Bentonite Clay
Also called bentonite, montmorillonite, calcium montmorillonite, NovaSil, smectite, edible clay.
Best grade B across 8 graded outcomes Other Last checked
The short answer
From 14 sourcesBentonite is a montmorillonite clay sold as a "detox" drink. Refined calcium montmorillonite lowered aflatoxin exposure markers in randomized trials in Ghana and Texas, and medicinal smectite clays shortened childhood diarrhea. No trial tested retail bentonite powder, and FDA found elevated lead in one product marketed for drinking.
Every graded outcome on this page
8 rows · line = participants- BGrade BDuration of acute infectious diarrhea in childrenDiarrhean 2,209
- BGrade BAbdominal pain or discomfort in IBSIBSn 524
- BGrade BBlood and urine markers of aflatoxin exposureAflatoxinn 177
- CGrade CBlood aflatoxin marker (AFB-lysine)Aflatoxinn 234
- CGrade CUrine aflatoxin marker (AFM1)Aflatoxinn 49
- DGrade DSafety and urine aflatoxin marker in children (60 days)Aflatoxinn 200
- DGrade DInfant diaper rash (cream on the skin)Skin (topical)n 100
- DGrade DSafety and urine aflatoxin marker in childrenAflatoxinn 63
- 5 more graded outcomes, in the evidence chapter
Key facts
- What it is
- A clay made mostly of montmorillonite; trials used refined, tested grades rather than retail powder17
- Aflatoxin
- 1.5 to 3 g/day for 3 months lowered blood and urine aflatoxin markers in Ghanaian adults; in Texas only the 1.5 g dose reached significance; 3 g/day lowered the urine marker within a week in Kenya2411
- Diarrhea
- Medicinal dioctahedral smectite (diosmectite, not bentonite) shortened acute diarrhea in children by about a day across 14 trials (2,209 children; low-certainty evidence)10
- IBS
- A 524-person trial of a purified clay missed its main endpoint; pain improved only in constipation-predominant IBS7
- Lead
- FDA warned consumers in 2016 about elevated lead in a bentonite clay sold to be mixed with water and swallowed8
What it is
Bentonite is a clay made mostly of montmorillonite, a mineral that binds toxins and water, sold as a powder to drink or apply to skin.
How it works
ProposedMontmorillonite has a layered structure with a large, charged surface that binds aflatoxin and other molecules in the gut so they pass out in stool. In a 3-month human trial it did not lower blood vitamins A and E or nutrient minerals, suggesting the binding was selective at the doses tested. Broader "detox" claims have no human data in our sources.23
Forms, side by side
3 forms named in our sources. The rest show what our data holds, and say plainly where it holds nothing yet.
Bentonite Clay forms compared
3 forms| 3 forms | Refined calcium montmorillonite (NovaSil, UPSN, ACCS100) | Dioctahedral smectite and beidellitic montmorillonite (pharmaceutical clays) | Retail bentonite clay powder |
|---|---|---|---|
| Absorption in people | Acts in the gut by binding aflatoxin; serum vitamins A and E and nutrient minerals did not change over 3 months at up to 3 g/day.23 | Not absorbed; acts in the gut.7 | No human data in our sources. |
| GI tolerance | Side effects were rare and similar to placebo at 1.5 to 3 g/day for 3 months in adults and up to 1.5 g/day for 2 weeks in children.145 | Adverse effects were similar to control in the pooled diarrhea trials and no significant adverse events occurred in the 8-week IBS trial.67 | FDA found elevated lead in a retail bentonite clay sold to be mixed with water and swallowed.8 |
| Studied for | Lowering aflatoxin exposure markers | Acute diarrhea in children; IBS | No human trials in our sources |
- Refined calcium montmorillonite (NovaSil, UPSN, ACCS100)
- Absorption in people
- Acts in the gut by binding aflatoxin; serum vitamins A and E and nutrient minerals did not change over 3 months at up to 3 g/day.23
- GI tolerance
- Side effects were rare and similar to placebo at 1.5 to 3 g/day for 3 months in adults and up to 1.5 g/day for 2 weeks in children.145
- Studied for
- Lowering aflatoxin exposure markers
- Dioctahedral smectite and beidellitic montmorillonite (pharmaceutical clays)
- Retail bentonite clay powder
- Absorption in people
- No human data in our sources.
- GI tolerance
- FDA found elevated lead in a retail bentonite clay sold to be mixed with water and swallowed.8
- Studied for
- No human trials in our sources
What the human research says
Human trials only, one row per outcome. The form line shows what each trial actually tested. Grades follow our evidence-grading policy.
