Modulation of oxidative stress biomarkers by rooibos in adults at risk of developing coronary heart disease

Abstract

Observational studies link higher intake of polyphenols from plant based foods and beverages with a lower risk of cardiovascular disease (CVD) which remains the leading cause of death in the world. Although the mechanisms explaining this observation remains unclear, research suggest that polyphenols, with their potent antioxidant properties, may decrease oxidative stress by impairing the oxidation of lipids. Increased oxidation of lipids, particularly low density lipoproteins, is recognised as an important risk factor in coronary heart disease. Attention has focussed on dietary sources with antioxidant potential that are capable of modulating the body’s oxidative stress via various modes for example increasing the antioxidant capacity or shifting the antioxidant redox status.Rooibos (Aspalathus linearis) has been shown to possess potent antioxidant, immunemodulating and chemopreventive actions in various in vitro, ex vivo and animal models and consequently has been suggested to be potentially beneficial to human health. The aim of this study was to investigate the effect of rooibos consumption on parameters of oxidative stress and redox status in blood of humans at risk for coronary heart disease. A fourteen-week dietary intervention study was conducted in which forty volunteers consumed six cups of rooibos tea daily for six weeks which was preceded by a 2-week baseline and 2-week washout period and followed by a 4-week control period when water was consumed. Before and after the intervention, several parameters were measured including indices of antioxidant activity, lipid peroxidation (LPO) antioxidant redox status (ratio of reduced to oxidised glutathione i.e. GSH: GSSG) and antioxidant content. Plasma antioxidant capacity was not affected by the 6-week rooibos intake but total polyphenols were significantly (P<0.05) raised by 11 %. Significant (P<0.05) decreases were reported in markers of LPO (conjugated dienes and malondialdehyde), total cholesterol, low density lipoprotein-cholesterol as well as oxidized glutathione. Reduced glutathione as well as the ratio GSH:GSSG were both significantly (P<0.05) increased by the rooibos intervention compared to the control phase. Rooibos consumption did not cause any adverse effects in the study participants and neither were the serum iron levels alteredThese results suggest that rooibos consumption may impair lipid peroxidation in the body and therefore play a beneficial role in cardiovascular health in humans. In addition, the results confirm the safety of short term consumption of rooibos with regards to liver and kidney function as no toxicity was associated with its intake.