Modulation of postprandial oxidative stress by rooibos (aspalathus linearis) in normolipidaemic individuals

Abstract

Consumption of sucrose with a meal containing oxidised and oxidisable lipids cause an increase in oxidative stress which is referred to as postprandial oxidative stress. The modulating effect on postprandial oxidative stress by an antioxidant-rich beverage, fermented rooibos (Aspalathus linearis) was compared to that of a commercial soft drink (soda). Both study beverages contained sucrose and were consumed with a standardised fat meal.

The study consisted of two parts, a pilot study (Phase One) where participants consumed either a standardised fat meal with water (control group n = 5) or a standardised fat meal with a sucrose-containing commercial soda (treatment group n = 8) using a parallel design, and the experimental study (Phase Two) where participants (n = 14) consumed the standardised fat meal with the commercial soda (control group) or the rooibos beverage (treatment group) using a crossover design. Specific analytical techniques and methods for determination of plasma glucose, serum insulin, lipid profile, an inflammatory indicator (high sensitive C-reactive protein), plasma antioxidant capacity, whole blood redox status and plasma lipid oxidation biomarkers were used. Results from the pilot study indicated significantly (P<0.05) higher postprandial levels of glucose in the control group at 4 hr and 6hr postprandially. The inflammatory biomarker and triglyceride levels were significantly (P<0.05) elevated in both groups when compared to their respective baselines. Results also showed the total antioxidant capacity and total glutathione levels in the plasma of both groups to be significantly (P<0.05) lowered when compared to the baseline values. The level of lipid oxidation biomarkers in the plasma was significantly (P<0.05) higher at 2 hr, 4 hr and 6 hr post time intervals for thiobarbituric acid reactive substances and 4 hr post time interval for conjugated dienes in the participants consuming the standardised fat meal with soda when compared to the baseline value, while this was reflected only at 2 hr post time interval for thiobarbituric acid reactive substances, with the conjugated dienes levels being significantly (P<0.05) lowered at 6 hr post time interval in the control group. No differences were shown on inter group level for the pilot study. On inter group level, results from Phase Two showed significant (P<0.05) lower levels of plasma glucose at 6 hr post time interval in the treatment group when compared to the control group, with insulin levels being significantly (P<0.05) higher in the control group at 4 hr post time interval.