Herbs & Botanicals · West African chewing seed
Bitter kola
Garcinia kola · also called Bitter kola, bitter cola (a different spelling of the same seed)
Bitter kola is the seed of a West and Central African tree. People chew it for cough, stomach upset and general well-being, and it is also used in folk medicine for pain and infections. Human evidence is thin: one small knee-pain trial, one eye-drop trial and a few tiny tests. The most important caution is that it lowered quinine levels in healthy volunteers, so ask a doctor before mixing it with malaria medicine.
General information, not medical advice. Last substantive update · Not medically reviewed. A named clinician has not signed off on this page. How this page is made
About Bitter kola
Bitter kola is the seed of Garcinia kola, a tree of West and Central Africa. It is chewed as a custom and folk remedy. Human research is small, and most claims rest on animal and lab studies.
What it is
Bitter kola is the seed of Garcinia kola, a forest tree in the Clusiaceae (mangosteen) family. The accepted name was checked against the GBIF database. It is eaten fresh in West Africa, mostly as a chewed seed.
It is not cola nut. Cola nut (Cola nitida) is a different tree, belongs to a different family, and is the nut linked with caffeine. Gotu kola is a leafy herb that has nothing to do with either. Garcinia cambogia is the same genus but a different species, sold as a weight-loss supplement from fruit rind.
Traditional and current uses
In a 2026 survey of 152 Nigerians, most people ate fresh seeds, mainly for breathing symptoms, stomach upset and general well-being. Reviews also list fever, malaria, hepatitis and a stimulating effect among folk uses.
These are customs. They show how people use the seed, not that it works.
What the research shows
Human research is limited to a small knee osteoarthritis trial, an eye-drop trial, a tiny 1993 airflow test and a healthy-volunteer quinine study. The knee trial suggested less pain than placebo, but many people dropped out.
Everything else, including liver protection, blood pressure, blood sugar, fertility, germs and cancer, comes from animal and lab studies. A critical review says these are confirmed only in animals and notes that many kolaviron studies used very high doses.
At a glance
Traditional uses history, not proof
- West African custom: chewed at ceremonies and social gatherings, and for cough, breathing complaints and stomach upset (2026 survey of 152 Nigerians).
- Folk medicine: fever, malaria, hepatitis, pain and a stimulating effect are listed in reviews. These are traditional statements, not proof.
Studied for research
- Knee osteoarthritis pain, low (one small trial)
- Eye pressure with prepared eye drops, very low (one trial, not the seed)
- Airflow in healthy men, insufficient
- Liver, blood pressure, blood fats, blood sugar, germs and cancer: animal and lab studies only, insufficient
- Male fertility and aphrodisiac claims: mixed in rats; one rat study found no sex-enhancing effect
Main compounds
- Kolaviron, a mixture of biflavonoids and the most studied compound
- Kolaflavanone, a biflavonoid in the seed
- Garcinol, a benzophenone that one review calls more promising than kolaviron
Common forms
- Fresh seed, chewed (the usual traditional form)
- Dried or powdered seed in preparations
- Purified kolaviron and a 0.5% eye drop (research preparations)
Research links: PubMed: knee osteoarthritis trial · PubMed: quinine interaction study · PubMed: 2026 Nigerian survey of traditional use · Research Library · Genes & Biomarkers Library
The plant and its history
- Accepted scientific name
- Garcinia kola Heckel
- Naming authority
- Heckel
- Common names
- Bitter kola (English)
- Botanical family
- Clusiaceae (the mangosteen family, order Malpighiales)
- Classification
- Plantae > Malpighiales > Clusiaceae > Garcinia > Garcinia kola
- Native range
- West and Central Africa (from the 2026 survey and a 2023 review); not checked against POWO or IUCN.
- Habitat
- Forest tree. Details were not verified in this build.
- What the plant looks like
- Roots: Not covered in the sources read.; Stems: Not covered in the sources read.; Leaves: Not covered in the sources read.; Flowers: Not covered in the sources read.; Fruit: The seed is the part chewed and the main part used.
- Cultivation
- Not covered in sources read.
- Harvest and processing
- Seeds are eaten fresh; dried or powdered seeds appear in preparations (from our summary).
- Look-alikes and adulterants
- Name: Cola nut (Cola nitida); Note: A different plant in a different family (Malvaceae) with a caffeine reputation; see the cola nut page.; Name: Gotu kola (Centella asiatica); Note: A leafy herb unrelated to bitter kola despite the word 'kola'.; Name: Garcinia cambogia; Note: Same genus, different species (fruit rind, weight-loss supplements). Findings do not carry over.
- Sustainability and conservation
- A 2026 survey describes it as a vulnerable species in places; not checked against IUCN or POWO and NOT verified.
Traditional use and history history, not clinical proof
| Tradition or era | Documented use | Source |
|---|---|---|
| West African folk medicine and social custom | Chewed seeds are used at ceremonies and for cough, breathing complaints, stomach upset, fever, malaria, hepatitis and general well-being, according to a 2026 survey of 152 Nigerians and reviews. These are traditional-use statements, not proof of effect. | p41699612 |
Traditional use shows how a plant was used. It does not show that a supplement works or is safe today.
What is inside, and how it may work
What the plant contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.
Main compounds
| Compound | Family | Where it is concentrated | Activity studied | Level of evidence |
|---|---|---|---|---|
| Kolaviron | biflavonoid mixture (GB1, GB2 and kolaflavanone) | Seed | The most studied compound; reviews describe antioxidant and anti-inflammatory effects in lab and animal work. A critical review says its research has flaws such as very high doses. It is a mixture so PubChem has no single record we could find. 12 6 | Animal research |
| Kolaflavanone PubChem 155169 | biflavanone | Seed | A biflavonoid in the seed; activity in people unknown. 16 | Laboratory research |
| Garcinol PubChem 5281560 | benzophenone | Seed | A critical review says garcinol was tested under better conditions than kolaviron and looks promising in cancer, microbe and nerve work (lab and animal only). The CID was matched by name only. 12 16 | Animal research |
| Other classes | xanthones, benzofurans, vitamin E derivatives, phytosterols | Seed, roots and other parts | Listed in the critical review as isolated from the plant; activity mostly untested in people. 12 | Laboratory research |
Mechanisms, receptors and pathways
| Target or pathway | Gene or receptor | What was found | Level |
|---|---|---|---|
| Antioxidant and anti-inflammatory activity | Not established | Reviews attribute most reported effects to kolaviron's antioxidant and anti-inflammatory properties, in cell and animal models only. 6 12 | Animal research |
| Drug absorption and breakdown | Not established | In 24 healthy volunteers the seed lowered peak quinine and its breakdown product, suggesting an effect on drug handling. Mechanism not tested. 7 | Human data |
Absorption, metabolism and elimination
- Absorption
- Not studied for the seed's own compounds in people.
- Distribution
- Not studied.
- Metabolism
- Not studied in people. The seed changed quinine levels in volunteers.
- Elimination
- Not studied.
- Bioavailability
- Unknown for kolaviron or garcinol in people.
Isolated compounds versus whole extracts
Most research uses kolaviron, a purified mixture, or extracts, not the chewed seed. A review warns many kolaviron studies used very high doses, so results should not be assumed to apply to eating the whole seed.
