Chlorogenic acid

Pharmacology & Research

Chlorogenic acid — 5-O-caffeoylquinic acid, the caffeic-acid ester of quinic acid — is the dominant polyphenol of green coffee and one of the most abundant hydroxycinnamates in the human diet. Two facts frame its pharmacology. First, most human “chlorogenic acid” trials actually dose green coffee bean extract, a standardised multi-compound prep, not the pure molecule — so extract results don’t cleanly transfer to the isolate ^{1,6Reference 1Kozuma K et al. · 2005RCTAntihypertensive effect of green coffee bean extract on mildly hypertensive subjects — dose-response RCTView study →Reference 6Mubarak A et al. · 2012RCTAcute effects of chlorogenic acid on nitric oxide status, endothelial function, and blood pressure in healthy volunteers — randomised trial (pure chlorogenic acid)View study →}. Second, the molecule is extensively dismantled before it reaches the bloodstream: only about a third is absorbed intact in the small intestine, and the rest is broken down by gut bacteria into smaller phenolic acids, so what circulates is mostly metabolites, not chlorogenic acid itself ^{15,16,21Reference 15Olthof MR et al. · 2001Chlorogenic acid and caffeic acid are absorbed in humans (~33% of chlorogenic acid absorbed in the small intestine)View study →Reference 16Stalmach A et al. · 2010Bioavailability of chlorogenic acids following acute ingestion of coffee by humans with an ileostomyView study →Reference 21Clifford MN et al. · 2020ReviewBioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humans — reviewView study →}. Read the modest human evidence — and the one discredited claim — with both in mind.

1. Blood pressure & hypertension

The strongest signal, and the one with a real pure-molecule trial. A dose-response RCT in mildly hypertensive men (n=117, green coffee extract 46–185 mg/day, 28 days) found dose-related systolic falls of ~4.7–5.6 mmHg ^{1Reference 1Kozuma K et al. · 2005RCTAntihypertensive effect of green coffee bean extract on mildly hypertensive subjects — dose-response RCTView study →}. Crucially, a separate RCT used isolated chlorogenic acid (140 mg/day) in essential hypertension and showed significant systolic and diastolic reductions — one of the few true-isolate BP trials ^{2Reference 2Watanabe T et al. · 2006RCTThe blood pressure-lowering effect and safety of chlorogenic acid from green coffee bean extract in essential hypertension — RCT (isolated chlorogenic acid, 140 mg/day)View study →}. A chlorogenic-acid-specific meta-analysis (5 RCTs, n=364) put the effect at systolic −4.3 mmHg, diastolic −3.7 mmHg ^{3Reference 3Onakpoya IJ et al. · 2015Meta-analysisThe effect of chlorogenic acid on blood pressure — systematic review and meta-analysis of randomised clinical trials (5 RCTs, n=364)View study →}, and green-coffee-extract meta-analyses concur on modest BP lowering ^{4,5Reference 4Han B et al. · 2019Meta-analysisThe effect of green coffee extract supplementation on blood pressure — systematic review and meta-analysis of randomised controlled trialsView study →Reference 5Samavat S et al. · 2024Meta-analysisThe effects of green coffee bean extract on blood pressure and heart rate — systematic review and dose-response meta-analysis of randomised controlled trialsView study →}.

Gap: the trials are small, short (≤12 weeks), almost entirely in Asian populations, largely manufacturer-funded, and statistically heterogeneous (I² 65–97%); the effect is moderate and of unproven durability, with no cardiovascular-event data ^{3,4Reference 3Onakpoya IJ et al. · 2015Meta-analysisThe effect of chlorogenic acid on blood pressure — systematic review and meta-analysis of randomised clinical trials (5 RCTs, n=364)View study →Reference 4Han B et al. · 2019Meta-analysisThe effect of green coffee extract supplementation on blood pressure — systematic review and meta-analysis of randomised controlled trialsView study →}.

