A reader expressed the following comment after reviewing the recently posted The Yoga of Fasting: Is it Good for you or Not?:

“In your interesting article about fasting, you omit something about fasting with water which has been added with clay.  I know first hand that in that way even 28 day fasting is less dangerous.”

I’m grateful to the reader for bringing up the subject of adding clay to water fasts to prevent toxicity.  Clays are promoted as cleansers by many marketers.

Although it sounds strange, humans and animals have been eating clay and other forms of dirt for hundreds of years.  If you’re curious, here’s an interesting article about the history of clay ingestion.

There are many theories about why we’ve done that as a species. The foremost ones are that by eating clay we are taking in minerals lacking in our diets, that we are preventing the absorption of naturally occurring toxins such as aflatoxins from molds, and that in times of famine we have simply needed to fill our bellies with something.

It’s true that clay absorbs toxins like PCBs, but there are many types of clay, and each type will have different absorptive properties that cause it to bind to one thing but not another. Primarily bentonite clay in used during cleanses, but there are different forms of that as well.  Although it likely does bind some, I haven’t found any direct evidence that bentonite specifically absorbs particular environmental toxins released with fasting.  Its ability to limit the absorption of primary vitamins and nutrients has not been well studied either, but there is some evidence that it significantly impairs the ability of the intestines to absorb zinc which is needed by more than 300 different types of enzymes for them to function properly.  The antioxidant Cu-Zn -superoxide dismutase (SOD) has been shown to have decreased activity when low zinc levels are present.  The result is excess free radicals that damage cells and lead to disease and cancer, and that’s exactly the opposite intention of a fast.

When it comes to subtle damage like that caused by free radicals, there’s no way to know just by how you feel whether you were hurting or harming yourself with a 28 day fast with clay.  Other dangers exist beneath the surface too, ones that you won’t feel or be conscious of while fasting.  Lead, mercury, arsenic, and other environmental toxins may contaminate the source, even those obtained commercially as there is little regulation or quality control.

Also, don’t forget that when fasting on water with clay for 28 days, you won’t be renewing glutathione which runs out after about the first 24 hours.  Glutathione is needed to prevent toxicity and free radical damage.  The metabolic rate slows down after a couple of days without nutrition, and eating clay provides no source of energy to prevent that.  With a slower metabolic rate, when you go back to eating real food, the same number of calories will cause you to gain more weight than they did before the fast.

Fasting for 24 hours on water only is healthy.  Plenty of evidence is accumulating to prove it.  Fasting longer than that on water only, or water with clay, may cause more harm to the body than good.

Eating Clay