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Rooibos and Health

A reference on rooibos and health, sorted by how strong the evidence is: what is settled (caffeine-free, low in tannins, antioxidant-rich), what one small human trial suggests, what is shown only in animals, and what has no clinical support at all.

The Ministry of Rooibos 6 min read 9 sources

Contents
  1. The short answer
  2. What is settled
  3. What "antioxidant" does and does not mean
  4. The best human evidence: a modest help for cholesterol
  5. Blood sugar: shown in animals, untested in people
  6. Where the whole body of human evidence stands
  7. Claims with no clinical support
  8. Safety
  9. Sources

The short answer

Settled: no caffeine, low in tannins, rich in antioxidants. One small trial on blood fats. Nothing at all for detox or cures.

Three things are settled: rooibos contains no caffeine, it is low in tannins, and it is rich in antioxidants.

Explainer · The body

How strong is the evidence

Each claim sits on the rung its evidence reaches, with what exists and what is missing.

  1. SettledRung 4 of 4

    Caffeine-free · Low in tannins · Rich in antioxidants, chiefly aspalathin

    What exists
    The make-up of the plant and of the cup, measured.
    What is missing
    Nothing for these facts themselves. Being rich in antioxidants describes the tea; it is not a shown effect in the body.

  2. One small human trialRung 3 of 4

    Blood fats

    What exists
    40 adults at raised risk drank six cups a day for six weeks. LDL fell about 15 percent, triglycerides 29 percent, and HDL rose 33 percent.
    What is missing
    No confirming trial since.
    Change after six weeks, one trial of 40 adults
    LDL about −15%
    Triglycerides −29%
    HDL +33%

  3. Animals onlyRung 2 of 4

    Blood sugar

    What exists
    Two rooibos compounds lowered glucose in diabetic rodents.
    What is missing
    Any clinical study in people.

  4. NoneRung 1 of 4

    Detox · Cures · Weight loss · Anti-ageing

    What exists
    No trial at all.
    What is missing
    Any trial.

What is settled

Rooibos is naturally caffeine-free. The caffeine was never there to remove, unlike a decaffeinated coffee or a decaffeinated black tea, where it is stripped out after the fact. This is why rooibos can be drunk in the evening.

Rooibos is low in tannins. Rooibos carries far less of them than black tea does.

Rooibos is rich in antioxidants. Its signature compound is aspalathin5, a flavonoid (a C-glucosyl dihydrochalcone) that has so far been detected in almost no other plant, alongside a smaller relative called nothofagin. Green rooibos carries considerably more aspalathin than the familiar red type, because the oxidation step that reddens the leaf converts most of the aspalathin into other compounds. In healthy volunteers, some studies have measured a rise in the blood's antioxidant capacity for a few hours after a cup, though the effect has not shown up consistently across every lab assay used to test it.

  1. Stander et al., Visualization of Aspalathin in Rooibos (Aspalathus linearis) Plant and Herbal Tea Extracts Using Thin-Layer Chromatography, Molecules (2019)

What "antioxidant" does and does not mean

"Antioxidant" describes how a molecule behaves in a laboratory: it neutralises reactive oxygen species, the unstable molecules that can damage cells. Rooibos genuinely does this in a test tube, and aspalathin is a large part of why.

What the word does not do is promise a health outcome. A higher reading on a laboratory antioxidant assay, or a few hours of raised antioxidant capacity in the blood, is not the same as a longer life, a lower risk of disease, or any specific benefit a person can feel. McGill University's Office for Science and Society puts it plainly: the antioxidant content is a real laboratory finding that, on its own, "doesn't have much meaning for consumers."

In the European Union, claims for botanical ingredients like rooibos sit on an "on hold" list pending the European Commission's and Member States' final consideration.

The best human evidence: a modest help for cholesterol

In a six-week trial, Marnewick and colleagues (2011)2 had forty adults at risk for cardiovascular disease drink six cups of fermented rooibos a day. Over the six weeks the blood-fat picture improved: LDL ("bad") cholesterol and triglycerides fell, HDL ("good") cholesterol rose, and markers of oxidative stress in the blood went down. The 2023 scoping review that gathered the human studies recorded the size of these moves as roughly a 15 percent fall in LDL, a 29 percent fall in triglycerides, and a 33 percent rise in HDL.

  1. Marnewick et al., Effects of rooibos (Aspalathus linearis) on oxidative stress and biochemical parameters in adults at risk for cardiovascular disease, Journal of Ethnopharmacology (2011)

It is one trial: forty people, all already at elevated risk, drinking six cups a day for six weeks, with no large confirmatory trial since.

