01 — Evidence
Evidence Summary
Kaempferol's evidence sits almost entirely in cells and animals. There is no human cancer trial of any kind — the human tier is dietary pharmacokinetics and basic tolerability. Animal studies show reduced tumor growth and, most consistently, reduced metastasis; cell studies map a broad multi-pathway mechanism at concentrations far above what an oral dose reaches.
Human
Clinical Record
Pharmacokinetics, tolerability, and diet-cancer epidemiology
No trial has tested kaempferol as a cancer treatment. The human evidence is how it is absorbed, whether it is tolerated, and inconsistent diet-and-cancer associations.
- No completed trial has tested isolated kaempferol against tumor response, progression, or survival
- An oral dose from food appeared in blood mostly as conjugates (chiefly the 3-glucuronide), with free kaempferol a smaller fraction
- Diet studies link higher kaempferol intake to lower risk of some cancers (ovarian, pancreatic), but findings are inconsistent and not treatment evidence
Animal
Preclinical Signal
Several tumor models; anti-metastatic
In animal models across several cancers, kaempferol reduced tumor growth — and, most consistently, reduced metastasis.
- Reduced tumor-cell colonisation of the lungs in two independent injected-cell models (renal and bile-duct cancer)
- Suppressed tumor growth in gallbladder and lung cancer models
- Increased anti-tumor immune-cell infiltration and added to a checkpoint immunotherapy in a colorectal model
In Vitro
Cell Model Data
Broad mechanism panel; concentration-dependent
Across many cancer cell lines kaempferol suppresses growth and survival signaling and triggers cell death — but at concentrations far above achievable blood levels.
- Lowered PI3K/AKT/mTOR and Wnt/β-catenin growth signaling and arrested the cell cycle
- Triggered mitochondrial cell death, though potency varied widely between cell lines
- Collapsed tumor-cell sugar metabolism in one lab's colorectal work — a distinctive but single-source signal
Human
Clinical Record
No completed trial has tested isolated kaempferol as a cancer treatment — nothing measures its effect on tumor response, progression, or survival. The human record instead has three strands: how kaempferol is absorbed, whether it is tolerated, and observational diet-and-cancer studies that point in inconsistent directions.[1,40]
Continue reading — full research detail+
The anchor human pharmacokinetic study gave eight healthy adults a single 9 mg oral dose of kaempferol from endive. Plasma kaempferol reached a mean peak of about 0.1 µmol/L at a median of 5.8 hours, and only 1.9% of the dose was recovered in urine over 24 hours; the major circulating and excreted form was kaempferol-3-glucuronide, though free kaempferol was also detected and made up a substantial fraction (reported as about 40% of plasma total kaempferol) — and no quercetin appeared, indicating kaempferol is not appreciably hydroxylated in the body.[1,2] That roughly 0.1 µM total plasma peak is the benchmark the rest of the page is measured against, set beside cell-study concentrations of 5–100 µM. It is an approximate exposure comparison, not an aglycone-to-aglycone match.
Human observational studies add real but inconsistent oncology signal. In the Nurses' Health Study, women with the highest dietary kaempferol intake had a lower incidence of ovarian cancer (relative risk about 0.60 versus the lowest intake, a significant trend),[40] and a large multiethnic cohort found an inverse trend for pancreatic cancer, stronger in smokers.[42] But a later population case-control study found no ovarian-cancer association for kaempferol,[41] and large colorectal cohorts were null.[43] Dietary kaempferol tracks foods like tea and broccoli and many other nutrients and behaviours, so these associations cannot establish a kaempferol-specific effect and support no therapeutic inference.
The interventional trial register reflects the treatment gap. It holds a healthy-volunteer kaempferol pharmacokinetic study and non-oncology dermatology/dental trials, plus one completed trial of a flavonoid mixture (kaempferol among several) with an antiviral in hepatitis-B cirrhosis and liver cancer — which posts no results and cannot isolate kaempferol.[29] Notably, the one directly relevant study now recruiting is KAPE (NCT07322406), which gives healthy adults oral kaempferol once daily for eight days with serial pharmacokinetic, metabolite and safety measures — designed to answer exactly the repeated-dose exposure question the field has not resolved.[29]
On tolerability, the human evidence is indirect: a randomised study raised plasma kaempferol as a downstream metabolite of rutin (500 mg/day for six weeks) and reported no adverse blood-chemistry or liver-function changes in 18 healthy women.[27] That is reassurance about a dietary-level exposure achieved through rutin, not a demonstration that supplemental doses of isolated kaempferol are tolerated.
