Effect of onion juice supplementation on antioxidant status in participants with mild hypercholesterolemia

Hypercholesterolemia is known to be associated with enhanced oxidative stress related to increased lipid peroxidation. Several epidemiological and clinical studies have reported the benefits of consuming fruits and vegetables, leading to reduced risks for cardiovascular diseases and several types of cancers. Flavonoids are potential antioxidants found in foods such as onions. The aim of this study was to investigate the effect of decocted onion juice (about 300 g onion) supplementation for 10 weeks on antioxidant status in mild hypercholesterolemic subjects. Twenty-seven participants were studied in a randomized, single-blind, placebo-controlled, crossover design. Indices of antioxidant status used were plasma total antioxidant capacity, antioxidant vitamins, LDL oxidation, erythrocyte antioxidant enzyme activity, and leukocyte DNA damage. After 10 weeks of consuming decocted onion juice, there were no significant differences in all the tested parameters. In conclusion we failed to find any antioxidant effect of onion supplementation in subjects with mild hypercholesterolemia.