"...exhibits bactericidal activity against E. coli, ESBL [Extended-Spectrum Beta-Lactamases] E. coli, S. enterica serovar Typhimurium, P. aeruginosa, and M. marinum, and significantly reduces growth of S. aureus, PRSA, MRSA, and nonpathogenic M. smegmatis approximately 1,000-fold compared to cultures grown without added mineral products."
Falkinham et al. studied the antibiotic and antimicrobial activity of red clays from the Kingdom of Jordan (Jordan's Red Soil). The authors conclude that the antibiotic activity of Jordan's red clays is likely due to the proliferation of antibiotic-producing bacteria, that is induced by the clay.
Clays contain massive amounts of trace minerals, necessary for good health. (For example, it is common to see as many as 75 different trace minerals in Montmorillonite clays.) This may explain many of the healing properties of clay. Specific trace minerals that various clays possess vary very widely. Also, the amount of any particular trace mineral in any specific clay varies a lot among clays from different locations. For example, the amount of iron in various bentonite clays can vary from well below 1%, and up to 10%
According to one hypothesis,
"In the stomach, the negative electrical charges of tiny clay particles attract positively charged toxins from stomach fluids. This clumping prevents very small particles, such as toxic molecules, from passing through the walls of the intestines and entering the bloodstream."
The author notes further that, together with the clay, the toxins are then eliminated harmlessly out of the body through the kidneys, despite not entering the bloodstream, or through the bowel.
There are many over the counter remedies for internal use that contain clay. The examples are the tablets such as Kaopectate (Upjohn), Rheaban (Leeming Div., Pfizer), and Diar-Aid (Thompson Medical Co.). The labels on all of these showed the active ingredient to be Attapulgite, each tablet containing 600 (or 750 mg) of this component along with inert materials or adjuvants.
Numerous medicines also use Kaolinite clay, which has long been a traditional remedy to soothe an upset stomach. Also, Kaolin is or has been used as the active substance in liquid anti-diarrhea medicines such as Kaomagma. Such medicines were changed away from aluminium substances due to a scare over Alzheimer's disease, but have since changed back to compounds containing aluminium as they are most effective.
Clays have proven to be effective against the Candida albicans infections. This is a type of a fungus (or yeast), which is a causal agent of opportunistic oral and genital infections. This type of infection, known as Candidiasis, also may enter the bloodstream, and become a systemic Candida infection.
In 1971, the influence of bentonite clay on the growth of Candida lipolytica has been studied by Maignan and Pareilleux. A clearly unfavorable effect of bentonite on Candida lipolytica growth in vitro was observed 
Later on, the same authors have concluded that,
"The respiration of Candida lipolytica on n-tetradecane is decreased in the presence of bentonite."
According to a 2009 study by Ghiaci et al. published in Applied Clay Science, bentonite clay acts very strongly against Candida:
"The modified bentonite with monolayer surfactant (BMS), was the best support, for immobilization."
Chelation therapy is the use of chelating agents to detoxify poisonous metal agents such as mercury, arsenic, and lead by converting them to a chemically inert form that can be excreted without further interaction with the body, to treat cases of severe heavy metal poisoning. It is also used as a dangerous, scientifically unsupported treatment for heart disease and autism.
Clay has proven to be a very effective chelating agent.
Oyanedel-Craver and Smith have studied sorption of four heavy metals (Pb, Cd, Zn and Hg) to 3 kinds of bentonite clay. The overall conclusion of the study was that the organoclays studied have considerable capacity for heavy metal sorption.
"[B]eidellitic montmorillonite is efficient for C-IBS patients (suffering from constipation-predominant irritable bowel syndrome)..."
Aflatoxins are naturally occurring mycotoxins that are produced by many species of Aspergillus, a fungus. Aflatoxins are toxic and among the most carcinogenic substances known. They cause Aflatoxicosis, which can afflict both animals and humans.
Bentonite clay has proven to show a very strong protective effect against Aflatoxicosis.
"The addition of bentonite or HSCAS [hydrated sodium calcium aluminosilicate] to the AF-contaminated diet diminished most of the deleterious effects of the aflatoxin. Pathological examinations of liver and kidney proved that both bentonite and HSCAS were hepatonephroprotective agents against aflatoxicosis."
"The addition of sodium bentonite was significantly effective in ameliorating the negative effect of aflatoxicosis on the percentage and mean of phagocytosis."
Pregnant women in many indigenous and traditional cultures very commonly consume clay, especially to reduce nausea. Since clays contain a very large amount of trace minerals of all sorts, this most likely contributes to the development of a healthy fetus.
Scientific analyses of clays selected by pregnant women in Nigeria show that eating as little as 500 mg (about the equivalent of two Tylenol capsules) per day can satisfy nearly 80 percent of a pregnant woman's calcium needs.
The effects of weightlessness on human body were studied by NASA back in the 1960s. Experiments demonstrated that weightlessness leads to a rapid bone depletion, so various remedies were sought to counter that. A number of pharmaceutical companies were asked to develop calcium supplements, but apparently none of them were as effective as clay. The special clay that was used in this case was Terramin, a reddish clay found in California. Dr. Benjamin Ershoff of the California Polytechnic Institute demonstrated that the consumption of clay counters the effects of weightlessness. He reported that "the calcium in clay ...is absorbed more efficiently ... [clay] contains some factor or factors other than calcium which promotes improved calcium utilization and/or bone formation." He added, "Little or no benefit was noted when calcium alone was added to the diet."
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