- Hibiscus tea (from Hibiscus sabdariffa calyces) and beetroot juice (a rich source of dietary nitrate) have both been tested for blood pressure. A 2015 meta-analysis of five hibiscus trials (390 people) found systolic pressure fell by 7.58 mmHg and diastolic by 3.53 mmHg, and called for better-designed trials (Serban et al. 2015).
- A larger 2022 review of 17 hibiscus trials found a placebo-controlled systolic fall of 10.05 mmHg, but with a very wide confidence interval (−17.58 to −2.51) and very high inconsistency between trials (I² 81%). Only 6 of 17 trials described allocation concealment, and the authors rated the evidence as moderate risk of bias (Ellis et al. 2022).
- For beetroot, a 2013 meta-analysis of 16 crossover trials (254 people) found systolic pressure fell by 4.4 mmHg (95% CI −5.9 to −2.8), with no clear diastolic change (Siervo et al. 2013). A 2017 analysis of longer trials found the fall appeared only in clinic readings, not in 24-hour or home monitoring (Ashor et al. 2017).
- Hibiscus can interact with medicines. A small Sudanese study found a hibiscus drink sharply reduced chloroquine absorption (Mahmoud et al. 1994). In rats and rabbits it raised hydrochlorothiazide levels and urine output (Ndu et al. 2011). Using either remedy alongside blood-pressure medicines has not been properly tested.
- Product strength varies. Trials used capsules and teas from 15 mg to 9 g a day, and the 2022 review says poor product characterisation may explain part of the inconsistency (Ellis et al. 2022).
- Money trail: The meta-analyses we read were academically funded (UK Medical Research Council, an Iranian university grant, a UK university scholarship and BBSRC award) or reported no funding. The most-cited hibiscus tea trial was co-funded by a tea maker, Hain Celestial (BeverageDaily). A key beetroot trial in hypertension used juice supplied by the brand owner James White Drinks (Kapil et al. 2015).
- Evidence grade: Weak to moderate for a modest systolic fall with beetroot nitrate in clinic readings. Weak for hibiscus tea, because trials are small and inconsistent. Insufficient for long-term outcomes such as strokes or heart attacks. Risk for drug interactions and over-lowering of pressure.
Independent evidence review · Supplement
Hibiscus tea and beetroot juice probably lower systolic blood pressure by a few points over weeks, but neither has been shown to prevent a stroke or heart attack, and neither replaces measured, medicine-based care. The hibiscus evidence rests on small, inconsistent trials of very different products. The beetroot evidence is steadier, but the benefit shrinks or disappears when pressure is measured over 24 hours or at home. Several important trials had commercial ties, such as a tea-maker co-funder or a juice supplier. Our confidence: low to moderate that a small systolic effect exists; low that it matters clinically; very low for any long-term benefit.
Table of contents
- Evidence summary
- What hibiscus tea and beetroot juice are
- How they work
- What works and what does not
- Benefits by claim
- Risks and side effects
- Interactions
- Who should be cautious
- Doses studied and product quality
- Follow the money: who makes it and who funded the evidence
- Related research
- Frequently asked questions
- Sources and funding notes
Evidence summary
| Claim | Evidence | Source | Funding / conflict | Strength |
|---|---|---|---|---|
