A new study conducted by the Applied Microbial and Health Biotechnology Institute at the Cape Peninsula University of Technology (CPUT) has provided valuable insights into the potential cardiovascular benefits of Rooibos.
The study, led by Prof Jeanine Marnewick, Director of the Institute and researcher, Maria Hartnick, builds on previous research, which indicated Rooibos’ ability to modulate risk factors associated with cardiovascular disease (CVD). However, this latest study takes a significant step further by using advanced diagnostic methods to assess heart function in real-time.
The key objective of this new research was to evaluate the impact of Rooibos on cardiovascular function in individuals at risk of developing CVDs. This followed findings from earlier research that demonstrated Rooibos’ ability to mitigate oxidative stress and improve lipid profiles, including reductions in low-density lipoprotein (LDL) cholesterol, commonly referred to as "bad" cholesterol and triglyceride levels.
Prof Marnewick explains, “While our previous studies focused on biochemical markers, we wanted to take a deeper look into how Rooibos impacts the actual functioning of the heart. This is where the use of transthoracic echocardiography, a diagnostic ultrasound examination, came into play.”
Echocardiography, commonly referred to as “sonar”, enabled the team to observe the heart in real-time, providing a more detailed understanding of Rooibos’ potential health benefits. This was the first time such technology had been used to explore the effects of Rooibos on heart health, with the aim of detecting early cardiovascular changes in individuals at risk.
The results of the study were promising, particularly in relation to several key cardiovascular parameters. “We observed a significant reduction in left atrium dimensions, interventricular septum thickness and left ventricular mass in participants who consumed Rooibos, particularly green Rooibos,” says Hartnick. “These reductions are indicative of improvements in cardiac structure and function, which can reflect better endothelial function (flow of blood by relaxing and tightening the blood vessels) and overall cardiovascular health.”
The study involved both male and female participants with at least two modifiable risk factors for CVD, such as high blood pressure, elevated cholesterol and unhealthy lifestyle habits. The participants consumed the equivalent of six (6) cups of either fermented (red) or unfermented (green) Rooibos daily for 12 weeks. These results underscore the potential for Rooibos, particularly in its green form, to positively influence heart health.
The importance of antioxidants in Rooibos
One of the unique aspects of this study was its focus on the consumption of whole Rooibos, rather than isolating individual compounds. “We used a water extract of Rooibos to simulate a ‘cup of tea’,” says Prof Marnewick. “This was important, because Rooibos is often consumed as a beverage and we wanted the results to be as applicable to daily life as possible.”
While previous studies have identified compounds like aspalathin and nothofagin as potent antioxidants in Rooibos, this study took a holistic approach to the tisane’s cardiovascular benefits. The antioxidants in Rooibos are thought to help reduce inflammation and oxidative stress, which are key contributors to cardiovascular disease.
New methods for new insights
This study was designed differently from earlier research. Instead of a six-week, crossover study, this was a randomised, placebo-controlled, parallel design that spanned 12 weeks. This design provided more robust data and allowed for the inclusion of echocardiographic measurements, which had never been done before in Rooibos research.
“Baseline and post-intervention echocardiograms were used to measure changes in heart function,” Hartnick explains. “We adhered to strict guidelines from the American Society of Echocardiography to ensure accuracy and reliability. This methodology has given us a much clearer picture of how Rooibos can affect cardiovascular health.”
Key findings and unexpected outcomes
The study's most significant finding was the reduction in left atrium size, interventricular septum thickness and left ventricular mass. These are critical markers for hypertensive heart disease, which is a major risk factor for heart failure and other cardiovascular complications. “To see these parameters improve with Rooibos consumption is a major breakthrough,” says Prof Marnewick. “It’s the first time we’ve been able to show these effects in humans.”
Although the clinical significance of these findings needs further investigation, the results are an exciting step forward. The researchers note that while Rooibos is not a curative solution for cardiovascular disease, it holds promise as a preventive strategy that can be easily incorporated into daily life, along with a healthy lifestyle.
Public health implications
The global burden of non-communicable diseases (NCDs), particularly cardiovascular disease, highlights the need for effective and accessible preventive measures. “Our research contributes to the growing body of evidence that Rooibos could be a valuable part of the solution,” says Hartnick. “By promoting the regular consumption of Rooibos, especially in at-risk populations, we could help reduce the incidence of CVD.”
Prof Marnewick envisions this research playing a role in shaping public health guidelines around Rooibos consumption. “We believe this study has the potential to influence future dietary recommendations, particularly in countries like South Africa where Rooibos is readily available,” she says. “As a natural, low-cost intervention, Rooibos could be part of broader public health strategies aimed at improving cardiovascular outcomes.”
Next steps in Rooibos research
Looking ahead, researchers plan to continue investigating the long-term cardiovascular effects of Rooibos. “We’ve laid the groundwork with this study, but there’s still much to explore,” says Prof Marnewick. “Future research will focus on understanding the clinical relevance of these findings and how Rooibos can be used as part of a comprehensive approach to heart health.”
In the meantime, Rooibos enthusiasts have yet another reason to enjoy their favourite brew – it may just be helping to keep their hearts healthy.
Research Team
Researcher and Doctoral student:
Ms Maria Hartnick 1
Supervisory team:
Prof JL Marnewick 2 (Rooibos bioactivity expert)
Prof P Engel-Hills 2(Imaging expert)
Dr M Kemp 3 (Imaging expert).
Authors affiliations
1 Department of Medical Imaging and Therapeutic Sciences, Faculty of Health and Wellness Sciences, Cape Peninsula University of Technology, Bellville, 7530 Cape Town, South Africa
2 Applied Microbial and Health Biotechnology Institute, Cape Peninsula University of Technology, Bellville, 7530, Cape Town, South Africa
3 Department of Health and Care Professions, Faculty of Health and Life Sciences, University of Exter, United Kingdom
This study was co-funded by the SA Rooibos Council and the Department of Science and Innovation under the Sector Innovation Fund Programme which aims to advance Industry Innovation Partnerships that contribute to increased competitiveness through research, development and innovation.
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