by SAVIOUS KWINIKA
JOHANNESBURG, (CAJ News) – ROOIBOS, South Africa’s iconic herbal tea, is showing potential protective effects against estrogen-driven breast cancer cells, according to preliminary research led by Dr Nicky Verhoog, senior lecturer in biochemistry at Stellenbosch University.
The laboratory study, funded by the South African Rooibos Council (SARC) and the Department of Science, Technology and Innovation (DSTI), found that Rooibos extracts slowed the growth of estrogen receptor-positive breast cancer cells and prevented them from spreading.
“Rooibos appears to act in a protective way against estrogen-driven breast cancer cells in the lab,” said Dr Verhoog.
“It doesn’t mimic estrogen, but rather inhibits its action. Importantly, we also found that it didn’t interfere with tamoxifen, a standard breast cancer therapy, which suggests Rooibos could be safely consumed by women undergoing treatment.”
The extracts showed a preference for activating ERβ, a receptor linked to tumour suppression, while blocking ERα, which encourages tumour growth.
“The results were encouraging, similar in effect to fulvestrant, a drug used to block estrogen activity,” she added.
Breast cancer is the most common cancer among South African women, with 11,000 to 15,000 new cases annually, accounting for nearly a quarter of female cancer diagnoses.
Early detection can push survival rates above 90%.
However, Dr Verhoog cautioned that the findings remain preliminary.
“Lab studies involve single cell types and don’t replicate the complexity of the human body. Our next step is pre-clinical trials in 2026 to understand how Rooibos behaves when metabolised.”
While Rooibos is not being tested as a treatment, the research supports its safety and contributes to its reputation for broad health benefits, including heart, brain, and diabetes support.
“This is a step toward understanding how this uniquely South African tisane may support health in a variety of ways,” said Dr Verhoog.
– CAJ News