's Best Quercetin Bromelain, 180 Veggie Caps
Amazon Best Sellers Rank: #4 in Bromelain Nutritional Supplements
Amazon Best Sellers Rank: #12 in Flavonoid Vitamin SupplementsRatings: 4.7 out of 5 - more than 3,000 global ratings
- Non-GMO, Vegan, Gluten Free, Soy Free
- Bromelain 3000 GDU per capsule, has 500 Mg of Quercetin with 250 Mg Bromelain for a Serving size of 2 Capsules
- Quercetin and Bromelain enhances each other's antioxidant and anti-inflammatory potential. Quercetin is a bioflavonoid that has potent antioxidants while bromelain works as protein-digesting enzyme. Bromelain helps increase your body’s absorption and use of Quercetin.
- Helps support immune health, heart health, joint comfort, healthy digestions, respiratory health and inflammatory response.
- Quercetin helps ensure appropriate immune response, inhibits formation of free radicals and promotes circulatory health in part by supporting the integrity of small blood vessels.
Review: i have sleep apnea and have TO sit up in a recliner to sleep because i can not use a CPAP. QUERCETIN CLEARS MY SINUS SO BOTH NOSTRILS ARE OPENED WITH OUT ANY NEGATIVE PHARMCEUUTICAL DRUG SIDE EFFECTS . i now sleep lying flat. thank you drs best. you formula.
Amazon Best Sellers Rank: #12 in Flavonoid Vitamin Supplements
- Bromelain 3000 GDU per capsule, has 500 Mg of Quercetin with 250 Mg Bromelain for a Serving size of 2 Capsules
- Quercetin and Bromelain enhances each other's antioxidant and anti-inflammatory potential. Quercetin is a bioflavonoid that has potent antioxidants while bromelain works as protein-digesting enzyme. Bromelain helps increase your body’s absorption and use of Quercetin.
- Helps support immune health, heart health, joint comfort, healthy digestions, respiratory health and inflammatory response.
- Quercetin helps ensure appropriate immune response, inhibits formation of free radicals and promotes circulatory health in part by supporting the integrity of small blood vessels.
Benefits of Quercetin Supplements
Quercetin is a bioflavonoid found in certain fruits, vegetables, and
grains. Bioflavonoids like quercetin provide benefits by working as
antioxidants.
You may already get a small amount of quercetin in your normal diet: quercetin is found in onions, kale, tomatoes, broccoli, asparagus, berries, red wine, citrus fruits, cherries, and tea. Many people also take quercetin in supplement form.
In fact, it’s estimated that the average person consumes about 10 to 100 mg of quercetin per day through a normal diet. Quercetin is one of the most abundant flavonoids in the human diet.
Quercetin is a pigment that belongs to a group of plant compounds called flavonoids (also known as bioflavonoids). Flavonoids are naturally present in fruits, grains, teas, and wine. Researchers have linked flavonoids to a variety of benefits, including a reduced risk of heart disease, cancer, and degenerative brain disorders.
What does science have to say about quercetin? Can quercetin really fight inflammation and reduce the risk of disease? Let’s dive into the science behind quercetin.
You may already get a small amount of quercetin in your normal diet: quercetin is found in onions, kale, tomatoes, broccoli, asparagus, berries, red wine, citrus fruits, cherries, and tea. Many people also take quercetin in supplement form.
In fact, it’s estimated that the average person consumes about 10 to 100 mg of quercetin per day through a normal diet. Quercetin is one of the most abundant flavonoids in the human diet.
Quercetin is a pigment that belongs to a group of plant compounds called flavonoids (also known as bioflavonoids). Flavonoids are naturally present in fruits, grains, teas, and wine. Researchers have linked flavonoids to a variety of benefits, including a reduced risk of heart disease, cancer, and degenerative brain disorders.
What does science have to say about quercetin? Can quercetin really fight inflammation and reduce the risk of disease? Let’s dive into the science behind quercetin.
As of April 2023, there have been 10 published studies of quercetin and COVID-19 (c19quercetin.com) showing an average improvement of 44%. Based on the mortality studies, the amount of people dying from COVID in the control arm are more than 10 times as compared to those who are on quercetin.
