Modulation of cardiovascular function by rooibos in adults at risk for cardiovascular disease

Abstract

Introduction: Cardiovascular disease (CVD), diabetes and stroke collectively represent the second leading cause of mortality among South African adults. These non-communicable diseases pose a significant global health threat, emphasising the importance of adopting and maintaining a healthy lifestyle with optimal dietary habits. Failure to address this issue will likely result in a substantial increase in the burden of non-communicable diseases (NCDs) in South Africa in the coming decades. In 2017, coronary heart disease and stroke emerged as the predominant non-communicable disease (NCD) globally and resulted in an estimated 17.8 million fatalities, with over 75% of these fatalities occurring in low-income and middle-income countries. This fact underscores the critical need for further investigation and interventions in the field of cardiovascular health. One of the root causes underlying many non-communicable diseases, including CVD, cancer, and diabetes, is a redox imbalance resulting in ‘chronic’ oxidative stress. To mitigate these risks and potentially enhance the quality of life and lifespan, the utilisation of bioactives, such as antioxidants to support the redox balance, is imperative. Aim: This research aims to determine the prevalence and characteristics of CVD and its associated risk factors in a South African cohort, assess the impact of Rooibos (Aspalathus linearis) on cardiovascular function in adults at risk for CVD using Transthoracic Echocardiography (TTE), and establish an association between CVD findings and dietary interventions. Method: Using a randomised, placebo-controlled parallel design, this study investigated the impact of regular consumption of two types of Rooibos on key cardiovascular parameters using TTE. The cohort of participants (n=219) included three parallel groups that were matched according to age and gender. They were randomly assigned to consume either the placebo or fermented Rooibos, or green Rooibos. The Rooibos capsules contained standardised water-soluble extracts, and participants were requested to consume one capsule (equivalent to two cups of Rooibos herbal tea) three times a day with meals (morning, midday, and evening) for 12 weeks. Cardiovascular function was assessed using TTE. All echocardiograms were performed according to the American Society of Echocardiography (ASE) guidelines, standards and recommendations. Results: Objective 1: The results indicate that the population was moderately obese: Body Mass Index (BMI) = 31 kg/m²; the average systolic blood pressure (SBP) = 131 mmHg; average diastolic blood pressure (DBP) = 84 mmHg; total serum cholesterol = 5.5 mmol/l; fasting plasma glucose = 4.51 mmol/L, within normal limits. Of the 219 participants, 118 (53.9%) were at a lower risk for cardiovascular disease, and 101 (46.1%) were at a higher risk for cardiovascular disease. Objective 2: The effect of daily Rooibos consumption over 12 weeks on the cardiovascular system included the following outcomes: grade 1 diastolic dysfunction counts decreased from 63 (28%) to 47 (21.5%), grade 2 diastolic dysfunction decreased from 46 (21%) to 24 (11%) and grade 3 diastolic dysfunction decreased from 5 (2.3%) to 3 (1.4%). There was no effect on the aortic size (AO) in all the intervention groups, while the left atrium (LA) significantly (p=0.01) decreased in size from 3.83 cm ± 0.07 cm to 3.68 cm ± 0.07 cm. The LA / AO ratio did not change significantly in all the intervention groups. Interventricular septum diameter (IVSd) in the placebo group decreased significantly (p=0.002) from 1.33 cm ± 0.030 cm to 1.25 cm ± 0.03 cm with no positive change in the fermented rooibos group, while the green rooibos group demonstrated a significantly (p=0.002) decreased diameter from 1.28 cm ± 0.04 cm to 1.19 cm ± 0.03 cm. In all three intervention groups no significant changes for the left ventricle posterior wall (LVPWd) were detected. The placebo (p=0.300) and green rooibos (p=0.292) groups demonstrated no significant changes for the left ventricle mass (LVM), while the fermented rooibos group showed a significant (p=0.015) decreased mass (from 204.1 g ± 7.1 g to 191.4 g ± 6.7 g). No significant positive changes were seen in all the groups with regard to the left ventricle in diastole diameter (LVIDd), left ventricle in systole diameter (LVISd) and the ejection fraction (EF). Conclusion: In general, this study reveals evidence suggesting that the regular consumption of Rooibos may be associated with cardiovascular protective effects, with specific focus on the left atrium (LA), interventricular septum (IVS) and left ventricular mass (LVM). These findings underscore the potential benefits of incorporating Rooibos into the daily dietary habits as a means to promote heart health and reduce the risk for cardiovascular diseases. Further research and clinical investigations are warranted to elucidate the precise mechanisms underlying these protective effects and to explore the long-term implications of Rooibos consumption on overall cardiovascular well-being.