Trial map
8 graded outcomes, largest study first8 graded outcomes: 6 improved, 2 mixed. The largest, a 2018 meta-analysis of 2,209 people on duration of acute infectious diarrhea in children, found an improvement.
1Duration of acute infectious diarrhea in children
Improved · Grade B · Meta-analysis, 2,209 people, 2018
Children aged 1 month to 18 years with acute infectious diarrhea (Cochrane review: 18 trials, 2,616 children)
Dose, result and source| Outcome | Found | People | Study | Who was studied |
|---|---|---|---|---|
| Duration of acute infectious diarrhea in children | Improved | 2,209 | Grade B · Meta-analysis, 2018 | Children aged 1 month to 18 years with acute infectious diarrhea (Cochrane review: 18 trials, 2,616 children) |
| Abdominal pain or discomfort in IBS | Mixed | 524 | Grade B · RCT, 2005 | Adults with IBS (Rome I), France |
| Blood aflatoxin marker (AFB-lysine) | Mixed | 234 | Grade C · RCT, 2016 | Healthy adults in south Texas |
| Safety and urine aflatoxin marker in children (60 days) | Improved | 200 | Grade D · RCT, 2022 | Children aged 2 to 9 in Ghana with detectable urine aflatoxin |
| Blood and urine markers of aflatoxin exposure | Improved | 177 | Grade B · RCT, 2008 | Adults in Ghana at high risk of dietary aflatoxin exposure |
| Infant diaper rash (cream on the skin) | Improved | 100 | Grade D · RCT, 2015 | Infants with diaper dermatitis (mean age about 6 to 7 months) |
| Safety and urine aflatoxin marker in children | Improved | 63 | Grade D · RCT, 2014 | Children aged 3 to 9 in Ghana |
| Urine aflatoxin marker (AFM1) | Improved | 49 | Grade C · Crossover RCT, 2017 | Healthy adults in a district of Kenya with recurring aflatoxicosis outbreaks |
Every graded row
8 rowsShowing 8 of 8 outcomes. Human trials only.
BGrade BDuration of acute infectious diarrhea in childrenDiarrhea-24 hMeta-analysis · 14 studies
n 2,209 · 2018
Improved Smectite may shorten diarrhea by about a day (-24.4 hours, 95% CI -30.9 to -17.9; 14 studies, 2,209 children) and may raise recovery by day 3 (RR 2.10; 5 trials, 312 children). It did not change hospital admission or need for IV fluids. Constipation, the most common side effect, did not differ, and no deaths or serious adverse effects were reported.
- Design
- Meta-analysis, 14 studies, n = 2,209, 2018
- Population
- Children aged 1 month to 18 years with acute infectious diarrhea (Cochrane review: 18 trials, 2,616 children)
- Form
- Dioctahedral smectite (diosmectite), a pharmaceutical clay, added to rehydration; bentonite was not studied
- Dose
- As used in the pooled trials
- Duration
- Acute illness
- Source
- Reference 10 · PubMed 29693719 (opens PubMed)
BGrade BAbdominal pain or discomfort in IBSIBSMixedRCT
n 524 · 2005
Mixed In all patients, success rates did not differ significantly (51.7% vs 45.2%). In constipation-predominant IBS, pain improved more than placebo (49.4% vs 31.5%). Stool frequency did not change, and no significant adverse events occurred.
- Design
- RCT, n = 524, 2005
- Population
- Adults with IBS (Rome I), France
- Form
- Beidellitic montmorillonite (a purified clay)
- Dose
- 3 g three times daily vs placebo
- Duration
- 8 weeks
- Source
- Reference 7 · PubMed 15709995 (opens PubMed)
BGrade BBlood and urine markers of aflatoxin exposureAflatoxinImprovedRCT
n 177 · 2008
Improved At 3 months, the blood aflatoxin-albumin marker was significantly lower at both doses than placebo, and the urine metabolite AFM1 was up to 58% lower at 3 g/day. The companion paper reported rare side effects (nausea, diarrhea, heartburn, dizziness) at similar rates in all groups.
- Design
- RCT, n = 177, 2008
- Population
- Adults in Ghana at high risk of dietary aflatoxin exposure
- Form
- Refined calcium montmorillonite clay (NovaSil) capsules
- Dose
- 1.5 or 3 g/day before meals vs placebo
- Duration
- 3 months
- Source
- Reference 2 · PubMed 18478481 (opens PubMed)
CGrade CBlood aflatoxin marker (AFB-lysine)AflatoxinMixedRCT
n 234 · 2016
Mixed The blood aflatoxin marker fell significantly only at 1.5 g/day, not at 3 g/day. Adverse events, blood chemistry and blood counts did not differ between groups.
