Chitin is a natural fiber and one of the most abundant polysaccharides on the planet, second only to cellulose. This material serves as a primary structural component, forming the protective exoskeletons of insects and the rigid cell walls of fungi. Its function is often compared to that of keratin, the protein that makes up hair and nails in humans.
Edible Sources of Chitin
The most common dietary sources of chitin come from three categories: crustaceans, fungi, and insects. While many people do not consume the hard outer shells of crustaceans like shrimp and crab directly, small amounts can be ingested. These shells contain between 15% and 40% chitin by dry weight, making seafood processing waste a major commercial source for its extraction.
Fungi are another significant source of dietary chitin. When we eat common mushrooms such as shiitake or portobello varieties, we consume the chitin that comprises their cell walls. This chitin content provides structural integrity to the fungus, similar to how cellulose supports plants.
The practice of entomophagy, or eating insects, is a growing source of dietary chitin. Crickets, grasshoppers, and mealworms are examples of insects with chitin-rich exoskeletons that are increasingly farmed for human food. These insects are viable sources for both direct consumption and for the industrial extraction of chitin and its derivatives.
Chitin and Human Digestion
When consumed, chitin behaves much like other forms of dietary fiber. It passes through the body largely undigested because most humans do not produce sufficient quantities of the enzyme needed to break it down. While this enzyme, acidic mammalian chitinase (AMCase), is produced in the stomach, its levels in many people are not high enough to fully degrade large amounts of ingested chitin.
This indigestibility allows chitin to function as a prebiotic. It travels through the digestive system intact, eventually reaching the large intestine where it becomes a food source for beneficial gut bacteria. These microbes ferment the chitin, a process that supports their growth and influences the overall health of the gut ecosystem.
Studies have shown that consuming chitin can promote the growth of beneficial bacteria like Bifidobacterium and Lactobacillus. For instance, research involving daily consumption of cricket powder was associated with an increase of these beneficial microbes. This fermentation process also produces short-chain fatty acids, which have various effects on the body.
Health Implications of Dietary Chitin
By nourishing beneficial gut bacteria, chitin supports a healthy gut microbiome, which is connected to digestive function, nutrient absorption, and intestinal health. A well-supported gut microbiota also contributes to a properly functioning immune system. Research in mice has shown that chitin consumption can activate an immune response linked to reduced weight gain and less body fat.
Dietary fiber, including chitin, can also contribute to feelings of fullness, or satiety, which helps in managing appetite. This may play a role in weight management strategies. Some studies suggest the immune response triggered by chitin has metabolic benefits, potentially reducing weight gain and body fat.
A common point of confusion involves shellfish allergies. These allergic reactions are caused by proteins, such as tropomyosin, found in the flesh of shellfish, not by the chitin in their shells. Although chitin is not the allergen, individuals with a shellfish allergy are often advised to avoid products derived from shellfish shells because of the potential for cross-contamination.
Chitin in Food Production and Supplements
Beyond whole food sources, chitin is processed for various uses in the food industry. It can be used as a natural food additive, serving as a stabilizer or thickener. However, a chemically modified derivative of chitin, known as chitosan, is more widely used in commercial applications, including dietary supplements.
Chitosan is produced by treating chitin with an alkaline substance in a process called deacetylation, making it more soluble. Chitosan is frequently marketed in supplement form for weight management and cholesterol control. The European Food Safety Authority (EFSA) has authorized the claim that a daily intake of 3 grams of chitosan contributes to maintaining normal blood cholesterol levels.
This processed form can be incorporated directly into foods like pasta or baked goods to create functional food products. Chitosan’s ability to bind with fats and cholesterol in the digestive tract is the primary mechanism behind its use in these supplements. It can also be used as a carrier for encapsulating compounds like vitamins, protecting them from degradation in the stomach.