Getting dirty to stay healthy is a foreign notion to many of us - and eating dirt to stay healthy even more so. While it may seem primitive, eating earth (geophagy) is a universal phenomenon even today. Soil consumption among animals appears to be an instinctive behaviour to overcome nutrient deficits, and some animal feeds still contain small amounts of soil. This may be because soil, including kaolinitic and montmorillonitic clays, contains considerable amounts of organic material, including live microorganisms.

Humans have removed themselves - at least consciously - from such practices, yet we do it without thinking every time we take indigestion remedies such as Tums, Remegel, Maalox and Kaopectate. These products are made of earth compounds such as clays (kaolin) or certain earths (calcium carbonate). Eating salt is another way that we surreptitiously ingest rock compounds.

For people with inflammatory bowel disease, deliberately ingesting ‘dirt’ may reap benefits. According to Canadian researchers (Can J Microbiol, 1985; 31: 50-3), a form of clay known as bentonite can absorb and remove viruses, aflatoxins (produced by some types of fungi and moulds), pesticides and herbicides from the body. Early studies showed that just two tablespoons in distilled water daily can relieve diarrhoea in 97 per cent of individuals in just over three days (Med Ann DC, 1961; 30: 328).

Bentonite clay is available from Neal’s Yard (0845 262 3145), £1.20 per 100 g, and The Herbal Apothecary (0116 260 2690), £4.99 for 500 g.