Week 25 Blog- Quercetin the Antioxidant

What is Quercetin?

Quercetin belongs to a group of plant pigments called flavonoids which is why it’s found in deeply colored, nutrient-packed fruits and vegetables. It is one of the most abundant antioxidants in the human diet, quercetin plays an important part in fighting the damage from the “wild child” free radicals. This damage causes aging and inflammation. It’s been shown in dozens of studies to have anti-carcinogenic, anti-inflammatory and have antiviral activities.  Also, according to the Department of Pathology and Diagnostics at the University of Verona in Italy, quercetin and other flavonoids are “anti-viral, anti-microbial, anti-inflammatory and are anti-allergic agents.” https://draxe.com/nutrition/quercetin/    From the research paper titled, Quercetin, Inflammation and Immunity, originally published In MDPI (Molecular Diversity Preservation International) and then again in National Center for Biotechnology Information (NCBI), states -Quercetin has unique biological properties that may improve mental/physical performance and reduce infection risk.  They also say-  These properties form the basis for potential benefits to overall health and disease resistance, including being anti-carcinogenic, anti-inflammatory, antiviral, antioxidant, and psychostimulant activities, as well as many more. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4808895/

Quercetin may help protect against heart disease and cancer. Quercetin can also help stabilize the cells that release histamine in the body and thereby have an anti-inflammatory and antihistamine effect.

Up to this point we know- Research shows that flavonoids like Quercetin that are found in the deeply colored fruits and vegetables, can help manage a number of inflammatory health problems, including heart disease and blood vessel problems, allergies, infections, chronic fatigue, and symptoms related to autoimmune disorders like arthritis.  Quercetin and other flavonoids are “anti-viral, anti-microbial, anti-inflammatory and anti-allergic. Let’s look closer at what quercetin can do:

- anti-inflammatory, antioxidant properties - that can help combat certain diseases. They hunt the free radicals which damage cell membranes, tamper with DNA, and even cause cell death. Antioxidants like Quercetin can neutralize free radicals and may reduce or even help prevent some of the damage that the “wild child” free radicals’ cause. Quercetin is considered to be the most widely distributed and extensively studied flavonoid, according to a 2018 review. One study found that 500 mg of quercetin a day could improve symptoms of rheumatoid arthritis. There are reports of people with RA who had fewer symptoms when they switched from a typical Western diet to a vegan diet with lots of uncooked berries, fruits, vegetables, nuts, roots, seeds, and sprouts containing quercetin and other antioxidants. 


-Supports Heart Health- Because of its ability to lower inflammation and oxidative stress, quercetin seems to be beneficial for people with heart and blood vessel-related disorders. For example, eating lots of deeply colored fruits and veggies that contain flavonoids is linked to a lower risk of vascular disease, cardiovascular disease, and even death, in older adults. It’s also been connected to reduced risk for type 2 diabetes and obesity, which have many of the same risk factors as heart disease. Antioxidants also seem to protect the body from experiencing increases in LDL “bad” cholesterol and can help regulate blood pressure levels. Flavonoids like quercetin, resveratrol, and catechins (all found in high concentrations in red wine) may help reduce the risk of atherosclerosis which is a plaque buildup in arteries that can lead to heart attack or stroke.


- Helps Fight Pain- Taking quercetin supplements may help lower pain associated with autoimmune conditions such as arthritis and infections, including those of the prostate and respiratory tract. Studies suggest quercetin reduces inflammatory pain.


- Might Help Improve Energy and Endurance- Quercetin is added to some athletic supplements because it’s believed to help increase athletic performance and endurance. This happens because of its positive effects on blood flow. Researchers from the School of Applied Physiology at the Georgia Institute of Technology found that, on average, “quercetin provides a statistically significant benefit in human endurance exercise capacity (VO2 max) and endurance exercise performance).” While improvements were at times small, it makes sense that antioxidants could boost physical performance since they help increase the health of blood vessels, which carry oxygen and nutrients to muscle and joint tissue.