| Hibiscus tea lowers blood pressure (2015 pooled analysis) | 5 RCTs, 7 arms, 390 people. Systolic −7.58 mmHg, diastolic −3.53 mmHg (fixed-effect meta-regression). Larger falls when baseline pressure was higher. Authors ask for better-designed trials. | Serban 2015 | No grant listed in the Europe PMC record. Full-text declarations not read. | Weak |
| Hibiscus beats placebo (2022 pooled analysis) | 17 RCTs overall. Systolic −10.05 mmHg (95% CI −17.58 to −2.51, I² 81%). Diastolic −5.60 mmHg (95% CI −13.05 to 1.85), not significant. Moderate risk of bias. | Ellis 2022 | University of Leeds scholarship and BBSRC award; authors declare no conflicts. | Weak |
| Hibiscus works as well as blood-pressure drugs | Pooled systolic difference versus active drugs 2.13 mmHg (95% CI −2.81 to 7.06), not significant. Individual comparisons were small and varied: similar to captopril, weaker than lisinopril and ramipril. | Ellis 2022 | As above | Insufficient |
| Hibiscus tea in prehypertension (single trial) | 65 adults, 3 cups a day for 6 weeks. Systolic fell 7.2 versus 1.3 mmHg on placebo (P=0.030); diastolic difference not significant (P=0.160). | McKay 2010 | Reported as co-funded by USDA ARS and Hain Celestial (trade press); journal funding statement not read. | Weak |
| Beetroot juice or nitrate lowers systolic pressure | 16 crossover trials, 254 people. Systolic −4.4 mmHg (95% CI −5.9 to −2.8); diastolic −1.1 mmHg (95% CI −2.2 to 0.1), not significant. | Siervo 2013 | UK Medical Research Council grant G0700718B | Moderate |
| Beetroot juice lowers pressure (2017 pooled analysis) | 22 RCTs. Systolic −3.55 mmHg, diastolic −1.32 mmHg. Trials with nitrate-depleted beetroot placebo showed weaker effects. | Bahadoran 2017 | Shahid Beheshti University of Medical Sciences grant; no conflicts declared | Moderate |
| The beetroot effect lasts and is real-world | 13 trials of 1 to 6 weeks (325 people): systolic −4.1 mmHg (95% CI −6.1 to −2.2), diastolic −2.0 mmHg (95% CI −3.0 to −0.9). Significant only in clinic readings, not 24-hour or home monitoring. | Ashor 2017 | UK Medical Research Council grant MR/N007921/1 | Weak |
| Beetroot lowers pressure in people with hypertension | 68 patients enrolled; 4 weeks of 250 mL beetroot juice versus nitrate-free juice. Clinic −7.7/−2.4 mmHg; 24-hour ambulatory −7.7/−5.2 mmHg. | Kapil 2015 | British Heart Foundation; juice and placebo supplied by James White Drinks; one author a director of Heartbeet Ltd | Weak |
| Hibiscus reduces chloroquine levels | 600 mg chloroquine taken with Karkadi (hibiscus drink) substantially cut peak level and area under the curve in healthy men. | Mahmoud 1994 | University of Khartoum; PubMed record lists a US NIH (NIAID) grant, AI-16312-011 | Risk |
| Hibiscus interacts with hydrochlorothiazide | In rats and rabbits, the extract increased and prolonged hydrochlorothiazide levels and raised urine volume. Human data not found. | Ndu 2011 | No funding information in the record | Risk (animal data) |
Independent evidence and credibility scorecard
Independence tiers: 1 = regulator or government body; 2 = academic or review team with no declared commercial funding for the work; 3 = authors or trials with declared industry ties, supplied product or minor commercial links; 4 = manufacturer or seller. Credibility runs from A (highest) to D. We could not open a regulator, guideline or health-service source that addresses these two remedies, so no source below sits in tier 1.
