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Algin and Alginate

What are algin, alginic acid and alginate?

  • Algin is a natural, indigestible polysaccharide extracted from brown marine algae, such as kelps and wracks [1,6].
  • Alginic acid is a gel-forming substance obtained by adding mineral acids to algin.
  • Alginates are salts of alginic acid; examples are sodium, calcium and ammonium alginate.

The term algin is often used for all algin compounds, including alginic acid and alginates.


Algin is composed of mannuronic and guluronic acid [1].

Sodium Alginate Is a Viscous Soluble Fiber

Sodium alginate is a viscous soluble fiber. It is fermentable by normal intestinal bacteria to short-chain fatty acids (SCFAs), which can be absorbed and may provide up to 2 kilocalories per gram of algin [2,5]. Physically, alginates are gels or hydrocolloids, which are semi-solid substances when dissolved in water.


Sodium, potassium, ammonium and magnesium alginate are soluble, while calcium alginate and alginic acid are insoluble in water [1].

Alginate as a Food Additive

Alginates can be used as thickeners in dairy products (creams), bakery jellies, cake fillings, beer (as a foam stabilizer), pre-cooked foods, ready-to-eat cereals, vinegars and soybean products. On the food products in the EU, algin is labeled as E400 (alginic acid), E401 (sodium alginate), E402 (potassium alginate), E403 (ammonium alginate), E404 (calcium alginate) and E405 (propylene glycol alginate) [4].

Supplements Health Benefits

Sodium alginate supplements are available as powder or capsules.

There is insufficient scientific evidence about effectiveness of alginate in reducing blood cholesterol or glucose levels, slowing gastric emptying or reduction of absorption of radioactive elements from foodstuffs after nuclear accidents [7]. In one study in overweight adults, adding alginate supplements to meals did not help in weight loss [8].

Sodium Alginate as an Antacid

Sodium alginate, either used alone or in combination with antacids, are effective in preventing heartburn (a common symptom of gastroesophageal reflux disease – GERD) in infants and children [11].

Safety and Side Effects

Alginates used in foods are Generally Recognized As Safe (GRAS) by the U.S. Food and Drug Administration (FDA) [10]. Some individuals who are allergic to shellfish may be also allergic to alginate.

According to one 2103 systematic review of studies, alginate is safe and effective in treatment of gastroesophageal reflux (GERD) in pregnancy [3], but more research is warranted.

Other Seaweeds Used in Foods

  1. Algin – a brown seaweed polysaccharide  Food and Agriculture Organization of the United Nations (FAO)
  2. 2 Torsdottir, I. et al, 1991, A Small Dose of Soluble Alginate-Fiber Affects Postprandial Glycemia and Gastric Emptying in Humans with Diabetes  The Journal of Nutrition
  3. Quartarone, G., 2013, Gastroesophageal reflux in pregnancy: a systematic review on the benefit of raft forming agents  PubMed
  4. Commission regulation (EU) No 1129/2011 The Official Journal of the European Union (eur-lex.europa.eu)
  5. Michel, C. et al, 1996, In vitro fermentation by human faecal bacteria of total and purified dietary fibres from brown seaweeds  PubMed
  6. The seaweed site: information on marine algae  Alginates
  7. Algin  WebMD
  8. Birketvedt, GS et al, 2005, Experiences with three different fiber supplements in weight reduction  PubMed
  9. Effects of a Mixing Tea Drink Containing Depolymerized Sodium Alginate on Serum Total Cholesterol and Assessment of its Safety280 Institut de l’information scientifique et technique
  10. List of GRAS substances  U.S. Food and Drug Administration (FDA)
  11. Mandel et al, 2001, Review article: alginate-raft formulations in the treatment of heartburn and acid reflux  Wiley Online Library

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