Apples and onions. Somehow, these two seemingly unrelated foods have the highest quantities of a compound called quercetin. Also known as a bioflavonoid, quercetin is found in many vegetables and fruits and is incredibly well studied.
Like most other bioflavonoids, quercetin is an antioxidant and has cancer preventing properties , but the scientific evidence does not point to any significant benefit taking this antioxidant alone.
What quercetin lacks alone, it makes up for as a synergistic supplement with a variety of other compounds including green tea catechins and resveratrol. The bioflavonoid is one of the most well-studied and considered GRAS (generally regarded as safe) by the U.S. Food and Drug Administration (FDA) .
Also Known As
Apple extract, 3, 4, 5, 7-pentahydroxylflavone
Editors’ Thoughts on Quercetin
My first and second experiences with quercetin came on the same day. After having never heard of the compound, I received Qualia (a blended nootropic) which noted quercetin as an ingredient. Later, I had lunch with a friend who’s naturopathic doctor recommended he take quercetin (along with others) for his inflammation.
When fate puts something in my path more than once, makes me pay attention. While I have not seen the long-term benefits of quercetin yet, I am encouraged that doctor Alexis Shields, N.D. recommended that as an anti-inflammatory for my friend.
Mansal Denton, Nootropedia Editor
While quercetin seems like a basic bioflavonoid with no benefits besides antioxidant properties, the molecule is more complex. Similar to caffeine, quercetin is an adenosine receptor antagonist , which means this can have some wakefulness effects similar to caffeine. Unfortunately, quercetin is not highly absorbed, which means it is not potent.
The main benefit of quercetin is as a neuroprotective agent and as anti-inflammatory support. One study showed that quercetin could protect neurons from oxidative stress . Another showed anti-inflammatory benefits that could help protect against Alzheimer’s and Parkinson’s disease .
Although not well-researched, another potential benefit of quercetin is against cancer. One study from the Boston University School of Medicine showed that diets rich in quercetin had a decreased risk of cancer .
Another great benefit of quercetin is as a stress-reducing agent after heavy exercise. Anyone who competes in physical sports or simply engages in intense activity knows that difficult workouts can be taxing on the body. Studies show a notable decline in stress after these types of workouts 
As mentioned earlier, the best part of this antioxidant is how it interacts with other substances. Below, we will describe some of the more popular combinations.
How Does Quercetin Work?
Quercetin works similar to most bioflavonoids by attacking free radicals and removing oxidative stress. However, combined with other nutrients, quercetin has more benefits and is even more effective.
- Quercetin and Yerba Mate – yerba mate is a drink most commonly found in south America, which has a unique polyphenol composition. Combined with this antioxidant, there is a synergistic interaction that helps further reduce inflammation .
- Quercetin and Resveratrol – both bioflavonoids, the two work well together to increase bioavailability and absorption. The benefits of each are accentuated through a function called AMPK activation .
- Quercetin and Green Tea Catechins – similar to resveratrol, combining green tea extract is highly effective. The quercetin helps with catechol-o-methyl transferase inhibition, which means green tea extract gets absorbed better .
Side Effects of Quercetin
There is much evidence on this antioxidant, but little to suggest there are any negative side effects. One study in animals showed quercetin reduced memory and learning ability , but the evidence is not conclusive.
Just because this nutrient is naturally derived, does not make it automatically healthy. High doses of quercetin can be associated with headaches and tingling in the arms and legs. There is also some evidence that quercetin supplements can interact with blood-thinning medications.
If you stay within the recommended dosage range, there are few side effects of quercetin that seem problematic.
The most effective quercetin dosage seems to be in the range of 12.5 – 25 mg per kg of bodyweight. This translates to a range of approximately 1100 – 2300 mg of daily consumption.
However, if you buy quercetin, it is best to also include bioflavonoids like resveratrol, green tea extract, and others to increase the potency and reduce your daily dosage. Find quercetin supplements that are dihydrate as they have the most bioavailability.
How and Where to Buy Quercetin
This antioxidant is a common bioflavonoid widely available both online and in your local health food store. We recommend you buy quercetin online in order to find the most affordable outlet. Now Foods is a popular and well-established brand, but note that their product has bromelain. While bromelain works synergistically with this antioxidant, these are two separate compounds.
If you find quercetin for sale and want to take full advantage of this natural antioxidant, you may also want to buy green tea extract or resveratrol as well. Both of these compounds increase the efficiency of this antioxidant in different ways to the bromelain mentioned above.
Selected Community Experiences
“I got home from Thanksgiving in Colorado… and return to my normal stack…200 mg EGCG 500 mg quercetin…”  – MisterYouAreSoDumb
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