Today I’m really excited to share with you an interview on clays (specifically bentonite) with Ian Hutcheon, Professor Emeritus in Geochemistry at the University of Calgary. Bentonite clay has quite a bit of lore surrounding it in the DIY world. It’s not at all difficult to find people suggesting that ingesting it or applying it topically will result in miraculous “detoxing”. Its charge is frequently cited as the reason the clay should never, ever come into contact with metal of any kind, lest the clay be rendered useless or harmful. A quick search of Pinterest tells me I can use it to detoxify my armpits, heal bug bites, make mascara, eliminate food allergies, cure food poisoning, and prevent breast cancer. There’s enough ra-ra sentiment out there about bentonite clay to pique the interest of pretty much anyone. Whenever I publish a recipe calling for a clay that isn’t bentonite, people want to know if they can use bentonite instead. Out of all the ingredients I use, not one has prompted more people to call me a know-nothing idiot than bentonite clay—the “no metals” thing gets people quite aggressively worried. However, for all the worry, it’s been difficult for me to find verifiable information about what is actually up with bentonite clay in the realm of DIY and beauty. So, I sought out an expert and asked.
Generally speaking, what is “clay”?
“Clay” is a general term that really refers to grain size (less than 0.002mm). However the term is ambiguous because there also are minerals referred to as “clay minerals”. Frequently, clay minerals are smaller than 0.002mm, but they can be much larger. So it is a bit confusing, a mass of clay (less than 0.002 mm grains) may be comprised of minerals (for example very fine quartz) that are not clay minerals. Alternatively, a mass of clay minerals may have grains that are larger than 0.002 mm. The most commonly identified clay minerals are kaolinite, illite and bentonite (montmorillonite and smectite are similar minerals), although there are probably more than 100 different clay minerals. All clay minerals are hydrous (contain water as part of their crystal structure) and most are a framework of silicon and aluminum with many other elements as part of their structure.
How does bentonite clay differ from clays like kaolin or illite?
Kaolinite is a bit unique as a clay minerals because it has a very narrow range of composition—it is pretty much all silicon, aluminum and water. Illite has a fairly restricted chemical composition also (add potassium, iron and magnesium mainly). Bentonite is much different—it is primarily silicon, aluminum and water, but can have nearly any element as part of its composition.
The most important difference between Bentonite (smectite, montmorillonite) and Illite or kaolinite is that its crystal structure, and therefore its chemical composition, is variable over a wide range. Whereas kaolinite and Illite have relatively well defined crystal structure and a narrow range of chemical composition, Bentonite has many variations in structure and composition.
Essentially all clay minerals have to varying degrees a weak electric change on their crystal surface. Some also have ions (like sodium or calcium) that are weakly bound to their structure.
What makes bentonite clay unique from a chemistry and geology point of view?
The main factor that makes Bentonite unique is its wide variation in crystal structure that results in the ability to absorb large quantities of water and the ability to exchange ions in, or absorbed, to its structure with ions dissolved in water. This ability leads to properties that are unique (at least in their magnitude) to this clay mineral.
Could bentonite clay be used to “detox” the body by absorbing heavy metals (internally or externally)?
In theory, because of the ability to exchange ions with water (humans are mostly water), Bentonite could be used as a detoxification agent. The idea would be that a relatively benign ion, for example sodium, would be exchanged from the Bentonite, for a toxic metal in water in body tissues. Although this [ion exchange] might be a way of removing toxic heavy metals within the body, I’m not sure the chemistry that would need to be understood is being invoked by someone taking bentonite to detoxify themselves. To be useful as a healthy related aid, it would be necessary to identify the ions in question that would be removed and “pre condition” the clay to exchange these ions for something more benign. That is not trivial chemistry.
Claims people make about detoxification need to be considered in the context of the ion exchange properties of the clay mineral in question. The idea that ion exchange might take the bad heavy metals out of your system by exchange for benign ions like sodium or calcium would need to be considered in the context of a wide range of chemical and physical factors that will determine how much toxic metals can be attracted to the clay.
I don’t think there’s any effective way that Bentonite could be used externally for detoxification unless it was on an open wound.
Detoxification in this instance would be a complex chemical reaction and unless specific metal toxins were identified and the necessary chemical processes quantified, I personally would be reluctant to ingest Bentonite. Think back to the very fine particle size. The particles in Bentonite are primarily silicon aluminum (silicate), not very different in grain size, chemistry and physical properties than asbestos, a known carcinogen.
Is there any risk associated with bentonite clay contacting metal?
In water there’s the possibility that it could exchange ions with the metal. If the metal is toxic and then the Bentonite is ingested I could see that being an issue. However, normally there should not be any issues.
I am skeptical that simply contacting clay with a metal spoon would do much, especially if the clay is dry. For any kind of transfer of metal ions between clay and a metal, there would need to be water present so the metal could be in ionic form. Even with water present, unless the water was either very acidic or very basic (alkaline), there would not be any significant dissolution of metals and therefore no ion transfer. In general terms, anything with a pH below 3 would be considered acidic or strongly acidic, a pH above 10-11 would be very basic. Normal surface water ranges from pH 4-8, with the majority around 5-7. These are general terms. The effect of pH on a particular reaction would depend on the nature of the reactants, including the clay.
Would you recommend the consumption of bentonite clay?
Definitely not. As I noted above, the fine grain size and poorly defined chemical composition makes it a potentially dangerous substance. If the chemical composition is known it would mitigate some of the risk, but Bentonite is usually mined from geological deposits that are not necessarily well characterized, either chemically or in terms of other contamination.
What are your thoughts on the use of bentonite clay as a poultice/mask or toothpaste?
I’m not sure how it would work as a poultice. It is a mild abrasive, so it would be helpful in toothpaste. I think I’d be worried about removing tooth enamel, since the abrasive would be a silica based material, which is considerably harder than the Calcium phosphate material that comprises tooth enamel.
- In theory it is possible for bentonite to perform a detox function; however, the specifics of whatever that exchange might be would be very difficult to quantify or guarantee, and the risk of ingesting bentonite outweighs the potential benefits. In short: in theory the idea is good, but in reality it’s much messier and much more complicated than just drinking a slurry of bentonite clay and hoping it sucks all the lead out of your body.
- Bentonite clay should not be ingested as its chemical composition is unknown (it is not uncommonly recalled for dangerous lead levels) and it is similar in some physical and chemical properties to asbestos.
- When mixed with water, bentonite clay could possibly exchange ions with metal. So, when bentonite clay is dry, contact with metal is of absolutely no concern. In short: Use your metal measuring spoons, it’s fine.
- You probably shouldn’t use it to brush your teeth as bentonite contains components that are harder than tooth enamel.
- Bentonite clay should not be mixed with heavy metals and then ingested, but in general you shouldn’t be playing with heavy metals.
- From Ian: “I’m certain there are a number of things people do with clays that are helpful, beneficial for some process or other, and harmless. Extravagant claims about their properties are probably not true, or at least difficult to verify.”
A huge thank you to Ian for taking the time to answer my questions!