2. Endothelial & vascular function

Mechanistically the cleanest human data — and it includes the pure molecule. Two crossover RCTs found coffee matched for caffeine but higher in chlorogenic acids improved flow-mediated dilation, and purified 5-CQA (450 mg) alone improved it too, tracking the plasma appearance of chlorogenic-acid metabolites ^{7Reference 7Mills CE et al. · 2017RCTMediation of coffee-induced improvements in human vascular function by chlorogenic acids and its metabolites — two randomised, controlled, crossover trials (incl. pure 5-CQA arm)View study →}. An acute dose-response trial of coffee-derived chlorogenic acids supports a vascular effect ^{8Reference 8Naylor LH et al. · 2021RCTAcute dose-response effect of coffee-derived chlorogenic acids on the human vasculature in healthy volunteers — randomised controlled trialView study →}, and pure chlorogenic acid acutely improved nitric-oxide status and endothelial function in healthy volunteers ^{6Reference 6Mubarak A et al. · 2012RCTAcute effects of chlorogenic acid on nitric oxide status, endothelial function, and blood pressure in healthy volunteers — randomised trial (pure chlorogenic acid)View study →}.

Gap: almost all of this is acute, single-dose, in healthy young adults, using a surrogate endpoint (FMD) — no chronic dosing, no patient populations, no clinical outcomes. Strong for mechanism, weak for “does it treat anything” ^{7,8Reference 7Mills CE et al. · 2017RCTMediation of coffee-induced improvements in human vascular function by chlorogenic acids and its metabolites — two randomised, controlled, crossover trials (incl. pure 5-CQA arm)View study →Reference 8Naylor LH et al. · 2021RCTAcute dose-response effect of coffee-derived chlorogenic acids on the human vasculature in healthy volunteers — randomised controlled trialView study →}.

3. Glucose & metabolic markers

A meta-analysis of green-coffee-extract trials found modest, significant reductions in fasting blood glucose with a signal on insulin/HOMA-IR ^{9Reference 9Nikpayam O et al. · 2019Meta-analysisEffects of green coffee extract on fasting blood glucose, insulin concentration and HOMA-IR — systematic review and meta-analysis of interventional studiesView study →}, and a cardiovascular-risk meta-analysis reported small favourable shifts in metabolic and lipid markers ^{10Reference 10Pourmasoumi M et al. · 2021Meta-analysisThe effect of green coffee bean extract on cardiovascular risk factors — systematic review and meta-analysisView study →}. Mechanistically plausible — inhibition of glucose-6-phosphatase and of intestinal glucose absorption, plus AMPK activation.

Gap: the effects are small and heterogeneous, almost entirely from green-coffee extract not the isolate, in mixed metabolic-syndrome populations, with recurring publication bias and manufacturer funding. Clinically marginal ^{9,10Reference 9Nikpayam O et al. · 2019Meta-analysisEffects of green coffee extract on fasting blood glucose, insulin concentration and HOMA-IR — systematic review and meta-analysis of interventional studiesView study →Reference 10Pourmasoumi M et al. · 2021Meta-analysisThe effect of green coffee bean extract on cardiovascular risk factors — systematic review and meta-analysisView study →}.

4. Body weight & obesity

This is the classic supplement-hype node, and it does not hold up. A 2011 meta-analysis of 3 green-coffee-extract RCTs reported −2.5 kg versus placebo — but the authors themselves flagged every trial as high risk of bias, and the pool included a trial (Vinson 2012) that was later retracted ^{11,12Reference 11Onakpoya I et al. · 2011Meta-analysisThe use of green coffee extract as a weight loss supplement — systematic review and meta-analysis of randomised clinical trials (trials high risk of bias)View study →Reference 12Vinson JA et al. · 2012RCTRETRACTED: Randomized, double-blind, placebo-controlled, linear dose, crossover study to evaluate the efficacy and safety of a green coffee bean extract in overweight subjectsView study →}. The retraction followed an FTC action against the sponsor, whose study had altered subject weights and misstated the trial design; the company paid a $3.5M settlement ^{13Reference 13Retraction notice · 2014RCTRandomized, double-blind, placebo-controlled, linear dose, crossover study to evaluate the efficacy and safety of a green coffee bean extract in overweight subjectsView study →}.