Signal maturity: the human tier is genuinely pre-oncology. Quantified human exposure data and some diet-cancer associations exist, but there is no efficacy evidence, no repeated-dose isolated-kaempferol study yet reporting results, and no oncology-population safety study — the entire tumor-directed case below is preclinical.
Animal
Preclinical Signal
A recurring whole-animal signal for kaempferol is anti-metastatic, appearing in two independent cancer models — renal cell carcinoma and cholangiocarcinoma (bile-duct cancer). An important caveat frames both: they are experimental-metastasis models — cancer cells were injected directly into the bloodstream, so they test survival in circulation and colonisation of the lung, not the earlier steps of a tumor shedding cells from a primary site. Tumor-growth suppression with a defined mechanism was shown separately in gallbladder, lung, and colorectal models.[13,14,10]
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In the renal-cancer study, 786-O cells were injected into the tail veins of SCID mice, then oral kaempferol (2 or 10 mg/kg/day) was given for 150 days; at the high dose, lung tumor colonies fell from about 38 to about 5 per animal (roughly 87%), with lower MMP-2, phospho-Akt, and focal adhesion kinase, and no cytotoxicity at the anti-invasive concentrations in the parallel cell work.[13] This is a striking result, but the group sizes were very small (three animals per arm), and because the cells were placed directly in the circulation the model bypasses primary-tumor invasion and shedding. In the cholangiocarcinoma study, cells were again injected by tail vein and kaempferol (20 mg/kg/day, intraperitoneal) reduced the number and volume of lung foci, while a separate subcutaneous xenograft (tumor volume 0.15 vs 0.6 cm³) tested primary-tumor growth.[14] So the whole-animal evidence supports reduced pulmonary colonisation and reduced primary-tumor growth; the earlier steps of the metastatic cascade rest on the in-vitro invasion, migration, and EMT-marker data below.
Tumor-growth suppression with mechanism was shown elsewhere: in gallbladder cancer, kaempferol prevented xenograft progression while inducing cell-cycle arrest and mitochondrial cell death;[18] in non-small-cell lung cancer, it suppressed an A549 xenograft by restricting the Met receptor and its downstream PI3K/AKT/mTOR signaling, alongside inducing autophagic cell death.[15] An immunocompetent colorectal model added an immune dimension absent from the others: kaempferol (50/100 mg/kg) suppressed MC38 tumor growth dose-dependently, increased CD4+ and CD8+ T-cell infiltration, lowered IL-17A, and improved the effect of a PD-L1 checkpoint inhibitor — with IL-17A overexpression reversing the benefit.[10]
Signal maturity: the anti-metastatic finding is real and appears in independent models, and one study used a fully immunocompetent host — but the two flagship metastasis experiments are injected-cell colonisation models (one with only three animals per group), so they show reduced lung colonisation rather than prevention of spontaneous spread. These are also weight-adjusted animal doses the human pharmacokinetics above cannot approach.
In Vitro
Cell Model Data
Across colorectal, ovarian, renal, gallbladder, esophageal, and lung cell lines, kaempferol suppresses the growth and survival pathways cancer cells rely on and triggers cell death — a broad, well-replicated mechanistic panel. The load-bearing caveat runs through all of it: the effective concentrations sit at 5–100 µM, roughly 50 to 1000 times the ~0.1 µM an oral dose reaches in blood.[5,1]
Continue reading — full research detail+
The recurring signature is a suppression of PI3K/AKT/mTOR and Wnt/β-catenin growth signaling with cell-cycle arrest (lower CDKs and cyclins), reversal of EMT markers, and intrinsic mitochondrial cell death (Bax up, Bcl-2 down, caspase-9/-3 activation, cytochrome-c release), reported across ovarian, colon, gallbladder, and esophageal lines.[11,16,17,18,19] The inflammatory and angiogenic programs are hit too — NF-κB/STAT3 and VEGF/HIF-1α — the same nodes that carry over into the animal anti-metastatic result.
A distinctive metabolic layer runs through one group's colorectal work: kaempferol lowered the glycolytic enzyme PKM2 (by raising microRNAs that suppress the splicing factors hnRNPA1 and PTBP1), inhibited transketolase and aldolase A, and reduced glucose consumption, lactate, and ATP — collapsing tumor-cell sugar metabolism toward a ROS-driven death.[7,8,9] This is mechanistically deep and genuinely distinctive, but it comes entirely from a single laboratory, is cell-based only, and acts at 63–98 µM — so it is surfaced in the Expanded Pathway Map below rather than scored as a metabolic role.
Potency is not uniform, and the page states so plainly: in one oral-cancer line, kaempferol's concentration for half-maximal killing exceeded 100 µM (essentially inactive) in the same assay where a sister flavonol was active at around 18 µM.[31] Kaempferol's cell-death activity is real but concentration- and cell-line-dependent, which — read alongside the human plasma peak — is the honest frame for every in-vitro finding on this page.