| Source | Who funds it | Country | Independence tier (1–4) | Credibility (A–D) | Why it would tell the truth / residual bias |
|---|---|---|---|---|---|
| Serban et al. 2015 (hibiscus meta-analysis) | No grant listed in the Europe PMC record; authors at universities in Romania, Iran, Australia and Poland | Multi-country (Romania, Iran, Poland, Australia) | 2 | B | Academic authors rewarded for publication. Only five trials, fixed-effect model, and the authors themselves ask for better trials. |
| Ellis et al. 2022 (hibiscus meta-analysis) | University of Leeds scholarship; BBSRC seeding award; funders had no role | UK | 2 | B+ | Pre-registered (PROSPERO), rates trial quality, reports heterogeneity openly and shows the result is fragile. Residual bias: pooled very different products. |
| Hopkins et al. 2013 (hibiscus narrative review) | US NIH National Center for Complementary and Alternative Medicine training grant T32AT001287; funder had no role | US | 2 | B− | A narrative review, not a pooled analysis, mixing animal and human data. Calls the evidence promising and the studies of insufficient quality. |
| McKay et al. 2010 (hibiscus tea trial) | Reported by trade press as co-funded by the US Department of Agriculture and Hain Celestial Group (BeverageDaily) | US | 3 | B | Randomised, double-blind, placebo-controlled. Co-funder sells herbal teas, so it benefits from a positive result. Small (65 people). |
| Mahmoud et al. 1994 (chloroquine) | US NIH (NIAID) grant AI-16312-011 listed in the PubMed record; authors at University of Khartoum pharmacology department | Sudan | 2 | B− | No obvious commercial gain either way. Small study in healthy men with a single design; no replication found. |
| Ndu et al. 2011 (hydrochlorothiazide) | No funding information in the record | Nigeria | 2 | C | Animal study with a non-standardised extract. Useful as a warning, not as proof of a human effect. |
| Siervo et al. 2013 (nitrate meta-analysis) | UK Medical Research Council | UK | 2 | B+ | Public funder with no product to sell. Mostly short crossover trials in healthy people. A later group paper by the same authors found weaker real-world effects. |
| Bahadoran et al. 2017 (beetroot meta-analysis) | Shahid Beheshti University of Medical Sciences; no conflicts declared | Iran | 2 | B | Academic funder. Transparent about weaker effects in nitrate-depleted-placebo trials. Pools 22 trials (47 intervention and 43 control groups, 1,248 participants), so group counts are not trial counts. |
| Ashor et al. 2017 (medium-term nitrate) | UK Medical Research Council | UK | 2 | B+ | Tests whether the effect lasts and reports the null result for ambulatory and home readings, which cuts against hype. |
| Bonilla Ocampo et al. 2018 (beetroot systematic review) | Stated "no external funding"; two authors report consulting for dietary supplement companies | Colombia / Spain / other (multi-country) | 3 | C+ | No external funder, but declared supplement-industry advisory roles. Narrative synthesis of 11 small trials (310 people), not pooled. |
| Kapil et al. 2015 (beetroot in hypertension) | British Heart Foundation (study hosted in an NIHR biomedical research unit); juice and placebo supplied by James White Drinks; one author declares a directorship of Heartbeet Ltd | UK | 3 | B | Public charity and government funders, double-blind with a nitrate-free placebo. Declared supplier and commercial links mean readers should weigh it with that in mind. |
| Beet It / James White Drinks (company claims) | Seller of the juice and sports shots | UK | 4 | D | Sells the product, so treat its research and performance claims as marketing. It does publish a clear statement that it supplies placebo shots to researchers. |
All pooled analyses were produced by academic teams in the UK, Iran, Romania, Poland, Australia and the US. The two interaction studies come from Sudan and Nigeria. Eight of the twelve sources are tier 2 and none comes from a regulator, so the verdict mainly reflects academic and publicly funded views of a few small trials.
What hibiscus tea and beetroot juice are
Hibiscus tea is made from the dried red calyces of Hibiscus sabdariffa, also called roselle, sorrel, karkadeh, jamaica or zobo. Its authors credit anthocyanins as the main active compounds, with polyphenols and hibiscus acid also implicated (Hopkins et al. 2013). Trials have used brewed tea and also capsules of powder or extract (Ellis et al. 2022). It is not the same plant as ornamental garden hibiscus.
Beetroot juice is a vegetable juice rich in inorganic nitrate. Many trials used a concentrated shot or 250 mL daily, and compared it with nitrate-depleted beetroot juice as the placebo (Kapil et al. 2015). Nitrate capsules have also been tested, with a similar effect on blood pressure in healthy volunteers (Kapil et al. 2010).
We could not open a regulator or national-health-service page setting out the legal status of either product, so we make no statement about licensing by country (see the gaps paragraph).