Gap: with the pivotal trial’s data invalidated and the remainder small, biased and industry-funded, the weight-loss claim is not reliably supported — the nominally “positive” meta-analysis is contaminated at its source ^{11,13Reference 11Onakpoya I et al. · 2011Meta-analysisThe use of green coffee extract as a weight loss supplement — systematic review and meta-analysis of randomised clinical trials (trials high risk of bias)View study →Reference 13Retraction notice · 2014RCTRandomized, double-blind, placebo-controlled, linear dose, crossover study to evaluate the efficacy and safety of a green coffee bean extract in overweight subjectsView study →}.

5. Mood, cognition & alertness

The one direct test of the isolate is negative. In an acute crossover trial (n=39), pure chlorogenic acid did not improve cognition versus placebo; only the whole decaffeinated green-coffee blend improved sustained attention — i.e. the benefit tracked the food matrix, not the isolated molecule ^{14Reference 14Camfield DA et al. · 2013RCTA randomised placebo-controlled trial to differentiate the acute cognitive and mood effects of chlorogenic acid from decaffeinated coffee (pure chlorogenic acid showed no cognitive benefit)View study →}.

Gap: a single small acute study, and the isolate arm failed. No chronic or clinical mood data exist ^{14Reference 14Camfield DA et al. · 2013RCTA randomised placebo-controlled trial to differentiate the acute cognitive and mood effects of chlorogenic acid from decaffeinated coffee (pure chlorogenic acid showed no cognitive benefit)View study →}.

Mechanisms

Target / pathway	Effect	Relevant to
Antioxidant → nitric-oxide / endothelial support	preserves NO, improves endothelium-dependent vasodilation	blood pressure, vascular function
ACE inhibition (mild)	vasodilation, lower vascular tone	blood pressure
Glucose-6-phosphatase inhibition + slowed intestinal glucose absorption	lowers hepatic glucose output, blunts post-prandial glucose	glucose & metabolic
AMPK activation	improves insulin sensitivity, anti-lipogenic	glucose, weight
Lipid-absorption / lipogenesis modulation	reduces fat absorption (largely animal/in-vitro)	weight

Much of the AMPK, lipid-absorption and glucose-6-phosphatase work is animal and in-vitro at intact-chlorogenic-acid concentrations not reached in human plasma — see Pharmacokinetics.

Pharmacokinetics

Chlorogenic acid’s defining fact is that most of what circulates is not chlorogenic acid. In the classic ileostomy study, only about one-third of a pure dose is absorbed intact in the small intestine; the rest passes to the colon ^{15,16Reference 15Olthof MR et al. · 2001Chlorogenic acid and caffeic acid are absorbed in humans (~33% of chlorogenic acid absorbed in the small intestine)View study →Reference 16Stalmach A et al. · 2010Bioavailability of chlorogenic acids following acute ingestion of coffee by humans with an ileostomyView study →}. There, gut bacteria hydrolyse the ester to caffeic acid and reduce it further to dihydrocaffeic, ferulic and dihydroferulic acids, down to hippuric acid — which the liver then conjugates to glucuronides, sulfates and methylated forms ^{17,18Reference 17Olthof MR et al. · 2003Chlorogenic acid, quercetin-3-rutinoside and black tea phenols are extensively metabolised in humansView study →Reference 18Stalmach A et al. · 2009Metabolite profiling of hydroxycinnamate derivatives in plasma and urine after ingestion of coffee by humans — biomarkers of coffee consumptionView study →}. The species actually measured in blood are these small conjugated phenolic acids, not the parent ester ^{18,21Reference 18Stalmach A et al. · 2009Metabolite profiling of hydroxycinnamate derivatives in plasma and urine after ingestion of coffee by humans — biomarkers of coffee consumptionView study →Reference 21Clifford MN et al. · 2020ReviewBioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humans — reviewView study →}.