Signal maturity: the growth-signaling, apoptosis, and anti-metastasis mechanisms are broad and reproduced across many laboratories and cancer types. The evidence ceiling is the concentration gap and the absence of any human efficacy data; the anti-glycolysis mechanism, though deep, is single-source and treated as emerging.
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02 — Pathways
Pathway Interaction Profile
Kaempferol engages several biological pathways relevant to tumor behavior, grouped below by the functional role each one supports. These are direct anti-tumor mechanisms from cell and animal studies, followed by a separate set of host-protection findings. All of it is preclinical — no pathway here has been confirmed at human-achievable exposure.
Kaempferol's Contain classification rests on reported suppression of the tumor-niche and metastatic program — inflammatory signaling, blood-vessel growth, and the invasion machinery that lets cancer cells break away — across several cancer types. It is the compound's sturdiest tumor-directed evidence, corroborated beyond cell studies by two independent whole-animal anti-metastasis results, but it remains preclinical with no human exposure anchor, so the role is partial.
Block Seeding & Niche Formation
Research concerning formation of supportive pre-metastatic niches at distant sites.
NF-κB / TNF-α / IL-6 inflammatory axis
In an immunocompetent colorectal-cancer model (MC38), kaempferol has been reported to downregulate IL-6, TNF-α and IL-17A while inhibiting STAT3 and NF-κB activation, increasing CD4+ and CD8+ tumor infiltration and reducing IL-17A+ γδ T cells; it suppressed tumor growth dose-dependently and improved the effect of a PD-L1 checkpoint inhibitor, with IL-17A overexpression reversing the benefit.[10] This study examined the primary-tumor immune microenvironment rather than distant pre-metastatic niche formation, so it is read here as local inflammatory-microenvironment modulation. The same NF-κB/IL-6/IL-17A/TNF-α suppression is corroborated in a non-cancer (psoriasis) mouse model — mechanistically consistent, but outside oncology.[33]
Angiogenesis / VEGF / HIF-1α
In human ovarian cancer cells (OVCAR-3, A2780/CP70), kaempferol (5–20 µM) has been reported to inhibit VEGF expression through both HIF-1α-dependent and -independent routes — lowering HIF-1α, phospho-Akt and the orphan receptor ESRRA — and to suppress OVCAR-3-induced blood-vessel growth and tumor growth in a chick chorioallantoic-membrane assay.[11] Under hypoxia in colon cancer cells, kaempferol has been reported to suppress HIF-1α stabilization and downstream VEGF/ANG1/VEGFR2.[12]
Prevent Tumour Cell Shedding
Research concerning invasion and escape from existing lesions (EMT and ECM breach).
EMT & metastatic invasion
In cell studies, kaempferol has been reported to reduce invasion and migration and reverse epithelial–mesenchymal transition — the steps by which cells break away from a primary tumor. In renal cell carcinoma (786-O) it lowered MMP-2 expression and activity, without cytotoxicity at those concentrations, by downregulating phospho-Akt and focal adhesion kinase (FAK);[13] in cholangiocarcinoma (HCCC9810, QBC939) it reduced migration and invasion via lower phospho-Akt, TIMP2 and MMP2;[14] and under hypoxia in colon cancer it reversed EMT markers, raising E-cadherin and lowering N-cadherin, vimentin and MMP-2/9.[12] The whole-animal corroboration is narrower than the cell data: in both the renal and cholangiocarcinoma studies the metastasis experiments injected tumor cells directly into the bloodstream (tail-vein models), so they show kaempferol reduced pulmonary colonisation — a later step — rather than preventing the earlier shedding and invasion the in-vitro work addresses.[13,14] A further TGF-β/ALK5/Smad EMT-reversal was shown for kaempferol-3-O-gentiobioside — a glycoside, not the aglycone — in ovarian cancer, carried here only as analog support.[34]
Kaempferol's Weaken classification is its best-replicated tumor-directed theme: suppression of the core growth-signaling pathways cancer cells depend on to proliferate, with animal corroboration in several models. It is partial because no human exposure reaches the concentrations at which these effects were measured.
Expansion Suppression
Research concerning proliferation, cell-cycle progression, and the capacity of lesions to add durable mass.