How they work
Beetroot. The proposed pathway is dietary nitrate to nitrite to nitric oxide, a gas that relaxes blood vessels. In humans, the 2010 crossover study found that potassium-nitrate capsules and beetroot juice both raised plasma nitrite and lowered blood pressure, and the authors linked sex differences to the entero-salivary circulation of nitrate (Kapil et al. 2010). The 2017 meta-analysis found weaker effects when the placebo was nitrate-depleted beetroot juice, which the authors read as a hint of nitrate-independent effects (Bahadoran et al. 2017).
Hibiscus. The leading explanation is that anthocyanins and other plant compounds relax vessels and have mild diuretic activity. Much of the supporting mechanism work comes from animals: the 2013 review says animal studies consistently show dose-dependent falls in pressure, while the human trials were mixed in quality (Hopkins et al. 2013). What is proven in people is a small average fall in some trials, not the mechanism.
What works and what does not
| Claim | Verdict | Why |
|---|---|---|
| Beetroot juice lowers systolic pressure in clinic readings | Works (small) | Systolic fell 4.4 mmHg in the 2013 pooled analysis (Siervo) |
| Beetroot lowers 24-hour or home pressure | Mixed | Not significant in pooled analysis of medium-term trials (Ashor), yet significant in one trial in hypertension (Kapil) |
| Hibiscus tea lowers systolic pressure | Mixed | Pooled falls of 7.58 and 10.05 mmHg, but very inconsistent trials (Serban; Ellis) |
| Hibiscus lowers diastolic pressure | Insufficient | Not significant versus placebo in the 2022 pooled analysis (Ellis) |
| Either remedy replaces blood-pressure medicine | Insufficient | Drug comparisons were small and varied; one captopril comparison was similar, others favoured the drug (Ellis) |
| Either remedy prevents heart attack or stroke | Insufficient | The trials we opened measured blood pressure and vessel function, not clinical events |
Benefits by claim
Does hibiscus tea lower blood pressure?
The honest answer is: possibly, by a few points, and we cannot say how reliably. The 2015 analysis pooled five trials and found systolic −7.58 mmHg and diastolic −3.53 mmHg, with larger effects in people with higher starting pressure (Serban et al. 2015). The 2022 review included 17 trials, found a placebo-controlled systolic fall of 10.05 mmHg, and flagged I² of 81% and 94% for systolic and diastolic results, meaning the trials disagreed strongly. Removing one trial (Nwachukwu 2015) changed the diastolic result from non-significant to significant, which shows how fragile the pooled numbers are (Ellis et al. 2022).
The best-known single trial gave 65 prehypertensive or mildly hypertensive adults three 240 mL cups of hibiscus tea a day or a placebo drink for 6 weeks. Systolic fell 7.2 mmHg versus 1.3 on placebo (P=0.030). Diastolic did not differ (P=0.160) (McKay et al. 2010). Trade press reported that trial as co-funded by a tea maker (see the funding section).
Does hibiscus work as well as medicine?
Ellis and colleagues found no significant difference between hibiscus and active drugs (systolic 2.13 mmHg, 95% CI −2.81 to 7.06), but they warn that the comparisons are small and heterogeneous. Individual trials went in different directions: hibiscus looked similar to captopril, weaker than lisinopril and ramipril, and better than hydrochlorothiazide in one trial (Ellis et al. 2022). A non-significant difference in small trials does not show equivalence.
Does beetroot juice lower blood pressure?
Yes, modestly and more reliably in clinic readings. Siervo and colleagues pooled 16 crossover trials (254 people) and found systolic −4.4 mmHg, with the effect linked to nitrate dose (Siervo et al. 2013). Bahadoran and colleagues pooled 22 trials and found systolic −3.55 and diastolic −1.32 mmHg, with larger effects at higher doses and longer durations. Their result held when low-quality trials were removed (systolic −2.95 mmHg, 95% CI −4.16 to −1.74) (Bahadoran et al. 2017).
Does the beetroot effect last, and does it show up at home?