Because absorption happens at two separated sites, the plasma curve is biphasic — an early peak (~0.5–1 h) from small-intestinal uptake and a large late peak (~4–6 h) from colonic catabolites — and total concentrations of the intact compound stay sub-micromolar to low-single-digit µmol/L even after a substantial dose ^{18,19,21Reference 18Stalmach A et al. · 2009Metabolite profiling of hydroxycinnamate derivatives in plasma and urine after ingestion of coffee by humans — biomarkers of coffee consumptionView study →Reference 19Monteiro M et al. · 2007Chlorogenic acid compounds from coffee are differentially absorbed and metabolised in humansView study →Reference 21Clifford MN et al. · 2020ReviewBioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humans — reviewView study →}. The pattern varies enormously between people because it is driven by the gut microbiome, and the three coffee isomers (3-, 4-, 5-CQA) are absorbed and metabolised differently ^{19Reference 19Monteiro M et al. · 2007Chlorogenic acid compounds from coffee are differentially absorbed and metabolised in humansView study →}. Green-coffee extract is, counter-intuitively, reasonably bioavailable once the microbial metabolites are counted — but again, almost none of it is the parent ester ^{20Reference 20Farah A et al. · 2008Chlorogenic acids from green coffee extract are highly bioavailable in humansView study →}. The upshot: cell studies using 10–100 µmol/L of intact chlorogenic acid test a chemical species, and a concentration, that human oral dosing does not produce ^{21Reference 21Clifford MN et al. · 2020ReviewBioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humans — reviewView study →}.

Clinical trials

Chlorogenic acid has been tested in dozens of small investigator- and industry-led RCTs — chiefly blood pressure, vascular function and metabolic markers — plus a cluster of green-coffee weight-loss trials of poor quality, one of which was retracted. As a cheap, off-patent food molecule it attracts little rigorous registered trial activity, and many “chlorogenic acid” trials in fact used branded green-coffee extracts.

Completed	Planned	Terminated	Retracted	Preclinical
Many (small)	Several	—	1 (weight loss)	Extensive

Last checked: July 2026.

Isolate vs. Plant Studies

Chlorogenic acid is unusually prone to being over-read, in three ways.

First, the “isolate” trials usually aren’t the isolate. Most human chlorogenic-acid evidence comes from green coffee bean extract — a standardised multi-compound prep (an isomer mix of caffeoylquinic acids, often with residual caffeine), not the pure molecule ^{1,4Reference 1Kozuma K et al. · 2005RCTAntihypertensive effect of green coffee bean extract on mildly hypertensive subjects — dose-response RCTView study →Reference 4Han B et al. · 2019Meta-analysisThe effect of green coffee extract supplementation on blood pressure — systematic review and meta-analysis of randomised controlled trialsView study →}. Only a handful of studies dosed pure chlorogenic acid: the Watanabe hypertension trial ^{2Reference 2Watanabe T et al. · 2006RCTThe blood pressure-lowering effect and safety of chlorogenic acid from green coffee bean extract in essential hypertension — RCT (isolated chlorogenic acid, 140 mg/day)View study →}, the pure-5-CQA arms of the vascular studies ^{6,7Reference 6Mubarak A et al. · 2012RCTAcute effects of chlorogenic acid on nitric oxide status, endothelial function, and blood pressure in healthy volunteers — randomised trial (pure chlorogenic acid)View study →Reference 7Mills CE et al. · 2017RCTMediation of coffee-induced improvements in human vascular function by chlorogenic acids and its metabolites — two randomised, controlled, crossover trials (incl. pure 5-CQA arm)View study →}, and the (negative) cognition trial ^{14Reference 14Camfield DA et al. · 2013RCTA randomised placebo-controlled trial to differentiate the acute cognitive and mood effects of chlorogenic acid from decaffeinated coffee (pure chlorogenic acid showed no cognitive benefit)View study →}. Extract results and isolate results are not interchangeable.

