You’ve most likely ingested this bioactive plant compound before in the form of apples, onions, or tea, but increasing evidence suggests it might be worth supplementing. Here, we break down the benefits of quercetin, how to get more in your diet, and whether supplementing is right for you. Like all flavonoids, quercetin is an antioxidant, meaning it helps scavenge and neutralize free radicals that might otherwise accelerate aging, contribute to inflammation, and fuel a range of chronic diseases from cancer to heart disease. Quercetin may be most well known for its ability to ease seasonal allergy symptoms, but it’s proving to be quite the versatile plant compound. “Quercetin is a powerful antioxidant providing anti-inflammatory, antihistamine, and antiviral properties, as well as serving the ability to reduce blood clots and oxidative stress in arteries,” says Ali Miller, R.D., L.D., CDE, registered dietitian and integrative functional medicine practitioner. “The current pandemic makes this nutrient even more of an important player as we see oxidative stress, inflammation, and clotting factors as concerns.” “The main reason I’ve prescribed quercetin for over 30 years is because it works, it is safe, and its use is based on solid published evidence,” says Robert Rountree, M.D., renowned integrative physician. “I also prescribe it a lot because it is so versatile as a preventive or treatment for so many kinds of health conditions.” Here are some specific ways quercetin may enhance health: This flavonoid has even helped reduce the frequency and severity of herpes outbreaks among Rountree’s patients. According to Rountree, quercetin’s mechanism of combating viruses isn’t totally understood, but it appears to be a combination of immune modulation, prevention of viral entry into cells, and inhibition of viral replication. Quercetin also acts synergistically with other immune-boosting nutrients. For example, “Quercetin acts as a zinc shuttle, getting natural antiviral zinc into cells where it can help mitigate viral replication,” Vincent Pedre, M.D., integrative physician, recently told mbg. It’s too early to say whether or not quercetin would help against COVID-19—but research is beginning to be published2 on quercetin’s potential value in prevention and treatment, and it’s been one of Rountree’s top recommendations to support the immune system during the pandemic. Several studies are underway to explore this, so stay tuned. More research is needed in humans, but lab studies—including one published in the journal Molecules—show that quercetin can help combat conditional allergic rhinitis3. How exactly? It seems to help prevent the overactivation of mast cells, which secrete histamine—an inflammatory chemical that’s involved in allergy symptoms like itching and sneezing. Vitamin C may enhance quercetin’s allergy-fighting potential. In fact, several studies like this one published in the European Journal of Clinical Nutrition have found that supplementing with about 500 mg of quercetin4 per day helps lower levels of the inflammatory biomarker c-reactive protein (CRP), which is elevated in conditions like heart disease, rheumatoid arthritis, metabolic syndrome, and diabetes. Another study5 published in the Journal of the American College of Nutrition, which looked at 50 women with rheumatoid arthritis, found that 500 mg of quercetin per day for eight weeks helped reduce morning stiffness and pain. More studies are needed on humans, but research on mice6 has found that quercetin injections reduced several markers of Alzheimer’s disease and improved performance on memory tasks. Abundant lab and animal studies demonstrate quercetin’s ability to curb cancer cell growth and even prompt cancer cell death in multiple types of cancer (breast7, colon8, ovarian9, lung10, and prostate to name a few), but more research is needed on humans. Some research suggests15 that quercetin may cause headaches or tingling nerve sensations, but Rountree says he has not seen this among his patients and that quercetin is on his “A-list of supplements” that most people could benefit from taking every day. Who should avoid quercetin? If you’re currently taking another medication, it’s always a good idea to talk to your health care provider about potential interactions. For example, because quercetin can thin the blood and help reduce blood clots, it may interfere or amplify the effects of blood thinners; there’s also some evidence it could interfere with medications that have a narrow therapeutic window such as transplant anti-rejection drugs. Pregnant women should also steer clear since no good studies exist on the safety of quercetin during pregnancy (food sources are totally fine). A typical dose of quercetin is 500 to 1,000 mg per day (this is the dosage often used in clinical studies16). However, quercetin is somewhat poorly absorbed through the intestinal wall, so Rountree recommends quercetin phytosome—a form where quercetin is attached to a phospholipid complex17, which has been shown to dramatically enhance absorption18. Another way to get more nutritional bang for your quercetin buck: Combine it with vitamin C. “I recommend a form of quercetin with a food-derived vitamin C source like acerola cherry and bioflavonoids from citrus,” says Miller. “This will provide some synergistic effects, which will get outcomes at a lower dosage.” Keep in mind: When it comes to supporting overall immunity, quercetin should be just one component of your routine (nothing works in isolation, after all). To give your immune system an extra leg up, get seven to nine hours of sleep a night, eat immune-boosting foods, consider additional expert-backed supplements for immune health, stay active, and manage stress or any existing health conditions you may have.
