What Is Quercetin?

Quercetin is a plant pigment, or flavonoid, found in many plants and foods.  Quercetin also has antioxidant and anti-inflammatory effects that may help reduce swelling, induce apoptosis (natural cell death), control blood sugar, and help prevent heart issues. Quercetin is most commonly used for conditions of the heart and blood vessels and to potentially prevent cancerous cell growth.

Sources of Quercetin

Quercetin is the most abundant flavonoid in the diet. It’s estimated that the average person consumes 10–100 mg of it daily through various food sources. Foods that commonly contain quercetin include: onions, apples, grapes, berries, broccoli, citrus fruits, cherries, green tea, coffee, red wine, and capers.

Benefits of Quercetin

Reduce Inflammation

Flavonoids, (aka bioflavonoids or bioflavonoide) including quercetin, are important anti-inflammatories because they act as antioxidants, which mean they literally fight the natural process of “oxidation” that takes place over time as we age. Quercetin can help stop damaging particles in the body known as free radicals, which negatively impact how cells work — including damaging cell membranes, changing the way DNA works, increasing cell mutations and causing healthy cells to die. This can reduce expression of inflammatory genes such as interleukin. Research now shows us that inflammation is the root of most diseases, including heart disease, cognitive decline, some mental disorders and autoimmune disorders.

Assist with Allergies

Some consider quercetin to be a natural antihistamine and an anti-inflammatory, possibly making it effective for lowering the effects of seasonal and food allergies, plus asthma and skin reactions. Histamines are chemicals that are released when the immune system detects an allergy or sensitivity, and they are what account for the uncomfortable symptoms when the body has an allergic reaction. Quercetin can help stabilize the release of histamines from certain immune cells, which results in decreased symptoms like coughs, watery eyes, runny noses, hives, swollen lips or tongue, and indigestion.

Quercetin has long been used in ancient Chinese herbal formulas created to block allergies to certain foods (such as peanuts). Studies conducted on mice suggest that it may be equivalent at fighting allergies as some prescription medications, all with little to no side effects. However, few human studies have been completed to date.

Heart Health

Due to its ability to lower inflammation and oxidative stress, quercetin seems to be beneficial for people with heart and blood vessel-related disorders. Most people are aware that eating lots of deeply colored fruits and veggies lower the risk of cardiovascular disease and other vascular diseases, that is thought to be in part because they contain flavonoids. Studies done in animal and some human populations show that various types of flavonoids (quercetin, resveratrol and catechins, for example) can help reduce the risk of atherosclerosis, which is a dangerous condition caused by plaque building up within the arteries. Cut-off blood flow in the arteries is one of the primary risk factors for experiencing a heart attack or stroke.

Antioxidants also seem to protect the body from experiencing increases in LDL “bad” cholesterol and can help regulate blood pressure levels. Certain studies show that quercetin prevents damage to LDL cholesterol particles. By extension people who eat the most flavonoid-rich foods typically have healthier and lower cholesterol levels.

Who Should Use Quercetin?

There isn’t a daily recommended amount of quercetin intake, so dosage recommendations can vary depending on your health condition. Estimates show that most people typically get between 5 and 40 mg of it a day from eating common plant foods; however, if you stick with a nutrient-dense diet overall, you’re likely to take in much more — as much as 500 mg daily according to a some reports.

Optimal doses of quercetin have not been established for any specific conditions by the FDA or any other governing health authority at this time, so it’s up to you and your doctor to decide what amount works best for you. For people who turn to quercetin supplements, common oral dosages are 500 mg taken twice daily, but it’s also definitely possible to experience benefits when taking lower doses.

Who Shouldn’t Use Quercetin?

According to most studies there are little to no side effects in people eating nutrient-dense diets high in quercetin or taking supplements by mouth short term. If supplementing daily, amounts up to 500 mg 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.

However, of course, 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. Quercetin supplementation can interact with the effectiveness of antibiotics, chemotherapy and blood-thinner medications, so use caution if you currently take any of these. 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.