Bentonite and clay (kaolin) are readily hydratable aluminium silicates. Bentonite is used to assist in the clarification of juices, beverages, and other food products, as a binding agent for the preparation of pelleted animal feeds, and as an ingredient of coatings and adhesives for food packaging materials. The Select Committee is not aware of any instance in current practice where use of bentonite in the processing or packaging of foods for human consumption results in the retention of more than minute amounts in the final product and assumes the current practice will continue. Nevertheless, food grade standards for bentonite should be established, particularly with respect to soluble constituents and heavy metal cations that may be present in commercial products.
Clay (kaolin) is GRAS only as an ingredient of paper and paperboard products used in food packaging. There are no data available concerning the amounts of clay (kaolin) that might migrate to foods from this source but the Select Committee believes the amounts can only be very small.
Apparently, very little, if any, bentonite is absorbed after oral administration and as much as 3 percent in the diet has no observable adverse effects on experimental animals. Diets containing 10 to 25 percent can cause growth retardation both because of dilution of the diet and the tendency of some bentonites to adsorb vitamin A in mixed diets and otherwise interfere with the absortion of this vitamin in the intestinal tract.
Very little, if any, kaolin is absorbed after oral administration. Bowel obstruction occurs at very high doses, about 100g per kg body weight in rats being fatal to 1 percent, about 150 per kg being fatal to 50 percent.
No adverse effects have been observed at dietary levels as high as 12 percent in experimental animals. The human therapeutic dose for diarrhea is about 250 to 1,000 mg per kg.
It is noted that clay (kaolin) administered under conditions that damage mucosal tissues, tends to produce granulomatous lesion. However, the generally high tolerance for kaolin under normal conditions makes it improbable that such effects could result as it is currently used.
Based upon consideration of the data presented in this report and assuming the establishment of appropriate food grade standards fro bentonite, the Select Committee concludes that:
There is no evidence in the available information on bentonite that demonstrates or suggests reasonable grounds to suspect, a hazard to the public when it is used in the manner now practiced or that might reasonably be expected in the future.
There is no evidence in the available information on clay (kaolin) that demonstrates, or suggests reasonable grounds to suspect, a hazard to the public when it is used as an ingredient of food packaging materials in the manner now practiced or that might reasonably be expected in the future.