Quercetin is a plant flavonoid that’s found in a wide range of plant-based foods, including citrus fruits, berries, leafy green vegetables, herbs, spices, buckwheat, legumes, tea, and even cocoa. (1) Like other plant flavonoids, such as beta carotene found in orange plant foods, quercetin is an antioxidant, which means it works to scavenge free radicals in the body that threaten to damage DNA and cells.
In a combination of cellular, animal, and human studies, quercetin has exhibited antioxidant, anti-inflammatory, and anticancer properties. (1) Like most compounds with a range of interesting properties, quercetin has been studied for an extremely wide range of health issues. For example, it’s been studied for diabetes, obesity, allergy attacks, circulatory issues, inflammatory disease, and even mood disorders. (2) Studies have shown that quercetin and other plant flavonoids may protect against heart diseases like atherosclerosis and other studies have shown that quercetin can reduce blood pressure in those with hypertension. (3)
Quercetin may also be able to help protect the body against viruses. For example, a study published in 2013 showed that supplementation with quercetin reduced the incidence of upper respiratory tract infections, which are typically caused by viruses. (4) And finally, studies have also shown that consuming quercetin-rich food is associated with a decreased risk of lung cancer, especially in those that smoke cigarettes. (3)
On top of the emerging health benefits I already mentioned, quercetin is probably most famously used as a natural remedy for allergies. And research on quercetin has shown that it may be able to hinder allergic reactivity. (5) Researchers have been able to demonstrate that quercetin can stabilize the membranes of mast cells (the cells that are responsible for immediate allergic reactions) and reduce the release of histamine, which is what causes the common symptoms of allergies that many of us struggle with. Animal studies have even shown that quercetin can suppress the anaphylactic response and inhibit asthmatic inflammation. (5)
Pretty wild, right?
If you have a serious allergy, you should always follow the advice of your doctor and keep your medication close for emergency situations. But if you have seasonal allergies or asthma, quercetin may be a great complementary or alternative remedy to reduce uncomfortable symptoms. In my practice, I’ve seen many patients with troublesome seasonal allergies or allergy-related asthma see improvements with consistent quercetin supplementation.
You can buy quercetin in powder- or capsule-form at most health foods stores or online. The average daily dose is about 500 to 1,000 mg. Typically, the quercetin in supplements is derived from the Sophora japonica tree, which contains high levels of the flavonoid in its flowers and buds. (6) You’ll sometimes see quercetin in combination with vitamin C or an enzyme called bromelain. The purpose of this is to increase the absorption of quercetin in the digestive tract and I recommend looking for quercetin with these added ingredients!
A word before you buy a quercetin supplement: make sure you carefully assess the quality of the company. A great supplement company won’t add unnecessary fillers, sugar, or artificial colors of flavors to their supplements. I also recommend opting for supplement companies that rigorously lab test their products for contaminants as well as potency and purity — and they should be able to provide a TON of detailed information about how they test their products and when.
Why is this important? Unfortunately, it’s because the supplement industry isn’t very well-regulated. Supplements aren’t approved by the FDA before they are put on the market. Instead, the FDA retroactively regulates supplements by investigating a company if there are any reports of adverse events. (7) This allows a lot more freedom for new supplements to come on the market quickly and easily (Which is great!) but it also leaves the responsibility for finding a high quality supplement in the hands of the consumer — in YOUR hands. Once you find a great product, I recommend taking quercetin for at least a few weeks before you judge your symptoms.
If you struggle with allergies, which can flare at virtually any time of year (fall allergies, anyone?), quercetin is a great supplement to try out. Who knows, it may even make the difference between having to take an allergy pill, or not!
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