Guarana

In the Amazon, various indigenous cultures have used this herb as a stimulant, astringent, analgesic, febrifuge, general tonic. It’s used for diarrhea, hypertension, migraines, neuralgia, dysentery, and more modernly to prevent cardiovascular disease ^{8Reference 8Basile et al. · 2005In vitroAntibacterial and antioxidant activities of ethanol extract from Paullinia cupana — in vitroView study →}.

The Satere-Mawe Indians used a mortar and pestle to grind the seeds, then mixed with water to form a paste, which was then shaped into cylinders and sun-dried. This formed a sort of “stick” which was usually then smoked and could last upwards of a year and preserved the characteristics of the plant quite well.

A study conducted on the effects on health associated with long term consumption of guarana noticed a significantly higher prevalence of males ingesting guarana long term over females. These researchers suggested this may be due to the indications for guarana in this region (Maue Brazil) being as an aphrodisiac, and to decrease fatigue, combined with the labor-intensive work of fishing, and agricultural work most often conducted by males.

The Satere-Mawe are most often associated with this botanical historically and referred to the beverage as Çapó. This was drunk by women during their period, while pregnant, and after giving birth. The males consumed this beverage during festivals, in mourning, before hunting trips, and after their wives gave birth.

The Jesuit’s expedition into South America revealed the first reports of guarana to the outside world in 1669 when the missionary João Felipe Bettendorf recorded the use of the herb by the Satere-Mawe Indians ^{1Reference 1Schimpl et al. · 2013ReviewGuarana: revisiting a highly caffeinated plant from the Amazon — reviewView study →}.

Guarana’s stimulant reputation rests on its caffeine — the seed is the richest natural source known ^{1Reference 1Schimpl et al. · 2013ReviewGuarana: revisiting a highly caffeinated plant from the Amazon — reviewView study →} — and human trials do detect acute effects, but they are modest. A 2023 systematic review and meta-analysis of eight placebo-controlled studies (328 participants, guarana 37.5–500 mg) found a faster response time for guarana versus placebo (Hedge’s g = 0.20) but no benefit on accuracy, and no dose-response relationship ^{2Reference 2Hack et al. · 2023Meta-analysisEffect of guarana (Paullinia cupana) on cognitive performance — systematic review and meta-analysisView study →}. An early double-blind RCT (n=28) reported improved attention-task speed after a single 75 mg dried extract, with some evidence of reduced accuracy ^{3Reference 3Kennedy et al. · 2004RCTImproved cognitive performance following guarana extract — randomised, placebo-controlled trialView study →}, and a randomised crossover trial around maximal-intensity cycling found cognitive effects comparable to an equivalent caffeine dose ^{5Reference 5Gurney et al. · 2023RCTCognitive effects of guarana supplementation with maximal intensity cycling — randomised controlled trialView study →}. Against these, a double-blind crossover trial directly comparing 500 mg guarana (130 mg caffeine) with low-dose caffeine found reaction time and heart-rate variability unaffected ^{6Reference 6Talik et al. · 2024RCTAcute guarana ingestion on mental performance and vagal modulation — randomised controlled trialView study →}. A 2025 controlled study additionally assessed guarana alongside green tea on students’ intellectual performance ^{7Reference 7Amaritei et al. · 2025Effects of guarana and green tea consumption on students’ intellectual performance — controlled studyView study →}. Interpretation is complicated because several of the strongest “guarana” cognition trials use vitamin/mineral complexes rather than the herb alone.

Gap: The pooled human effect is small and confined to reaction speed; there is no evidence guarana outperforms an equivalent dose of plain caffeine, and its non-caffeine “adaptogenic” cognitive claim is not supported by controlled data.

This is guarana’s most consistent activity across study types. The ethanol seed extract shows strong radical-scavenging in vitro, attributed to its polyphenol fraction — catechol and the flavanols catechin and epicatechin ^{8Reference 8Basile et al. · 2005In vitroAntibacterial and antioxidant activities of ethanol extract from Paullinia cupana — in vitroView study →}. Condensed tannins isolated from the seed scavenge DPPH radicals potently ^{9Reference 9Yamaguti-Sasaki et al. · 2007In vitroAntioxidant capacity and in vitro prevention of dental plaque by extracts and condensed tannins of Paullinia cupana — in vitroView study →}, and a tannin-rich, methylxanthine-free fraction retains both antioxidant and anti-inflammatory activity — showing the effect is polyphenol- rather than caffeine-driven ^{11Reference 11Machado et al. · 2021In vitroTNF-α inhibition, antioxidant effects and chemical analysis of guaraná seed powder — in vitroView study →}. The one human-relevant signal: elderly habitual guarana consumers showed 27% lower LDL oxidation than non-consumers, with the extract also suppressing conjugated-diene and TBARS formation in vitro ^{10Reference 10Portella et al. · 2013In vitroGuaraná effects on LDL oxidation in elderly people — in vitro and in vivo studyView study →}. Reported potency varies widely with origin and processing ^{1Reference 1Schimpl et al. · 2013ReviewGuarana: revisiting a highly caffeinated plant from the Amazon — reviewView study →}.

