Alginate (Sodium Alginate)

Sodium alginate is a purified polysaccharide extracted primarily from brown seaweed (Phaeophyceae), composed of linear chains of β-D-mannuronic acid (M blocks) and α-L-guluronic acid (G blocks) linked by 1,4-glycosidic bonds. As a refined compound, it contains negligible calories (~2-3 kcal/g in some estimates, though largely indigestible), no meaningful fat, and no protein in purified form. Carbohydrate content is essentially 100% of dry weight, entirely in the form of non-digestible dietary fiber (soluble fiber). It is not hydrolyzed by human digestive enzymes, classifying it as a functional dietary fiber with zero net caloric contribution in practical use. Sodium content is notable: pure sodium alginate contains approximately 8–10% sodium by molecular weight (sodium counterion to the uronate groups), relevant for individuals monitoring sodium intake. No significant vitamins are present in the purified compound. Mineral bioavailability is a key concern: alginate strongly binds divalent cations including calcium (Ca²⁺), iron (Fe²⁺/Fe³⁺), zinc (Zn²⁺), and magnesium (Mg²⁺) through ionic gelation, potentially reducing their bioavailability from co-consumed foods by 20–40% depending on dose and food matrix. Gel-forming capacity in aqueous environments is high, with viscosity dependent on molecular weight (typically 200–500 cP for food-grade grades at 1% solution). Bioactive properties stem from its gel-forming, viscous nature rather than nutritional density. No significant phytochemicals, antioxidants, or vitamins are retained in the refined extract.