Quercetin has been shown to reduce inflammation in multiple studies. In this 8 week study (Javadi 2017) involving 50 women with rheumatoid arthritis, participants took 500mg of quercetin per day or a placebo. The quercetin group reported less early morning stiffness, morning pain, and after-activity pain.
Early studies on quercetin and inflammation are promising, although more large scale human studies need to be performed to verify these benefits.
There’s evidence that quercetin reduces allergy symptoms. Researchers believe quercetin’s anti-inflammatory effects may relieve allergy symptoms.
This study published in Molecules in 2016, for example, found that quercetin could be effective for treating the anaphylactic (allergic) reaction in someone with peanut allergies. A similar study from 2006 concluded that quercetin was a “safe, natural therapy that may be used as primary therapy or in conjunction with conventional methods” for blocking allergies.
It’s possible that quercetin has the same anti-allergy effect in humans, although more research needs to be done.
There’s also some evidence that quercetin has cancer-fighting properties. Researchers believe quercetin can fight cancer cells with its powerful antioxidant properties.
In 2015, researchers reviewed available test tube and animal studies on quercetin and prostate cancer. After reviewing available evidence, researchers found that quercetin suppressed cell growth and induced cell death in prostate cancer cells.
This study published in 2017 in Oncology Reports took things a step further, finding that quercetin induced cancer cell death in nine types of cancer, including prostate cancer, colon cancer, and breast caner.
Early research on the cancer-fighting benefits of quercetin is promising, although more research needs to be performed to verify these effects in humans.
Other evidence suggests quercetin lowers your risk of chronic brain disorders, including Alzheimer’s and dementia.
In this study published in Neuropharmacology in 2015, researchers gave quercetin to mice with Alzheimer’s, injecting them with quercetin every two days for three 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 a separate study published in 2018, researchers gave mice with Alzheimer’s a quercetin-rich diet. Researchers found the diet improved brain function in mice with early-middle stage Alzheimer’s, although it had no significant effect on middle-late stage Alzheimer’s.
You may have heard that coffee is linked to a reduced risk of Alzheimer’s. There’s certainly some research to back that claim up. However, research has suggested that quercetin (not caffeine) is the primary compound in coffee responsible for protective effects against Alzheimer’s.
Some people use quercetin to reduce blood pressure and improve other measurements of cardiovascular health. High blood pressure raises your risk of heart disease, which is the leading cause of death in the United States. Approximately 1 in 3 American adults have high blood pressure.
Research suggests that quercetin reduces blood pressure levels. In this study published in 2002, researchers found that quercetin exhibited vasodilator effects, widening blood vessels and reducing blood pressure.
Multiple studies on humans have suggested similar benefits. Researchers reviewed nine human studies involving 580 people. After reviewing available evidence, researchers found that taking more than 500 mg of quercetin supplement per day reduced systolic and diastolic blood pressure by 5.8mm Hg and 2.6 mm Hg, respectively. In other words, quercetin was shown to significantly improve blood pressure readings.
Some people take quercetin for its anti-aging effects. Antioxidants and anti-inflammatories – including quercetin – seem to have powerful anti-aging benefits. One study on young mice found that quercetin reduced mortality and extended lifespan. Another study from 2017 on human cells in test tubes found that quercetin reduced aging markers, with researchers concluding there was “anti-aging potential” for quercetin.
Others take quercetin supplements to improve endurance and exercise performance. This 2011 study reviewed 11 quercetin studies involving 254 human subjects and found that quercetin provided a statistically significant benefit in human endurance exercise capacity (VO2 max) and endurance exercise performance, although the effect “is between trivial and small”.
Finally, some diabetics take quercetin to help manage blood sugar. This study from 2019 found that taking 500mg of quercetin per day significantly reduced fasting plasma glucose (FPG) levels, suggesting that quercetin helped control fasting blood sugar. This study in 2019 found similar results, finding that quercetin lowered serum glucose levels at doses of 10, 25, and 50mg per kg.
Dosage
Most quercetin studies use a dosage of around 500mg per day, although some studies use a dosage of 500mg taken twice per day.Most supplements have a similar dosage, offering from 500mg to 1,200mg of quercetin per serving.
In some studies, researchers have given participants up to 5,000mg of quercetin per day with no reported side effects.
Quercetin has poor bioavailability. You might take a 1,200mg quercetin supplement, but your body only absorbs a small percentage of it. That’s why many quercetin supplements contain vitamin C or bromelain, as some evidence suggests they boost absorption.
