Quercetin is a pigment found in a number of plants, herbs, vegetables, and fruits. The human body is able to metabolize it and preliminary research shows it may have a wide range of health benefits when taken as a supplement.
Quercetin supplements are marketed as something of a new wonder drug, as it has shown promising signs in treating or improving a wide range of health conditions. However, it's important to note that most of these claims are based on research that is either in very preliminary stages with human subjects, or has only been done on rats or in test tubes.
Among the things that quercetin is marketed and taken for:
- Seasonal allergies/hay fever
- High cholesterol
- Interstitial cystitis
- Prostate inflammation
- Heightened metabolism
- Athletic endurance
Quercetin may be useful for treating allergy symptoms and has shown promise in lowering blood pressure and cholesterol.
It's also a very potent antioxidant.
Studies in humans demonstrate that quercetin may be useful for treating allergy symptoms and has shown promise in lowering blood pressure and cholesterol.
Two test tube studies conducted in 2013 suggested that quercetin may be a good candidate for treating the symptoms of allergic rhinitis (hay fever) and asthma.[1, 2] A 2009 study conducted on human patients found that quercetin was effective in specifically relieving the symptoms of Japanese cedar allergies.
Heart disease and blood pressure
A 2009 study of 93 obese or overweight patients found that quercetin supplementation over the course of six weeks reduced blood pressure in the entire group and specifically reduced "bad" cholesterol in most of the group.
A 2007 study found that quercetin was effective in reducing blood pressure in rats with hypertension.
A 1999 study found that quercetin reduced inflammation and pelvic pain in patients with prostatitis.
Quercetin is not regulated by the FDA and has no established recommended daily allowance (RDA). Dosages shown to provide benefits in studies vary greatly depending on the condition it is taken for. For general use, supplement manufacturers usually package quercetin in capsules ranging from 200mg to 1g. The benefits seen in studies generally have not exceeded a maximum dose of 500mg, twice daily (1g per day total).
Like most supplements derived from plants and herbs, quercetin is sold almost exclusively in capsule form. Quercetin ascorbate is available as a powder, with a large amount of additional vitamin C added as a preservative.
There have been anecdotal reports of headaches and gastrointestinal discomfort as a result of taking large doses (500mg or more) of quercetin.
Though quercetin is a potent anti-inflammatory, it may induce inflammation with doses larger than 1g.
Seasonings derived from leaves are the richest natural sources of quercetin — particularly capers, lovage, sorrel, dill, and cilantro. The richest foods in quercetin are radish leaves (used in Indian cooking) and carob powder (sold as a high-fiber substitute for cocoa). Vegetables and fruit don't have as much quercetin, but there are a number that have at least some — red onions, watercress, kale, dark-colored berries, black plums, and sweet potato are the best sources. Lots of other fruits, vegetables, and tea leaves have very small amounts.
Speak to a doctor before beginning any new program of supplementation to ensure there are no contraindications with medications or supplements you're currently taking. Herbal supplements are not regulated by the FDA.
Quercetin is contraindicated for certain antibiotics. Consult with a doctor if you are on antibiotics to ensure there is no conflict.
Quercetin may induce kidney damage in doses greater than 1g per day.
Where to buy
Quercetin supplements can be purchased right here at PricePlow and at 30% to 50% off of retail pricing. Let PricePlow do the comparison shopping so you can focus on staying healthy.
- Sakai-Kashiwabara, M, et. al; Evidence-based Complementary and Alternative Medicine; "Inhibitory action of quercetin on eosinophil activation in vitro;" June 2013
- Hattori, M, et. al; International Immunopharmacology; "Quercetin inhibits transcriptional up-regulation of histamine H1 receptor via suppressing protein kinase C-δ/extracellular signal-regulated kinase/poly(ADP-ribose) polymerase-1 signaling pathway in HeLa cells;" January 2013
- Hirano, T, et. al; Allergology International; "Preventative effect of a flavonoid, enzymatically modified isoquercitrin on ocular symptoms of Japanese cedar pollinosis;" September 2009
- Edwards, RL, et. al; Journal of Nutrition; "Quercetin reduces blood pressure in hypertensive subjects;" 2007
- Egert, S, et. al; The British Journal of Nutrition; "Quercetin reduces systolic blood pressure and plasma oxidised low-density lipoprotein concentrations in overweight subjects with a high-cardiovascular disease risk phenotype: a double-blinded, placebo-controlled cross-over study;" April 2009
- Shoskes, DA, et. al; Urology; "Quercetin in men with category III chronic prostatitis: a preliminary prospective, double-blind, placebo-controlled trial;" December 1999
- Hillard, JJ, et. al; Advances in Experimental Medicine and Biology; "A comparison of active site binding of 4-quinolones and novel flavone gyrase inhibitors to DNA gyrase;" 1995