Rooibos Health Research in Scientific Literature [See Research References]

Scientists around the world are working on Rooibos to gain a better understanding of this unique, South African herbal tea. Some are investigating the health benefits of Rooibos and its potential to combat a range of diseases, while others are trying to understand exactly how the bioactive components in Rooibos work.

Scientific articles published over the last decade prove the therapeutic ability of Rooibos to fight cancer, protect the liver against disease, boost the immune system, as well as to relieve allergies and treat digestive disorders. The research studies summarised below show that the beneficial effects of Rooibos have been well documented and established in the international scientific literature.

NEW EVIDENCE THAT ROOIBOS PROTECTS LIVER AND MAY HELP TO PREVENT METABOLIC DISEASE – FINDINGS FROM SPAIN

A consortium of researchers in Spain, working at a number of hospitals and universities in the country, have published new evidence that Rooibos tea protects the liver against the accumulation of fat and can help to prevent metabolic diseases. As part of this study, the research team was able to identify 25 different polyphenols (plant antioxidants) in Rooibos. They published their findings in the acclaimed journal Phytomedicine, on 4 January 2011 (e-publication, printed version in press).

The benefits of Rooibos were particularly visible in mice that had elevated levels of fats in their blood after being fed a high-fat Western-type diet. The rooibos helped to significantly reduce cholesterol, triglycerides and free fatty acids in the blood of these mice. It also changed the number and size of their fat cells and completely prevented the development of fatty liver disease – a condition where fat accumulates in liver cells. The researchers point out that, by preventing the liver from storing excessive amounts of fat, Rooibos may prevent the development of more serious health conditions. This study confirms earlier findings that Rooibos protects the liver against disease.

Based on data gathered during the study, the researchers believe that the effect of Rooibos may be due to the polyphenols in the tea that help to activate a key liver enzyme that, in turn, help to control metabolic processes in the liver cells. This enzyme – also known as AMPK – helps liver cells to switch from producing fatty acids and cholesterol to oxidising (using) fatty acids and glucose. It is a novel and highly relevant finding. They therefore recommend adding polyphenols – found abundantly in Rooibos – to the daily diet.

In line with earlier findings, this research team recommends using the complete Rooibos extract (tea) rather than taking individual, isolated compounds. Earlier Rooibos studies from South Africa showed that people can get the optimum health benefit from drinking six cups of Rooibos spread throughout the day.

Given the worldwide increase in obesity and related medical conditions, the polyphenols in Rooibos are increasingly investigated as a possible way to provide safe and effective complementary therapy. Rooibos (Aspalathus linearis) is a rich source of plant polyphenols without any calories or stimulants (caffeine).

Scientific reference

Beltrán-Debóna, et al. 2011. Continuous administration of polyphenols from aqueous rooibos (Aspalathus linearis) extract ameliorates dietary-induced metabolic disturbances in hyperlipidemic mice. Phytomedicine. [Epub ahead of print – 4 Jan 2011]

Abstract at: http://www.ncbi.nlm.nih.gov/pubmed/21211952

ROOIBOS BOOST ANTIOXIDANT LEVELS IN BLOOD

A human study with 15 healthy volunteers proved for the first time that the antioxidants in Rooibos are potent enough to measurably elevate the antioxidant levels in blood, thereby boosting the body's internal defence systems against disease. The effect peaks about one hour after drinking 500 ml Rooibos tea. Villano, D.,Pecorari, M., Testa, M.F., Raguzzini, A., Stalmach, A,. Crozier, A., Tubili, C., Serafini, M. 2010. Unfermented and fermented rooibos teas (Aspalathus linearis) increase plasma total antioxidant capacity in healthy humans. Food Chemistry 123, 679-683.