-Brain Health- Improved circulation improves brain health as well. But quercetin can protect the brain in many other ways. It may reduce inflammation and protect brain cells from toxins. Its antioxidant powers could lower the risk of Alzheimer's disease and other degenerative diseases of the brain. https://www.webmd.com/diet/foods-high-in-quercetin#1

-Anti- cancer Effects- When free radicals damage cells in the body, those cells sometimes develop into cancer. Quercetin and other antioxidants reduce the risk of cancer by fighting free radicals. A few studies have targeted quercetin particularly. In one study, it slowed tumor growth. In another, it lowered the risk of lung cancer. The third study found that quercetin had the ability to attack leukemia cells. A Boston University School of Medicine study published in the Journal of Biological Regulators and Homeostatic Agents shows a link between a nutrient-dense diet rich in quercetin plus other antioxidants with a lowered risk of cancer. Quercetin seems to have potential chemo-preventive activity and might have a preventative or slowing of growth effect on cancerous cells, making it an effective addition to any natural cancer treatment approach. Quercetin and other flavonoids have been shown in these studies to inhibit the growth of cancer cells from breast, colon, prostate, ovarian, endometrial, and lung tumors. One study even suggests that quercetin is more effective than resveratrol in terms of inhibiting tumor growth. Another found that frequent intake of quercetin-rich foods was associated with lower lung cancer risk. The association was even stronger among subjects who smoked more than 20 cigarettes daily, and a third suggests that quercetin slows tumor growth in the laboratory (in leukemia cells). This is very exciting but more research is needed. https://www.mountsinai.org/health-library/supplement/quercetin

-Others- Quercetin plays a role in protecting liver health, Skin Health, fighting Allergies, asthma, hay fever and hives


Dietary Sources

Fruits and vegetables are the primary dietary sources of quercetin, particularly citrus fruits, apples, parsley, sage, green and black tea, red wine, and onions. In red onions, higher concentrations of quercetin occur in the outermost rings and in the part closest to the root. One study found that organically grown tomatoes had 79% more quercetin than chemically grown fruit.

Olive oil, grapes, dark cherries, and dark berries such as blueberries, blackberries.

 Brassica vegetables. Brassica vegetables are members of the Brassica genus of plants and include the related plants broccoli, cauliflower, kale, Cabbage, Brussels sprouts, and turnip. These vegetables are low in calories and are generally very nutritious.

Capers, shallots as well as many seeds, nuts, flowers, barks, and leaves.

Available Forms

Quercetin supplements are available as pills or capsules. On its own your body absorbs it poorly. That’s why the supplements may include other compounds, such as vitamin C or digestive enzymes like bromelain, an enzyme found in pineapple) because both are anti-inflammatories and they may increase absorption. If you look for a supplemental form of Quercetin, look for the form with bromelain and with C added. 

I will provide the link to a June 2020 study that showed evidence that vitamin C and quercetin taken together gives a synergistic antiviral action due to overlapping antiviral and immunomodulatory properties and the capacity of ascorbate (vitamin c) to recycle quercetin, increasing its efficacy. In their summary they stated “Quercetin displays a broad range of antiviral properties which can interfere at multiple steps of pathogen virulence -virus entry, virus replication, protein assembly- and that these therapeutic effects can be augmented by the co-administration of vitamin C. Furthermore, due to their lack of severe side effects and low-costs, we strongly suggest the combined administration of these two compounds for both the prophylaxis and the early treatment of respiratory tract infections, especially including COVID-19 patients.”

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7318306/- Quercetin and Vitamin C: An Experimental, Synergistic Therapy for the Prevention and Treatment of SARS-CoV-2 Related Disease (COVID-19)

-Quercetin and zinc team:

Zinc and quercetin work together in the body. Quercetin helps enhance the absorption of zinc, and both have similar antiviral functions. Zinc is a positively charged ion so it makes it difficult for it to penetrate the fat-soluble cell membrane, as they are not permeable to positively charged ions. This means that zinc needs a transporter to cross the cell membrane. Many fat-soluble nutrients can do this, including curcumin and EGCg. But quercetin seems to be particularly useful as a zinc ionophore. An ionophore is a substance that transports particles across the cell wall barrier into the center of the cell.  The center of the cell is where zinc needs to be to have the immune system effect. Viruses reproduce in the center of the cells. Zinc needs to be in the center of the cell to stop viral reproduction. An all-natural zinc ionophore is quercetin. It may also enhance the antiviral activities of zinc.