- Design
- RCT, n = 234, 2016
- Population
- Healthy adults in south Texas
- Form
- Refined calcium montmorillonite clay (ACCS100)
- Dose
- 1.5 or 3 g/day vs placebo
- Duration
- 3 months, then 1 month off
- Source
- Reference 4 · PubMed 27321368 (opens PubMed)
CGrade CUrine aflatoxin marker (AFM1)AflatoxinImprovedCrossover RCT
n 49 · 2017
Improved Urine AFM1 was about half as high while taking the clay as on placebo (ratio 0.49, 95% CI 0.32 to 0.75). Self-reported adverse events and ratings of taste, texture and appearance did not differ.
- Design
- Crossover RCT, n = 49, 2017
- Population
- Healthy adults in a district of Kenya with recurring aflatoxicosis outbreaks
- Form
- Refined calcium montmorillonite clay (ACCS100)
- Dose
- 3 g/day (1 g three times daily) vs calcium carbonate placebo
- Duration
- 7 days per treatment, 5-day washout
- Source
- Reference 11 · PubMed 27603954 (opens PubMed)
DGrade DSafety and urine aflatoxin marker in children (60 days)AflatoxinImprovedRCT
n 200 · 2022
Improved Urine AFM1 fell 60% from baseline with clay, while it rose in the placebo group. Blood counts did not change apart from a rise in hemoglobin with clay, and blood chemistry was unchanged apart from calcium.
- Design
- RCT, n = 200, 2022
- Population
- Children aged 2 to 9 in Ghana with detectable urine aflatoxin
- Form
- NovaSil (refined calcium montmorillonite) mixed into food
- Dose
- 1.5 g/day vs calcium carbonate placebo
- Duration
- 60 days
- Source
- Reference 12 · PubMed 36133399 (opens PubMed)
DGrade DInfant diaper rash (cream on the skin)Skin (topical)ImprovedRCT
n 100 · 2015
Improved Lesions began improving within 6 hours in 88% with bentonite vs 54% with calendula, and cleared within 3 days in 86% vs 52% (both P < 0.001).
- Design
- RCT, n = 100, 2015
- Population
- Infants with diaper dermatitis (mean age about 6 to 7 months)
- Form
- Bentonite cream applied to the skin, versus calendula cream
- Dose
- Cream applied by mothers
- Duration
- 3 days
- Source
- Reference 14 · PubMed 26831423 (opens PubMed)
DGrade DSafety and urine aflatoxin marker in childrenAflatoxinImprovedRCT
n 63 · 2014
Improved Blood counts and blood chemistry did not differ from placebo and no adverse events were attributed to the clay; urine AFM1 fell at 1.5 g/day.
- Design
- RCT, n = 63, 2014
- Population
- Children aged 3 to 9 in Ghana
- Form
- Uniform Particle Size NovaSil (refined calcium montmorillonite)
- Dose
- 0.75 or 1.5 g/day vs calcium carbonate placebo
- Duration
- 14 days
- Source
- Reference 5 · PubMed 25135766 (opens PubMed)
What the numbers add up to
Each point is worked out from the data and the sources numbered on this page, with the arithmetic shown under it. It adds no new data and is not medical advice.
The "detox" evidence is specific
More clay was not better
In the Texas trial only the lower 1.5 g/day dose significantly lowered the aflatoxin marker.4
Studied doses
Doses used in research, shown against the official limits. They describe the studies, not a recommendation for you.
Studied doses in research, not advice. These are amounts used in research, not personal advice. Your clinician or pharmacist can say what fits you.
Doses studied in human trials
When trials measured an effect
4 outcomes| Outcome | Measured at | Basis |
|---|---|---|
| Urine aflatoxin marker | Within a 7-day treatment period | Kenya crossover trial at 3 g/day: urine AFM1 lower on clay than on placebo11 |
| Blood aflatoxin marker | 3 months (no difference at 1 month) | Ghana trial at 1.5 or 3 g/day: aflatoxin-albumin similar to placebo at 1 month, lower at 3 months2 |
| Acute diarrhea in children (diosmectite) | About 1 day shorter; more recovered by day 3 | Cochrane review: -24.4 hours (14 studies) and RR 2.10 for recovery by day 3 (5 trials)10 |
| Infant diaper rash (bentonite cream) | Improvement within 6 hours; cleared within 3 days in 86% | 100-infant trial versus calendula cream14 |
Interactions and safety
Published interactions only: each row cites a source. No row means none was found in our sources, not that a combination is safe.