There’s also some evidence that quercetin has a synergistic effect when combined with other flavonoid supplements. That’s why some quercetin supplements contain resveratrol, catechins, genistein, and other flavonoids.
Quercetin Side Effects
Quercetin is generally recognized as safe. It’s found in many fruits and vegetables, and most people will experience no side effects when taking normal dosages of quercetin.There have been few reported side effects for quercetin supplements.
In some studies, large doses of quercetin (over 1,000mg) were linked with headaches, digestive issues, and tingling sensations. However, these symptoms were mild and uncommon.
Quercetin from food sources is safe for pregnant and breastfeeding women to take. However, there’s limited research on quercetin supplements in pregnant or breastfeeding women.
Although there are 30 CYP450 (Cytochrome P450) liver enzymes that metabolize drugs, only 6 do most of the work. Quercetin inhibits 5 of them (Source).
Therefore, you should talk to your doctor before taking quercetin, especially if you are taking antibiotics or blood pressure medication.
Therefore, you should talk to your doctor before taking quercetin, especially if you are taking antibiotics or blood pressure medication.
Frequently Asked Questions About Quercetin
This section will help to answer some of the most commonly asked questions about Quercetin.What are the best foods for quercetin?
A: Capers, peppers (yellow and green), onions (red and white), shallots, asparagus, cherries, tomatoes, red apples, red grapes, broccoli, kale, red leaf lettuce, cranberries, blueberries, raspberries, green tea, black tea, and coffee are all excellent foods for quercetin.
The key difference between quercetin and quercetin dihydrate is that quercetin is a plant flavonoid, whereas quercetin dihydrate is a synthetic chemical compound. Moreover, quercetin is a yellow crystalline powder, whereas quercetin dihydrate is a bright yellow colour powder.
Quercetin Dihydrate has the highest bioavailability when it comes to quercetin supplements.
According to Examine.com, this form is preferable to glycosides, aglycone and rutinoside versions.
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.
Additionally, some research indicates that quercetin has a synergistic effect when combined with other flavonoid supplements, such as resveratrol, genistein, and catechins.
Most in vitro studies used a form of quercetin called 'quercetin aglycone'.
However, this particular form of quercetin is never found in the blood, even
after ingested, as it it gets changed in the liver.
Often referred to as “Vitamin P”, Rutin is comprised of a quercetin molecule bound to a sugar molecule called rutinose. It is chemically very similar to Quercetin and the two compounds are invariably found together in fruits and vegetables.
How much quercetin should you take per day?
A: Researchers typically use a dose of 500 mg of quercetin per day in supplement form. Most quercetin supplements contain between 500 and 1200 mg of quercetin, although this can vary. Check out the nutritional label for your quercetin supplement to be sure.
Does quercetin help allergies?
A: Many people take quercetin supplements to avoid allergy symptoms. There’s evidence that quercetin has powerful anti-allergy benefits, although more research needs to be done.
Q: Does quercetin fight cancer?
A: Early research in test tube and animal models shows that quercetin may have cancer-fighting properties. While these findings are promising, more large scale human studies need to be performed. Research is not definitive. Consult your physician before using any supplement to improve your cancer.
Q: Does quercetin reduce the risk of Alzheimer’s?
A: Studies show that quercetin may reduce the onset of Alzheimer’s, particularly in the early and middle stages of the condition. However, studies have mostly been performed on mice and test tubes – not in humans.
Q: What are other names for quercetin?
A: Quercetin goes by a number of different names. You might see quercetin supplements labeled as bioflavonoid concentrate, bioflavonoid extract, or citrus bioflavonoid, for example.
Q: Can quercetin help you recover after exercise?
A: Some studies show that quercetin boosts recovery after exercise. In some small studies, athletes taking quercetin after exercise had faster recovery than a control group. Researchers believe quercetin reduces oxidative stress and post-exercise inflammation, helping your body recover.
Q: What are the side effects of quercetin?
A: Most people experience no side effects from quercetin, and any side effects tend to be mild. Quercetin side effects include tingling and numbness, headache, and nausea. Your chance of experiencing side effects increases at higher dosages (over 1,000mg).
Q: Why do so many quercetin supplements contain bromelain?
