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Novel zebrafish research shows green rooibos tea may help to reduce anxiety

Press statement issued by Stellenbosch University

New research shows that drinking green rooibos tea may help reduce anxiety. Novel research conducted on zebrafish, which share genetic similarities with humans.

A new study conducted on zebrafish by researchers at Stellenbosch University (SU), has shown that the consumption of rooibos tea – and specifically unfermented or green rooibos – may help to reduce anxiety.

The beneficial properties of rooibos tea (Aspalathus linearis), a uniquely South African product which grows mainly in the Cederberg area of the Western Cape, range from its caffeine-free and anti-inflammatory nature to the antioxidants, vital minerals and vitamins it contains, as well as its positive role in pain and allergy reduction and in heart health.

The recent finding that it also has anxiolytic properties – meaning it prevents or lessens the degree of anxiety a person experiences – makes this tea even more desirable as a daily supplement, said Prof Carine Smith, who heads the Medicine Research Laboratories at SU’s Faculty of Medicine and Health Sciences (FMHS).

The study was conducted at the FMHS’ new Zebrafish laboratory, which uses the tropical zebrafish for medical research.

The laboratory was launched just over a year ago and has been working on several studies involving advanced analytical pharmacology, toxicology, therapeutic target identification and drug discovery. Zebrafish are uniquely suited for the laboratory’s research purposes, because genetically they are quite similar to humans – for more than 80% of the genes known to cause disease in humans, there are similar genes represented in zebrafish.

One of the first projects to stem from the new laboratory was the recent publication of a research article in the high-impact journal Food & Function which looks at the findings of the study into the potential neuroprotective and anxiolytic properties of unfermented (green) rooibos tea.

The research was done in collaboration with Spanish researchers from the San Jorge University and a local pharmaceutical industry contributor.

Smith said she was delighted that the first data published from the Zebrafish Research Unit was related to something “so proudly South African”.

“We are also thrilled to have done this study in collaboration with a Spanish university. Even though we are a new research unit in terms of zebrafish data generation, it’s wonderful to already be good enough to be part of an international team. It’s also great that this is such a proudly South African topic, as rooibos can only be cultivated here.”

In an interview Smith pointed out that the World Health Organisation has classified South Africa as one of the most stressed countries in the world. “The results of this study mean that we could have uncovered nature’s contribution to treating some of our country’s health problems. It shows that drinking green rooibos tea may have a calming effect if you suffer from anxiety.”

She added that zebrafish, which originate in Malaysia, may be “the new rodent in research”. “In the larval stage they have the attribute of being fairly transparent, so they are great for microscopy.

“We have a couple of tanks where we breed with the adult stock. The fish can live up to three years in a laboratory, compared to about a year in nature. What makes them so desirable for research is that most of our research is done at the early larval stage, when they are not yet considered a sentient animal. This makes our model a more ethical way of using a live organism in research, as they cannot experience pain at that stage,” she said.

Elaborating on the research, Smith said her group studies the connection between psychological stress and chronic inflammatory disease. “Zebrafish are ideal for drug discovery in this context, as we are able to do thorough testing including not only behavioural assessment and treatment mechanisms of action, but also risks of overdosing and long-term use.”

Smith said the study found, among other things, that green rooibos tea could be considered as a “functional brain food” and “may be a good option as a starting ingredient in the development of new nutraceuticals”. (A nutraceutical is a pharmaceutical alternative which claims physiological benefits.)

The laboratory’s research into the properties of rooibos are ongoing thanks to financial support by the South African Rooibos Council.

Smith, who herself consumes rooibos every day, said: “We all know it is an antioxidant and that it has diuretic functions – the latter helping people with high blood pressure – as well as great cardio-vascular benefits. To date, research has not demonstrated a single negative effect of rooibos, therefore long-term consumption can be regarded as generally safe.”

Adding the neuroprotective and anxiolytic properties to the list of rooibos’ benefits is hugely significant, Smith concluded. “In the midst of the many unsubstantiated claims of health benefits being made for various supplements, it is satisfying to be able to contribute to the scientific data supporting the use of rooibos tea as a functional food capable of positively affecting health on many fronts.”

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