Quercetin is the most abundant of the flavonoids. Quercetin belongs to the flavonoids family and consist of 3 rings and 5 hydroxyl groups. Quercetin is also a building block for other flavonoids. Quercetin occurs in food as an aglycone (attached to a sugar molecule). Only a small percentage of the ingested quercetin will get absorbed in the blood. Quercetin is found in many common foods including apple, tea, onion, nuts, berries, cauliflower and cabbage.
Quercetin belongs to a group of plant pigments called flavonoids that give many fruits, flowers, and vegetables their color.
Flavonoids, such as quercetin, are antioxidants -- they scavenge damaging particles in the body known as free radicals, which damage cell membranes, tamper with DNA, and even cause cell death. Antioxidants can neutralize free radicals and may reduce or even help prevent some of the damage they cause. They also help keep LDL ("bad") cholesterol from being damaged, which scientists think may contribute to heart disease. In test tubes, quercetin has strong antioxidant properties, but researchers aren't sure whether taking quercetin (and many other antioxidants) has the same effects inside the body.
Quercetin acts like an antihistamine and an anti-inflammatory, and 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 effect.
Quercetin, a member of the flavonoids family, exerts many beneficial health effects, including improvement of cardiovascular health, reducing risk for cancer, protection against osteoporosis. This phytochemical has anti-inflammatory, anti-allergic and antitoxic effects. Most of these properties are linked to its strong antioxidant action of quercetin but quercetin also modulates the expression of specific enzymes. Quercetin induces apoptosis and influences protein and lipid kinase signaling pathways. Quercetin is a candidate for preventing obesity-related diseases.
Quercetin may help to reduce symptoms of diabetes patients. One study showed that quercetin reduced blood glucose level and improved plasma insulin levels in streptozotocin-induced diabetic rats. An in-vitro study concluded that quercetin may have a pharmacological application in treating cardiovascular disease in diabetes mellitus patients.
Quercetin shows anti-inflammatory action by its direct antioxidant action and inhibition of inflammatory mediators and enzymes, such as lipoxygenase. Quercetin also inhibits the release of histamine, which causes congestion, by basophils and mast cells. Studies have shown an improved lung function and lower risk of certain respiratory diseases (asthma and bronchitis) for people with high apple (rich in quercetin) intake. Patients with increased levels of inflammation and oxidative stress might benefit most from a quercetin supplementation.
Studies demonstrate that flavonoid-rich diets protect against myocardial infarction and stroke. As many other flavonoids, quercetin inhibits oxidation of LDL (bad) cholesterol, lowers blood pressure and reduces the risk of heart disease.
Studies have shown that quercetin reduces cancer risk of prostate, ovary, breast, gastric and colon cells. Numerous in-vitro studies show that quercetin induces apoptosis of cancer cells through different mechanisms.
Quercetin supplementation has been linked with improved performance, but supporting evidence is weak and often conflicting. Scientists suggest that quercetin may aid performance through its anti-inflammatory properties or by stimulating the activity of mitochondria.
There are very few known Quercetin side effects. Prolonged consumption of Quercetin is presumed to be safe; however, if it is taken in large amounts, in conjunction with an antioxidant it may cause some problems.
If Quercetin is taken in conjunction with an antioxidant such as vitamin C other problems can possibly manifest. This could reverse the anti-inflammatory effect that you get from vitamin C. This may not seem a big deal but if this is left untreated it can cause serious issues. Undefined research has suggested that this will only happen if you use Quercetin over a long period of time. As this is not a definite side effect of Quercetin, it is still the preferred treatment of choice.
Those people who have stomach issues or problems, Quercetin can cause reflux and heartburn, if taken in large amounts when you have not eaten. This is easily fixed; you just take your Quercetin supplement after a meal.
As already stated Quercetin has few side effects, it can however, cause negative interactions with some types of medication. This can potentially be lethal.