ROOIBOS PROMOTES HEART HEALTH

Chrysoeriol, an antioxidant present at low levels in Rooibos, can prevent and treat vascular disease in humans. Chrysoeriol is able to inhibit the migration of smooth muscle cells inside the aorta, a key cause of atherosclerosis (narrowing or hardening of the arteries). The research was done on human aorta cells. Scientists therefore recommend the use of chrysoeriol to prevent and treat the repeated narrowing of blood vessels following coronary angioplasty. During angioplasty, a small balloon is used to open up a blocked or narrowed heart artery. Note: Often only trace quantities of chrysoeriol are found in Rooibos. Cha, B., Shi, W.L., Yonezawa, T., Teruya, T., Nagai, K., Woo, J., 2009. An inhibitory effect of chrysoeriol on platelet-derived growth factor (PDGF)-induced proliferation and PDGFreceptor signaling in human aortic smooth muscle cells. Journal of Pharmacological Science 110, 105-110.

Swedish researchers found that Rooibos could help to promote heart health in humans. They found that 30 and 60 minutes after drinking 400 ml of Rooibos, the activity of a specific enzyme (called angiotensin-converting enzyme, or ACE) is significantly inhibited. This enzyme is believed to be involved in the development of cardiovascular disease, and therefore ACE inhibitors are used to treat hypertension and heart disease. The research team could not demonstrate the same effect with green tea and black tea in the group of 17 healthy volunteers who participated in the study. Persson, I.A., Persson, K., Hägg, S., Andersson, R.G.G., 2010. Effects of green tea, black tea and Rooibos tea on angiotensin-converting enzyme and nitric oxide in healthy volunteers. Public Health Nutrition 3(5), 730-737.

A South African study in humans showed that taking six cups of Rooibos every day for a period of six weeks significantly reduced several of the pertinent biomarkers associated with cardiovascular disease and protects the body against oxidative damage of blood lipids. The liver and kidney functions of the 40 participants were monitored and no adverse effects from taking six cups of rooibos per day were found. Marnewick, J.L., 2010. Rooibos and honeybush: Recent advances in chemistry, biological activity and pharmacognosy. In: African natural plant products: New discoveries and challenges in chemistry and quality. Juliani, H.R., Simon, J.E., Ho, C.T. (Eds). ACS Symposium Series Volume 1021, American Chemical Society, Washington DC, USA, pp 277-294.

ROOIBOS MAY HELP TO CONTROL DIABETES AND ITS COMPLICATIONS

A study in the Slovak Republic found that Rooibos provides effective protection against oxidative stress in diabetic rats. These scientists recommend the use of Rooibos for the prevention and therapy of diabetic vascular complications, especially to protect ocular (eye) membrane systems against peroxidation. Uličná, O., Vančová, O., Boek, P., Čársky, J., ebeková, K., Boor, P., Nakano, M., Greksák, M., 2006. Rooibos tea (Aspalathus linearis) partially prevents oxidative stress in streptozotocin-induced diabetic rats. Physiology Research 55, 157-164.

Two South African researchers, Professor Elizabeth Joubert and Dr Johan Louw, are co-applicants of a worldwide patent (filed in 2007) to develop and produce an anti-diabetic extract of Rooibos, particularly for the treatment of type 2 diabetes. Their invention will provide new uses for aspalathin and rutin in the prevention and treatment of this disease.A 2009 study in Japan found that aspalathin helped to improve the glucose uptake of muscle cells (and thereby helped to maintain normal blood sugar levels) in mice with type 2 diabetes. Aspalathin also stimulates pancreatic beta-cells to secrete insulin and helps to improve impaired glucose tolerance in these animals. Kawano, M., Nakamura, H., Hata, S., Minakawa, M., Miura, Y., Yagasaki, K., 2009. Hypoglycemic effect of aspalathin, a rooibos tea component from Aspalathus linearis, in type 2 diabetic model db/db mice. Phytomedicine 16, 437-443.

THE BIOAVAILABILITY OF ROOIBOS

A German research group found that aspalathin is metabolised in pig intestine and that aspalathin metabolites were present in their urine (pigs are considered a good model for humans). Kreuz, S., Joubert, E., Waldman, K., Ternes, W., 2008. Aspalathin, a flavonoid in Aspalathus linearus (rooibos), is absorbed by pig intestine as a C-glycoside. Nutrition Research 28, 690-701.