Nutritional composition
Not assessed; no nutrient data were read in this build.
1 mixed findings1 low certainty1 very low certainty6 not enough evidence
What is Bitter kola good for?
The main proposed uses and how strong the human evidence is for each. 'Insufficient' means no good human trials exist. Nothing here is a reason to use bitter kola instead of medical care.
Benefits, one by one
Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.
Knee osteoarthritis pain
Low certaintyOne small trial in Nigeria found less knee pain on a bitter kola preparation than on placebo. The result was not statistically different from two common pain medicines. It has not been repeated in the sources we read.
1 studiesThe product is not clearly described in the abstract. Do not treat th…
Studies, doses and limits
What the trials found
One randomized, placebo-controlled, double-blind trial in 143 recruited adults (84 finished) compared a bitter kola preparation with placebo, naproxen and celecoxib for 6 weeks. Pain, stiffness and walking improved more than with placebo. Against the two drugs there was no statistically significant difference, and onset and duration of relief were shorter than with the drugs. About 11 people who stopped had relief for a mean of 17 days.
Results
Pain, stiffness and walking improved versus placebo (reported p < 0.001); not significantly different from naproxen or celecoxib.
Effect sizes as reported
Pain score changes were reported as significant versus placebo; no confidence intervals in the abstract.
Why this rating
One small trial with 41% of people not finishing, unclear product description and no repeat study. We cannot tell if the effect is real or how large.
Form and dose studied
The product is not clearly described in the abstract. Do not treat this as a guide to what to buy or take; ask a doctor or pharmacist.
Who was studied
Adults with knee osteoarthritis at one Nigerian hospital.
Limits
Single trial; high dropout; typos in reported p-values; no independent replication found.
Why researchers looked
Many people with knee arthritis do not want long-term anti-inflammatory pills and look for herbal options.
Traditional use
Bitter kola seed is used in West African folk medicine for pain and inflammation.
Proposed mechanism Preliminary mechanism
Lab and animal work suggests the seed has anti-inflammatory and antioxidant effects, but how it works in people is unknown.
A proposed mechanism does not show that the effect happens in people.
The abstract reports no significant heart, kidney or drug-related adverse reaction over 6 weeks. That is short and small, so it does not rule out other harms. See the Safety tab.
Eye pressure (glaucoma) with eye drops
Very low certaintyA 2010 trial in Nigeria tested prepared bitter kola eye drops against timolol drops and found a similar fall in eye pressure. This is about a special eye drop, not the chewed seed, and it is not something to try at home.
1 studiesA 0.5% aqueous drop made for the trial. Not the seed or a supplement.
Studies, doses and limits
What the trials found
One randomized, double-masked, multicentre trial of 178 people with newly found open-angle glaucoma or raised eye pressure compared 0.5% bitter kola drops with 0.5% timolol drops for 24 weeks.
Results
Eye pressure fell by about 48% in both groups (12.93 versus 13.09 mmHg), with no significant difference. Side effects were mild and similar.
Effect sizes as reported
12.93 +/- 2.3 mmHg (bitter kola) versus 13.09 +/- 2.8 mmHg (timolol), P > 0.05
Why this rating
Single trial, no placebo group, a comparison with timolol only, and no repeat study. Eye drops are sterile medical products; this is not a reason to put seed extracts in the eye.
Form and dose studied
A 0.5% aqueous drop made for the trial. Not the seed or a supplement.
Who was studied
Adults with newly found open-angle glaucoma or ocular hypertension.
Limits
One trial; no independent repeat; effect size is unusually large and needs checking.
Why researchers looked
Glaucoma can damage sight, and lowering eye pressure is the main treatment. Researchers looked for plant-based drops.
Traditional use
Not a traditional eye use that we could verify; the drops are a modern preparation.
Proposed mechanism Preliminary mechanism
Not described in the abstract.
A proposed mechanism does not show that the effect happens in people.
Glaucoma needs an eye doctor. Do not treat it yourself or stop prescribed drops.
Airflow and breathing (cough, asthma)
Not enough evidenceBitter kola is eaten in West Africa for cough and breathing trouble. The only human measurement we found is a tiny 1993 test in healthy young men, which showed a small rise in one airflow reading. No one with cough or asthma has been tested in a trial.
2 studiesThe seed was eaten in the test. Amounts and products vary a lot.
Studies, doses and limits
What the trials found
19 healthy male students ate the seed and were tested for 90 minutes. Only peak expiratory flow rose significantly, at 60 minutes. There was no placebo group and nobody had asthma or cough.
Results
Peak flow rose at 60 minutes (p < 0.05); other lung measures did not change significantly.
Effect sizes as reported
Numbers not given in the abstract.
Why this rating
One tiny uncontrolled test in healthy men. No trials in cough or asthma.
Form and dose studied
The seed was eaten in the test. Amounts and products vary a lot.
Who was studied
Healthy young Nigerian men.
Limits
No placebo, very small, short, healthy volunteers only.
Why researchers looked
Seeds are widely chewed for cough, bronchitis and breathing complaints.
Traditional use
Respiratory symptoms were the main reason respondents gave in a 2026 Nigerian survey of 152 people.
Proposed mechanism Preliminary mechanism
Reviewers describe a possible airway-relaxing effect from lab and animal work; not shown in people with lung disease.
A proposed mechanism does not show that the effect happens in people.
Do not use bitter kola in place of asthma medicine or for a cough that lasts. See the Safety tab.
General well-being and a 'stimulating' effect
Not enough evidenceBitter kola is chewed for a lift in energy and a general feeling of well-being, and reviews mention a stimulating effect in folk use. We found no human study that measured energy, alertness or mood, so this is custom, not evidence.
2 studiesFresh seed chewed.
Studies, doses and limits
What the trials found
No human trial of energy, mood or alertness was found.
Results
Not tested in humans.
Effect sizes as reported
None.
Why this rating
Only survey and review statements of traditional use.
Form and dose studied
Fresh seed chewed.
Who was studied
Adults in West Africa (survey).
Limits
Survey of customs, not a test of effect.
Why researchers looked
The seed is chewed at ceremonies, social gatherings and as a daily habit.
Traditional use
In a 2026 survey of 152 Nigerians most people ate fresh seeds for breathing symptoms, stomach upset and general well-being. A review lists a stimulating and aphrodisiac effect among folk uses.
Proposed mechanism Pharmacological theory
No mechanism has been shown in people. We did not find a source that measured caffeine in bitter kola (see the Safety tab); do not assume it behaves like cola nut.
A proposed mechanism does not show that the effect happens in people.
Chewing many seeds was linked in survey reports with dry mouth, hunger, stomach upset and dizziness; see the Safety tab.
Liver protection (animal studies only)
Not enough evidenceMany rat and mouse studies report that bitter kola seed or its extract kolaviron limits chemical liver damage. No human liver study was found. A critical review warns that many kolaviron studies used very high doses.
2 studiesSeed extract and kolaviron in animals.
Studies, doses and limits
What the trials found
No human trial was found.
Results
In animals, protection from chemical liver injury is reported. In people: unknown.
Effect sizes as reported
Not applicable to people.
Why this rating
Animal and cell work only; a critical review says activities are confirmed in animals only and flags very high doses and poor controls.