The following medications may interact badly with Quercetin,
Quinolone, this is an antibiotic. Quercetin may cause the antibiotics to halt the process of combatting bacteria. Some other antibiotics that may also have a reaction to Quercetin are trovafloxacin, ciprofloxacin, norfloxacin and sparfloxacin.
Cyclosporin has a negative effect with Quercetin. Quercetin can increase the symptoms that are a result of using cyclosporin, so this effect can be either good or bad.
Some medications which the liver changes can have negative effects when used in conjunction with Quercetin. The speed at which your liver changes the medication may increase or decrease. This can potentially cause liver failure. Some medications changed by the liver are, celecoxib, diclofenac, glipizide and ibuprofen.
The interaction between these medications and Quercetin may not be severe, but I advise if you have already taken these in conjunction with Quercetin, that you seek medical advice. Do not leave any effect untreated, this can make the problem worse and it is detrimental to your health.
Always do adequate research on any medication you are thinking of taking.
Reviewer: 35-44 Female on Treatment for 5 to less than 10 years (Consumer)
Comment: I use 500-1000 mg of quercitin a day to treat my interstitial cystitis (I take it with 100 mg of bromelin, which acts as a catalyst for quercitin and increases effectiveness). I was diagnosed with IC 8 years ago, and decided not to take Elmiron because of cost and potential effects on the liver. I did extensive research and found articles from European and British medical journals regarding the use and effectiveness of quercitin in reducing IC symptoms (pain, frequency, etc). It may work by helping to increase the mucous layer/lining in the bladder (?) Taking it regularly has helped greatly in reducing my symptoms by about 90%, so I can lead a normal life again. It has also helped reduce symptoms related to allergies. For me, it is literally [extremely good], because my pain was so chronic and acute... However, no doctor I have spoken to knows about it, and I can't find the use of quercitin for IC in any American medical sources, including books written about IC. I don't know if it works in everyone. I didn't realize there potential side effects to the kidneys. However, my recent physical shows no problems with my kidneys after eight years of daily use. Now that I am aware of this, I will be more careful to track this and consider my dosage level.
Reviewer: 35-44 Female on Treatment for 2 to less than 5 years (Consumer)
Comment: I have suffered from terrible sinus headaches for years. I started Quercetin about two years ago. I just take it when i am having problems. My sinus issues are related to allergies. Quercetin is pretty effective, and much more effective with less side-effects than any of the presecriptions I had been given. I would not recommend it for people with ulcers or stomach/intestinal problems however. And the brand you use makes a difference, it seems.
Reviewer: 55-64 Female on Treatment for less than 1 month (Consumer)
Comment: Started taking this for sarcoidosis. Since taking it I am able to get a better nights sleep. Started taking it for its anti inflammatory effect. I believe it is helping me with the pain also.
Reviewer: 45-54 Male on Treatment for 1 to 6 months (Consumer)
Comment: Increases energy without feeling jittery or nervous. Has a subtle effect you hardly notice, until you're half way thru your workout and don't feel as tired as before you tried the supplement.
Reviewer: 25-34 Female on Treatment for 10 years or more (Consumer)
Comment: I love this for my seasonal allergies. I have been using it since the late 90s. It has allowed me to almost completely get off of OTC allergy medicine, not that it worked that well. I start a few weeks before the trees start in my area and use it mostly through the summer and into fall. Usually take one 600mg cap in the morning. If I start to feel allegery symptoms I will take one at night also. I can't say enough about it. Don't care what this website says it totally works for me and I encourage others to try it. Like stinging nettle too! Helps reduce symptoms when they happen.
Reviewer: 7-12 Female on Treatment for 6 months to less than 1 year (Consumer)
Comment: My daughter has severe asthma. She takes Singulair but has side effects. I wanted to try to wean her off of the Singulair but due to her severity of asthma was scared to completely take her off. After 1 bottle, we are taking 1/2 of the singulair and 1 500 mg Quercetin per day. She has not had an asthma attack or breathing treatment during this time. I did check with her doctor prior to starting this regimen. I think we could go off of the singulair, I just don't want her to suffer and so I have been leary to completely do it.