Chitosan

Chitosan is a form of fiber that is found in chitin, the main material in the exoskeleton shells of crustaceans. In the late twentieth century, scientists began experimenting with chitosan as a possible medicine or dietary supplement. Most claims about chitosan relate to its uses when ingested into the digestive system. Like other forms of fiber, it is not digestible but may bind with fat and other potentially unhealthy materials and remove them from the body before they can be absorbed. Tests of this claim have been highly mixed. Some scientists and medical personnel recommend chitosan for other tasks, including cleaning the teeth, reducing inflammation, and improving the healing of damaged skin.

Background

Crustaceans are a group of animals found in many habitats, most often in water. Although there are more than 50,000 kinds of crustaceans, they all share a few key similarities. Most notably, they have a carapace, or shell. This shell is more specifically referred to as an exoskeleton because, like the internal skeletons of other animals, it helps give structure to the body. The exoskeleton is also vital for defense as it protects vulnerable fleshy areas.

An exoskeleton presents an ongoing difficulty for a crustacean as it proceeds through its lifespan. A crustacean’s body grows over time, but its exoskeleton does not; once formed, it stays at one size and location like a plate of armor. To allow the body to grow and develop, a crustacean undergoes a process called molting. During molting, the existing shell comes off and a new, larger shell forms.

Prior to molting, a crustacean absorbs calcium carbonate and other materials from the outgrown shell and then swells its body to push the shell away from the flesh. After about fifteen minutes of labor, the crustacean will have extracted itself from the exoskeleton. However, the animal is now unprotected and vulnerable and must use extra caution during the coming weeks while it grows a new, larger carapace. This new carapace contains many materials, mainly a fiber-like substance known as chitin.

Since ancient times, people have used crustaceans for food, and many cultures today value seafood for its taste and nutritional benefits. Scientists have also explored possible uses of crustacean parts, including indigestible parts such as the shell as a medicine or dietary supplement. In particular, some scientists have proposed that chitosan, a material derived from the chitin in crustacean exoskeletons, may offer an array of health benefits for humans.

Overview

Chitosan is a fiber found in the exoskeleton chitin of crustaceans such as crayfish and crabs. Like other forms of fiber, chitosan is not digestible to humans. If eaten, it would pass through and out of the digestive system without the body absorbing any nutrients from it. Therefore, it would seem that the body would receive little or no benefits from ingesting chitosan.

However, some scientists have proposed that the indigestibility of chitosan can be used as a means of improving internal health. Dietary fiber, while not digestible, helps to clean the digestive system and provides other benefits for the body. Proponents of chitosan claim that this material is even more effective than regular dietary fiber because, as it passes through the intestines, chitosan may bind to small molecules of fat from foods. Then, when the chitosan passes out of the body, it carries the fat, thus keeping the fat from being absorbed into the body.

This proposed interaction between chitosan and fat has led many to believe that taking chitosan supplements can help people cut fat, lose weight, and experience related benefits including reduced levels of harmful cholesterol. These supplements are most often taken in powdered form via a pill, though they can be used in other ways, including baking them into food.

Major examination of chitosan’s possible health benefits began in the late 1990s. Research tests provided mixed results. Many tests seemed to prove the claim that chitosan was a powerful dietary aid, with some tested individuals experiencing a significant reduction of weight, cholesterol, and blood pressure. This seemed particularly prevalent among people with type 2 diabetes—some had a reduction in harmful cholesterol but no significant weight loss.

However, many other tests failed to show any significant benefit to chitosan. In some cases, test participants taking chitosan supplements did not experience any beneficial effects and even saw a slight elevation in the level of triglycerides, a type of fat found in the blood. Scientists have also cautioned users about possible negative side effects of chitosan use. These include the disruption of the body’s absorption of fat-soluble vitamins, including A, D, E, and K, as well as fat-soluble medications including birth-control pills. Additionally, chitosan users who are allergic to shellfish may want to take special cautions or avoid chitosan.

Proponents of medicinal chitosan have also used the material for a range of other health purposes. Scientists continue to study the uses of chitosan in these contexts and suggest that further investigation is necessary to ensure that chitosan is beneficial and safe. Some of these uses include treatment for Crohn’s disease, a condition involving the inflammation of the bowels; dental cavities and swollen gums; and the effects of kidney disease or failure.

Chitosan is also being evaluated as a treatment for the skin during plastic surgery. Scientists have determined some potential benefits of chitosan in helping wounds to heal and reducing scar tissue during skin grafts and similar procedures. In addition, pharmacists sometimes add chitosan to pills as filler, a dissolving agent, or a means of improving taste.

Bibliography

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“Dietary Fiber: Essential for a Healthy Diet.” Mayo Clinic, 2019, www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/in-depth/fiber/art-20043983. Accessed 6 May 2019.

Gades, Matthew D. and Judith S. Stern. “Chitosan Supplementation and Fat Absorption in Men and Women.” Journal of the Academy of Nutrition and Dietetics, Jan. 2005, jandonline.org/article/S0002-8223(04)01630-X/pdf. Accessed 6 May 2019.

Goosen, Mattheus F.A. Applications of Chitin and Chitosan. Taylor & Frances Limited, 1997.

Harding, David and Hitoshi Sashiwa. Advances in Marine Chitin and Chitosan. MDPI Books, 2015.

Moore, Shelley. “What Is Chitosan Used For?” Livestrong, 2019, www.livestrong.com/article/225178-what-is-chitosan-used-for/. Accessed 6 May 2019.

Stevens, Bradley G. “Molting: How Crabs Grow.” National Oceanic and Atmospheric Administration, www.afsc.noaa.gov/kodiak/shellfish/cultivation/crabgrow.htm. Accessed 6 May 2019.

“The Major Groups of Crustaceans.” Marine Education Society of Australasia, 2015, www.mesa.edu.au/crustaceans/. Accessed 6 May 2019.