Gap: The human data are limited to an ex vivo LDL-oxidation marker in an observational sample; no trial has shown that guarana’s antioxidant activity changes a clinical outcome, and sugary commercial guarana drinks are in fact pro-oxidant ^{16Reference 16Chisté et al. · 2019AnimalWorsening of oxidative stress, DNA damage and atherosclerotic lesions with guarana soft drinks in LDLr-knockout mice — animal modelView study →}.

Guarana inhibits platelet aggregation through a mechanism that appears independent of caffeine. Aqueous extracts reduced ADP- and arachidonate-induced aggregation of human and rabbit platelets in vitro and in vivo, with the active material being water-soluble, heat-resistant and distinct from known xanthines ^{14Reference 14Bydlowski et al. · 1988In vitroInhibition of platelet aggregation by aqueous guaraná extract — in vitro and in vivo (rabbit)View study →}, and decreased platelet thromboxane synthesis in rabbit platelets ^{13Reference 13Bydlowski et al. · 1991In vitroAn aqueous extract of guaraná decreases platelet thromboxane synthesis — animal/in vitroView study →}. HPLC/MS fractionation identified catechin, epicatechin and their dimers — with only a small amount of caffeine — as the likely antiaggregatory factors ^{12Reference 12Subbiah et al. · 2008In vitroAnti-platelet aggregatory factors in guarana seeds — in vitroView study →}. The observational Amazonian cohort linking habitual guarana intake to lower rates of hypertension, obesity and metabolic syndrome sits alongside this mechanistically ^{15Reference 15Krewer et al. · 2011ObservationalHabitual intake of guaraná and metabolic morbidities — observational epidemiological studyView study →}, as does the reduced LDL oxidation seen in habitual users ^{10Reference 10Portella et al. · 2013In vitroGuaraná effects on LDL oxidation in elderly people — in vitro and in vivo studyView study →}.

Gap: All direct cardiovascular data are in vitro, animal or observational — no randomised trial has tested a cardiovascular endpoint. The epidemiological association is confounded, and guarana’s caffeine acutely raises blood pressure, so any net benefit likely requires tolerance and excludes people with uncontrolled hypertension.

Guarana’s best-studied clinical application, and its most contested. A breast-cancer crossover RCT (n=75) reported that 50 mg twice daily significantly improved FACIT-F and Brief Fatigue Inventory scores versus placebo during chemotherapy ^{19Reference 19de Oliveira Campos et al. · 2011RCTGuarana improves fatigue in breast cancer patients undergoing systemic chemotherapy — randomised controlled trialView study →}. But subsequent, better-powered trials were negative: a pilot RCT in post-radiation breast-cancer patients found no benefit over placebo for fatigue or depression ^{20Reference 20da Costa Miranda et al. · 2009RCTGuaraná for postradiation fatigue and depression — randomised, double-blind pilot trial (null)View study →}, and two double-blind RCTs of a standardised purified extract (PC-18) failed to beat placebo, attributed partly to an unexpectedly strong placebo response ^{21Reference 21Sette et al. · 2018RCTPurified dry Paullinia cupana (PC-18) extract for chemotherapy-induced fatigue — two double-blind randomised trials (null)View study →}. A phase II study in head-and-neck cancer even found worsening quality of life in the guarana arm during chemoradiotherapy ^{23Reference 23Martins et al. · 2017RCTDry guarana extract in head-and-neck tumour patients undergoing chemoradiotherapy — placebo-controlled, double-blind, randomised studyView study →}. The two meta-analyses split accordingly: a 2021 review of breast-cancer trials found no benefit (very low GRADE quality) ^{17Reference 17de Araujo et al. · 2021Meta-analysisGuarana as a dietary supplement for fatigue in cancer patients — systematic review with meta-analysisView study →}, while a 2024 meta-analysis of five studies reported a significant effect (SMD −0.77) despite high heterogeneity ^{18Reference 18Maselli-Schoueri et al. · 2024Meta-analysisNatural supplementation to treat cancer-induced fatigue: meta-analysis on guaraná — systematic review and meta-analysisView study →}.

