What Is Quercetin
What Is Quercetin?
Quercetin is a pigment that belongs to a group of plant compounds called flavonoids.
Flavonoids are present in:
· vegetables
· fruits
· grains
· tea
· wine
They’ve been linked to several health benefits, including reduced risks of heart disease, cancer, and degenerative brain disorders (1Trusted Source, 2Trusted Source).
The beneficial effects of flavonoids like quercetin come from their ability to function as antioxidants inside your body (3Trusted Source).
Antioxidants are compounds that can bind to and neutralize free radicals.
Free radicals are unstable molecules that may cause cellular damage when their levels become too high.
Damage caused by free radicals has been linked to numerous chronic conditions, including cancer, heart disease, and diabetes (4Trusted Source).
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 (5Trusted Source).
Foods that commonly contain quercetin include onions, apples, grapes, berries, broccoli, citrus fruits, cherries, green tea, coffee, red wine, and capers (5Trusted Source).
It’s also available as a dietary supplement in powder and capsule form.
People take this supplement for several reasons, including to:
· boost immunity
· fight inflammation
· combat allergies
· aid exercise performance
· maintain general health
Research has linked quercetin’s antioxidant properties to various potential health benefits.
Here are some of its top science-based benefits.
May reduce inflammation
Free radicals may do more than simply damage your cells.
Research shows that high levels of free radicals may help activate genes that promote inflammation. Thus, high levels of free radicals may lead to an increased inflammatory response (3Trusted Source).
While a little inflammation is necessary to help your body heal and fight infections, persistent inflammation is linked to health problems, including certain cancers, as well as heart and kidney diseases (6Trusted Source).
Studies show that quercetin may help reduce inflammation.
In test-tube studies, quercetin reduced markers of inflammation in human cells, including the molecules tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) (7Trusted Source, 8Trusted Source).
An 8-week study in 50 women with rheumatoid arthritis observed that participants who took 500 mg of quercetin experienced significantly reduced early morning stiffness, morning pain, and after-activity pain (9Trusted Source).
They also had reduced markers of inflammation, such as TNFα, compared to those who received a placebo (9Trusted Source).
While these findings are promising, more human research is needed to understand the compound’s potential anti-inflammatory properties.
May ease allergy symptoms
Quercetin’s potential anti-inflammatory properties may provide allergy symptom relief.
Test-tube and animal studies found that it may block enzymes involved in inflammation and suppress inflammation-promoting chemicals, such as histamine (10Trusted Source, 11Trusted Source, 12Trusted Source).
For example, one study showed that taking quercetin supplements suppressed peanut-related anaphylactic reactions in mice (13Trusted Source).
Still, it’s unclear whether the compound has the same effect on allergies in humans, so more research is needed before it can be recommended as an alternative treatment.
May have anticancer effects
Because quercetin has antioxidant properties, it may have cancer-fighting properties (14Trusted Source).
In a review of test-tube and animal studies, quercetin was found to suppress cell growth and induce cell death in prostate cancer cells (15).
Other test-tube and animal studies observed that the compound had similar effects in liver, lung, breast, bladder, blood, colon, ovarian, lymphoid, and adrenal cancer cells (16Trusted Source, 17Trusted Source, 18Trusted Source, 19Trusted Source).
Though these findings are promising, human studies are needed before quercetin can be recommended as an alternative treatment for cancer.
May lower your risk of chronic brain disorders
Research suggests that quercetin’s antioxidant properties may help protect against degenerative brain disorders, such as Alzheimer’s disease and dementia (20Trusted Source).
In one study, mice with Alzheimer’s disease received quercetin injections every 2 days for 3 months.
By the end of the study, the injections had reversed several markers of Alzheimer’s, and the mice performed much better on learning tests (21Trusted Source).
In another study, a quercetin-rich diet reduced markers of Alzheimer’s disease and improved brain function in mice at the early middle stage of the condition.
However, the diet had little to no effect on animals with middle-late stage Alzheimer’s (22Trusted Source).
Coffee is a popular beverage that has been linked to a lower risk of Alzheimer’s disease.
In fact, research shows that quercetin, not caffeine, is the primary compound in coffee that’s responsible for its potential protective effects against this illness (23Trusted Source).
Though these findings are promising, more research in humans is needed.
May reduce blood pressure
High blood pressure affects 1 in 3 American adults. It raises your risk of heart disease — the leading cause of death in the United States (24).
Research suggests that quercetin may help reduce blood pressure levels. In test-tube studies, the compound appeared to have a relaxing effect on blood vessels (25Trusted Source, 26Trusted Source).
When mice with high blood pressure were given quercetin daily for 5 weeks, their systolic and diastolic blood pressure values (the upper and lower numbers) decreased by an average of 18% and 23%, respectively (27Trusted Source).
Similarly, a review of 9 human studies in 580 people found that taking more than 500 mg of quercetin in supplement form daily reduced systolic and diastolic blood pressure by an average of 5.8 mm Hg and 2.6 mm Hg, respectively (28Trusted Source).
Although these findings are promising, more human studies are needed to determine whether the compound could be an alternative therapy for high blood pressure levels.
Other potential benefits
Here are several other potential benefits of quercetin:
· May help combat aging. Test-tube and animal research suggests that quercetin may help rejuvenate or eliminate aging cells and reduce markers of aging. However, more human research is needed (29Trusted Source, 30Trusted Source, 31Trusted Source).
· May aid exercise performance. A review of 11 human studies found that taking quercetin may slightly improve endurance exercise performance (32Trusted Source).
· May aid blood sugar control. Human and animal research indicates that the compound may reduce fasting blood sugar levels and protect against complications of diabetes (33Trusted Source, 34Trusted Source, 35Trusted Source).
SUMMARY
Quercetin may improve inflammation, blood pressure, exercise performance, and blood sugar management.
In addition, it may have brain-protective, anti-allergy and anticancer properties. Still, more research in humans is needed.
Source：https://www.healthline.com/nutrition/quercetin#
By Ryan Raman, MS, RD — Medically reviewed by Kathy W. Warwick, R.D., CDE, Nutrition — Updated on July 1, 2020