The metabolism of aspalathin was confirmed in humans in a collaborative study by researchers in the UK and Switzerland. They found metabolites of aspalathin in the urine of the study participants. Courts, F.L. & Williamson, G., 2009. The C-glycosyl flavonoid, aspalathin, is absorbed, methylated and glucuronidated intact in humans. Molecular Nutrition & Food Research, 53(9), 1104-1111.

Unpublished research from Germany found unmetabolised aspalathin in the blood of human study participants when they consumed green Rooibos. Poster paper presented at 38th German Food Chemists Day, 14-16 September 2009, Berlin, Germany.

A study in taly found flavonoid metabolites in the urine of ten human volunteers after they had drunk 500 ml green and fermented Rooibos. Most metabolites were excreted within five hours of tea consumption. Stalmach, A., Mullen, W., Pecorari, M., Serafini, M., Crozier, A., 2010. Bioavailability of C-linked dihydrochalcone and flavanone glucosides in humans following ingestion of unfermented and fermented rooibos teas. Journal of Agricultural and Food Chemistry, 57 (15), 7104-7111.

Joint research between the Agricultural Research Council and the Medical Research Council were able to show that two Rooibos antioxidants aspalathin and nothofagin are changed by the liver enzymes in vitro. Van der Merwe, J.D., Joubert, E., Manley, M., De Beer, D., Malherbe, C., Gelderblom, W.C.A., 2010. In vitro hepatic biotransformation of aspalathin and nothofagin, dihydrochalcones of rooibos (Aspalathus linearis), and assessment of metabolite antioxidant activity. Journal of Agricultural and Food Chemistry 58, 2214-2220.

PHYTOESTROGENS FROM ROOIBOS

Japanese researchers have been investigating the estrogenic activity of Rooibos compounds (in vitro) and were able to show that three of these compounds had potential estrogenic activity. Such plant-derived estrogens are of interest because of their potential as an alternative to the estrogens in hormone replacement therapy. Shimamura, N., Miyase, T., Umehara, K., Warashina, T., Fujii, S., 2006. Phytoestrogens from Aspalathus linearis. Biology and Pharmacology Bulletin 29, 1271-1274.

ROOIBOS CAN PREVENT OR SLOW DOWN CANCER

The ability of South African herbal teas (Rooibos and Honeybush extracts) to act as 'chemopreventors' in skin cancer was highlighted by a South African research team using an animal model. They showed that topical (external) application of tea fractions significantly suppressed tumour growth in mice with skin cancer, when using processed and unprocessed tea. Marnewick, J.L., Joubert, E., Joseph, S., Swanevelder, S., Swart, P., Gelderblom, W.C.A., 2005. Inhibition of tumour promotion in mouse skin by extracts of rooibos (Aspalathus linearis) and honeybush (Cyclopia intermedia), unique South African herbal teas. Cancer Letters 224, 193-202.

South African researchers collaborated to compare the potential of different kinds of tea (Rooibos, Honeybush, black oolong and green tea) to suppress mutations, and thereby prevent cancer. Their results confirmed that the phenolic compounds in herbal tea extracts have a strong anti-mutagenic effect (in vitro study using cell lines). Van der Merwe, J.D., Joubert, E., Richards, E.S., Manley, M., Snijman, P.W., Marnewick, J.L., Gelderblom, W.C.A., 2006. A comparative study on the antimutagenic properties of aqueous extracts of Aspalathus linearis (rooibos), different Cyclopia spp. (honeybush) and Camellia sinensis teas. Mutation Research 611, 42-53.

ROOIBOS AS A TREATMENT FOR STOMACH CRAMPS AND DIARRHOEA

Acknowledging that Rooibos is widely used to treat gastrointestinal upsets, researchers in Pakistan, Canada and Germany joined forces to explore the mechanism of this effect of Rooibos. They used rabbit jejunum (intestine) tissue for this study. Their results explain the biochemistry of how the flavonoids and other active ingredients in Rooibos achieve this calming effect on the digestive system. They concluded that it is justified to use Rooibos for the treatment of gastrointestinal disorders, such as gut spasms. Gilani, A.H., Khan, A., Ghayur, M.N., Ali, S.F., Herzig, J.W., 2006. Antispasmodic effect of rooibos tea (Aspalathus linearis) is mediated through K+ channel activation. Basic Clinical Pharmacology and Toxicology 99, 365-373.