PI3K–AKT–mTOR (signaling)
In non-small-cell lung cancer (A549, H1299), kaempferol has been reported to restrict the Met receptor and thereby inhibit downstream PI3K/AKT/mTOR signaling, promoting autophagic cell death and reducing proliferation; Met overexpression rescued the effect, and an A549 xenograft was suppressed in a live animal, with lower tumor weight and bioluminescence.[15] Review-level synthesis across tumor types names PI3K/AKT downshift among kaempferol's core mechanisms.[5]
Wnt / β-catenin
In colorectal cancer, kaempferol has been reported to inhibit metastasis through a circular-RNA route — binding the RNA-binding proteins HNRNPK and HNRNPL to lower circ_0000345, releasing miR-205-5p, suppressing the demethylase JMJD2C and reducing β-catenin activation — with reduced migration and invasion in cells and reduced lung metastasis in a live animal (target engagement confirmed by thermal-shift assay and docking).[16] Under hypoxia, kaempferol also lowered β-catenin, c-Myc, cyclin D1 and LEF1 while raising the tumor-suppressors APC and Axin-2 in colon cancer cells.[12]
Cell cycle checkpoints (CDK4/6–RB–E2F, G1/S, G2/M)
In colon cancer cells (HT-29, 0–60 µM), kaempferol has been reported to cause G1 arrest within hours and G2/M arrest by half a day, inhibiting CDK2 and CDK4 kinase activity and lowering CDK2, CDK4, cyclin D1, cyclin E and cyclin A with reduced Rb phosphorylation, and lowering the G2/M regulators Cdc25C, Cdc2 and cyclin B1.[17] In gallbladder cancer (GBC-SD, SGC996) it produced G0/G1 arrest through the CDK4/CDK6/cyclin D1 axis, with tumor-growth suppression corroborated in a xenograft.[18]
Estrogen Receptor (ERα/ERβ) Signalling
In estrogen-driven breast cancer, kaempferol has been reported to act on the estrogen-receptor axis rather than as a general growth signal: in MCF-7 cells it opposed the proliferation driven by estradiol and by the environmental estrogen triclosan, working through ERα and downstream IGF-1R signaling (lower phospho-IRS-1, phospho-AKT and phospho-MEK1/2), and it suppressed estrogen- or triclosan-driven tumor growth in a mouse xenograft.[44] An important caveat: kaempferol is a phytoestrogen with SERM-like behavior — whether it acts as an estrogen-receptor agonist or antagonist can vary with concentration and hormonal context, so this is best read as ER-axis modulation, not simple estrogen blockade.
Kaempferol's Attack classification rests on intrinsic mitochondrial cell death reported across gallbladder and esophageal models, with one xenograft corroboration — but its direct kill potency is not uniform, varying by an order of magnitude between cell lines, so the role is partial.
Direct Tumour-Directed Killing
Research concerning regulated tumour-cell death (apoptosis, ferroptosis, necroptosis).
Intrinsic apoptosis (mitochondrial / Bcl-2)
In gallbladder cancer (GBC-SD, SGC996), kaempferol has been reported to promote cytochrome-c release from mitochondria to the cytoplasm, activate cleaved caspase-3 and caspase-9, raise Bax and lower Bcl-2, and induce DNA damage — with tumor-growth suppression corroborated in a xenograft.[18] In esophageal squamous carcinoma (Eca-109) it dose-dependently reduced proliferation and induced mitochondria-dependent apoptosis, with Bax mRNA up, Bcl-2 mRNA down, and caspase-3/-9 activation.[19] The honest caveat: kaempferol's cytotoxic potency is not uniform — in human oral-cancer cells (KB/KBv200) its concentration for half-maximal killing exceeded 100 µM (essentially inactive) in the same assay where a sister flavonol was active at around 18 µM, so this cell-death signal is genuine but concentration- and cell-line-dependent.[31]
Kaempferol's Protect classification is scored on host-outcome evidence, and here it is preclinical — whole-animal studies in which kaempferol shielded a normal organ (the heart) from two different chemotherapy drugs, supported by cell-level renal and cardiac mechanism. There is no completed human cancer-care host outcome, so the clinical Oncology Host-Status sub-scope is empty and omitted; the role stands on the animal organ-protection findings below, and is partial for that reason.
Other Organ-System Reserve
Research concerning renal, cardiac, pulmonary, and other non-hepatic organ reserve under stress.
Doxorubicin cardiotoxicity — whole-animal protection
In rats, kaempferol pretreatment (10 mg/kg, intraperitoneal, before each doxorubicin dose over a 28-day course) has been reported to attenuate doxorubicin cardiotoxicity, reducing cardiac injury and mitochondrial apoptosis (p53/Bax, ERK1/2).[35] The mechanism was corroborated in rat cardiomyocytes (H9c2), where kaempferol inhibited mitochondrial-ROS-dependent ferroptosis via the Nrf2/SLC7A11/GPX4 antioxidant axis and restored GPX4.[21]
5-fluorouracil cardiotoxicity — whole-animal protection
In a rat model of 5-fluorouracil cardiotoxicity, kaempferol and a kaempferol-nanoparticle formulation (1 mg/kg, intraperitoneal, for 14 days) have been reported to reduce cardiac-enzyme elevation, oxidative stress (MDA), COX-2 and histopathological injury.[36] A second whole-animal protection result against a different core chemotherapy agent.
