An ancient alternative to antibiotics: Clays

The use of clays in medicine is a practice developed in ancient times, recorded in antiquity (Aristotle; 4th century BC), and the health benefits have been documented on all continents [1]. But few in the field of infectious disease research think seriously about why natural minerals were used, other than as a pre-historic Band-Aid or digestive [2].

I’m a geologist, but I grew up in a family of physicians and was acquainted with the fascinating pictures of diseases in medical textbooks. I never was fond of bacterial biofilms (slime), but somehow I was drawn to playing in the mud. Professionally, I ended up studying clays, which mixed with water makes mud (also slime), called a poultice when used in medical applications. The chemistry of particular clays, when hydrated, is key to their antibacterial properties.

Clays are microscopic minerals (<2µm) that comprise sediments. Because of their small particle size and layered structure, one group of clay minerals, called smectites, have a surface area up to 700 m2/g [3]! That’s an enormous mineral surface in contact with water; just 7g of this clay could cover a football field in a monolayer, creating an immense chemical factory.

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