ROOIBOS TO TREAT INFLAMMATORY BOWEL DISEASE

A Japanese study showed that Rooibos could reduce inflammation in rats with colitis (open sores in the colon) via increased antioxidant activity with a consequent reduction in damage to DNA caused by oxidation. These researchers recommend Rooibos as a safe and useful way to reduce oxidative stress. Baba, H., Ohtsuka, Y., Haruna, H., Lee, T., Nagata, S., Maeda, M. Yamashiro, Y., Shimizu, T., 2009. Studies of anti-inflammatory effects of Rooibos tea in rats. Pediatrics International 51, 700-704.

ROOIBOS, RESPIRATORY DISEASE AND BLOOD PRESSURE

Researchers in Pakistan found that chrysoeriol (a bioactive components of Rooibos, but usually only present at low levels) acted effectively as a bronchodilator, with an associated effect on lowering blood pressure and relieving spasms. Aorta, trachea and other tissue from rabbits and guinea-pigs were used to illustrate this effect. Chrysoeriol is known for its antioxidant, anti-inflammatory, antitumor, antimicrobial, antiviral and free radical scavenging abilities. Khan, A., Gilani, A.H., 2006. Selective broncholdilatory effect of rooibos tea (Aspalathus linearis) and its flavonoid, chrysoeriol. European Journal of Nutrition 45, 463-469.

ROOIBOS RESTORES IMMUNE FUNCTION

Research teams in Japan demonstrated that the active ingredients in a water-soluble fraction of Rooibos restored immune function in immune-suppressed rats. These results hold significant potential for future research into the immune-boosting properties of Rooibos that could potentially benefit people living with HIV/AIDS. Ichiyama, K., Tai, A., Yamamoto, I., 2007. Augmentation of antigen-specific antibody production and IL-120 generation with a fraction from rooibos (Aspalathus linearis) tea. Bioscience, Biotechnology and Biochemistry 71, 589-602.

ROOIBOS SLOWS DOWN AGEING

Researchers from the Slovak Republic were able to demonstrate the anti-ageing effect of Rooibos in Japanese quails. The birds were given Rooibos to drink and had ground Rooibos added to their food. The hens on the Rooibos diet laid more eggs and kept on laying eggs as they were getting older, compared to quail hens on a standard diet. Juráni, M., Lamoová, D., Máčajová, M., Kostál, L., Joubert, E., Greksák, M., 2008. Effect of rooibos tea (Aspalathus linearis) on Japanese quail growth, egg production and plasma metabolites. British Poultry Science 49, 55-64.

COMPREHENSIVE REVIEWS OF ROOIBOS RESEARCH

The research reviews listed below provide a comprehensive overview of recent research into the potential health benefits, production and quality aspects of Rooibos and related products.

• Joubert, E. & Schulz, H., 2006. Production and quality aspects of rooibos tea and related products. A review. Journal of Applied Botany and Food Quality 80, 138-144.
• McKay, D.L., & Blumberg, J.B., 2007. A review of the bioactivity of South African herbal teas: Rooibos (Aspalathus linearis) and Honeybush (Cyclopia intermedia). Phytotherapy Research 21, 1-16.
• Joubert, E., Gelderblom, W.C.A., Louw, A., De Beer, D., 2008. South African herbal teas: Aspalathus linearis, Cyclopia spp. and Athrixia phylicoides - A review. Journal of Ethnopharmacology, 119, 376-412.
• Joubert, E., Gelderblom, W.C.A., Louw, A., De Beer, D., 2008. Phenolic contribution of South African herbal teas to a healthy diet. Natural Product Communications 4, 1-18.