Limited clinical studies exist to recommend red bush tea for any indication. Due to the plant’s potential for improving oxidative stress, it may have a role in diabetes and cardiovascular disease.
Dosing
The traditional dosage of the tea is 1 to 4 teaspoons of dry leaf tea per cup taken up to 3 times per day. Limited studies have used 6 cups of rooibos tea daily for 6 weeks.
Contraindications
Contraindications have not been identified.
Pregnancy/Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Interactions
In a study using human serum, rooibos acted as an angiotensin-converting enzyme (ACE) inhibitor in a manner similar to that of enalaprilat.
Adverse Reactions
Information regarding adverse effects is lacking. A study of human volunteers receiving 6 cups of tea daily for 6 weeks noted increased serum levels of creatinine, as well as ALT and AST enzymes.
Toxicology
Long-term, high-dose use may impair kidney and liver function, but few case reports exist.
Scientific Family
Fabaceae (bean)
Botany
Rooibos ("red bush") grows as a low shrub, reaching a height of 1.2 to 1.5 m. It has long, needle-like leaves and small yellow flowers. The plant is native to South Africa and is cultivated extensively for its commercial value as a substitute for common tea. The leaves and twigs are collected, washed, bruised, fermented, dried, cut, and packaged for use as teas. During this process, the leaves change from green to brick red due to the release of a red pigment found in the leaves and stems.1 Synonyms are Borbonia pinifolia Marloth or Aspalathus contaminata (Thunb.) Druce.
History
"Bush teas" are common throughout Africa and are frequently used as substitutes for common tea. Red bush tea has been popular in South Africa for decades, and commercial preparations are sometimes found in Europe and the United States. In 1994, an American company registered the name "Rooibos" with the United States Patent and Trademark Office. However, the American Herbal Products Association and a number of import companies successfully petitioned to defeat the trademark in 2005, returning the name to the public domain.2 In 2013, the South African Department of Trade and Industry issued geographic indicator trade restrictions on the name rooibos in that country.3
The tea’s lack of caffeine and tannin make it popular as a fragrant and bittersweet, nonstimulating beverage. It has also been used to treat asthma, colic, eczema, headache, nausea, and mild depression.1, 3, 4, 5
Chemistry
Chemical constituents detailed for red bush tea primarily consist of flavonoids (ie, catechin, quercetin, rutin, vitexin, dihydrochalcones aspalathin, nothofagin) and phenolic acids (ie, caffeic, p-coumaric, ferulic, vanillic acids).5, 6, 7, 8, 9 Aspalathin, a dihydrochalcone C-glucoside, was identified in 1965,10 with green (unfermented) rooibos possibly containing more aspalathin than the commercial fermented rooibos tea.11 An enolic phenylpyruvic acid glucoside has also been identified.12
Phenolic content of extracts varies by season and production methods.13
Red bush tea contains no caffeine or pyrrolizidine alkaloids and low amounts of tannins (less than 5%), as determined by spectrophotometry and gas chromatography.14 The tea contains a relatively high level of vitamin C, as well as some sodium, potassium, magnesium, calcium, and zinc.5, 6
Uses and Pharmacology
Antioxidant effects
Animal data
Antioxidant activity has been demonstrated in laboratory experiments and in cellular systems, and in vivo studies have been conducted in rodents and quails.9, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26 Reported total antioxidant activity varies depending on the assay method and on fermentation and processing methods.27
Clinical data
A small, single-dose study among healthy human volunteers did not detect any change in total antioxidant capacity using the oxygen radical absorbance capacity assay,28 while another study found small increases.29 Following consumption of 6 cups of rooibos tea daily for 6 weeks, improved antioxidant status and lipid profiles (decreased low-density lipoprotein [LDL] and triacylglycerol, increased high-density lipoprotein [HDL]) were reported among adults with risk markers for cardiovascular disease.30
Cancer
Animal data
Suppression of mutagenic activity has been demonstrated in rodents, including studies of liver and skin tumorigenesis,27, 31, 32, 33, 34 with rooibos tea lowering activity to a greater extent than green tea in at least 1 study.31
Clinical data
No clinical data exist regarding the use of rooibos in cancer.
