I am going to a college reunion soon and wonder if I should baste and stuff myself with bentonite clay (like a Thanksgiving Turkey) in order to look svelte and have glowing skin?  According to some celebrities, bentonite clay is absolutely guaranteed to erase the damage caused by too many nights munching comfort food while on call in the ER.

After all, we are told that it was the beauty secret of the Egyptian queen, Cleopatra. Prior to these celebrity endorsements, I thought that Cleopatra used milk as her beauty hack but I am sure that the celebrities have done thorough research to back up their claims?

We are also told that bentonite is ‘natural’ which is the usual marketing trick used to dupe us into parting with our hard earned money. When will someone tell these uninformed marketers that ‘natural’ is not always synonymous with ‘safe’ or ‘good for you’? As an example, ebola qualifies as ‘natural’.

Not everyone agrees with the benefits of bentonite. According to the Huff Post, eating clay (like bentonite) is a ‘faddish health trend that we want to leave behind’.

Apart from the shallow benefits of impressing my college mates, bentonite is also promoted for fibromyalgia, cancer, endocrine regulation and immune boosting.

Fad, fact or fiction? I only trust source data (apologies rich and famous celebrities). What does the actual original research have to say?

What Actually Is Bentonite Clay?

There is plenty of evidence to suggest that ancient civilizations relied on what they had readily available to heal and adorn. That would include clays such as bentonite.

There are some interesting terms to understand in order to talk about bentonite.


This is a fine particulate matter with a diameter size of less than 2 micrometers. Clays are used both topically and are taken orally. According to folk medicine, topical clay is supposed to draw toxins out to the skin surface (like a poultice) and oral clay is supposed to play a dual role of providing essential minerals and detoxifying the gut.

Bentonite is a clay.


Clay + water = mud. Bentonite can be a mud.


Pica is an eating disorder which is defined as inappropriate eating of non-nutritional substances that are culturally inappropriate for at least one month. This often includes clay, ice or wood. Pica are seen in pregnant women sometimes and in children who are on the autistic spectrum.


Geophagy specifically refers to eating clay and is an ancient practice. In some cultures, geophagy is considered socially abnormal (i.e. a pica) while in others it is an acceptable social practice.

Traditionally, there have been two main theories about the origins of geophagy:

  1. it is an adaptive behavior designed to reduce nutrient deficiency or protect against pathogens or toxins
  2. it is a non-adaptive behavior designed to reduce hunger or is itself a symptom of nutrient deficiency.

A complex analysis of 330 counts of geophagy in 297 mammals, birds and reptiles evaluated the cultural context of geophagy to try to understand the physiological function served by this practice (1).

They noticed that human geophagy evolved primarily in children, pregnant women and areas with high burdens of parasitic infections. They generated the hypothesis that human geophagy evolved to protect against chemicals, parasites, and pathogens while geophagy in animals evolved to reverse micronutrient deficiency and protect against parasites, pathogens and chemicals.


These are silicates which again include (but are not limited to) bentonite. The term comes up in research about bentonite.

Fuller’s Earth refers to any clay with adsorptive capacity which includes (but is not limited) to bentonite

Now to bentonite itself.


Bentonite (Al2O34SiO2nH2O) is an absorbent colloidal aluminum phyllosilicate clay. It is also known as Montmorillonite clay. The two names for this clay (bentonite and Montmorillonite) come from Fort Benton in Wyoming where large sources of the clay can be found and Montmorillon, France where the clay was first discovered (2).

Bentonite contains varying quantities of iron, alkalies and alkaline earths. It also contains mica, silica (1-20%) and feldspar. The geology of an area has a direct effect on the chemical composition of the soil in that region. Depending on the cations present, natural deposits of bentonite range in color from white to gray, yellow, green, or blue.

Bentonite can exchange cations and has both adsorbent and absorbent properties.

Two more scientific terms need to be understood in relation to the science of bentonite- adsorbent, and absorbent.

Absorption refers to taking materials into another substance e.g. water into a sponge.