Second, in plants it is an isomer mixture, and much “chlorogenic acid” is something else. Foods and herbs carry 3-CQA (neochlorogenic), 4-CQA (cryptochlorogenic) and 5-CQA (chlorogenic acid proper), plus di-caffeoylquinic acids. Several herb findings attributed to “chlorogenic acid” actually rest on di-CQAs — the anti-inflammatory activity in goldenrod is from 3,5-dicaffeoylquinic acid, and coltsfoot’s antitussive effect is carried by chlorogenic acid together with dicaffeoylquinic acids, not by 5-CQA alone. Across this database chlorogenic acid is named in the antioxidant phenolic fraction of many herbs — burdock, dandelion, eleuthero, horsetail and others — almost always as a contributor to a whole-extract effect rather than an isolated-compound result. (One repo source, calendula, actually quantifies true 5-O-caffeoylquinic acid.)

Third, the active species in the body is a metabolite mixture, not the plant molecule ^{17,21Reference 17Olthof MR et al. · 2003Chlorogenic acid, quercetin-3-rutinoside and black tea phenols are extensively metabolised in humansView study →Reference 21Clifford MN et al. · 2020ReviewBioavailability and metabolism of chlorogenic acids (acyl-quinic acids) in humans — reviewView study →}. So a whole-plant antioxidant effect, an isolated-CGA cell result, and a human oral dose are three different things — read each on its own terms.

Prevalence in Nature

Chlorogenic acid is one of the most abundant hydroxycinnamates in the human diet, occurring across many families but concentrated in a few: Rubiaceae (coffee), Asteraceae (artichoke, sunflower, chicory, burdock, yerba maté), Solanaceae (potato, eggplant) and Rosaceae (apple, pear, plum) ^{22,29Reference 22Alcázar Magaña A et al. · 2021ReviewCaffeoylquinic acids: chemistry, biosynthesis, occurrence, analytical challenges, and bioactivity — reviewView study →Reference 29Clifford MN · 1999Chlorogenic acids and other cinnamates — nature, occurrence and dietary burdenView study →}. It rarely occurs alone — foods carry an isomer mixture of 3-, 4- and 5-CQA plus di-caffeoylquinic acids — and which isomer dominates is source-specific: coffee and artichoke are 5-CQA-rich, whereas prunes and other Prunus fruits are dominated by 3-CQA (neochlorogenic), so fruit “chlorogenic acid” figures are best read as total caffeoylquinic acids ^{22Reference 22Alcázar Magaña A et al. · 2021ReviewCaffeoylquinic acids: chemistry, biosynthesis, occurrence, analytical challenges, and bioactivity — reviewView study →}.