Less clearly. The 2017 analysis of trials lasting at least a week found that the falls were significant only in clinic settings and not with 24-hour ambulatory or home monitoring, which the authors called a limit on the evidence (Ashor et al. 2017). One 4-week trial in 68 people with hypertension did find falls in clinic, ambulatory and home readings (Kapil et al. 2015). The 2018 review of 11 small trials (310 people) judged the juice a possible strategy but did not pool the results, and several trials found no significant change (Bonilla Ocampo et al. 2018).
Does either remedy protect the heart?
We did not find a trial of either remedy that measured heart attacks, strokes or deaths. A six-week trial of beetroot juice in 69 people with high cholesterol improved a vessel-function measure (flow-mediated dilation), but that is a surrogate marker, not a clinical outcome (Velmurugan et al. 2016).
Risks and side effects
Hibiscus. Animal toxicity studies show low acute toxicity, with possible liver effects at very high doses in one animal study. Very high doses raised uric acid in rodents, and one study reported testicular effects and lower sperm count at very high doses. These are animal findings and we cannot say they apply to tea (Hopkins et al. 2013). In people, the 2022 review reported minimal side effects, but the safety data come from short trials.
Beetroot. Common expected effects are pink or red urine (beeturia) and stool discolouration. A trial in people with hypertension saw no change in transcutaneous methaemoglobin in a subset of 19 patients (Kapil et al. 2015). The Kapil 2015 authors note that patients predisposed to oxalate kidney stones may need to avoid high-nitrate, high-oxalate vegetables such as beetroot, and that long-term safety of juice as a treatment is not certain; we did not open an independent kidney-stone source, so ask a clinician.
Interactions
| Medicine | What was found | How strong the evidence is |
|---|---|---|
| Chloroquine (malaria) | A hibiscus drink given with 600 mg chloroquine substantially reduced peak plasma concentration and area under the curve in healthy men. The authors said this could plausibly lower antimalarial effect (Mahmoud et al. 1994). | One small human study; not replicated in what we found |
| Hydrochlorothiazide (diuretic) | In rats and rabbits, the extract increased and prolonged hydrochlorothiazide levels, cut urinary sodium and raised urine volume (Ndu et al. 2011). The 2013 review concluded hibiscus should not be used with the drug (Hopkins et al.). The 2022 review notes the rat dose does not translate directly to people (Ellis et al.). | Animal data only |
| ACE inhibitors, other blood-pressure drugs | The 2022 review states that hibiscus and ACE-inhibitor interactions remain unestablished (Ellis et al.). Because hibiscus lowers pressure in some trials, an additive effect is plausible but untested in combination. | Unstudied; our inference |
| Paracetamol (acetaminophen) | The 2013 review reports hibiscus enhanced acetaminophen elimination in adult males and suggested taking it 3 to 4 hours before a hibiscus drink (Hopkins et al.). | Small human data summarised in a review |
| Nitrate heart medicines and erectile-dysfunction drugs | We could not open a primary source on beetroot with these drugs. Because dietary nitrate lowers pressure, a clinician should be asked. See our guide to nitrate safety and sex with heart disease. | Not verified |
For wider interaction context, see Supplements and heart medicines and Blood pressure medicines.
Who should be cautious
- People taking chloroquine or hydrochlorothiazide, because of the interaction findings above.
- People on any blood-pressure medicine, or with low or borderline-low pressure, because of additive effects and dizziness. This is a reason to talk to the prescriber, not a reason to stop prescribed treatment.
- Pregnancy and breastfeeding (hibiscus). We found no adequate safety data. The only human pregnancy work we found is a small completed pilot of 10 women registered on ClinicalTrials.gov (NCT07175597), which does not establish safety. Avoid unless a midwife or doctor agrees.
- Children. We found no controlled trials of either remedy in children.
- Kidney disease, kidney stones, diabetes (beetroot). We could not verify specific advice from an authoritative source. Ask a clinician.
- Before surgery. We did not find a source on either remedy and anaesthesia; mention both to the anaesthetist.