Adsorption refers to accumulating materials on the surface of another substance e.g. dust on a cloth.

Bentonite can adsorb materials onto its surface and can absorb materials into its interlaminar space.

Because of the adsorptive and absorptive properties of bentonite, it is used in the clarification of wine by removing any materials that cause cloudiness in wine (3). Though some wine connoisseurs claim that bentonite also removes the aroma of wine.

Bentonite buffers are also used to protect against radioactive radiation (4).

It is also used to reduce phosphorus in aquatic systems.

The main use of bentonite clay is in the reduction of mycotoxins in animal feeds (5).

Super, but I am not a broiler chick, wine nor an aquatic system.

There are over 1,000 bentonite products for sale on Amazon. Clay for beauty purposes retails at $2 per pound weight while organic food grade costs closer to $5 per pound weight.

Is There Any Research?

There are over 1,000 publications on bentonite clay which includes just 17 clinical trials and just 11 human clinical trials. This compares poorly to vitamin C (another skin and wellness remedy I might use before the reunion) which has 60,000 publications and almost 3000 clinical trials.

Does Bentonite Clay Heal Skin?

An Iranian study examined the effect of a one-time application of zeolite-bentonite powder to the wounded skin of 24 Sprague-Dawley rats (6).

The zeolite-bentonite was used as a hemostatic agent i.e. an agent to control bleeding. Half of the rats had their wounds treated with normal saline and the other half had their wounds treated with zeolite-bentonite. Significant differences were noted in the healing ability of the two groups of rats in favor of the normal saline group. It was concluded that zeolite-bentonite could impair healing by vasoconstriction and inhibition of angiogenesis (new blood vessels). Both vasodilation and angiogenesis are needed for wound healing.

 Diaper dermatitis is caused by prolonged exposure of the skin to urine, moisture or stool. Bentonite is a potential candidate for diaper dermatitis due to its ad(b)sorptive capacity.

Another group of Iranian investigators studied the effects of bentonite and calendula on diaper dermatitis in 100 infants aged one year or under (7).

The infants were randomized to either bentonite or calendula. There was a statistically significant difference in improvements in the skin lesions within 6 hours in the bentonite group versus the calendula group (88% versus 54%). Additionally, statistically more lesions were completely healed within 3 days in the bentonite group as compared to the calendula arm (85% versus 52%). Both treatments were well tolerated.

A US-based group of investigators evaluated the effects of a cream containing quaternium plus bentonite in 211 study subjects with a known history of poison oak allergic dermatitis (8)

Both arms  of the study subjects (literally the physical arms of the study subject and not the arms of the study) were patch tested with urushiol (which is the allergic resin in poison ivy). One arm was pre-treated with the test cream while the other arm was used as the control. A total of 144/211 study subjects had positive skin reactions to urushiol. A statistically significant reduction in skin reactions was noted between the treated and control arms of the study subjects.

Bottom Line

There is some evidence from small studies that bentonite can help with diaper dermatitis and poison ivy allergic reactions. However, animal data do not support its role in controlling bleeding. This is not quite robust enough to make any recommendations.

 Does It Promote Weight Loss?

A 2015 paper in the journal Nature reported on findings relating to montmorillonite on lipids (9).

We know that bentonite can ab(d)sorb materials and this study showed that this property extends to the adsorption of lipids in the bowel.

Rats were fed either a normal diet, a high-fat diet or a high-fat diet plus bentonite for 25 days.

The bentonite prevented obesity (using histologic analysis of adipose tissue) and prevented weight gain in the high-fat diet rat group. Additionally, plasma lipids were lower in the bentonite treatment group as compared to the high-fat diet arm of the study. Increases in lipid excretion via feces was noted in the bentonite group and bentonite was identified in the feces.

The investigators also carried out a related in vitro study and examined the effect of bentonite on lipids in a glass tube. The bentonite was found to adsorb or immobilize the lipids in the glass tube. Putting all this together, the investigators concluded that the bentonite adsorbed or immobilized the lipids, thus preventing their absorption from the gut.