Green (unroasted) coffee beans are by far the richest common source, at roughly 4–14% of dry weight (about 4–8% for arabica, up to ~10–14% for robusta) ^{22,29Reference 22Alcázar Magaña A et al. · 2021ReviewCaffeoylquinic acids: chemistry, biosynthesis, occurrence, analytical challenges, and bioactivity — reviewView study →Reference 29Clifford MN · 1999Chlorogenic acids and other cinnamates — nature, occurrence and dietary burdenView study →}. Roasting destroys most of it — controlled HPLC work shows green coffee at ~5.4% falling to ~0.9% by dark roast, an ~83% loss, with 5-CQA the most heat-labile isomer ^{27,28Reference 27Awwad S et al. · 2021Quantification of caffeine and chlorogenic acid in green and roasted coffee samples using HPLC-DAD and evaluation of the effect of degree of roasting on their levelsView study →Reference 28Moon JK et al. · 2009Role of roasting conditions in the level of chlorogenic acid content in coffee beans — correlation with coffee acidityView study →}. That is why supplements are made from green, not brewed, coffee. Two other concentrate-class sources rival coffee by dry weight but are consumed differently: yerba maté leaves (single-digit % dry weight, partly surviving toasting) ^{32Reference 32Meinhart AD et al. · 2016Distribution of major chlorogenic acids and related compounds in Brazilian green and toasted Ilex paraguariensis (maté) leavesView study →} and sunflower seed kernels (~3 g/100 g, the seed’s dominant phenolic and the cause of sunflower-flour’s greenish tinge) ^{34Reference 34Weisz GM et al. · 2009Identification and quantification of phenolic compounds from sunflower (Helianthus annuus L.) kernels and shells by HPLC-DAD/ESI-MSn (chlorogenic acid ~3 g/100 g, dominant phenolic)View study →}. Among everyday whole foods (fresh weight) the leaders are globe artichoke and eggplant, then blueberry, prune, potato (mostly the peel) and apple (mostly the skin) — see the Content-by-Source chart ^{30,31,33Reference 30Mattila P et al. · 2006Phenolic acids in berries, fruits, and beveragesView study →Reference 31Šilarová P et al. · 2019Monitoring of chlorogenic acid and antioxidant capacity of Solanum melongena L. (eggplant) under different heat and storage treatmentsView study →Reference 33Wichrowska D et al. · 2022Phenolic acid content and antioxidant properties of edible potato (Solanum tuberosum L.) with various tuber flesh coloursView study →}.

Biosynthetically it is a phenylpropanoid end-product: phenylalanine is processed (via PAL / C4H / 4CL) to p-coumaroyl-CoA, and the HCT/HQT hydroxycinnamoyl transferases, with C3′H hydroxylation, esterify a caffeoyl group onto quinic acid to give chlorogenic acid ^{22Reference 22Alcázar Magaña A et al. · 2021ReviewCaffeoylquinic acids: chemistry, biosynthesis, occurrence, analytical challenges, and bioactivity — reviewView study →}. It serves the plant as an antioxidant and defence metabolite — a radical scavenger and the polyphenol-oxidase substrate behind the browning of cut apple, potato and eggplant. There is essentially no non-plant source: animals and ordinary bacteria do not make it.

Discovery & Synthesis

The name is a chemistry pun that misleads twice over. “Chlorogenic” is from Greek chlōros (“pale green”) + -genos (“giving rise to”) — it describes a substance that turns green on oxidation (its ammoniacal solution greens in air), not a compound that is green, and despite the “chloro-” it contains no chlorine ^{26Reference 26Clifford MN et al. · 2017ReviewChlorogenic acids and the acyl-quinic acids: discovery, biosynthesis, bioavailability and bioactivity — review (naming, structure, 1976 IUPAC renumbering)View study →}. The name is commonly attributed to Anselme Payen around 1846, with an earlier isolation of coffee’s acidic fraction credited to Robiquet and Boutron-Charlard (~1837); these attributions come from secondary reviews rather than a verifiable primary source, so treat the date and author as “commonly cited,” not settled ^{26Reference 26Clifford MN et al. · 2017ReviewChlorogenic acids and the acyl-quinic acids: discovery, biosynthesis, bioavailability and bioactivity — review (naming, structure, 1976 IUPAC renumbering)View study →}. The structure — an ester of caffeic acid with a hydroxyl of L-quinic acid — was established in 1932 (Fischer) ^{26Reference 26Clifford MN et al. · 2017ReviewChlorogenic acids and the acyl-quinic acids: discovery, biosynthesis, bioavailability and bioactivity — review (naming, structure, 1976 IUPAC renumbering)View study →}.

A nomenclature trap follows the molecule to this day: IUPAC reversed the quinic-acid ring numbering in 1976, so the compound older papers call “3-caffeoylquinic acid” is the same molecule modern usage calls 5-caffeoylquinic acid ^{26Reference 26Clifford MN et al. · 2017ReviewChlorogenic acids and the acyl-quinic acids: discovery, biosynthesis, bioavailability and bioactivity — review (naming, structure, 1976 IUPAC renumbering)View study →}. Both conventions persist in the literature. Commercially, chlorogenic acid is not made by total synthesis — it is extracted and purified from green (unroasted) coffee beans, the richest practical source, which is why decaffeinated green-coffee extract is the standard raw material for standardised supplements ^{22Reference 22Alcázar Magaña A et al. · 2021ReviewCaffeoylquinic acids: chemistry, biosynthesis, occurrence, analytical challenges, and bioactivity — reviewView study →}.

