Effect of Brazil nut supplementation on the blood levels of selenium and glutathione peroxidase in hemodialysis patients

Abstract Objective In patients who have undergone hemodialysis, large amounts of reactive oxygen species (ROS) are produced and, at higher concentrations, ROS are thought to be involved in the pathogenesis of cardiovascular disease. It has been proposed that selenium (Se) may exert an antiatherogenic influence by reducing oxidative stress. The richest known food source of selenium is the Brazil nut ( Bertholletia excelsa , family Lecythidaceae), found in the Amazon region. We evaluated the effect of Brazil nut supplementation on blood levels of Se and glutathione peroxidase (GSH-Px) activity in patients on hemodialysis. Methods A total of 81 patients on hemodialysis (52.0 ± 15.2 y old, average time on dialysis 82.3 ± 91.4 mo, body mass index 24.9 ± 4.4 kg/m2 ) from the RenalCor and RenalVida Clinics in Rio de Janeiro, Brazil, were studied. All patients received one nut (around 5 g, averaging 58.1 μg Se/g) a day for 3 mo. The Se concentrations in the nuts and in plasma and erythrocytes were determined by atomic absorption spectrophotometry with hydride generation (Hitachi, Z-500). GSH-Px levels were measured using Randox commercial kits. Results Plasma Se (18.8 ± 17.4 μ g/L) and erythrocyte (72.4 ± 37.9 μ g/L) levels were below the normal range before nut supplementation. After supplementation, the plasma level increased to 104.0 ± 65.0 μ g/L and erythrocytes to 244.1 ± 119.5 μ g/L ( P < 0.0001). The activity of GSH-Px also increased after supplementation, from 46.6 ± 14.9 to 55.9 ± 23.6 U/g of hemoglobin ( P < 0.0001). Before supplementation, 11% of patients had GSH-Px activity below the normal range (27.5–73.6 U/g of hemoglobin). After supplementation, all patients showed GSH-Px activity within the normal range. Conclusion The data revealed that the investigated patients presented Se deficiency and that the consumption of only one Brazil nut a day (5 g) during 3 mo was effective to increase the Se concentration and GSH-Px activity in these patients, thus improving their antioxidant status.