Alginates are a group of viscous polysaccharides derived from brown seaweeds and produced as an extracellular matrix by some bacterial species. Traditionally, alginates have been used as thickeners, emulsifiers and stabilising agents in a number of food applications. A number of new food applications are emerging for alginates, based on their unique biochemical and biophysical properties. These applications are discussed within this review, as are the nutritional properties of dietary alginates, and their physiological actions in humans.