Cisplatin nephrotoxicity — cell-model support
In human kidney (HEK-293) cells, kaempferol (25 µg/mL) has been reported to protect against cisplatin toxicity — improving viability and reducing DNA damage and reactive oxygen species, with the injury marker NGAL implicated.[20] This is in-vitro protection of a normal cell type, carried as mechanistic support beneath the whole-animal cardioprotection above rather than as an organ-level result. (A separate mouse cisplatin-nephrotoxicity study is deliberately excluded here — it was retracted.)
Block Seeding & Niche Formation
Research concerning formation of supportive pre-metastatic niches at distant sites.
NF-κB / TNF-α / IL-6 inflammatory axis
In a colorectal model, kaempferol lowered inflammatory signaling (IL-6, TNF-α, NF-κB, STAT3), increased anti-tumor immune-cell infiltration, and added to a checkpoint immunotherapy.
Prevent Tumour Cell Shedding
Research concerning invasion and escape from existing lesions (EMT and ECM breach).
Kaempferol reduced invasion and reversed EMT markers, and cut lung metastasis in two independent animal models (renal and bile-duct cancer) — its strongest whole-animal finding.
Expansion Suppression
Research concerning proliferation, cell-cycle progression, and the capacity of lesions to add durable mass.
Kaempferol lowered PI3K/AKT/mTOR growth signaling across tumor models, with a lung-cancer xenograft suppressed in a live animal. It also attenuated Wnt/β-catenin and arrested the cell cycle.
Direct Tumour-Directed Killing
Research concerning regulated tumour-cell death (apoptosis, ferroptosis, necroptosis).
Intrinsic apoptosis (mitochondrial / Bcl-2)
Kaempferol triggered mitochondrial cell death (Bax up, Bcl-2 down, caspase activation) in gallbladder and esophageal cancer cells — but its potency varied widely between cell lines.
Other Organ-System Reserve
Research concerning renal, cardiac, pulmonary, and other non-hepatic organ reserve under stress.
Organ protection from chemotherapy drugs
In preclinical studies — including whole-animal rat models — kaempferol protected the heart from two chemotherapy drugs (doxorubicin and 5-fluorouracil), an antioxidant action opposite to the ROS-raising effect it has on tumor cells.
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03 — Pharmacokinetics
Pharmacokinetics and Administration
How kaempferol moves through the body is the fact that governs everything else on this page. It is poorly absorbed and almost completely converted to conjugates once absorbed, so free kaempferol in blood peaks near 0.1 µM — a fraction of the concentrations that produce the effects described above.
Absorption
Kaempferol is poorly absorbed and, once absorbed, is rapidly converted to conjugates. After an oral dose from food, the blood peak was about 0.1 µM, almost entirely as the glucuronide form rather than free kaempferol.
The Concentration Gap
Cell studies use kaempferol at 5–100 µM. The measured human blood peak sits 50–1000× lower — the central reason a strong lab result cannot be assumed to carry over to a person.
Clinical Dose Context
Supplements and diet deliver milligram-range daily intakes, but most of what is absorbed circulates as conjugates. No oncology dose target has ever been defined, because no cancer trial has been run.
Formulation Effects
A phospholipid-complex formulation raised oral exposure about 2.75–4× in rats. These gains are preclinical, and a larger blood level is evidence of better absorption, not a proportionally larger effect.
Metabolism
Kaempferol is heavily glucuronidated and sulfated, and its disposition is shaped by BCRP/MRP efflux transporters — so the blood carries mostly conjugates, not the free compound.
Co-Dosing Considerations
Lab studies flag possible CYP1A2/3A interaction (inhibition and, separately, induction), competition for conjugation enzymes, and an antithrombotic effect — all mechanistic cautions, none confirmed in patients.
Absorption
Kaempferol has poor oral bioavailability, driven by low water solubility and extensive first-pass phase-II conjugation. In eight healthy adults given a single 9 mg oral dose from endive, plasma kaempferol reached a mean peak of about 0.1 µmol/L at a median 5.8 hours, and only 1.9% of the dose was recovered in urine over 24 hours. The major circulating and excreted form was kaempferol-3-glucuronide, but free kaempferol was also detected and made up a substantial fraction (reported as about 40% of plasma total kaempferol); no quercetin appeared, indicating kaempferol is not appreciably hydroxylated in the body.[1,2]
Absorbed kaempferol is rapidly metabolised in the liver and circulates as methyl, glucuronide and sulfate conjugates, with the glucoside forms found in foods such as onions the most bioavailable.[2] The practical consequence is a persistent translation gap: free kaempferol in blood is low and short-lived, while the effects described in the pathway profile cluster at 5–100 µM.