Cardiovascular
Animal data
In hyperlipidemic mice, aqueous rooibos extract reduced serum cholesterol, triglyceride, and free fatty acid concentrations, and decreased adipocyte size and number.35 An in vitro study demonstrated inhibition of adipogenesis following treatment with hot water–soluble solids from fermented rooibos.36 Anticoagulant activity has been described for aspalathin and nothofagin in human umbilical endothelial cells and in mice.37 These 2 chemical constituents have also shown activity in inhibiting various mechanisms involved in vascular inflammation.6, 38, 39 In mice, hypotensive effects were demonstrated, possibly via potassium channel modulation.40
Clinical data
Following daily consumption of 6 cups of rooibos tea for 6 weeks, improved antioxidant status and lipid profiles (decreased LDL and triacylglycerol, increased HDL) were reported among adults with risk markers for cardiovascular disease.30 In a study using human serum, rooibos acted as an ACE inhibitor in a manner similar to that of enalaprilat.41
Diabetes
Animal data
Experiments in rodents suggest that extracts of rooibos may have antidiabetic effects, with suppressed increases in fasting blood glucose levels demonstrated. Increased glucose uptake and insulin secretion, as well as reduced insulin resistance, are possible mechanisms of action. Green rooibos,11, 42 aspalathin alone,43 and in combination with rutin,44 and an enolic phenylpyruvic acid glucoside have all been studied.12, 44
Clinical data
There are no clinical data regarding the use of rooibos in diabetes.
Inflammation
Animal data
Anti-inflammatory effects of rooibos and of the constituents aspalathin and nothofagin have been studied in models of colitis and vascular inflammation. Suppression of tumor necrosis factor-alpha and interleukin has been demonstrated.16, 39, 45
Clinical data
There are no clinical data regarding the use of rooibos as an anti-inflammatory agent.
Other uses
The effect of rooibos, aspalathin, and nothofagin on steroid hormone biosynthesis has been investigated.46, 47 Rooibos consumption increased cortisone plasma levels in males and reduced cortisol to cortisone ratios in both males and females.48
Aspalathin was shown to inhibit xanthine oxidase activity and reduce plasma uric acid levels in mice.49
Bronchodilator and antispasmodic effects were demonstrated in mice, possibly via potassium channel modulation.40
Rooibos extracts may possess antibacterial activity, as demonstrated in limited experiments.25, 50
Dosing
The traditional dosage of the tea is 1 to 4 teaspoons of dry leaf tea per cup taken up to 3 times per day.5
Limited studies have used doses of 6 cups of rooibos tea per day for 6 weeks.30, 48 Urinary excretion of rooibos metabolites when taken as a tea has been investigated.51
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking. Phytoestrogenic effects have been suggested.52, 53, 54 Rooibos tea has been shown to interfere with steroidogenesis in vivo,53 possibly due to antioxidant properties, and to improve sperm motility in rats.17, 55
Interactions
No effect on iron absorption has been reported.27 In a study using human serum, rooibos acted as an ACE inhibitor in a manner similar to that of enalaprilat.41 Anticoagulant activity has been described for aspalathin and nothofagin in human umbilical endothelial cells and in mice.37 A study on the interaction of rooibos with cimetidine was inconclusive in its findings.56
Adverse Reactions
Information regarding adverse effects is lacking.27 Although microbial contaminants (including Salmonella) may be present due to the fermentation process used to derive the tea product, few reports of contamination exist.4, 57
Animal studies have shown increased creatinine levels, but no changes in kidney tissue on histology.55 A study of human volunteers receiving 6 cups of tea daily for 6 weeks noted increased serum levels of creatinine, as well as ALT and AST enzymes.30 A case of hepatotoxicity has been reported in a 37-year-old man who consumed 10 cups/day of red bush tea for more than a year. He was scheduled for an emergency appendectomy where his preoperative work-up revealed elevated liver enzymes and thrombocytopenia. All other causes for the hepatotoxicity were ruled out and the tea was deemed to be the responsible agent.60
Toxicology
Long-term, high-dose use may impair liver and kidney function, but few case reports exist.14, 30, 55, 58 Interference with the acrosome reaction, required for penetration into an egg, has been suggested.55
Index Terms
Aspalathus contaminata (Thunb.) Druce
Borbonia pinifolia Marloth
References
Disclaimer
This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.
This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.
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