Chitosan (Deacetylated Chitin)

Chitosan is a linear polysaccharide composed of β-(1→4)-linked D-glucosamine (deacetylated units) and N-acetyl-D-glucosamine (acetylated units), derived from the deacetylation of chitin (typically ≥75% degree of deacetylation). It is not a traditional nutrient source and contains negligible macronutrients (essentially 0 kcal, 0 g fat, 0 g digestible carbohydrate, 0 g sugar). Key bioactive characteristics: Molecular weight ranges from 50–2000 kDa depending on processing, with low molecular weight (LMW, <150 kDa) forms generally exhibiting higher bioavailability and solubility. It is a rich source of dietary fiber (approximately 80–90% on a dry weight basis), classified as an insoluble, non-digestible polysaccharide in the human GI tract. Contains approximately 5–8% nitrogen by weight due to its amine groups, which are responsible for its cationic nature at acidic pH (<6.5). Ash content is typically 0.5–2.0%, with trace minerals including calcium (0.1–0.5%), phosphorus, and residual sodium depending on source (primarily crustacean shells: shrimp, crab, lobster). No vitamins are present in meaningful quantities. Key bioactive compounds and functional groups: free amine groups (–NH₂) at the C-2 position confer fat-binding capacity (can bind 4–5 times its weight in lipids in vitro), bile acid-binding activity, and antimicrobial properties. Chitosan oligosaccharides (COS, MW <10 kDa) are the most bioavailable form, with intestinal absorption estimated at 8–12%, whereas high molecular weight chitosan is largely unabsorbed and acts locally in the GI tract. Bioavailability is highly pH-dependent: soluble and protonated at gastric pH (~1.5–3.0), but precipitates and becomes insoluble at intestinal pH (>6.5), which limits systemic absorption of intact polymer. Typical supplemental doses range from 1,000–3,000 mg/day. Contains no significant levels of essential amino acids, fatty acids, or fat-soluble vitamins. Moisture content in commercial preparations is generally 5–10%.