Form and dose studied
Seed extract and kolaviron in animals.
Who was studied
Rats and mice.
Limits
Doses used in animals are far from human eating habits and not a guide to safety.
Why researchers looked
Bitter kola is used in West Africa for hepatitis and other liver complaints.
Traditional use
Hepatitis and liver disease are among the traditional uses named in reviews and a 2026 survey.
Proposed mechanism Animal research
Antioxidant and anti-inflammatory activity in animal tissue.
A proposed mechanism does not show that the effect happens in people.
Liver protection in animals does not mean the seed is safe for human liver. See the Safety tab.
Blood pressure and blood fats (animal and lab studies)
Not enough evidenceA systematic review of 22 laboratory and animal studies found kolaviron lowered blood pressure and improved blood fats in those studies. No human trial was found.
3 studiesKolaviron in animals.
Studies, doses and limits
What the trials found
None in humans.
Results
In the reviewed animal and lab studies, kolaviron lowered blood pressure and improved blood fats. A 90-day rat study also found lower cholesterol, triglycerides and LDL and higher HDL.
Effect sizes as reported
Not applicable to people.
Why this rating
Preclinical only; quality scores modest.
Form and dose studied
Kolaviron in animals.
Who was studied
Rats and lab models.
Limits
No human data.
Why researchers looked
Bitter kola is traditionally used for high blood pressure.
Traditional use
Hypertension is listed among folk uses in reviews.
Proposed mechanism Animal research
Reviews report vessel-relaxing, antioxidant and anti-clotting effects in animals.
A proposed mechanism does not show that the effect happens in people.
Animal findings suggest it might add to blood-pressure medicines; this has not been tested in people.
Blood sugar (animal studies only)
Not enough evidenceReviews list antidiabetic effects in animals and cells. No human trial of blood sugar was found, and no one has tested bitter kola with diabetes medicines.
2 studiesSeed extracts and kolaviron in animals.
Studies, doses and limits
What the trials found
None in humans.
Results
Reported in animals and cells; not tested in people.
Effect sizes as reported
Not applicable to people.
Why this rating
Animal and cell studies only.
Form and dose studied
Seed extracts and kolaviron in animals.
Who was studied
Animals and cells.
Limits
No human trial; mixed quality.
Why researchers looked
Diabetes is among the folk uses named in reviews.
Traditional use
Diabetes and metabolic disorders appear in traditional use lists.
Proposed mechanism Animal research
Antioxidant and glucose-handling effects in animal and cell models.
A proposed mechanism does not show that the effect happens in people.
If you take diabetes medicines, ask your doctor before using it; blood sugar could drop further in theory.
Male fertility and aphrodisiac claims
Mixed findingsBitter kola is chewed as an aphrodisiac. In a rat study the extract did not raise sex hormones or most sexual behaviour. Other rat studies show mixed hormone effects, and a review links heavy seed eating to low fertility. No human study was found.
4 studiesDifferent extracts and doses.
Studies, doses and limits
What the trials found
No human trial.
Results
One rat study of an aqueous extract found no meaningful sex-enhancing effect. A 90-day kolaviron rat study found higher FSH and testosterone and a non-significant rise in sperm count. A polyphenol fraction partly protected against arsenate damage but hormone levels stayed lower than in healthy untreated rats. A review links excessive seed eating with low fertility.
Effect sizes as reported
Mixed and not applicable to men.
Why this rating
Animal studies point in different directions; no human data.
Form and dose studied
Different extracts and doses.
Who was studied
Male rats.
Limits
Different extracts, doses and models; not comparable.
Why researchers looked
The seed has a reputation as a male tonic in West Africa.
Traditional use
Aphrodisiac and 'male vigour' use is described in a review and surveys.
Proposed mechanism Animal research
Hormone effects in rats vary by extract, dose and model.
A proposed mechanism does not show that the effect happens in people.
Heavy seed eating has been linked to low fertility in a review. Men trying to conceive should talk with a doctor.
Germs, malaria, cancer and other lab findings
Not enough evidenceReviews report germ-fighting, antimalarial, anti-cancer and other effects in test tubes and animals. None of this has been confirmed in people.
2 studiesExtracts and isolated compounds in cells and animals.
Studies, doses and limits
What the trials found
No human trials.
Results
Lab and animal effects only.
Effect sizes as reported
Not applicable to people.
Why this rating
A critical review says confirmed only in animal models.
Form and dose studied
Extracts and isolated compounds in cells and animals.
Who was studied
Cells and animals.
Limits
Not applicable.
Why researchers looked
Fever, malaria and infections are traditional uses.
Traditional use
Fever and malaria appear among folk uses in the 2026 survey and reviews.
Proposed mechanism Laboratory research
Kolaviron and garcinol are the most studied compounds; garcinol looks more promising in better-run studies according to one review.
A proposed mechanism does not show that the effect happens in people.
A possible quinine interaction was found in healthy volunteers; do not use it alongside malaria medicine without a doctor. See the Safety tab.
Connections to the rest of health
How Bitter kola connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.
Explore every connection: goals, body systems, organs, symptoms, genes
A. Wellness goals
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Joint Support | Potential benefit | Low certainty | Knee osteoarthritis pain: One small trial in Nigeria found less knee pain on a bitter kola preparation than on placebo. The result was not statistically different from two common pain medicines. It has not been repeated in the sources we read. | 2 |
| Inflammation Balance | Potential benefit | Low certainty | Knee osteoarthritis pain: One small trial in Nigeria found less knee pain on a bitter kola preparation than on placebo. The result was not statistically different from two common pain medicines. It has not been repeated in the sources we read. | 2 |
| Immune Support | Traditional use | Not enough evidence | Airflow and breathing (cough, asthma): Bitter kola is eaten in West Africa for cough and breathing trouble. The only human measurement we found is a tiny 1993 test in healthy young men, which showed a small rise in one airflow reading. No one with cough or asthma has been tested in a trial. | 11 13 |
| Energy Boost | Traditional use | Not enough evidence | General well-being and a 'stimulating' effect: Bitter kola is chewed for a lift in energy and a general feeling of well-being, and reviews mention a stimulating effect in folk use. We found no human study that measured energy, alertness or mood, so this is custom, not evidence. | 13 12 |
| Liver Support | Preliminary mechanism | Not enough evidence | Liver protection (animal studies only): Many rat and mouse studies report that bitter kola seed or its extract kolaviron limits chemical liver damage. No human liver study was found. A critical review warns that many kolaviron studies used very high doses. | 12 6 |
