Does it work? Can rooibos tea cut risk of heart disease?
BACKGROUND:Herbal teas have become commonly available in recent years. The potential health effects of green tea, black tea and oolong tea have received considerable attention. At the same time, other teas have been generating some interest.
Foremost among these is rooibos tea, whose name comes from the Afrikaans word for red bush. Its green needle-like leaves and stems are harvested and turn red as they dry in the sun. The rooibos, or Aspalathus linearis, grows only in the Western Cape region of South Africa. This region contains several unique plant species that will not grow elsewhere because of the area’s distinct climate and soil. Both green and red varieties of the tea are available.
Rooibos tea contains no caffeine and is very low in tannins (the ingredients that give black tea its bitter taste). The plant has been used medicinally in the region for centuries, and has been linked to various health claims in recent decades. Interest has developed because of claims that rooibos tea is very high in antioxidants. Lower antioxidant levels have been associated with heart disease, leading to claims that rooibos tea helps reduce the risk of heart disease.
EVIDENCE FROM STUDIES
Rooibos tea contains numerous ingredients called flavonoids, which have antioxidant activity. Studies in animals have confirmed that rooibos tea does lead to an increase in blood antioxidant capacity. However, in laboratory tests, ordinary black tea and green tea were found to have higher antioxidant activity than rooibos tea.
Angiotensin-converting enzyme (ACE) is believed to play a role in the development of cardiovascular disease. Pharmaceuticals called ACE inhibitors are used to treat high blood pressure and congestive heart failure. A study published last year asked 17 healthy volunteers to drink 400ml of rooibos tea. An hour later, significant ACE inhibition was measured in the participants, suggesting that rooibos tea could have cardiac benefits.
What is believed to be the first controlled clinical trial of rooibos tea in humans was published this year. In this study, 40 people at higher risk of coronary heart disease drank six cups of rooibos tea throughout the day for six weeks. At the end of this period, a number of blood tests showed improvements. Some, but not all, tests for antioxidant capacity had increased. Also, blood levels of total cholesterol and LDL-cholesterol (so-called “bad” cholesterol) had decreased significantly, while levels of HDL-cholesterol (“good” cholesterol) had significantly increased. All of these changes are associated with reducing someone’s risk of developing heart disease.
No adverse effects have been reported in the clinical trials conducted to date, although these have involved a very small number of people for short lengths of time.
The small amount of research conducted to date indicates that rooibos tea may have beneficial effects that can be linked to heart disease. However, the studies have examined various biomarkers for disease and not the impact on heart disease itself. Such effects are similar to the sorts of general benefits to be expected from consuming more plant products.
Given the results to date, further research is needed on rooibos tea. This is important to show whether the tea has any specific health benefit, but also because of the impact increased production is having on the ecosystem in South Africa. While this increase in production has helped the local economy, it is also starting to have some negative impacts. The ecosystem where rooibos grows is very fragile, and fields where it was cultivated in recent years have been abandoned because of over-cropping. A more sustainable approach is needed if the tea is to play an on-going role in the local economy or people’s health.
Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University. He is author of Alternative Medicine: The Christian Handbook, Updated and Expanded Edition, Zondervan, 2007