Doses studied and product quality
Hibiscus. Trials ranged from 15 mg to 9 g a day over 15 to 90 days, with 10 using capsules and 7 using tea. Anthocyanin content was quantified in only 9 trials, ranging from 3 to 250 mg a day. The 2022 authors found doses of 1 g a day or less were not significant for blood pressure but stated that no dose or duration can be recommended (Ellis et al. 2022). The McKay trial used three 240 mL servings of brewed tea a day for 6 weeks (McKay et al. 2010). One captopril-comparison trial used a 10 g calyx capsule dose, as summarised by Ellis. These are doses studied, not advice.
Product quality problems
The 2022 review says inconsistent or missing characterisation of products makes comparison difficult and may add to heterogeneity (Ellis et al.). Brewing time, tea-bag content and extract type will all change what a person actually drinks. We did not open an independent laboratory survey of commercial hibiscus teas, so we cannot quote brand differences.
Beetroot. The 2018 review lists trial doses of 70 to 500 mL of juice and durations from a single dose to 6 weeks (Bonilla Ocampo et al. 2018). The hypertension trial used 250 mL daily for 4 weeks (Kapil et al. 2015). Nitrate content differs by variety, processing and concentration, so a 70 mL shot and a 250 mL glass are not the same dose. Independent brand-by-brand nitrate testing was not found.
Follow the money: who makes it and who funded the evidence
Who makes and sells it
Hibiscus. Hibiscus is a widely traded commodity tea and food ingredient rather than a single branded product, so there is no single maker. The best-known trial was co-funded by Hain Celestial Group, a Colorado-based food maker (BeverageDaily 2008). A US Department of Agriculture page says related work was funded by Celestial Seasonings, a brand of Hain Celestial (USDA ARS 2011), though that page does not tie the funding to this trial specifically. The trade article also quotes a hibiscus-extract supplier commenting on the results; that supplier is not described as involved in the study.
Beetroot. The beetroot brand most linked with research is Beet It, owned by James White Drinks, whose address in the hypertension trial paper is Ipswich, UK (Kapil et al. 2015). A 2010 trade article names its managing director as Lawrence Mallinson, reports that the company launched a 70 mL one-shot beetroot juice as an alternative to energy shots, and records him saying "We see sports nutrition as a target market". It also says the product was renamed from Heartbeet to Beet It the previous year, to avoid an implied health claim (Food Manufacture, 2010).
Who funded the trials
The pooled analyses were publicly or academically funded: UK Medical Research Council (Siervo; Ashor), an Iranian university (Bahadoran), and a UK university scholarship plus a BBSRC seeding award (Ellis). The Hopkins review was supported by a US NIH training grant (Hopkins). The 2018 beetroot review had no external funding but two authors report consulting for dietary supplement companies (Bonilla Ocampo). We have not traced the funding sources of the British Heart Foundation, NIHR or BBSRC beyond naming them.
In the beetroot trials, product supply is a separate tie from funding. The 2015 hypertension trial was funded by the British Heart Foundation, but James White Drinks supplied both the nitrate-rich juice and the nitrate-depleted placebo, and one author declares a directorship of Heartbeet Ltd (Kapil et al. 2015). Beet It placebo shots are sold under a "Heartbeet Placebo" name on the company science page, but we could not determine whether Heartbeet Ltd, of which a Kapil author is a director, is the same business as James White Drinks, so we make no claim about a link. The cholesterol trial of beetroot juice was funded by the MRC, British Heart Foundation and NIHR (Velmurugan et al. 2016).
Sports-nutrition and company position. The Beet It website states its shots have been "independently used in over 300 published medical and sports performance research papers since 2009" (its science page instead says over 300 research projects; we could not check either count), says its products are Informed Sport certified, and promotes use by top-level athletes and an ambassador programme (beet-it.com). Its science page offers placebo shots to researchers worldwide and says it does not conduct, fund or commission animal research; as we read it, the page does not state whether the company funds human studies (Beet It science page). Supplying free or cheap product does not prove bias, but it is a tie that should be disclosed in each paper.
Documented integrity events
We found no regulatory action, recall, warning letter or retraction involving the hibiscus or beetroot research we reviewed. This reflects what we could open, not a clean bill of health. We did not search enforcement databases for individual brands.