The Concentration Gap
This is the central pharmacokinetic fact for kaempferol. The concentrations that produce its cell-study effects sit between roughly 5 and 100 µM, while the measured human plasma peak after an oral dose is about 0.1 µM and is dominated by the glucuronide conjugate. Even a generous comparison leaves a 50- to 1000-fold gap between what an oral dose reaches in blood and what triggers the in-vitro effects. The human study measured plasma rather than the concentration inside a tumor, and the activity of the dominant conjugates is uncharacterised — so the gap limits direct translation rather than proving activity impossible, but it is the reason every in-vitro finding on this page carries a caveat.
| Benchmark | Concentration | Interpretation |
|---|---|---|
| Human plasma peak — single 9 mg oral dose from food | ~0.1 µM | The reference point everything else is measured against; almost entirely the glucuronide conjugate, not free kaempferol[1] |
| Anti-angiogenic effect in ovarian cancer cells | 5–20 µM | Roughly 50–200× the human plasma peak — the lower end of the effective in-vitro range[11] |
| Cell-cycle arrest in colon cancer cells | up to 60 µM | Concentration range across which the CDK/cyclin effects were dose-dependent[17] |
| Anti-proliferation IC50 in the colorectal glycolysis study | 63–98 µM | Half-maximal growth inhibition in HCT116/DLD1 — roughly 600–1000× the human plasma peak[7] |
Clinical Dose Context
Dietary sources and retail kaempferol supplements deliver milligram-range daily intakes, but how systemic exposure scales with dose — whether it is proportional, saturable, or formulation-dependent — has not been established in humans, and no oncology-specific tumor-exposure target has ever been defined, because no cancer-efficacy trial has been run. The single interventional oncology-adjacent trial used a flavonoid mixture, not kaempferol alone, in hepatitis-B cirrhosis and liver cancer, so it cannot anchor a kaempferol dose either.[29] The recruiting KAPE study (healthy adults, oral kaempferol once daily for eight days) is designed to fill exactly this basic pharmacokinetic gap.[29]
Formulation Effects
Because kaempferol's native bioavailability is poor, delivery technology dominates its real-world exposure. The principal oral bioavailability-enhancement study identified here is a phospholipid complex, tested preclinically; other delivery systems (including a PEGylated liposomal kaempferol characterised by intravenous pharmacokinetics) exist but are not oral retail formats.
| Parameter | Fold change | Interpretation |
|---|---|---|
| Peak plasma concentration (Cmax) | ~2.75× | 3.94 vs 1.43 µg/mL — higher absorption, but still a rat model, not a human oncology exposure[4] |
| Total exposure (AUC over 48 h) | ~4.2× | 57.81 vs 13.65 mg·h/L — larger cumulative exposure; no formulation has been tested for a cancer outcome[4] |
A large fold-increase in rat plasma exposure is evidence of improved absorption, not proof of a proportionally larger biological effect in a person — and none of these formulations has been tested against an oncology endpoint.
Metabolism
After absorption kaempferol undergoes rapid and extensive phase-II conjugation. Its in-vivo exposure is governed by phase-II metabolic enzymes together with efflux transporters: kaempferol is biotransformed to kaempferol-3-glucuronide (the major metabolite), kaempferol-7-glucuronide and kaempferol-7-sulfate, and its disposition is controlled by the BCRP and MRP2/MRP1 efflux pumps.[3] In human in-vitro systems kaempferol is also a CYP1A2 substrate, hydroxylated toward quercetin[30] — but the dietary human study above detected no quercetin after kaempferol intake, so this metabolic capacity may not translate to appreciable conversion in vivo.[1]
Co-Dosing Considerations
No direct human pharmacokinetic drug-interaction study for kaempferol with any specific oncology drug is available. The rows below rest on in-vitro human-tissue and preclinical data, and each is flagged by the most cautious guidance that evidence supports. Context matters: human plasma kaempferol is around 0.1 µM, well below the micromolar concentrations at which these effects were measured.