A: Bromelain is a naturally occurring, protein-digesting enzyme found in the stem of the pineapple. Bromelain seems to boost the absorption of quercetin by inhibiting inflammatory chemicals called prostaglandins. Bromelain may also decrease inflammation on its own.
Q: What’s the difference between rutin or glycosidic quercetin?
A: Quercetin is found in two forms, including in rutin or glycosidic form. Quercetin glucosides, such as isoquercitrin and isoquercetin, seem to be much more bioavailable and more quickly absorbed than quercetin aglycone or quercetin glycosides, such as rutin (quercetin rutinoside).
Q: Can you overdose on quercetin?
A: In one study, researchers gave participants 2,000mg to 5,000mg of quercetin per day with no adverse effects or signs of toxicity reported. Generally, quercetin is safe to take even in high doses, although you may experience mild side effects like nausea, digestive issues, and headaches at high doses. Excessively high doses of quercetin could lead to kidney problems.
Q: How much quercetin should you take for hay fever?
A: Experts recommend taking 400mg of quercetin twice a day between meals for hay fever. Also consult your doctor to help provide a more comprehensive and effective treatment for hay fever.
Q: Can children take quercetin?
A: Most studies suggest that it’s safe to give quercetin to your child, although you should use only half the dose you'd use on an adult. Talk to your pediatrician before giving any quercetin to your child.
Q: How does quercetin manage allergy symptoms?
A: Studies have shown that quercetin stabilizes mast cells that release histamine. Histamine is the principal mediator of reactions to pollen and other allergies. This makes quercetin a natural antihistamine. Many people use quercetin to treat symptoms of hay fever, including runny nose, watering eyes, and itching.
Q: Can you take too much quercetin?
A: You should start with a quercetin dosage of around 500mg per day to assess your tolerance. However, researchers have given participants up to 5,000mg of quercetin per day with few reported side effects. Look for symptoms like upset stomach and diarrhea. Excessively high doses of quercetin could lead to kidney problems.
Q: Who should not take a quercetin supplement?
A: Quercetin appears safe for anyone to take when used in normal dosages. However, there’s limited research on how quercetin supplements affect women who are pregnant or breastfeeding. People with high blood pressure, or anyone taking blood pressure medication, may also want to take to their doctor before taking a quercetin supplement.
Q: Can you take a quercetin supplement with a pineapple allergy?
A: If you’re allergic to pineapples, you should avoid quercetin supplements with bromelain. Bromelain, an enzyme in pineapples, is added to quercetin supplements to boost bioavailability. Overuse of bromelain can create problems for consumers.
Q: Does quercetin work for anti-aging?
A: Several studies have examined the effect of quercetin on aging. Quercetin is rich with anti-inflammatories and antioxidants, which could make it a powerful anti-aging compound.
Q: Does quercetin help asthma?
A: Quercetin may help asthma by relaxing smooth muscles lining the airway, improving airway flow.
Q: What’s better – quercetin tablets, capsules, powders, or liquid?
A: Quercetin liquid claims to be more bioavailable than other sources of quercetin. You take the liquid sublingually (underneath your tongue). However, limited research shows quercetin capsules or powders are more effective, and all forms of quercetin are absorbed poorly by the body.
Q: Where does quercetin come from?
A: Most supplement companies use various plant or vegetable-based sources of quercetin. Check the label.
Q: Can you get citrus-free quercetin?
A: Some quercetin supplements are specifically marketed as citrus-free, making them ideal for those with citrus sensitivities. Read the label or official product website for your supplement to be sure that it is actually citrus-free.
Q: Does quercetin help with diabetes?
A: There’s some evidence that quercetin helps with diabetes, helping your body manage blood sugar levels during fasting. However, more research needs to be done to verify these benefits.
Q: Is quercetin non-GMO?
A: Quercetin supplements are generally labeled non-GMO. Check the label to verify your quercetin supplement is not made from genetically modified ingredients.
Some people take quercetin supplements for allergies. Others take it to boost the immune system. Others take quercetin for general anti-aging or health and wellness.
Early research on quercetin is promising, and new human studies are released every year validating certain quercetin benefits.
