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Quercetin
Description: Quercetin is a bioflavonoid which has antihistamine and anti-inflammatory properties. It also acts as an antioxidant.
Quercetin should be taken with Vitamin C.
Quercetin acts as a natural antihistamine.1 It may be effective in the prevention of asthma attacks; further research is still needed.
Quercetin is also effective in protecting against LDL cholesterol damage.2 Quercetin as found naturally may not be present in sufficient quantities to show a therapeutic result.3 Its use as a supplement has had greater success in protection against LDL.4,5
Quercetin helps to block the accumulation of sorbitol in the eye, and is especially helpful in the prevention of cataracts in patients with diabetes.6
Quercetin inhibits xanthine oxidase, the enzyme which makes uric acid,7 making it a useful treatment for gout.
Quercetin inhibits the growth of H. pylori.8 It may also help ease the pain of ulcers with their anti-inflammatory properties.9
Quercetin also inhibits aldose reductase, an enzyme which contributes to diabetic retinopathy.10

Natural Sources: Apples, Black Tea, Onions.

Useful in treatment of: asthma, atherosclerosis, cataracts, gout, hayfever, Peptic Ulcer, retinopathy.

Recommended Dosage: 200 to 400 mg twice daily.

Contraindications: None.

References:

1Pearce FL, et al. Mucosal mast cells III: effect of quercetin and other flavonoids on antigen-induced histamine secretion from rat intestinal mast cells. J Allergy Clin Immunol 1984;73:819-23.
2Ronzio RA. Antioxidants, nutraceuticals and functional foods. Townsend Letter for Doctors and Patients Oct 1996:34–35 [review].
3Hertog MGL, Sweetnam PM, Fehily AM, et al. Antioxidant flavonols and ischemic heart disease in a Welsh population of men: the Caerphilly Study. Am J Clin Nutr 1997;65:1489–94.
4Hertog MGL, Feskens EJM, Hollman PCH, et al. Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study. Lancet 1993;342:1007–11.
5Knekt P, Jarvinen R, Reunanen A, Maatela J. Flavonoid intake and coronary mortality in Finland: a cohort study. BMJ 1996;312:478–81.
6Varma SD et al. Diabetic cataracts and flavonoids. Science 1977;195:205.
7Busse W, Kopp D, Middleton E. Flavonoid modulation of human neutrophil function. J Allerg Clin Immunol 1984;73:801–9.
8Beil W, Birkholz C, Sewing KF. Effects of flavonoids on parietal cell acid secretion, gastric mucosal prostaglandin production and Helicobacter pylori growth. Arzneim-Forsch Drug Res 1995; 45:697–700.
9Wendt P, Reiman H, et al. The use of flavonoids as inhibitors of histidine decarboxylase in gastric diseases: Experimental and clinical studies. Naunyn-Schmeidbergs Arch Pharmakol 1980; 313(Suppl):238.
10Varma D. Inhibition of aldose reductase by flavonoids: Possible attenuation of diabetic complications. Prog Clin Biol Res 1986;213:343–58.
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