Patents: not yet researched (future patent-loop pass).

Toxicity & Safety

Chlorogenic acid and green-coffee extracts are generally well tolerated at supplement doses, with adverse effects that are mild and mostly gastrointestinal — nausea, abdominal discomfort, loose stools — plus occasional headache; the standardised-extract hypertension trial reported no serious adverse effects and normal safety labs ^{2,11Reference 2Watanabe T et al. · 2006RCTThe blood pressure-lowering effect and safety of chlorogenic acid from green coffee bean extract in essential hypertension — RCT (isolated chlorogenic acid, 140 mg/day)View study →Reference 11Onakpoya I et al. · 2011Meta-analysisThe use of green coffee extract as a weight loss supplement — systematic review and meta-analysis of randomised clinical trials (trials high risk of bias)View study →}. One genuine, human-demonstrated signal deserves flagging: high-dose chlorogenic acid raises plasma homocysteine. A controlled trial giving ~2 g of purified chlorogenic acid produced a modest but significant acute rise in total homocysteine (~10–12%), an effect shared with black-tea polyphenols and coherent with coffee’s known homocysteine-raising action ^{23Reference 23Olthof MR et al. · 2001Consumption of high doses of chlorogenic acid, present in coffee, or of black tea increases plasma total homocysteine concentrations in humansView study →}. The dietary increment is small, but concentrated green-coffee supplements plausibly nudge homocysteine upward — relevant for anyone with hyperhomocysteinaemia, low folate/B12, or established cardiovascular disease.

On interactions: the mild blood-pressure-lowering effect can be additive with antihypertensive drugs, so watch for hypotension ^{2Reference 2Watanabe T et al. · 2006RCTThe blood pressure-lowering effect and safety of chlorogenic acid from green coffee bean extract in essential hypertension — RCT (isolated chlorogenic acid, 140 mg/day)View study →}; and many green-coffee products retain caffeine, which carries its own cardiovascular, sleep and interaction profile and can offset the BP effect — so a decaffeinated-versus-caffeinated distinction matters. The relevant allergy hazard is not the molecule but green (unroasted) coffee bean as an occupational allergen — green-coffee dust causes IgE-mediated sensitisation, rhinitis and asthma in coffee-processing workers; roasting destroys the protein allergens, so this is an inhalational occupational issue, not a concern for consumers of roasted coffee or purified chlorogenic acid ^{24,25Reference 24Romano C et al. · 1995Factors related to the development of sensitisation to green coffee and castor bean allergens among coffee workersView study →Reference 25Thomas KE et al. · 1991Factors relating to the development of respiratory symptoms in coffee process workersView study →}.

Dosage

Human blood-pressure trials have most often used 120–185 mg/day of chlorogenic acid — either as the purified compound or as a standardised green-coffee extract titrated to chlorogenic-acid content — and the effect appears dose-related within that range ^{1,2Reference 1Kozuma K et al. · 2005RCTAntihypertensive effect of green coffee bean extract on mildly hypertensive subjects — dose-response RCTView study →Reference 2Watanabe T et al. · 2006RCTThe blood pressure-lowering effect and safety of chlorogenic acid from green coffee bean extract in essential hypertension — RCT (isolated chlorogenic acid, 140 mg/day)View study →}. With-food or divided dosing is common given the low, microbiome-dependent absorption.

These are doses used in research and are not a personal recommendation — appropriateness depends on the individual, their medications (see interactions above) and professional guidance. Note that “green coffee extract” products vary widely in chlorogenic-acid standardisation and caffeine content, and are not interchangeable with the pure isolate.

References