Disclaimer: The information on this website is not intended to replace
a one-on-one relationship with a qualified health care professional
and is not intended as medical advice. It is intended as a sharing of
knowledge and information from the research and experience of third
party sites. If you are pregnant, nursing, taking medication, or have
a medical condition, consult your health care professional before
using products based on this content.
Quercetin Dihydrate has the highest bioavailability when it comes to quercetin supplements.
According to Examine.com, this form is preferable to glycosides, aglycone and rutinoside versions.
That’s why the supplements may include other compounds, such as vitamin C or digestive enzymes like bromelain, as they may increase absorption.
Additionally, some research indicates that quercetin has a synergistic effect when combined with other flavonoid supplements, such as resveratrol, genistein, and catechins.
A new food-grade lecithin-based form of quercetin,
Quercetin Phytosome, was developed and validated in healthy volunteers. Quercetin Phytosome
overcomes the low bioavailability hurdle of quercetin and should help to
fulfill the great health benefit potential of this flavonoid in the diet and
as food supplements.
According to
Examine, the quercetin dihydrate form has the apparent best bioavailability
followed by glycosides, aglycone, and finally rutinoside.
Quercetin supplements come in different forms. Most of the quercetin ingredients on the market are in the quercetin
dihydrate form. Quercetin anhydrous and dihydrate differ in the amount of
water they contain. Quercetin anhydrous contains only 1% to 4% moisture and
the sugar molecules that are attached to quercetin in its natural form have
been extracted. This translates into 13% more quercetin per gram for
quercetin anhydrous vs quercetin dihydrate. For formula manufacturers, this
means there is substantially less bulk per capsule or tablet.
Rutin vs Quercetin
An animal study published in the Nature (Aug 2012), concluded that rutin exerts stronger protection against liver damage but has weaker antioxidant and anti-inflammatory activities and antifibrotic (anti-scarring) potential than quercetin
Another study (JCI May 2012) on rutin, commonly found in fruits and vegetables and sold over the counter as a dietary supplement, has been shown to inhibit the formation of blood clots in an animal model of thrombosis.
Do you get enough quercetin in your daily diet?
A: The average person gets 10 to 100 mg of quercetin per day through normal dietary sources. This can vary greatly. Carefully track your diet over an extended period to figure out if you have a dietary deficiency of quercetin.
A: The average person gets 10 to 100 mg of quercetin per day through normal dietary sources. This can vary greatly. Carefully track your diet over an extended period to figure out if you have a dietary deficiency of quercetin.
How much quercetin should you take per day?
A: Researchers typically use a dose of 500 mg of quercetin per day in supplement form. Most quercetin supplements contain between 500 and 1200 mg of quercetin, although this can vary. Check out the nutritional label for your quercetin supplement to be sure.
Does quercetin help allergies?
A: Many people take quercetin supplements to avoid allergy symptoms. There’s evidence that quercetin has powerful anti-allergy benefits, although more research needs to be done.
Q: Does quercetin fight cancer?
A: Early research in test tube and animal models shows that quercetin may have cancer-fighting properties. While these findings are promising, more large scale human studies need to be performed. Research is not definitive. Consult your physician before using any supplement to improve your cancer.
Q: Does quercetin reduce the risk of Alzheimer’s?
A: Studies show that quercetin may reduce the onset of Alzheimer’s, particularly in the early and middle stages of the condition. However, studies have mostly been performed on mice and test tubes – not in humans.
Q: What are other names for quercetin?
A: Quercetin goes by a number of different names. You might see quercetin supplements labeled as bioflavonoid concentrate, bioflavonoid extract, or citrus bioflavonoid, for example.
Q: Can quercetin help you recover after exercise?
A: Some studies show that quercetin boosts recovery after exercise. In some small studies, athletes taking quercetin after exercise had faster recovery than a control group. Researchers believe quercetin reduces oxidative stress and post-exercise inflammation, helping your body recover.
Q: What are the side effects of quercetin?
A: Most people experience no side effects from quercetin, and any side effects tend to be mild. Quercetin side effects include tingling and numbness, headache, and nausea. Your chance of experiencing side effects increases at higher dosages (over 1,000mg).
Q: Why do so many quercetin supplements contain bromelain?
A: Bromelain is a naturally occurring, protein-digesting enzyme found in the stem of the pineapple. Bromelain seems to boost the absorption of quercetin by inhibiting inflammatory chemicals called prostaglandins. Bromelain may also decrease inflammation on its own.