Research funding at a glance
12 sources graded. The counts below are the independence tiers assigned in the scorecard above. They count sources, not funding amounts or evidence quality.
Public funding alone does not prove independence, and commercial funding alone does not prove a claim false. Named funders, countries and relationships are in the scorecard and source notes.
Related research
For wider, evidence-graded context, see these Pure City Research guides:
- Blood Pressure Supplements: Benefits, Limits and Safety
- Garlic: Blood Pressure Evidence, Preparations and Safety
- Hypertension: Accurate Measurement, Treatment, Safety and Evidence Funding
- Blood Pressure Medicines: Types, Monitoring, Side Effects and Safety
- High Blood Pressure: Prevention and Management Evidence
- Home Blood Pressure Monitoring: Technique, Readings, Devices and Safety
- Supplements and Heart Medicines: Blood Thinners, Potassium, Herbs and Test Interactions
- Orthostatic Hypotension: Blood-Pressure Drops on Standing and Care
- Heart-Healthy Dietary Patterns: DASH, Food Choices and Medicine Safety
- Heart Disease Supplements: Benefits, Limits and Safety
- Sex and Heart Disease: Recovery, Intimacy, Erectile Dysfunction and Nitrate Safety
Frequently asked questions
Does hibiscus tea really lower blood pressure?
It may lower systolic pressure by a few points, but the trials disagree. The 2022 review found a 10.05 mmHg systolic fall against placebo with a very wide interval and I² of 81% (Ellis et al. 2022).
How many cups of hibiscus tea were used in trials?
The best-known trial used three 240 mL cups a day for 6 weeks (McKay et al. 2010). Across all trials, doses ranged from 15 mg to 9 g a day and no dose has been established (Ellis et al.).
Can hibiscus tea replace blood-pressure tablets?
No trial we opened shows that. Comparisons with drugs were small and varied, and the 2022 authors caution against over-reading them (Ellis et al.). Talk to the prescriber before changing treatment.
Is hibiscus tea safe with hydrochlorothiazide or chloroquine?
There is a warning for both. Hibiscus cut chloroquine absorption in a small human study (Mahmoud et al. 1994) and raised hydrochlorothiazide levels in animals (Ndu et al. 2011). Ask a pharmacist.
How much does beetroot juice lower blood pressure?
Pooled analyses put the systolic fall at about 3.5 to 4.4 mmHg (Siervo et al. 2013; Bahadoran et al. 2017). That is small compared with most blood-pressure drugs.
Does the beetroot effect show up on a home blood pressure monitor?
Not reliably. A pooled analysis found the effect in clinic readings only, not in 24-hour or home monitoring (Ashor et al. 2017), though one trial in hypertension did see falls on home readings (Kapil et al. 2015). See our guide to home monitoring.
Who pays for beetroot juice research?
Mostly public funders such as the British Heart Foundation and the MRC in the trials we opened, but the Beet It brand owner has supplied juice and placebo to trials (Kapil et al. 2015) and offers placebo shots to researchers (Beet It).
Is hibiscus tea safe in pregnancy?
That has not been established. We found only a 10-woman registered pilot (NCT07175597), which cannot show safety. Ask a midwife or doctor.
Sources and funding notes
What we could not verify: No regulator, guideline or national-health-service statement on hibiscus or beetroot for blood pressure (we searched for European Medicines Agency, Health Canada, NHS and European hypertension-guideline text and could not open a relevant primary page). The confidence intervals for the Serban 2015 result and its full-text declarations (we read the Europe PMC record only). The McKay 2010 funding statement in the journal itself (funding comes from a trade article and a USDA page). How many trials fed the Ellis 2022 placebo-controlled comparison. A 2013 Planta Medica conference abstract on hibiscus in pregnancy could not be opened (bot-protected) and was removed. Whether Heartbeet Ltd, named in the Kapil paper, is related to James White Drinks. Beet It sales figures (a trade report was blocked). Funding of sports-nutrition trials of beetroot generally. Evidence on beetroot oxalate and kidney stones, mouthwash effects on nitrate conversion, and combinations with nitrate or erectile-dysfunction drugs (only consumer sources surfaced, which we did not rely on). Independent laboratory testing of commercial hibiscus teas and beetroot shots. Original-paper details for several trials cited inside reviews (for example the captopril and lisinopril comparisons) come from Ellis 2022 and were not opened separately.