| Blood Pressure Support | Preliminary mechanism | Not enough evidence | Blood pressure and blood fats (animal and lab studies): A systematic review of 22 laboratory and animal studies found kolaviron lowered blood pressure and improved blood fats in those studies. No human trial was found. | 9 8 5 |
| Cholesterol Balance | Preliminary mechanism | Not enough evidence | Blood pressure and blood fats (animal and lab studies): A systematic review of 22 laboratory and animal studies found kolaviron lowered blood pressure and improved blood fats in those studies. No human trial was found. | 9 8 5 |
| Heart Health | Preliminary mechanism | Not enough evidence | Blood pressure and blood fats (animal and lab studies): A systematic review of 22 laboratory and animal studies found kolaviron lowered blood pressure and improved blood fats in those studies. No human trial was found. | 9 8 5 |
| Blood Sugar Balance | Preliminary mechanism | Not enough evidence | Blood sugar (animal studies only): Reviews list antidiabetic effects in animals and cells. No human trial of blood sugar was found, and no one has tested bitter kola with diabetes medicines. | 12 5 |
| Mens Vitality | Preliminary mechanism | Mixed findings | Male fertility and aphrodisiac claims: Bitter kola is chewed as an aphrodisiac. In a rat study the extract did not raise sex hormones or most sexual behaviour. Other rat studies show mixed hormone effects, and a review links heavy seed eating to low fertility. No human study was found. | 14 8 10 5 |
| Fertility Support | Preliminary mechanism | Mixed findings | Male fertility and aphrodisiac claims: Bitter kola is chewed as an aphrodisiac. In a rat study the extract did not raise sex hormones or most sexual behaviour. Other rat studies show mixed hormone effects, and a review links heavy seed eating to low fertility. No human study was found. | 14 8 10 5 |
| Immune Support | Preliminary mechanism | Not enough evidence | Germs, malaria, cancer and other lab findings: Reviews report germ-fighting, antimalarial, anti-cancer and other effects in test tubes and animals. None of this has been confirmed in people. | 12 13 |
B. Body systems
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Liver | Drug or supplement interaction | Not enough evidence | Liver protection reported in animals; no human data; Garcinia genus has liver cautions. Preparation or compound: Seed, kolaviron |
12 4 |
| Reproductive system | Adverse effect or risk | Not enough evidence | Rat cycle, ovulation and foetal findings; review links heavy seed eating with low fertility. Preparation or compound: Seed extract |
3 5 |
| Medicines handling | Drug or supplement interaction | Low certainty | Lowered peak quinine levels in healthy volunteers. Preparation or compound: Seed |
7 |
| Musculoskeletal System | Biological association | Low certainty | Studied for: Knee osteoarthritis pain | 2 |
| Nervous System | Biological association | Very low certainty | Studied for: Eye pressure (glaucoma) with eye drops Studied for: General well-being and a 'stimulating' effect | 1 13 12 |
| Respiratory System | Biological association | Not enough evidence | Studied for: Airflow and breathing (cough, asthma) | 11 13 |
| Hepatic System | Biological association | Not enough evidence | Studied for: Liver protection (animal studies only) | 12 6 |
| Cardiovascular System | Biological association | Not enough evidence | Studied for: Blood pressure and blood fats (animal and lab studies) | 9 8 5 |
| Endocrine System | Biological association | Not enough evidence | Studied for: Blood sugar (animal studies only) | 12 5 |
| Reproductive System | Biological association | Mixed findings | Studied for: Male fertility and aphrodisiac claims | 14 8 10 5 |
| Immune System | Biological association | Not enough evidence | Studied for: Germs, malaria, cancer and other lab findings | 12 13 |
I. Biomarkers
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Knee pain score (WOMAC pain scale) | Biological association | Low certainty | Measured in trials: lowered. A lab change is not the same as a health benefit. | 2 |
| Eye pressure (mmHg) | Biological association | Very low certainty | Measured in trials: lowered. A lab change is not the same as a health benefit. | 1 |
| Peak expiratory flow rate (PEFR) | Biological association | Not enough evidence | Measured in trials: raised. A lab change is not the same as a health benefit. | 11 |
| Blood pressure (animal studies) | Biological association | Not enough evidence | Measured in trials: lowered. A lab change is not the same as a health benefit. | 9 |
| Blood fats (cholesterol, triglycerides, LDL, HDL) in rats | Biological association | Not enough evidence | Measured in trials: mixed. A lab change is not the same as a health benefit. | 8 9 |
| Testosterone and FSH (male rats) | Biological association | Mixed findings | Measured in trials: mixed. A lab change is not the same as a health benefit. | 8 14 |
L. Active compounds
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Kolaviron | Biological association | Animal | The most studied compound; reviews describe antioxidant and anti-inflammatory effects in lab and animal work. A critical review says its research has flaws such as very high doses. It is a mixture so PubChem has no single record we could find. Preparation or compound: Seed |
12 6 |
| Kolaflavanone | Biological association | In vitro | A biflavonoid in the seed; activity in people unknown. Preparation or compound: Seed |
16 |
| Garcinol | Biological association | Animal | A critical review says garcinol was tested under better conditions than kolaviron and looks promising in cancer, microbe and nerve work (lab and animal only). The CID was matched by name only. Preparation or compound: Seed |
12 16 |
| Other classes | Biological association | In vitro | Listed in the critical review as isolated from the plant; activity mostly untested in people. Preparation or compound: Seed, roots and other parts |
12 |
Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 25, 2026).
The evidence
The research centre for Bitter kola. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.
Evidence by outcome
Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).
How we rate evidence
High certainty
Several well-run trials or reviews agree; further research is unlikely to change the picture much.
Moderate certainty
Good trials point the same way, but some doubt remains.
Low certainty
Small, short or inconsistent trials. The finding could change with better research.
Very low certainty
Very little or very weak human data. Treat as a possibility only.
Mixed findings
Trials or reviews disagree with each other.
Not enough evidence
Not enough human research to say either way.
Evidence against
Good research found no benefit, or found harm.
We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We read PubMed abstracts for the trials, reviews and animal studies cited, checked the plant name in GBIF and compounds in PubChem, and used our existing herb summary. Regulator pages (EMA, NCCIH, LiverTox, LactMed) were not found or read for this herb.
