Quercetin Protects DNA from Oxidative Damage in Diabetics

Quercetin Protects DNA from Oxidative Damage in Diabetics Diabetics have reduced antioxidant defenses and an increased risk for free-radical mediated conditions such as heart disease and retinopathy. Quercetin, a dietary flavonoid with antioxidant properties, has been shown to protect retinal pigment epithelial and cortical cells during oxidative stress in vitro1, and to inhibit tyrosine kinase, an enzyme that mediates vascular endothelial growth factor. Consumption of flavonoids, especially quercetin, has also been linked to a lower incidence of heart disease and stroke. In one clinical trial2, diabetics were treated for 2 weeks on a low flavonoid diet followed by 2 weeks on one of 2 diets supplemented with flavonoids, one diet predominately quercetin. Oxidative damage to lymphocyte DNA was significantly lower after consuming the high quercetin diet, suggesting protection against oxidative stress at the tissue level. The finding was not accounted for by any change in diabetic control or changes in plasma levels of other known antioxidants.