Chitin is the first polysaccharide identified by man. Chitin and its numerous oligomeric and monomeric, acetylated or deacetylated derivates have many physiological functions and applications. Chitin is found in the cuticles of arthropods and is a major constituent of cell walls from fungal, yeast and algae, from where chitin can be extracted chemically, enzymatically or by fermentation. The principal sources of chitin and chitosan are actually crustacean shells. Worldwide, more than 13.000.000 tons of crustaceans are caught from marine habitats each year, thus generating huge amounts of food waste. The unique biodegradability, biorenewability, biocompatibility, physiological inertness and hydrophilicity of chitin and chitosan make them of high interest for research and industry. In this chapter, we review the use of chitin, chitosan and their oligomers and monomers as food additives. In particular, their use in the regulation of lipid digestion and hypocholesterolemia, their functioning as an antigastritic agent and prebiotic is highlighted. Literature shows that oligomerization and the degree of deacetylation influences the development of chitin/chitosan-based nutraceuticals. The absence of chitinases and chitosanases in the human gut renders those biopolymers resistant to even partial degradation. For food applications, they are used as emulsifying, fining, thickening and stabilizing agents, antioxidants, and low calories food mimetics.