Rooibos tea, which comes from the Aspalathus linearis plant grown primarily in the Western Cape province of South Africa, is not only a delicious beverage, but also caffeine-free and has been found to possess anti-inflammatory properties. It can also ease pain, reduce allergies, and promote heart health.

The study focused on unfermented or green rooibos, which was found to contain anxiety-reducing properties. A Green Rooibos extract was tested on zebrafish, a species genetically like humans for more than 80% of the genes known to cause disease in humans. While human trials were not conducted due to the significant variability in anxiety severity, the results from the zebrafish experiments provide promising insight into the potential benefits of green Rooibos tea.

This study is among the first to emerge from the Zebrafish research unit at Stellenbosch University’s Faculty of Medicine and Health Sciences, which was established over a year ago. The research unit focuses on advanced analytical pharmacology, toxicology, therapeutic target identification, and drug discovery, and several other studies are currently underway.
Most of the research was conducted at the early larval stage when the zebrafish are not yet considered sentient animals. This approach is considered more ethical as the larvae cannot experience pain at this stage.

The researchers immersed zebrafish larvae in different concentrations of Rooibos, allowing them to absorb the tea through their skin and gills, since their mouth were not yet open. The researchers used specialized equipment to track the movement of the larvae and construct behavioral patterns. They the exposed the larvae to alternating bright light and darkness for short periods of time, creating a model of anxiety. The researchers assessed whether the larvae swimming in the Rooibos were able to remain calm by comparing their behavior to that of the un-supplemented larvae. Typically, in this model, the larvae would “freeze” in bright light, followed by hyperactivity during the periods of darkness. The Rooibos treated larvae also froze but did not exhibit anxious hyperactivity, indicating a potential calming effect.

At different points, specialized equipment tracked their movement, and this was used to construct behavioral patterns. Using a model of anxiety – which entails exposing the larvae to alternating bright light and darkness for short periods of time – they assessed whether the larvae swimming in rooibos were able to remain calm, by comparing their behavior to that of un-supplemented larvae. Normally, in this model, the larvae would “freeze” in bright light, followed by hyperactivity during the periods of darkness. In this study, rooibos-treated larvae also froze, but did not exhibit the anxious hyperactivity.

The researchers also conducted a test on live larvae's behavior to investigate a specific mechanism: the neurotransmitter GABA, which is known to produce feelings of well-being. By either enhancing or blocking its receptor, its signaling can be manipulated. When the receptor is blocked, the larvae exhibit a hyperactive, seizure-like behavior. The team found that rooibos was able to completely prevent this response, with similar results to an anti-epileptic drug that works through GABA.

The behavioral tests were complemented by whole-body analyses for oxidative stress and antioxidant activity, as well as cell culture work using human cells. In these models, the researchers showed that green rooibos could protect human neurons against oxidative stress, which increases during life and is responsible for aging. A product that can protect the brain from oxidative stress can slow down the aging process. This finding is particularly significant in a world where advances in medicine are allowing us to grow older, making it increasingly important to be able to prevent the brain from aging.

The connection between psychological stress and chronic inflammatory disease is particularly relevant in South Africa, where the South African Depression and Anxiety Group estimates that one in six South Africans suffer from anxiety or depression. Furthermore, inflammation is a common characteristic among the top 10 causes of death in South Africa, such as TB, diabetes, and respiratory disease.

Zebrafish are ideal for drug discovery especially in the context of neurological and inflammatory conditions. They can do thorough testing including not only behavioral assessment and seeing how specific treatments work, but also assessing the risks of overdosing and long-term use of potential treatments.

Collectively, the data suggest that green rooibos tea could be considered a functional brain food and a good starting ingredient for the development of new nutraceuticals, which are pharmaceutical alternatives that claim physiological benefits. These results indicate that nature may contribute to the treatment of some of South Africa's health problems.

The study's findings suggest that green Rooibos tea may be a natural and effective way to manage anxiety.