What Bentonite Clay meets
1 cited rowMedicines 1
Supplements and foods 0
No supplement rows in our sources.
- Measured in a human study
Choose a medicine or supplement above to read its cited rows here.
Also cited:
Oral medicines
PK studyMeasured in a human study
Oral medicines, for example diazepam: Clays bind other molecules in the gut. In healthy volunteers, smectite clay lowered and delayed the peak blood level of diazepam but did not change phenylbutazone, and it bound diazepam in the lab. Spacing clay apart from medicines and asking a pharmacist is the cautious approach.
Source 9, Eur J Clin Pharmacol (1985)
Interactions
1 agent| Agent | What the source says | Evidence |
|---|---|---|
| Medicines1 | ||
| Oral medicinese.g. diazepam | Clays bind other molecules in the gut. In healthy volunteers, smectite clay lowered and delayed the peak blood level of diazepam but did not change phenylbutazone, and it bound diazepam in the lab. Spacing clay apart from medicines and asking a pharmacist is the cautious approach.9 | PK study |
Check with what you take
Kept on this device onlyAdd what you take. We list every interaction our evidence profiles cite between Bentonite Clay and your picks, and between your picks.
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Add a supplement or medicine you take to check it against Bentonite Clay.
Starting from one medicine? The interaction checker rates how serious each pair is, on a curated list of 19 entries for 11 medicines. This cabinet has no severity rating: it lists every interaction row our supplement pages cite.
Who should be careful
3 groups- Lead contamination
- Clays are mined, and FDA found elevated lead in a retail bentonite marketed for drinking. Lead can damage the nervous system and kidneys, and children are most at risk.8
- Pregnancy and breastfeeding
- No clay trial in our sources included pregnant or breastfeeding women: the Ghana and Kenya aflatoxin trials screened out or excluded pregnancy, and LactMed has no bentonite entry, so there are no reliable data. Eating clay in pregnancy (geophagy) was linked to 22% higher blood lead in a study of 1,056 pregnant women in Tanzania.11113
Reading the label, and the cost per dose
Compare any product you already have by the amount it delivers, not by capsule count or front-of-pack weight.
How to read the label
2 checksRetail bentonite is not the trial clay
Look for heavy-metal testing
Because a retail bentonite was found to contain elevated lead, a label or certificate showing heavy-metal testing matters more than for most supplements.8
Have the bottle? Photograph its Supplement Facts panel and see each line, bentonite clay included, beside the doses and forms the trials used in Label X-Ray.
Cost per studied dose, without the sales pitch
Your numbers, no product dataEnter the price, servings and the amount per serving from your label.
Frequently asked questions
Short answers to common questions; the numbers link to the sources below.
Common questions
7 answersDoes bentonite clay detox the body?
Does bentonite help diarrhea?
A related pharmaceutical clay, dioctahedral smectite (diosmectite), shortened acute diarrhea in children by about a day across 14 trials (2,209 children) when added to rehydration, on low-certainty evidence. It did not reduce hospital admissions.10
Does clay help IBS?
A purified clay did not beat placebo across 524 IBS patients, but pain improved in the constipation-predominant subgroup.7
Does clay block nutrient absorption?
Does bentonite clay work on the skin?
One trial in 100 infants found a bentonite cream cleared diaper rash within 3 days in 86%, versus 52% with calendula cream. It was a single trial against another cream, not a placebo.14
Is drinking bentonite clay safe?
Sources
14 sources: trial abstracts, NIH fact sheets and reference databases. Numbers in the text link here.