Study library: every study we checked 16
| Study | Design | People | Product, dose, length | Result |
|---|---|---|---|---|
| Adefule-Ositelu 2010 Efficacy of Garcinia kola 0.5% Aqueous Eye Drops in Patients with Primary Open-Angle Glaucoma or Ocular Hypertension Middle East African Journal of Ophthalmology · PMID 20543944 · DOI |
Controlled trial |
178 Adults with newly diagnosed open-angle glaucoma or raised eye pressure, Nigeria |
0.5% aqueous Garcinia kola eye drops (a prepared drop, not the chewed seed) not stated in the abstract Drops twice daily as reported in the trial 24 weeks · vs Timolol 0.5% eye drops |
After 24 weeks eye pressure fell by 12.93 mmHg (47.8%) with bitter kola drops and 13.09 mmHg (48.2%) with timolol; not statistically different. Side effects were mild and similar between groups. Mean fall 12.93 +/- 2.3 vs 13.09 +/- 2.8 mmHg, P > 0.05 Methods, limits and fundingOutcomes: Change in eye pressure Limitations: Single trial. No placebo group, only a comparison with timolol. Does not apply to eating the seed. A reduction this large is unusual for any single drop, so repeat studies are needed. Read: abstract |
| Adegbehingbe 2008 Clinical effects of Garcinia kola in knee osteoarthritis Journal of Orthopaedic Surgery and Research · PMID 18667082 · DOI |
Controlled trial |
143 Adults with knee osteoarthritis at a Nigerian teaching hospital (143 recruited, 84 completed) |
Garcinia kola preparation (form not described in the abstract) seed (assumed; not stated in the abstract) 200 mg twice a day as reported in the trial (not advice) 6 weeks · vs Placebo, naproxen, celecoxib (Celebrex) |
Pain fell more on bitter kola than on placebo. It was not statistically different from naproxen or celecoxib. Stiffness and walking also improved versus placebo. The abstract reports no significant heart, kidney or drug-related adverse reaction. Reported as p < 0.001 versus placebo; no effect sizes or confidence intervals in the abstract Methods, limits and fundingOutcomes: Change in knee pain on the WOMAC pain visual scale; stiffness; walking Limitations: Only 84 of 143 (58.7%) finished. Single trial, not repeated in what we read. The abstract has p-value typos (for example 'p > 0.001' where a small value is meant). Product and plant part not clearly described. Authors ask for dose standardisation and long-term studies. Read: abstract |
| Akpantah 2005 Effects of garcinia kola seed extract on ovulation, oestrous cycle and foetal development in cyclic female sprague-dawley rats Nigerian Journal of Physiological Sciences · PMID 17220929 |
Animal research animal |
Cyclic and pregnant female rats | Garcinia kola seed extract seed 200 mg per kg (rats) Single dose, 6 weeks, or on set days of pregnancy · vs Untreated rats |
The cycle was disturbed for the first two weeks and then returned to normal. Ovulation was partly blocked. Foetuses were lighter, and 7% of foetuses from rats treated in the first days of pregnancy had a malformed upper limb. The authors suggest dose-and-duration-dependent teratogenicity. P < 0.05 for ovulation and foetal weight Methods, limits and fundingOutcomes: Oestrous cycle, ovulation, foetal weight and malformation Limitations: Small rat study at one dose. Female and pregnancy findings in rats do not prove the same in women, but they are a reason for caution. Read: abstract |
| Andueza 2021 Risks Associated with the Use of Garcinia as a Nutritional Complement to Lose Weight Nutrients · PMID 33572973 · DOI |
Narrative review |
Review of weight-loss supplements made from Garcinia (mainly Garcinia cambogia fruit) | Garcinia cambogia (hydroxycitric acid) supplements, a different species fruit rind Various Various · vs Various |
Most animal and human studies found these supplements safe, but some cases of liver toxicity, serotonin toxicity and mania were reported. This is a different species from bitter kola. Not applicable Methods, limits and fundingOutcomes: Weight loss and safety Limitations: Different species (Garcinia cambogia). Used here only to explain why the genus name raises liver questions; it does not describe bitter kola. Read: abstract |
| Dogara 2022 Biological Evaluation of Garcinia kola Heckel Advances in Pharmacological and Pharmaceutical Sciences · PMID 35528115 · DOI |
Narrative review animal |
Review of mostly laboratory and animal studies | Garcinia kola seed seed Various Various · vs Various |
Reports antioxidant, antimicrobial, antidiabetic, blood-pressure and anti-inflammatory activity in studies. It also reports that too much seed eating caused low fertility and toxicity. The authors say safety and efficacy have not been fully assessed in people. Not applicable Methods, limits and fundingOutcomes: Antioxidant, germ-killing, blood sugar, blood pressure, pain and toxicity findings Limitations: Narrative review of mixed-quality studies; abstract read only. Read: abstract |
| Erukainure 2021 Kolaviron: A Biflavonoid with Numerous Health Benefits Current Pharmaceutical Design · PMID 33185157 · DOI |
Narrative review animal |
Review of kolaviron studies | Kolaviron (seed biflavonoid mixture) seed Various Various · vs Various |
Reproductive-toxicity models were the most studied (25% of studies). Kolaviron was reported to protect liver, heart, nerves, stomach and kidney in models. The authors note toxicity data are lacking and most work is lab or animal. Not applicable Methods, limits and fundingOutcomes: Antioxidant, anti-inflammatory, organ-protection findings Limitations: Narrative review; abstract read only. Toxicity data lacking. Read: abstract |
| Igbinoba 2015 Effect of dehusked Garcinia kola seeds on the overall pharmacokinetics of quinine in healthy Nigerian volunteers Journal of Clinical Pharmacology · PMID 25328082 · DOI |
Controlled trial |
24 24 healthy Nigerian volunteers in two groups of 12 |
Dehusked Garcinia kola seed taken with quinine sulfate seed 12.5 g once a day (group A) or twice a day (group B) as reported in the study (not advice) 6 to 7 days · vs Each person's own quinine levels before bitter kola (randomized crossover) |
With bitter kola, the time to peak quinine fell by 48% (group A); peak quinine fell by 19% and 26%; total quinine exposure fell slightly. Peak levels of the 3-hydroxyquinine breakdown product fell by 29% and 32%. The authors concluded a herb-drug interaction was noted. Cmax -19% (A) and -26% (B); tmax -48% (A); metabolite Cmax -29% and -32% Methods, limits and fundingOutcomes: Quinine and 3-hydroxyquinine blood levels Limitations: Healthy volunteers, single drug, small groups. It shows altered quinine blood levels; it does not show whether malaria treatment worked less well. Funding and conflicts: Authors declare no conflict of interest Read: abstract |
| Olatoye 2023 Ninety-day oral toxicological profiling of Kolaviron (an extract of Garcinia kola) in male and female rats Drug and Chemical Toxicology · PMID 34866527 · DOI |
Animal research animal |
56 Wistar rats, males and females |
Kolaviron seed 20, 100 and 500 mg per kg a day by mouth (rats) 90 days plus 30 days of recovery · vs Vehicle (water/propylene glycol) |
No harmful changes in the vital organs on tissue examination. Blood fats fell and good cholesterol rose. Several white and red blood cell measures rose. Sperm count rose without significance, and FSH and testosterone rose significantly in males. The authors call long-term use 'considerably safe' in rats, with differences between the sexes. Significant at p < 0.05 for many measures; numbers not in the abstract Methods, limits and fundingOutcomes: Organ tissue, blood counts, blood chemistry, hormones, sperm Limitations: Rat study with a purified extract, not whole seed. Does not show safety in people. Authors are from a single lab; funding not stated in the abstract. Read: abstract |
| Olatoye 2024 The role of Kolaviron, a bioflavonoid from Garcinia kola, in the management of cardiovascular diseases: A systematic review Heliyon · PMID 38449600 · DOI |
Systematic review animal |
22 22 laboratory and animal studies |
Kolaviron or Garcinia kola seed Various Various · vs Various |