Blood sugar: shown in animals, untested in people

In one study, Kawano and colleagues (2009)4 found that aspalathin in the diet held down fasting blood glucose in diabetic mice for five weeks. A 2018 systematic review and meta-analysis3 found that two rooibos compounds, PPAG and isoorientin, lowered blood glucose in diabetic rodents, while whole rooibos extracts and aspalathin showed "little, if any, effect."

  1. Kawano et al., Hypoglycemic effect of aspalathin, a rooibos tea component, in type 2 diabetic db/db mice, Phytomedicine (2009)
  2. Sasaki et al., A Beneficial Role of Rooibos in Diabetes Mellitus: A Systematic Review and Meta-Analysis, Molecules (2018)

No clinical study has yet tested whether ordinary rooibos meaningfully controls blood sugar in people with diabetes. A few small human measurements have hinted at a dip in glucose after a single large serving, but they are preliminary and were not designed to answer the question.

Where the whole body of human evidence stands

The most complete survey is the 2023 scoping review1, which gathered the human studies on rooibos and health that met its criteria: eighteen publications in all, covering 488 people between them, aged from six to eighty-three.

  1. Afrifa et al., The health benefits of rooibos tea in humans (Aspalathus linearis): a scoping review, Journal of Public Health in Africa (2023)
Claim Evidence tier What exists What is missing
Caffeine-free Settled A property of the plant. It was never there to remove Nothing
Low in tannins Settled A property of the plant Nothing
Rich in antioxidants, chiefly aspalathin Settled as composition Aspalathin is detected in almost no other plant. Some studies measure a rise in blood antioxidant capacity for a few hours after a cup That the rise means anything for health. The effect has not appeared consistently across every lab assay
Helps blood lipids One small human trial Marnewick 2011: forty adults already at elevated risk, six cups a day for six weeks. LDL down about 15 percent, triglycerides down 29, HDL up 33, per the 2023 scoping review Any confirmatory trial since
Controls blood sugar Animal only A 2018 meta-analysis found two rooibos compounds, PPAG and isoorientin, lowered glucose in diabetic rodents; whole rooibos extracts and aspalathin showed little, if any, effect The trial that matters. No clinical study has tested whether ordinary rooibos controls blood sugar in people with diabetes
Detox, cures, weight loss, anti-ageing None Nothing Any clinical trial

The review reported the same encouraging hints described above, in antioxidant status, in blood lipids, and in glucose. In its own framing, the small number of human studies and the small total sample "make it very difficult to either confirm or refute" that rooibos has a significant effect on people, and it called for large, well-designed clinical trials before any firm health claim can be made.

Claims with no clinical support

The detox claims, the cure claims, and the weight-loss and anti-ageing claims have no controlled trial behind them.

Safety

A small number of case reports describe liver inflammation in people who had been drinking rooibos. In one report, Engels and colleagues (2013)6 describe a man who developed acute liver injury after a month of daily rooibos taken together with buchu, another South African herb; his liver recovered after he stopped. The authors suggest the injury may come from the variable make-up of small-batch herbal teas.

  1. Engels et al., Tea not Tincture: Hepatotoxicity Associated with Rooibos Herbal Tea, ACG Case Reports Journal (2013)

Sources

  1. Afrifa et al., The health benefits of rooibos tea in humans (Aspalathus linearis): a scoping review, Journal of Public Health in Africa (2023) ↩
  2. Marnewick et al., Effects of rooibos (Aspalathus linearis) on oxidative stress and biochemical parameters in adults at risk for cardiovascular disease, Journal of Ethnopharmacology (2011) ↩
  3. Sasaki et al., A Beneficial Role of Rooibos in Diabetes Mellitus: A Systematic Review and Meta-Analysis, Molecules (2018) ↩
  4. Kawano et al., Hypoglycemic effect of aspalathin, a rooibos tea component, in type 2 diabetic db/db mice, Phytomedicine (2009) ↩
  5. Stander et al., Visualization of Aspalathin in Rooibos (Aspalathus linearis) Plant and Herbal Tea Extracts Using Thin-Layer Chromatography, Molecules (2019) ↩
  6. Engels et al., Tea not Tincture: Hepatotoxicity Associated with Rooibos Herbal Tea, ACG Case Reports Journal (2013) ↩
  7. McGill University Office for Science and Society, You Asked: What is Rooibos tea?
  8. EFSA, Health claims (art. 13), on hold botanical claims
  9. South African Rooibos Council

healthscienceantioxidantsaspalathincaffeine-freecholesterolblood sugarsafety

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