sugar substitute: see sweetener, artificial.

fat substitute, substance used to replace dietary fat in the manufacture of foods. Fat substitutes are made in a variety of ways, mostly by manipulating natural food products such as egg whites, whey, and oats. Fat substitutes try to mimic the texture and flavor of fat while providing fewer calories and less metabolizable fat. The dietary consequences of consuming fat substitutes are under scrutiny.

blood substitute, substance that mimics the function of blood. Blood substitutes typically concentrate only on reproducing the function of hemoglobin, the molecule that carries oxygen through the body, and do not attempt to replicate the blood's other functions. Blood donated by humans must be refrigerated, can be contaminated by such diseases as AIDS and hepatitis, and is often in short supply. Designers of blood substitutes hope to eliminate these problems and develop genetically engineered or chemical products that will be tolerated by people of all blood types. Some blood substitutes under development use hemoglobin derived from human blood that is too old for use in blood transfusions.