Kolaviron lowered blood pressure and improved blood fats in the included studies. Mean quality score was about 5.9 on a modified animal-study checklist. Not given in the abstract Methods, limits and fundingOutcomes: Blood pressure, blood fats, clot, vessel and antioxidant findings Limitations: Preclinical studies only; no people were studied. Read: abstract |
| Omotola 2017 Assessment of the Effects of Graded Doses of Polyphenolic-Rich Fraction of Garcinia kola Seeds on Pituitary-Testicular Axis of Male Wistar Rats Dose-Response · PMID 29051716 · DOI |
Animal research animal |
35 Male Wistar rats given arsenate to damage the testes |
Polyphenol-rich fraction of Garcinia kola seed seed 300 and 600 mg per kg (rats) 21 days · vs Water or propylene glycol; arsenate-only group |
In rats damaged by arsenate, the fraction partly reversed and prevented the damage. Hormone levels (FSH, LH, testosterone) in treated groups stayed lower than in the untreated healthy group. Group differences reported as significant; numbers not in the abstract Methods, limits and fundingOutcomes: FSH, LH, testosterone; pituitary and testis tissue Limitations: Rats, with a chemical injury model; fraction not the whole seed. Read: abstract |
| Orie 1993 The bronchodilator effect of Garcinia Kola East African Medical Journal · PMID 8261939 |
Other |
19 19 healthy male Nigerian students aged 17 to 25 |
Garcinia kola seed eaten seed 15 g per person as reported (not advice) Up to 90 minutes · vs Each person was his own control (before versus after) |
All airflow measures rose over time but only peak expiratory flow rate rose significantly (p < 0.05), at 60 minutes. The authors read this as a mild bronchodilator effect. Significance at 60 minutes for peak flow only; no numbers in the abstract Methods, limits and fundingOutcomes: Peak flow, FEV1 and FVC every 30 minutes Limitations: Very small, healthy young men only, no placebo group. Nobody with cough or asthma was tested. Read: abstract |
| Tauchen 2023 Garcinia kola: a critical review on chemistry and pharmacology of an important West African medicinal plant Phytochemistry Reviews · PMID 37359709 · DOI |
Narrative review animal |
Review of laboratory, animal and plant-chemistry literature | Garcinia kola compounds, especially kolaviron and garcinol seed and other parts Various Various · vs Various |
Many activities (pain, cancer, diabetes, inflammation, malaria, germs, liver and nerve protection) were seen, but only in animal models. Kolaviron research has important flaws such as very high doses and inappropriate positive controls. Garcinol looks more promising. Human trials are needed. Not applicable Methods, limits and fundingOutcomes: Chemistry and pharmacology Limitations: Narrative critical review; abstract read only. Read: abstract |
| Ukut 2026 Traditional use of Garcinia kola Heckel in Nigeria - the results of questionnaire survey compared with scientific evidence BMC Complementary Medicine and Therapies · PMID 41699612 · DOI |
Other |
152 152 members of the Nigerian public (mostly Ibibio, Annang and Igbo) |
Questionnaire about traditional use seed (most users ate fresh seeds) Not applicable Not applicable · vs None |
Most people ate fresh seeds, mainly for breathing symptoms, stomach upset and general well-being. Authors say safety and standard doses for different plant parts still need study. Not applicable Methods, limits and fundingOutcomes: How people use bitter kola, what for, and perceived side effects Limitations: A survey of customs, not a trial. The authors also say some uses are 'supported by clinical studies' although few human trials exist. The knee trial appears cited for another use in one table, which looks like a citation slip. Quinine interaction mentioned only as an earlier report. Read: abstract |
| Yakubu 2012 Garcinia kola seeds: is the aqueous extract a true aphrodisiac in male Wistar rats? African Journal of Traditional, Complementary and Alternative Medicines · PMID 23983388 · DOI |
Animal research animal |
24 Male Wistar rats |
Aqueous Garcinia kola seed extract seed 25, 50 and 100 mg per kg (rats) Single dosing, observed over about 3 hours · vs Water |
Mounting frequency rose at two doses, but other sexual behaviour and the hormones did not change significantly. The authors concluded the seeds had no sex-enhancing potential as claimed. P < 0.05 for mount frequency at 25 and 100 mg per kg only Methods, limits and fundingOutcomes: Sexual behaviour; testosterone, LH, FSH Limitations: Rat study with six animals per group; says nothing about men. Read: abstract |
| s-gbif-garcinia-kola GBIF Backbone Taxonomy: Garcinia kola Heckel (usageKey 3189563) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-pubchem-bitter-kola PubChem compound records: kolaflavanone (CID 155169) and garcinol (CID 5281560) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text |
What we do not know yet
- What the evidence supports: low certainty for knee osteoarthritis pain and very low for eye drops; everything else is insufficient or animal only.
- What is uncertain: whether the knee result is real, whether the chewed seed does anything for the eye, breathing, liver, blood pressure or blood sugar.
- Missing: long-term safety, liver safety, pregnancy and breastfeeding safety, human enzyme (CYP) data, and any measurement of caffeine or stimulants in the seed.
- Missing: standard amounts and quality control; authors of reviews ask for both.
How new research is added
New studies are found by a saved PubMed search and are placed in a review queue. A person reads each one before it is added.
Lab markers
What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".
Hormonal 1
Testosterone and FSH (male rats)
Mixed results in trials
Male sex hormone and the pituitary hormone that drives sperm production.
Mixed findingsResults and what it means
Why it was measured
Checked in rat fertility and aphrodisiac studies.
Statistical vs. clinical meaning
Findings differ by extract and design.
Safety implication
Unknown effect on hormone-sensitive conditions in people.
Metabolic 1
Blood fats (cholesterol, triglycerides, LDL, HDL) in rats
Mixed results in trials
Fats carried in the blood.
Not enough evidenceResults and what it means
Why it was measured
Measured in the 90-day kolaviron rat study and the cardiovascular review.
Statistical vs. clinical meaning
Rat results do not show what happens in people.
Safety implication
None established.
| Study | Result | People | Product |
|---|---|---|---|
| 8 | Cholesterol, triglycerides, LDL and VLDL fell significantly and HDL rose in male and female rats (p < 0.05). | Wistar rats, 90 days | Kolaviron by mouth |
Other 4
Knee pain score (WOMAC pain scale)
Lowered in trials
A questionnaire score of pain in the knee joint.
Low certaintyResults and what it means
Why it was measured
Main outcome of the knee osteoarthritis trial.
Statistical vs. clinical meaning
A pain score is what patients feel, which matters, but one small trial with many dropouts is not a firm basis.
Safety implication
None specific; see Safety tab.
| Study | Result | People | Product |
|---|---|---|---|
| 2 | Mean WOMAC pain score fell significantly more than with placebo after 6 weeks (p < 0.001); not significantly different from naproxen or celecoxib. Exact numbers not in the abstract. | 84 completers of 143 adults with knee osteoarthritis | Garcinia kola preparation versus placebo, naproxen, celecoxib |
Eye pressure (mmHg)
Lowered in trials
The fluid pressure inside the eye. High pressure is the main treatable risk factor for glaucoma damage.
Very low certaintyResults and what it means
Why it was measured
Main outcome of the eye-drop trial.
Statistical vs. clinical meaning
Eye pressure is a stand-in for protecting sight; the trial did not measure vision loss.
Safety implication
Eye conditions need an eye doctor.
| Study | Result | People | Product |
|---|---|---|---|
| 1 | Fell 12.93 +/- 2.3 mmHg with bitter kola drops and 13.09 +/- 2.8 mmHg with timolol at 24 weeks (P > 0.05 between groups). | 178 people with new open-angle glaucoma or ocular hypertension | 0.5% Garcinia kola aqueous eye drops versus 0.5% timolol |
Peak expiratory flow rate (PEFR)
Raised in trials
How fast a person can blow air out; a quick measure of airway openness.
Not enough evidenceResults and what it means
Why it was measured
The one lung measure that changed in the 1993 test.