- Serban C et al. Effect of sour tea (Hibiscus sabdariffa L.) on arterial hypertension: a systematic review and meta-analysis. J Hypertens 2015 — hibiscus meta-analysis; no grant in the record.
- Ellis LR et al. A systematic review and meta-analysis of the effects of Hibiscus sabdariffa on blood pressure and cardiometabolic markers. Nutr Rev 2022 — hibiscus meta-analysis; University of Leeds scholarship and BBSRC.
- Hopkins AL et al. Hibiscus sabdariffa L. in the treatment of hypertension and hyperlipidemia: a comprehensive review of animal and human studies. Fitoterapia 2013 — narrative review; NIH NCCAM grant T32AT001287.
- McKay DL et al. Hibiscus sabdariffa L. tea (tisane) lowers blood pressure in prehypertensive and mildly hypertensive adults. J Nutr 2010 — RCT; reported USDA ARS and Hain Celestial co-funding.
- BeverageDaily: Hibiscus tea can lower blood pressure (2008) — trade-press report of funding of the McKay trial.
- USDA ARS: Don't underestimate the power of herbal teas (2011) — government news page; mentions Celestial Seasonings funding of related work.
- Mahmoud BM et al. Significant reduction in chloroquine bioavailability following coadministration with the Sudanese beverages Aradaib, Karkadi and Lemon. J Antimicrob Chemother 1994 — interaction study; University of Khartoum; PubMed record lists a US NIH NIAID grant. It also found that tamarind (Aradaib) and lemon drinks cut chloroquine levels similarly, so the effect is not specific to hibiscus.
- Ndu OO et al. Herb-drug interaction between the extract of Hibiscus sabdariffa L. and hydrochlorothiazide in experimental animals. J Med Food 2011 — animal study; funder not stated.
- Siervo M et al. Inorganic nitrate and beetroot juice supplementation reduces blood pressure in adults: a systematic review and meta-analysis. J Nutr 2013 — meta-analysis; UK MRC.
- Ashor AW et al. Medium-term effects of dietary nitrate supplementation on systolic and diastolic blood pressure in adults. J Hypertens 2017 — meta-analysis; UK MRC.
- Bahadoran Z et al. The nitrate-independent blood pressure-lowering effect of beetroot juice: a systematic review and meta-analysis. Adv Nutr 2017 — meta-analysis; Shahid Beheshti University of Medical Sciences.
- Bonilla Ocampo DA et al. Dietary nitrate from beetroot juice for hypertension: a systematic review. Biomolecules 2018 — systematic review; no external funding; supplement-industry consulting declared.
- Kapil V et al. Dietary nitrate provides sustained blood pressure lowering in hypertensive patients. Hypertension 2015 — RCT; British Heart Foundation; juice from James White Drinks.
- Kapil V et al. Inorganic nitrate supplementation lowers blood pressure in humans: role for nitrite-derived NO. Hypertension 2010 — crossover study; British Heart Foundation.
- Velmurugan S et al. Dietary nitrate improves vascular function in patients with hypercholesterolemia. Am J Clin Nutr 2016 — RCT; MRC, British Heart Foundation and NIHR.
- Food Manufacture: Beetroot takes on Red Bull with one-shot juice (2010) — trade press on James White Drinks; company quotes.
- Beet It homepage and science page — seller's own claims; James White Drinks.
- ClinicalTrials.gov NCT07175597 protocol: hibiscus drink in pregnancy pilot — seen in search results; sponsor not checked.
Educational research reviewed 6 October 2026. This article is not medical advice; talk to a qualified clinician or pharmacist before starting, stopping or combining treatments.
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