An insoluble colloidal acid in the form of a carboxylated polysaccharide that is abundant in the cell walls of brown algae (especially large kelp and wracks).

Used in jam, jellies and marmalades as defined in Directive 79/693/EEC and other similar fruit spreads including low-calorie products, an ingredient in antacid preparations (Gaviscon, Bisodol tablets, Asilone tablets Boots own etc) kelp is also available in tablet form as a dietary supplement.

Found in seaweed fertilizer preparations (approved by DEFRA's organic food standards but not by the Soil Association)

Alginates (E400 - E405) are also used as a thickening paste for colours in printing textiles, as a hardener and thickener for joining threads in weaving; the alginates may subsequently be dissolved away, giving special effects to the material. Other uses include glazing and sizing paper, special printers' inks, paints, cosmetics, insecticides, and pharmaceutical preparations. In the USA alginates are frequently used as stabilisers in ice cream, giving a smooth texture and body, and also as a suspending agent in milk shakes.

No known adverse effects, however large quantities may inhibit the absorption of some nutrients.

Permitted for use in animal feeds.

Researchers in the Gastro Intestinal Research Laboratory at McGill University in Montreal, Canada, reported that alginic acid, once ingested, is able to bind with heavy metals such as mercury, cadmium and lead in the body, carrying them out of the system. Alginic acid has also been found to remove traces of low level radioactive material