Statistical vs. clinical meaning
A small rise in healthy people does not show a benefit in cough or asthma.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 11 | Rose significantly at 60 minutes (p < 0.05); FEV1 and FVC did not rise significantly. | 19 healthy male students | Garcinia kola seed eaten, each person his own control |
Blood pressure (animal studies)
Lowered in trials
Pressure of blood in the arteries.
Not enough evidenceResults and what it means
Why it was measured
Reviewed as an outcome in kolaviron studies.
Statistical vs. clinical meaning
Animal results only.
Safety implication
Possible added effect with blood-pressure medicines (theory only).
| Study | Result | People | Product |
|---|---|---|---|
| 9 | Kolaviron lowered blood pressure in the reviewed animal and lab studies; numbers not in the abstract. | 22 animal and lab studies | Kolaviron or Garcinia kola |
Safety
What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.
Main points to know 4
- Safety in people has not been properly studied. Bitter kola seed has been eaten for generations in West Africa, but no safety trial in people over the long term was found. Authors of a 2022 review and a 2026 survey both say safe amounts, plant-part differences and long-term effects are still unknown. Most claims of safety come from animal work. Authoritative guidance 5 13
- If you take malaria medicine, tell your doctor first. In 24 healthy volunteers, eating bitter kola with quinine lowered peak quinine levels by 19 to 26% and shortened the time to the peak (by 48% in one group). The authors concluded there was a herb-drug interaction. We do not know if malaria treatment worked less well. Controlled trial 7
- Pregnancy, breastfeeding and children: no safety studies. No safety evaluation in pregnancy, breastfeeding or children was found. In one rat study, a seed extract disturbed the cycle, partly blocked ovulation and was followed by lighter foetuses and some limb malformations when given in early pregnancy. Rat data are not proof for women but are a reason to avoid it unless a doctor agrees. Animal research 3 13
- Not the same as cola nut, and not the same as Garcinia cambogia. Bitter kola (Garcinia kola) is a different plant from cola nut (Cola nitida), the caffeine-containing nut in cola drinks, and from Garcinia cambogia, a weight-loss supplement. Reports of liver injury with Garcinia cambogia products do not show the same for bitter kola, and caffeine facts about cola nut do not apply here automatically. Authoritative guidance 4 12
Side effects 3
| Effect | How often | Severity and recovery | Evidence |
|---|---|---|---|
| Hunger, dry mouth and tooth staining with many seeds Self-reported in a 2026 Nigerian survey of 152 people. Most respondents reported no side effects. No frequencies were given. | Not established | mild Not reported | Traditional use 13 |
| Dizziness, diarrhoea and heartburn Mentioned by some survey respondents. Not measured in trials. | Not established | mild to moderate Not reported | Traditional use 13 |
| No significant heart, kidney or drug-related adverse reaction in the knee trial Over 6 weeks in a small trial where 58.7% of recruits finished. This does not rule out rarer or longer-term harms. | Not established | none reported Not applicable | Controlled trial 2 |
Liver
We found no published human case of liver injury linked to bitter kola seed or kolaviron, and no human liver safety study. NIH LiverTox was not reachable in this search, so that source is not verified. Many animal studies report that the seed or kolaviron protects the liver from chemical damage. In a 90-day rat study of kolaviron, tissue examination of vital organs showed no abnormal findings, but that is not proof for people. A critical review warns that many kolaviron studies used very high doses and poor controls. A review of Garcinia cambogia supplements (a different species) reports some cases of liver toxicity, which is why we advise caution with any Garcinia supplement until bitter kola is studied. Absence of reports is not proof of safety. 8 12 4
How often. No frequency of human liver injury is known; no human data exist.
Monitoring. No agency monitoring advice was found. If you have liver disease or take liver-affecting medicines, talk to your doctor before using bitter kola. Stop and seek care for yellow skin or eyes, dark urine, pale stools or severe tiredness.
This is a safety connection. It is not evidence that Bitter kola supports liver health.
Medicines and supplements 4
| With | Why it matters | Importance | Evidence | What to do |
|---|---|---|---|---|
| Quinine (malaria and leg-cramp medicine) prescription | Bitter kola changed how quickly quinine was absorbed and lowered its peak blood level; the mechanism was not established. | In 24 healthy volunteers, peak quinine fell 19% and 26% in two groups and the time to peak was 48% shorter in one group; the breakdown product 3-hydroxyquinine fell 29% and 32%. Whether treatment worked less well was not tested. | Controlled trial Low certainty 7 | Tell your doctor or pharmacist before using it with quinine or other malaria medicines. |
| Diabetes medicines (insulin, metformin, sulfonylureas) prescription | Reviews describe blood-sugar-lowering effects in animals. If this occurred in people it could add to medicines. | No human study. A theoretical risk only. | Pharmacological theory Not enough evidence 12 5 | If you take diabetes medicines, talk to your doctor before using bitter kola and watch your blood sugar as advised. |
| Blood-pressure medicines prescription | A systematic review of 22 lab and animal studies found kolaviron lowered blood pressure in those studies. | No human study. A theoretical added effect. | Pharmacological theory Not enough evidence 9 | If you take blood-pressure medicine, ask your doctor first. |
| Medicines cleared by liver enzymes (CYP enzymes) prescription | Garcinia kola compounds are reported to act on liver enzymes in lab studies, and the quinine result suggests altered drug handling. We did not find a human CYP study. | Unknown. No verified human CYP data were read. | Pharmacological theory Not enough evidence 7 | Tell your pharmacist you use it if you take medicines with a narrow safe range. |
Who should check first 4
| Situation | Advice | Evidence |
|---|---|---|
| Pregnancy, trying to conceive, or breastfeeding | Avoid unless your doctor agrees. No human safety data; a rat study showed cycle, ovulation and foetal effects. | Animal research 3 13 |
| Taking quinine or other malaria medicine | Ask a doctor or pharmacist first because bitter kola lowered quinine peak levels in healthy volunteers. | Controlled trial 7 |
| Liver disease, or taking medicines that can affect the liver | Ask a doctor first; no human liver data exist. | Pharmacological theory 12 |
| Children | No safety studies in children were found, although families use the seed traditionally. Ask a paediatrician. | Traditional use 13 |
Overdose, product quality and regulators
Summary. The seed is a traditional food and chewed medicine. Controlled safety data in people do not exist. In animals, purified kolaviron for 90 days did not cause abnormal organ tissue findings in rats, but reviews warn about very high doses in other studies and link excessive seed eating with toxicity and low fertility.
Animal. A 90-day rat study at three kolaviron levels found no abnormal vital-organ tissue, lower blood fats, and higher FSH and testosterone in males. One rat study of a seed extract disturbed the cycle, partly blocked ovulation and lowered foetal weight.
Human doses studied. Human studies were small: a 6-week knee trial, a 1993 single-session airflow test, an eye-drop trial and a 7-day quinine study. Doses are not given here as advice.
High dose or long term signals. A 2022 review links excessive seed eating with low fertility and toxicity (animal evidence). Long-term human effects are unknown.
Overdose response. Not described in the sources read.
Genotoxicity. Not assessed in the sources read.
Toxic plant parts. The seed is the part used. Safety of bark, roots, leaves and fruit pulp was not assessed; the 2026 survey says safety by plant part still needs study.