Your body doesn’t absorb quercetin very effectively on its own. Some
studies have shown that bromelain boosts the absorption of quercetin,
which is why you find bromelain (or vitamin C) in many quercetin
supplements.
Q: What’s the difference between rutin or glycosidic quercetin?
A: Quercetin is found in two forms, including in rutin or glycosidic form. Quercetin glucosides, such as isoquercitrin and isoquercetin, seem to be much more bioavailable and more quickly absorbed than quercetin aglycone or quercetin glycosides, such as rutin (quercetin rutinoside).
Q: Can you overdose on quercetin?
A: In one study, researchers gave participants 2,000mg to 5,000mg of quercetin per day with no adverse effects or signs of toxicity reported. Generally, quercetin is safe to take even in high doses, although you may experience mild side effects like nausea, digestive issues, and headaches at high doses. Excessively high doses of quercetin could lead to kidney problems.
Q: How much quercetin should you take for hay fever?
A: Experts recommend taking 400mg of quercetin twice a day between meals for hay fever. Also consult your doctor to help provide a more comprehensive and effective treatment for hay fever.
Q: Can children take quercetin?
A: Most studies suggest that it’s safe to give quercetin to your child, although you should use only half the dose you'd use on an adult. Talk to your pediatrician before giving any quercetin to your child.
Q: How does quercetin manage allergy symptoms?
A: Studies have shown that quercetin stabilizes mast cells that release histamine. Histamine is the principal mediator of reactions to pollen and other allergies. This makes quercetin a natural antihistamine. Many people use quercetin to treat symptoms of hay fever, including runny nose, watering eyes, and itching.
Q: Can you take too much quercetin?
A: You should start with a quercetin dosage of around 500mg per day to assess your tolerance. However, researchers have given participants up to 5,000mg of quercetin per day with few reported side effects. Look for symptoms like upset stomach and diarrhea. Excessively high doses of quercetin could lead to kidney problems.
Q: Who should not take a quercetin supplement?
A: Quercetin appears safe for anyone to take when used in normal dosages. However, there’s limited research on how quercetin supplements affect women who are pregnant or breastfeeding. People with high blood pressure, or anyone taking blood pressure medication, may also want to take to their doctor before taking a quercetin supplement.
Q: Can you take a quercetin supplement with a pineapple allergy?
A: If you’re allergic to pineapples, you should avoid quercetin supplements with bromelain. Bromelain, an enzyme in pineapples, is added to quercetin supplements to boost bioavailability. Overuse of bromelain can create problems for consumers.
Q: Does quercetin work for anti-aging?
A: Several studies have examined the effect of quercetin on aging. Quercetin is rich with anti-inflammatories and antioxidants, which could make it a powerful anti-aging compound.
Q: Does quercetin help asthma?
A: Quercetin may help asthma by relaxing smooth muscles lining the airway, improving airway flow.
Q: What’s better – quercetin tablets, capsules, powders, or liquid?
A: Quercetin liquid claims to be more bioavailable than other sources of quercetin. You take the liquid sublingually (underneath your tongue). However, limited research shows quercetin capsules or powders are more effective, and all forms of quercetin are absorbed poorly by the body.
Q: Where does quercetin come from?
A: Most supplement companies use various plant or vegetable-based sources of quercetin. Check the label.
Q: Can you get citrus-free quercetin?
A: Some quercetin supplements are specifically marketed as citrus-free, making them ideal for those with citrus sensitivities. Read the label or official product website for your supplement to be sure that it is actually citrus-free.
Q: Does quercetin help with diabetes?
A: There’s some evidence that quercetin helps with diabetes, helping your body manage blood sugar levels during fasting. However, more research needs to be done to verify these benefits.
Q: Is quercetin non-GMO?
A: Quercetin supplements are generally labeled non-GMO. Check the label to verify your quercetin supplement is not made from genetically modified ingredients.
Wrapping It Up
Quercetin is a bioflavonoid with potent antioxidant and anti-inflammatory effects. Many take quercetin supplements daily to support various body systems.Some people take quercetin supplements for allergies. Others take it to boost the immune system. Others take quercetin for general anti-aging or health and wellness.
Early research on quercetin is promising, and new human studies are released every year validating certain quercetin benefits.
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