The same study group did a follow-on study which was published last year. This time they decided to study the cross-talk between adipose tissue, insulin resistance, systemic inflammation and gut dysbiosis which are believed to underlie obesity-related diseases (10). This is a complex and growing area of research. They studied bentonite in 30 young male mice who were again fed a normal diet, a high-fat diet or a high-fat diet plus bentonite.

This study again confirmed the results of the last study and showed that bentonite prevented high-fat diet induced obesity and weight gain. Additionally, the study showed that bentonite prevents insulin resistance, restores the integrity of tight junction in the gut and improves gut dysbiosis.

Bottom Line

The research here is very limited but does suggest a possible effect of bentonite on obesity and obesity-related diseases IN RODENTS. Sorry of for the big shouty capital letters but felt I had to do it, just in case someone is skimming the article. Big disclaimer here – these are all data from mice and rat models. It is way too early to try to apply this to humans.

Is It Good For Digestion?

Italian investigators carried out a prospective national case-control study in 804 children with acute diarrhea (11) The children were randomized to either oral rehydration solution alone or oral rehydration solution plus smectite. Administration of smectite was associated with a statistically significant decrease in the duration of diarrhea as determined by the stool frequency and consistency.

A multi-center double-blind placebo control study in 524 patients with irritable bowel syndrome was carried out in France (12). Patients were classified as having diarrhea dominant, constipation dominant or diarrhea/constipation alternating disease.

Looking at the overall study population, a non-statistically significant improvement in abdominal pain/discomfort was noted between the bentonite and placebo arms of the study. No difference was noted in the use of rescue medication or number of stools per day. However, a statistically significant improvement in pain was noted in the constipation dominant arm of the study.

Bottom Line

Smectite (and not specifically bentonite) helped with diarrhea in children. Bentonite helped with constipation dominant irritable bowel disease. This is a little confusing. If the mechanism of bentonite were consistent, would we not expect to find a benefit of bentonite in diarrhea dominant irritable bowel disease? This is an area that needs more research for clarification.

 Does it Have Anti Cancer Properties?

Bentonite obtained from India, Hungary, Argentina, and Indonesia was screened against cancer cell lines of the lung and brain in vitro (13).

Bentonite inhibited the growth of glioma cells (brain tissue) but promoted the growth of lung cancer cells.

In another study, bentonite induced oxidative stress and was cytotoxic to Caco-2 cells (cells from colorectal adenocarcinoma) (14).

Bottom Line

There is nothing useful to suggest a role for bentonite in cancer at this time.

Does It Help Thyroid Function?

Bentonite is used as an excipient (non-therapeutic additive in a medicine e.g. anti-disintegrating agent) in thyroid medications and is also used in the detection of thyroid antibodies. That is just interesting trivia and does not answer the real question.

A 1994 study in 20 fine wool lambs tried out an experimental diet of locoweed (Oxytropis sericea plus bentonite) for 35 days and found that locoweed did not affect growth hormone or prolactin levels but did result in a 50% decrease in T3 and T4 (thyroid hormone) levels (15). Oxytropis is a flowering plant.

More recently Chinese investigators evaluated the adsorbing ability of bentonite on thyroid hormone in the enterohepatic circulation (a recycling system between the liver and the gut) (16). An experimental rat hyperthyroidism model was used. The study showed that bentonite at a dose of 1mg/kg reduced T3 and T4 levels suggesting that bentonite has an antithyroid effect in rats.

Bottom Line

There are no human studies to link bentonite to ameliorating thyroid disease in humans.

 Does It Improve The Immune System?

Sodium bentonite was used as a feed additive in valuable freshwater stinging catfish, Heteropneustes fossilis (17). (What a great name).

Fish infected with Aeromonas hydrophila who were given a 5% and 10% bentonite enriched diets for 30 days had significantly improved growth performance, innate immunity, and disease resistance against the bacteria. Really, who cares?

Bottom Line

There is no proof that bentonite does anything for our immune systems.