Discuss whether to combine, separate, or avoid kaempferol and a medication with your treating oncology team or physician.
| Flag | Interaction |
|---|---|
| Caution | Medicines with narrow therapeutic indices that depend on CYP1A2 or CYP3A for clearance warrant clinician review — but the direction is not one-way. Kaempferol aglycone inhibited both enzymes in vitro (its glycosides did not),[25] yet in a separate cell system it induced CYP3A4 transcription through the PXR receptor,[38] and it is itself a CYP1A2 substrate.[30] So kaempferol can alter these enzyme systems experimentally, but the direction and magnitude of any human drug interaction are unknown, and the concentrations involved sit well above the ~0.1 µM plasma peak. |
| Caution | Anticoagulant or antiplatelet regimens (for example warfarin, clopidogrel, aspirin): kaempferol has a consistent preclinical antithrombotic effect — it inhibited platelet aggregation and delayed clotting in animal models, and separately inhibited thrombin and factor Xa and reduced thrombosis in three animal models.[26,39] An additive bleeding risk is therefore plausible, though unquantified in humans — worth raising with the care team, especially around surgery. |
| Monitor | Drugs cleared mainly by glucuronidation or sulfation: kaempferol is itself heavily conjugated by these same phase-II pathways and effluxed by BCRP/MRP2,[3] so at high supplemental intakes it could in principle compete for conjugation capacity. This is a mechanistic caution, not a demonstrated clinical interaction. |
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04 — Onset & Washout
Onset and Washout
Kaempferol's plasma clock and its biological effect are two different things. What is measured in humans is only the plasma clock: after an oral dose, kaempferol appears slowly and circulates mostly as a conjugate. How long any downstream effect lasts has never been measured, and no repeated-dose study of isolated kaempferol has yet reported steady-state exposure.
Immediate Onset
After an oral dose from food, kaempferol reached its blood peak at about six hours — a relatively slow appearance — and circulated almost entirely as the glucuronide conjugate. This describes plasma concentration only, not how long any effect lasts.
Steady State
The isolated-kaempferol human data are single-dose only. No repeated-dose study of steady-state exposure, accumulation, or sustained target engagement has reported results yet (the KAPE trial is now testing an eight-day course).
Accumulated Effect
Animal anticancer studies used repeated daily dosing over roughly two to four weeks. No human oncology schedule exists, and no study has compared a pulsed against a continuous schedule.
Dosing Pattern in Studies
Every animal study used repeated daily dosing. That is the regimen that has been studied — not proof that daily use is biologically required, nor that pulsed use fails.
Washout
How long kaempferol's influence can take to clear before it stops being a relevant factor for co-administered medications.
No clinically validated washout period exists. With only single-dose dietary pharmacokinetics and interaction signals whose duration is unmeasured, a washout interval cannot be calculated.
Two Distinct Clocks
Kaempferol's timeline splits into two genuinely different layers: how quickly it appears in the blood, and how long any biological effect lasts. Only the first has been measured in humans, and the two are not connected by any data available here.
The direct-pharmacology clock (Clock A) tracks kaempferol in plasma. In the human dietary study, plasma kaempferol reached its peak at a median of about 5.8 hours after a single oral dose — a relatively slow appearance consistent with absorption further down the gut — and the circulating analyte was predominantly kaempferol-3-glucuronide, with free kaempferol a smaller but real fraction.[1] That describes plasma concentration only. A slow appearance and a conjugate-dominated blood level do not establish when target engagement begins or ends, or how tissue concentrations track plasma — none of that has been measured for kaempferol in humans.
| Clock A — Measured Plasma Exposure | Clock B — Downstream Phenotypic Effect | |
|---|---|---|
| Onset | Slow appearance — plasma kaempferol peaks at about 6 hours after an oral dose | Unknown in humans — no human tumor-tissue or clinical readout has ever been measured for kaempferol |
| Persistence | Short-lived free fraction — blood carries mostly the glucuronide conjugate, whose activity is uncharacterised | Unknown — animal anti-tumor effects used repeated dosing over weeks, but the effect's duration was not isolated |
| What it covers | Measured plasma concentration only — not target engagement, tissue levels, or effect duration | The biological outcome — which for kaempferol exists only in cell and animal studies, not in people |
The downstream-effect clock (Clock B) — the biological outcome — has no human measurement for kaempferol at all. Animal anticancer studies dosed continuously over roughly two to four weeks, but none isolated how long a single dose's effect persists, and none tested a pulsed schedule. So the connection between plasma exposure and any downstream effect is entirely unmeasured here.
Steady State and Accumulation
Not established. Repeated dietary flavonol exposure has been studied over a few days, but no repeated-dose study of isolated supplemental kaempferol has confirmed steady-state plasma levels, accumulation, trough concentrations, or continuous target engagement (the recruiting KAPE trial is designed to measure exactly this over an eight-day course). Animal anticancer studies used repeated daily dosing, which supports daily administration as the studied regimen — it does not prove daily dosing is biologically necessary to sustain a pathway-level effect.