Although supplements may be essential during an active illness, the first place to start is to support the immune system with food. One way to do this is by including foods that are rich in zinc and quercetin. This might include adding food pairings such as:

Cashews with red grapes

Pork chops topped with baked apples

Steak tacos with tomato salsa

Greek yogurt with a variety of berries

https://blog.bioticsresearch.com/how-zinc-and-quercetin-work-together      https://www.healthfirstdc.com/blog/the-importance-of-zinc-and-quercetin-during-pandemic


There isn’t a daily recommended amount for quercetin. Estimates show that most people typically get between five and 40 milligrams of it a day from eating common plant foods. If you stick with a good quality, nutrient-dense diet rich in the foods we stated earlier, you’re likely to take in as much as 500 milligrams daily.  For people who turn to quercetin supplements the common oral dosages on a bottle are 500 milligrams taken twice daily.  You can experience benefits when taking lower doses as well. Always start with your diet- focus on the food first.

Is quercetin safe to take daily? Amounts up to 500 milligrams taken twice daily for 12 weeks appear to be very safe. If you plan to take this supplement for longer, it’s a good idea to speak with your doctor first. In very high doses there are some risks. Side effects can include headaches and tingling of the arms and legs. Very high doses taken intravenously have also been linked to cases of kidney damage, although this seems very rare. As in everything- Never megadose!

For women who are pregnant or breastfeeding, it doesn’t seem to have any negative effects, although there hasn’t been much research done in this population so it’s always a good idea to talk it over with your doctor first.


Possible Interactions:

If you are being treated with any of the following medications, you should not use quercetin supplements without talking to your health care provider first.

Antibiotics- There is some concern that quercetin may reduce the effectiveness of certain antibiotics.

Anticoagulants (blood thinners)- Quercetin may enhance the effect of these drugs, increasing your risk for bleeding. Anticoagulants include: Warfarin (Coumadin), Clopidogrel (Plavix), Aspirin

Chemotherapy- Test tube and animal studies suggest that quercetin may enhance the effects of doxorubicin and cisplatin, which are two chemotherapy medications used to treat cancer. In addition, some doctors believe taking antioxidants at the same time as chemotherapy can be harmful, while others believe it can be helpful. In one study, combining quercetin with the anti-tumor drug doxorubicin, increased the drug's beneficial effects on breast cancer cells. In another, taking quercetin alongside cisplatin reduced the medicines' therapeutic effects in ovarian cancer cells. Talk to your oncologist before taking any supplements if you are undergoing chemotherapy.

Corticosteroids-Quercetin may cause these drugs to stay in the body longer.

Cyclosporine- Quercetin may interfere with the body's absorption of this drug, which is used to suppress the immune system.

Digoxin-Quercetin use may increase the risks of digoxin.

Fluoroguinolones- Quercetin use may reduce their effectiveness.

 If you take multiple medications or the drugs I just listed please speak with your pharmacist, physician or specialist before adding Quercetin to your plan.

In closing:

Quercetin is a type of flavonoid antioxidant that’s found in plant foods. It’s technically considered a “plant pigment,” which is exactly why it’s found in deeply colored, nutrient-packed fruits and veggies.

Along with other flavonoids it has been shown to have antiviral, antimicrobial, anti-inflammatory and anti-allergic effects. Quercetin supplements and foods might help reduce inflammation, fight allergies, support heart health, combat pain, potentially improve endurance, fight cancer, and protect skin and liver health. It partners with Zinc for your immunity and Vitamin C and bromelain help quercetin to be better absorbed. We call that team work! Some of the top quercetin foods include apples, peppers, red wine, dark cherries, tomatoes, capers, onions, dark berries, cruciferous and leafy green veggies, citrus fruits, whole grains, legumes, herbs, and more. Most of these foods are readily available to you. Power up you’re fueling for fabulous antioxidant results that fight for you.