Gap: The signal is unstable and prep-dependent; the most rigorous individual RCTs were null, placebo responses are large, and pooled estimates swing with which trials are included. No definitive dose or extract has emerged.

Two double-blind crossover RCTs suggest a small ergogenic effect. In endurance-trained cyclists, 500 mg guarana (130 mg caffeine) increased work performed in a 15-minute time trial versus placebo — an effect graded trivial-to-small and not significantly different from an equivalent caffeine dose, with lower perceived exertion the likely driver ^{26Reference 26Penna et al. · 2024RCTGuarana but not low-dose caffeine improves cycling time-trial performance — randomised controlled trialView study →}. In under-17 soccer players, 3 g of seed powder improved intermittent-exercise capacity (Yo-Yo test) but not jump, sprint or agility ^{27Reference 27Estrázulas et al. · 2024RCTAcute ingestion of guarana on soccer player performance — randomised controlled trialView study →}.

Gap: Effects are small, inconsistent across performance domains, and appear centrally mediated (reduced perceived effort) rather than metabolic; there is no clear advantage over plain caffeine.

A tannin-rich, methylxanthine-free guarana fraction inhibited TNF-α in vitro alongside its antioxidant activity, indicating a polyphenol-driven anti-inflammatory action ^{11Reference 11Machado et al. · 2021In vitroTNF-α inhibition, antioxidant effects and chemical analysis of guaraná seed powder — in vitroView study →}. In rodent models, guarana prevented rises in IL-1β and IL-6 during methotrexate toxicity ^{29Reference 29Aldhahrani · 2023AnimalPaullinia cupana seed extract ameliorates methotrexate-induced testicular dysfunction — mouse modelView study →} and blunted lipotoxicity-associated inflammation on a high-fat background ^{34Reference 34Ruchel et al. · 2021Lipotoxicity-associated inflammation is prevented by guarana — comparative animal studyView study →}.

Gap: Entirely preclinical — no human anti-inflammatory endpoint has been measured, and the active fraction differs from the caffeine-rich material most people actually consume.

Rodent data are consistent and mechanistically coherent. Guarana powder (300 mg/kg for seven days) before a toxic paracetamol dose in rats prevented serum ALT, AST and ALP elevations (by 44%, 29% and 24%), reduced necrotic liver area, preserved glutathione and modulated SOD and catalase ^{28Reference 28Teixeira et al. · 2025AnimalPreventive guarana powder mitigates acute paracetamol-induced hepatotoxicity in rats — animal modelView study →}. A seed extract likewise ameliorated methotrexate-induced organ toxicity through antioxidant and anti-apoptotic pathways ^{29Reference 29Aldhahrani · 2023AnimalPaullinia cupana seed extract ameliorates methotrexate-induced testicular dysfunction — mouse modelView study →}.

Gap: Animal-only, using pre-treatment dosing against acute chemical injury; no human liver-protection data exist, and relevance to ordinary consumption is unestablished.

Preclinical antitumour activity is reproducible in cell lines. Guarana inhibited the AKT/mTOR/S6K and MAPK pathways and reduced colony formation in colorectal (HT-29) and breast (MCF-7) cancer cells without harming normal cells ^{30Reference 30Cadoná et al. · 2017In vitroGuaraná presents in vitro antitumour activity in colorectal and breast cancer cell lines via AKT/mTOR/S6K and MAPK pathways — in vitroView study →}, and increased HT-29 sensitivity to oxaliplatin while up-regulating p53 and the Bax/Bcl-2 ratio ^{31Reference 31Cadoná et al. · 2016In vitroGuaraná increases oxaliplatin sensitivity of colorectal HT-29 cells — in vitroView study →}. In vivo, guarana reduced proliferation and increased apoptosis of B16/F10 melanoma lung metastases in mice ^{32Reference 32Fukumasu et al. · 2008AnimalPaullinia cupana var. sorbilis reduces cell proliferation and increases apoptosis of B16/F10 melanoma lung metastases in mice — animal modelView study →}.

Gap: Confined to cell lines and one mouse metastasis model; the human oncology trials on guarana address fatigue, anorexia and hot flashes — symptom management — not antitumour efficacy ^{24,25Reference 24Palma et al. · 2016Clinical trialGuarana improves anorexia in patients with advanced cancer — phase II clinical trialView study →Reference 25Oliveira et al. · 2013Clinical trialPaullinia cupana for control of hot flashes in breast cancer patients — pilot clinical trialView study →}.