Dosing Pattern in Studies
Animal anticancer studies used repeated, continuous dosing over roughly two to four weeks (for example 50 or 100 mg/kg in the colorectal model, 2–10 mg/kg in the renal-metastasis model). None tested a pulsed or single-dose schedule, so there is no evidence on how a downstream effect would relate to the plasma-exposure pattern. Kaempferol is best described as studied under daily, continuous dosing — not because pulsed dosing has been shown to fail, but because it simply has not been tested. For what a mechanistically meaningful concentration would require at the cellular level, see The Concentration Gap under Pharmacokinetics and Administration.
Washout
No clinically validated kaempferol washout period has been established. The only human pharmacokinetic study is a single dietary dose, and the interaction signals under Co-Dosing Considerations — CYP1A2/3A inhibition, phase-II conjugation competition, and an antiplatelet effect — were measured in laboratory and animal systems that do not establish a human interaction magnitude or how long any effect would persist. A washout interval cannot reliably be calculated from a single-dose plasma profile alone, and none is recommended here. Any decision about timing kaempferol around chemotherapy or around anticoagulant/antiplatelet drugs belongs with the treating medical team, raised when the compound is started rather than deferred to a fixed interval.
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05 — Safety
Safety Profile
Dietary kaempferol is consumed widely with no established harm, and a human supplementation study that raised blood kaempferol reported no adverse blood-chemistry or liver-function changes. The consideration worth surfacing is a laboratory genotoxicity signal shared across the flavonol class, not a clinical adverse-event record — because no oncology-population safety study of kaempferol exists.
Laboratory genotoxicity signal — cultured-cell studies show both topoisomerase-II poisoning and DNA double-strand-break effects (not all of the DNA damage appears topoisomerase-II-dependent); seen at concentrations above ordinary blood levels, not demonstrated in supplement users.
Limited oncology safety data — tolerability at dietary levels appears acceptable, but there is no long-term or oncology-population human safety dataset for supplemental kaempferol.
Pregnancy — no dedicated human reproductive-safety data were identified; in that absence, use in pregnancy or when trying to conceive should be reviewed by a clinician.
Adverse Effects in Human Trials
Human tolerability at dietary levels appears acceptable, but the record for supplemental doses of isolated kaempferol is essentially empty. The nearest evidence is indirect: a randomised study in which 500 mg/day of rutin for six weeks raised plasma kaempferol as a downstream metabolite reported no adverse changes in blood chemistry or liver-function tests in 18 healthy women.[27] That reassures about a dietary-level exposure reached through rutin — it does not establish that supplemental doses of isolated kaempferol are tolerated. There is no completed oncology-population safety study, no long-term high-dose human safety dataset, and the only direct kaempferol exposure studied is a single small dietary dose;[1] the recruiting KAPE trial should provide the first dedicated repeated-dose human safety data.
Genotoxicity / Topoisomerase-II Signal (laboratory only)
This is the consideration worth surfacing for the flavonol class. In cell-free and human-enzyme systems, kaempferol acts as a topoisomerase-II poison — inhibiting topoisomerase II (without inhibiting topoisomerase I) and stabilising the enzyme–DNA cleavage complex.[23,28] In cultured mouse stem cells it induced DNA double-strand-break foci and chromosomal translocations — but, unlike some related flavonols, kaempferol's double-strand breaks were largely topoisomerase-II-independent (they increased, rather than decreased, when a topoisomerase-II inhibitor was added), so it is clastogenic by more than one route.[24] These are cultured-cell experiments at concentrations generally above ordinary blood exposure, not demonstrated in supplement users — but an unresolved signal for a widely sold flavonol.
Liver Signal and Reproductive Safety
No direct kaempferol drug-induced liver-injury signal was identified, and kaempferol has no LiverTox monograph; the only hepatic signal is indirect — a whole white-mulberry (Morus alba) leaf-extract study found mild liver enzyme changes at high doses and attributed them partly to the kaempferol and chlorogenic acid within the whole extract, not to isolated kaempferol.[32] This is an absence of reported injury for the compound itself, not a positive demonstration of hepatic safety in humans. Dedicated human pregnancy-safety data were not identified; avoidance during pregnancy is prudent unless use is specifically reviewed by a qualified clinician.
06 — Sourcing
Sourcing Guide
Because kaempferol is poorly absorbed and rapidly conjugated, formulation and delivery are the biggest factors in whether a product reaches the bloodstream at all — a phospholipid complex, for instance, raised oral exposure several-fold in preclinical work. Standardized content, brand quality, and ease of access matter too. Our Sourcing Guide offers a curated list of products available on the retail market we found to answer those concerns.
Kaempferol Sourcing Guide07 — Literature
References
Last reviewed: August 2026