 Does It Support Respiratory Health?

The Greek Centre For Disease Control and Prevention noted concerning signals from respiratory-related morbidity and mortality data coming from the island of Milos.

They speculated that perlite and bentonite dust from mining on Milos was responsible for the extra respiratory disease noted on the island.

To evaluate this theory, they undertook a study comparing respiratory disease on Milos to the data on respiratory disease on Oinofita which is an industrial region (18).

They used advanced statistical methods to control for possible confounders which as smoking, age and gender. The study showed a statistically significant increase in allergic rhinitis, pneumonia, chronic obstructive airways disease and bronchiectasis in Milos. There was also a non-statistically significant increase in asthma rates and deaths from pneumonia and chronic obstructive airways disease.

A 1994 case report describes post-mortem findings on a 73-year-old man who worked in the bagging section of a bentonite mine in Surrey, England (19).

The deceased had a three-year history of worsening shortness of breath prior to his death. Chemical analysis of material taken from his lung confirmed the presence of bentonite particles and pneumoconiosis. Pneumoconiosis is a disease of the lungs characterized by inflammation, coughing and lung fibrosis and is caused by inhalation of dust.

The physicians concluded that bentonite exposure can have a delayed effect and may have little effect on clinical presentation or radiological findings for up to 3 decades.

Workers in a Wyoming bentonite processing plant (Wyoming being the home of bentonite) were noted to have high rates of silicosis. High rates of silica in the mine dust was confirmed. A formal diagnosis of silicosis and silicotuberculosis was confirmed in at least 5 workers at the plant and lead to respiratory compromise and death (20). Silicosis is a pneumoconiosis caused by silica and silicotuberculosis is a dual diagnosis of silicosis plus tuberculosis.

Bottom Line

Bentonite is bad for your respiratory health.

Is Bentonite Clay Safe?

Bentonite clay is classified as generally regarded as safe by the FDA. That is except for a small issue of a baby bentonite product that was removed from the market because it was contaminated with lead.

  • Clay can cause hypertension in pregnancy and is best avoided.
  • Clay can impair the absorption of iron and worsen anemia.
  • It can also lower potassium levels due to its cation exchanging properties.
  • It is associated with lead poisoning, muscle weakness, intestinal blockage and respiratory problems.

The safety of calcium montmorillonite was  studied in 50 subjects (23 males and 27 females) who were randomly divided into two groups for a two-week study:

  • group 1  received nine capsules containing 1.5 g/day,
  • group 2 nine capsules containing 3.0 g/day (21).

Side effects noted were predominantly related to the gastrointestinal tract but there was no significant difference between the two dosing groups. Additionally, no significant differences were found in the complete blood count, liver and kidney function, vitamins A and E, and minerals.

Bentonite was also shown to be safe in Ghanian children who took bentonite for two weeks (22).

The pulmonary risks of occupational or environmental exposure to bentonite have been covered above and are really substantial.


As mankind evolves, some indigenous practices continue to serve us but some do not. There are three ways of being exposed to bentonite: lungs, skin or gastrointestinal tract.

In summary:

  1. bentonite may have a role topically for skin lesions but has not been conclusively proven (a ‘maybe/ possibly’ scenario)
  2. there is no solid evidence to support the use of bentonite orally (a ‘not sure’ scenario)
  3. inhaling bentonite is really not safe (a ‘definitive no’ scenario).

So what were those celebrities yakking about? Shailene Woodley recommends eating clay having learned about this from an African taxi driver. She blogged ‘ Seriously—ask your taxi drivers where they are from and about their customs. You will learn a lot’.

I have great respect for local African healers and indigenous medicine having worked in East Africa for 10 years.  Equally, I might enjoy talking to taxi drivers (from anywhere) but do not mix up taxi drivers with evidence-based science.

I was initially disappointed to learn that bentonite was not going to help me look like a diva at my class reunion, but have been feeling less worried since I heard that most of my friends have been photoshopping their Facebook pictures.

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