Mechanistic support is real but human evidence is confounded. In obese rats, guarana reduced body weight, white fat and hepatic steatosis by suppressing fatty-acid and triglyceride synthesis and increasing β-oxidation ^{33Reference 33Liang et al. · 2023AnimalEffect of guarana on lipid metabolism in obese rats: a lipidomics study — animal modelView study →}; guarana seed powder inhibited pancreatic lipase and reduced cholesterol micellar solubilisation and Caco-2 absorption in vitro ^{35Reference 35Figueira et al. · 2022In vitroEffect of guarana seed powder on cholesterol absorption in vitro and in Caco-2 cells — in vitroView study →}. Human weight-loss data, however, come from combinations — caffeine-containing ephedra-guarana formulas that raised heart rate, blood pressure, glucose and insulin ^{36Reference 36Haller et al. · 2005RCTShort-term metabolic and hemodynamic effects of ephedra and guarana combinations — randomised controlled trialView study →} — making guarana’s independent effect impossible to isolate.

Gap: Guarana-alone human weight-loss trials are absent; the positive human signal is inseparable from ephedra, yerba maté or green-tea co-ingredients, several of which carry their own cardiovascular risk.

In rodents with induced hyperlipidemia, guarana powder prevented memory impairment and normalised brain acetylcholinesterase activity while lowering total and LDL cholesterol ^{37Reference 37Ruchel et al. · 2017AnimalGuarana ameliorates memory impairment and modulates acetylcholinesterase in hyperlipidemic rat brain — animal modelView study →}. In human neuronal-like cells, guarana prevented protein glycation, β-amyloid aggregation and acrolein-induced toxicity — hallmarks relevant to Alzheimer’s pathology ^{38Reference 38Bittencourt et al. · 2014In vitroGuarana prevents β-amyloid aggregation, AGE generation and acrolein-induced cytotoxicity in neuronal-like cells — in vitroView study →}.

Gap: Cell and rodent data only, at doses and disease models far removed from human use; no clinical cognitive-decline or neurodegeneration data exist.

The ethanol extract of guarana seeds showed antibacterial activity in vitro against both gram-negative and gram-positive organisms, notably Pseudomonas aeruginosa, Proteus mirabilis, Proteus vulgaris and Escherichia coli ^{8Reference 8Basile et al. · 2005In vitroAntibacterial and antioxidant activities of ethanol extract from Paullinia cupana — in vitroView study →}.

Gap: A single in vitro report; no in vivo, spectrum-defining or clinical antimicrobial work, and no data on achievable tissue concentrations.

• Hypertension
• Over-stimulation
• Anxiety

Guarana seed is the richest known natural source of caffeine (roughly 2.5–8% by weight, ~4–5× coffee) ^{1Reference 1Schimpl et al. · 2013ReviewGuarana: revisiting a highly caffeinated plant from the Amazon — reviewView study →}, and its principal risks are those of a high caffeine load: insomnia, anxiety, palpitations, raised blood pressure, tachycardia and arrhythmia, with effects additive to other caffeine and stimulant sources. A controlled human study of ephedra-guarana combinations documented significant rises in heart rate, blood pressure, glucose and insulin plus reduced serum potassium, and such stimulant combinations have been linked to serious adverse events ^{36Reference 36Haller et al. · 2005RCTShort-term metabolic and hemodynamic effects of ephedra and guarana combinations — randomised controlled trialView study →}. Effects are dose- and preparation-dependent: sugary commercial guarana soft drinks were pro-oxidant and worsened hypertension, atherosclerosis and hepatic and gastric damage in a dyslipidemic mouse model, effects attributed largely to the added sugar rather than the extract itself ^{16Reference 16Chisté et al. · 2019AnimalWorsening of oxidative stress, DNA damage and atherosclerotic lesions with guarana soft drinks in LDLr-knockout mice — animal modelView study →}. People with uncontrolled hypertension, cardiac disease, arrhythmia or anxiety disorders should avoid it, and total caffeine intake should be kept under ~400 mg/day.

Interactions (scope). Guarana’s interactions have been only partially studied. A rat pharmacokinetic study found guarana delayed the absorption of phenytoin (delayed Tmax, lower metabolite exposure) ^{39Reference 39Alves et al. · 2026AnimalImpact of Paullinia cupana extract on the pharmacokinetics of phenytoin in rats — animal modelView study →}, and the controlled human trial above showed additive cardiovascular and metabolic effects when guarana was combined with ephedra ^{36Reference 36Haller et al. · 2005RCTShort-term metabolic and hemodynamic effects of ephedra and guarana combinations — randomised controlled trialView study →}. Caffeine’s own well-documented interactions — with CYP1A2 inhibitors (e.g. fluvoxamine, ciprofloxacin), other stimulants, theophylline, lithium, clozapine and MAO inhibitors — apply by extension but have not been tested for guarana specifically. Absence of a reported interaction here is not evidence of safety.