Sources cited on this page
14 sources- 1NovaSil clay intervention in Ghanaians at high risk for aflatoxicosis. I. Study design and clinical outcomes.RCT Food Addit Contam Part A Chem Anal Control Expo Risk Assess, 2008 · PMID 17852392
- 2NovaSil clay intervention in Ghanaians at high risk for aflatoxicosis: II. Reduction in biomarkers of aflatoxin exposure in blood and urine.RCT Food Addit Contam Part A Chem Anal Control Expo Risk Assess, 2008 · PMID 18478481
- 3NovaSil clay does not affect the concentrations of vitamins A and E and nutrient minerals in serum samples from Ghanaians at high risk for aflatoxicosis.RCT Food Addit Contam Part A Chem Anal Control Expo Risk Assess, 2008 · PMID 18569006
- 4Intervention trial with calcium montmorillonite clay in a south Texas population exposed to aflatoxin.RCT Food Addit Contam Part A Chem Anal Control Expo Risk Assess, 2016 · PMID 27321368
- 5Short-term safety and efficacy of calcium montmorillonite clay (UPSN) in children.RCT Am J Trop Med Hyg, 2014 · PMID 25135766
- 6Meta-analysis: Smectite in the treatment of acute infectious diarrhoea in children.Meta-analysis Aliment Pharmacol Ther, 2006 · PMID 16393300
- 7Symptomatic efficacy of beidellitic montmorillonite in irritable bowel syndrome: a randomized, controlled trial.RCT Aliment Pharmacol Ther, 2005 · PMID 15709995
- 8FDA Warns Consumers Not to Use "Best Bentonite Clay" (archived copy)Safety communication U.S. Food and Drug Administration, 2016 · web.archive.org
- 9Interactions between smectite, a mucus stabilizer, and acidic and basic drugs. In vitro and in vivo studies.PK study Eur J Clin Pharmacol, 1985 · PMID 3899678
- 10Smectite for acute infectious diarrhoea in children.Meta-analysis Cochrane Database Syst Rev, 2018 · PMID 29693719
- 11Evaluation of the efficacy, acceptability and palatability of calcium montmorillonite clay used to reduce aflatoxin B1 dietary exposure in a crossover study in Kenya.Crossover RCT Food Addit Contam Part A Chem Anal Control Expo Risk Assess, 2017 · PMID 27603954
- 12Safety and Efficacy of Novasil Clay (Calcium Montmorillonite) in Children Exposed to Aflatoxin in Ejura-Sekyedumase District in Ghana.RCT Glob Pediatr Health, 2022 · PMID 36133399
- 13The role of geophagy and artisanal gold mining as risk factors for elevated blood lead levels in pregnant women in northwestern Tanzania.Observational PLOS Glob Public Health, 2024 · PMID 38394051
- 14Comparing the effects of Bentonite & Calendula on the improvement of infantile diaper dermatitis: A randomized controlled trial.RCT Indian J Med Res, 2015 · PMID 26831423
What changed
Every dated change to this page: what changed, who made it and why.
Change log
4 entries| Date | Change | Who and why |
|---|---|---|
| evidence, who should avoid, studied doses, FAQ, questions, time to effect, related | Added a 2017 Kenya crossover trial (urine aflatoxin marker, grade C), a 60-day trial in 200 Ghanaian children (grade D) and a 2015 infant diaper-rash trial of bentonite cream (grade D); replaced the 2006 diarrhea meta-analysis row with the 2018 Cochrane review (14 studies, 2,209 children; still grade B, low certainty), keeping the older review as a cited source. Rewrote the pregnancy note to cover breastfeeding (trials excluded pregnancy; LactMed has no entry; a 2024 study linked clay eating in pregnancy to higher blood lead), extended the children note, studied doses, time-to-effect rows, two FAQ items, page questions and a goal-hub link. Interactions re-checked: LiverTox and LactMed have no bentonite or smectite entry; no new interaction found beyond the diazepam PK study. Not added: a 2012 fumonisin biomarker analysis (PMID 22324939; counts urine samples, not people) and a 2025 acne mask trial (PMID 41347526; bentonite combined with an herbal extract and an antibiotic). | Writer: Kymata Health EditorialTrigger: A–Z audit against docs/supplements/AUDIT-STANDARD.md |
| safety | Independent review: added a drug-absorption interaction (smectite delayed diazepam absorption, PubMed-verified PK study); lowered the childhood diarrhea row from grade A to B because the pooled trials had important limitations and tested pharmaceutical smectite, not bentonite. | Writer: Kymata Health EditorialTrigger: review |
| all | First draft. Every PMID checked against NCBI E-utilities esummary (title and year taken from the record) and abstracts read for every cited row. | Writer: Kymata Health EditorialTrigger: new page |
| all | Adversarial review pass: every evidence row's numbers machine-checked against its PubMed abstract, retraction and erratum flags checked for all PMIDs, unverified country and affiliation details removed, and claims not supported by the cited abstracts reworded or dropped. | Writer: Kymata Health EditorialTrigger: review |
Supplement & Nutrient Encyclopedia. Educational information only; it is not medical advice and does not replace a clinician. Dietary supplements are not intended to diagnose, treat, cure or prevent any disease. Statements about supplements have not been evaluated by the FDA.