We did not find a source on contamination or adulteration of bitter kola. Bitter kola, cola nut and gotu kola are different plants with similar-sounding names, so labels can confuse buyers. This is a naming risk, not a documented contamination finding.
| Body | Action | Date |
|---|
When to get medical help
- Swelling of the face, lips or throat, trouble breathing, or a widespread rash
- Yellow skin or eyes, dark urine, pale stools or severe tiredness
- Very low blood sugar signs (shakiness, sweating, confusion) if you take diabetes medicines
- Severe dizziness, fainting or a very slow heartbeat
- Pregnancy bleeding or severe abdominal pain
Stop the supplement and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.
General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.
Frequently asked questions
Is bitter kola the same as cola nut?
No. Bitter kola (Garcinia kola) and cola nut (Cola nitida) are different trees in different plant families. Cola nut is the nut linked with caffeine. We found no source on caffeine in bitter kola, so do not assume the two behave alike.
What is bitter kola used for?
In West Africa it is chewed for cough, breathing complaints, stomach upset and general well-being, and used in folk medicine for pain, fever and malaria. These are traditional uses, not proof.
Does bitter kola help with knee pain?
One small trial in Nigeria found less knee pain than placebo, with no statistical difference from naproxen or celecoxib. Only 84 of 143 people finished, and it has not been repeated, so certainty is low.
Does it lower eye pressure?
A 0.5% eye drop made for a trial lowered eye pressure about as much as timolol in 178 people. That was a special drop, not the seed, and it is not something to try at home. Glaucoma needs an eye doctor.
Is it good for the liver?
Does it interact with medicines?
Yes with quinine: in 24 healthy volunteers peak quinine levels fell 19 to 26%. Interactions with diabetes and blood-pressure medicines are theoretical and untested in people. We found no human enzyme study. Tell your doctor or pharmacist.
Is it safe in pregnancy or breastfeeding?
Does it affect male fertility or work as an aphrodisiac?
Does it help with cough or asthma?
Does it help with blood pressure or diabetes?
What side effects have people reported?
In a Nigerian survey most people reported none; others mentioned hunger, dry mouth, tooth staining with many seeds, dizziness, diarrhoea and heartburn. No frequencies were given.
Where can I get advice on how much is right?
Standard amounts have not been established. Ask a doctor or pharmacist.
Explore by health goal
Immune SupportJoint SupportInflammation BalanceEnergy BoostLiver SupportBlood Pressure SupportCholesterol BalanceHeart HealthBlood Sugar BalanceMens VitalityFertility Support
Editorial transparency
- Written by
- AlternativeMed editorial team. Research compiled with AI assistance, then checked against PubMed records.
- Medical review
- None. This page has not been reviewed by a physician or pharmacist.
- First published
- 2026-10-25
- Last substantive update
- 2026-10-25
- How we research
- We read PubMed abstracts for the trials, reviews and animal studies cited, checked the plant name in GBIF and compounds in PubChem, and used our existing herb summary. Regulator pages (EMA, NCCIH, LiverTox, LactMed) were not found or read for this herb.
- How we rate evidence
- See "How we rate evidence" in the Evidence tab.
- Independence
- No product is promoted on this page. No affiliate links are shown.
Sources 16
Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.
- Adefule-Ositelu AO, Adegbehingbe BO, Adefule AK, et al.. Efficacy of Garcinia kola 0.5% Aqueous Eye Drops in Patients with Primary Open-Angle Glaucoma or Ocular Hypertension. Middle East African Journal of Ophthalmology. 2010. PMID 20543944. DOI 10.4103/0974-9233.61224. (abstract)
- Adegbehingbe OO, Adesanya SA, Idowu TO, et al.. Clinical effects of Garcinia kola in knee osteoarthritis. Journal of Orthopaedic Surgery and Research. 2008. PMID 18667082. DOI 10.1186/1749-799X-3-34. (abstract)
- Akpantah AO, Oremosu AA, Noronha CC, et al.. Effects of garcinia kola seed extract on ovulation, oestrous cycle and foetal development in cyclic female sprague-dawley rats. Nigerian Journal of Physiological Sciences. 2005. PMID 17220929. (abstract)
- Andueza N, Giner RM, Portillo MP. Risks Associated with the Use of Garcinia as a Nutritional Complement to Lose Weight. Nutrients. 2021. PMID 33572973. DOI 10.3390/nu13020450. (abstract)
- Dogara AM, Hamad SW, Hama HA, et al.. Biological Evaluation of Garcinia kola Heckel. Advances in Pharmacological and Pharmaceutical Sciences. 2022. PMID 35528115. DOI 10.1155/2022/3837965. (abstract)
- Erukainure OL, Salau VF, Chukwuma CI, Islam MS. Kolaviron: A Biflavonoid with Numerous Health Benefits. Current Pharmaceutical Design. 2021. PMID 33185157. DOI 10.2174/1381612826666201113094303. (abstract)
- Igbinoba SI, Onyeji CO, Akanmu MA, et al.. Effect of dehusked Garcinia kola seeds on the overall pharmacokinetics of quinine in healthy Nigerian volunteers. Journal of Clinical Pharmacology. 2015. PMID 25328082. DOI 10.1002/jcph.414. (abstract)
- Olatoye FJ, Akindele AJ. Ninety-day oral toxicological profiling of Kolaviron (an extract of Garcinia kola) in male and female rats. Drug and Chemical Toxicology. 2023. PMID 34866527. DOI 10.1080/01480545.2021.1997543. (abstract)
- Olatoye FJ, Akindele AJ, Awodele O. The role of Kolaviron, a bioflavonoid from Garcinia kola, in the management of cardiovascular diseases: A systematic review. Heliyon. 2024. PMID 38449600. DOI 10.1016/j.heliyon.2024.e27333. (abstract)
- Omotola MB, Adeosun IO, Obuotor EM, et al.. Assessment of the Effects of Graded Doses of Polyphenolic-Rich Fraction of Garcinia kola Seeds on Pituitary-Testicular Axis of Male Wistar Rats. Dose-Response. 2017. PMID 29051716. DOI 10.1177/1559325817729260. (abstract)
- Orie NN, Ekon EU. The bronchodilator effect of Garcinia Kola. East African Medical Journal. 1993. PMID 8261939. (abstract)
- Tauchen J, Frankova A, Manourova A, et al.. Garcinia kola: a critical review on chemistry and pharmacology of an important West African medicinal plant. Phytochemistry Reviews. 2023. PMID 37359709. DOI 10.1007/s11101-023-09869-w. (abstract)
- Ukut UO, Csikos E, Papp N, et al.. Traditional use of Garcinia kola Heckel in Nigeria - the results of questionnaire survey compared with scientific evidence. BMC Complementary Medicine and Therapies. 2026. PMID 41699612. DOI 10.1186/s12906-026-05287-5. (abstract)
- Yakubu MT, Quadri AL. Garcinia kola seeds: is the aqueous extract a true aphrodisiac in male Wistar rats?. African Journal of Traditional, Complementary and Alternative Medicines. 2012. PMID 23983388. DOI 10.4314/ajtcam.v9i4.9. (abstract)
- . GBIF Backbone Taxonomy: Garcinia kola Heckel (usageKey 3189563). . . (full-text)
- . PubChem compound records: kolaflavanone (CID 155169) and garcinol (CID 5281560). . . (full-text)