Chitosan is actually a substance taken from chitin, a polysaccharide that's found in the exoskeletons of crustaceans. It is processed out by removing the shells from shellfish like shrimp, lobster, and crabs.

The human use of chitosan can be traced back to 1811 when chitin, the source from which it is derived, was first discovered by Braconnot, a professor of natural history in France. According to historians, while Braconnot conducted research on mushrooms, he isolated what was later to be called chitin.

Some 20 years later, an article on insects was published, which noted that a similar substance was present in the structure of insects and plants. The author called this substance "chitin." Basically, the name chitin came from the Greek word meaning "tunic" or "envelope". In 1843, Lassaigne showed the presence of nitrogen in chitin.

After the discovery of chitin came chitosan. It was first observed by Rouget during his experiments on chitin. Rouget observed that the compound of chitin could be manipulated through chemical and temperature treatments and become soluble. In 1878, Ledderhose showed chitin to be made of glucosamine and acetic acid. It was not actually until 1894 that Hoppe-Seyler named this supstance "chitosan."

By the early 20th century, a great deal of research had been performed on the subject of chitosan. It involved the sources of chitin, specifically crab shells and fungi. It was the work of Rammelberg in the 1930s that led to confirming chitosan in these sources. Experts determined (by hydrolyzing chitin) that chitin is a polysaccharide of glucosamine.

The 1950s arrived, and x-ray analysis advanced the study of chitosan in fungi. Only recently has technology proved reliable in identifying the presence of chitin and cellulose in cell walls. The first book on chitosan was published (in 1951) 140 years after Braconnot made his initial observations.

In the early 1960s, chitosan was studied for its ability to bind with the red blood cells. The substance was considered a hemostatic agent. For three decades now, chitosan has been used at water purification plants for detoxifying water. It gets spread over the surface of the water, where it absorbs grease, oils, and other potential toxins.

Today, it is famous as a dietary supplement that is good for weight loss. In Japan and Europe it has been marketed for weight loss for about 20 years. Many people call it the "fat blocker". It is this recent use for chitosan that brought the otherwise mundane substance to public attention.