E-numbers / Thickeners & emulsifiers / E400
also: Alginate · Algin
A natural fibre extracted from brown seaweed, used to thicken and stabilise foods such as ice cream, salad dressings and dairy desserts.
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Alginic acid is a naturally occurring polysaccharide (a long-chain carbohydrate) found in the cell walls of brown seaweeds such as Laminaria, Ascophyllum and Macrocystis species.
Alginic acid is a naturally occurring polysaccharide (a long-chain carbohydrate) found in the cell walls of brown seaweeds such as Laminaria, Ascophyllum and Macrocystis species. It is extracted by treating dried seaweed with an alkali, then precipitating the acid form. The result is an off-white powder that absorbs water readily and forms a viscous gel.
When dispersed in water, alginic acid swells and forms a thick, stable gel. This gives manufacturers control over texture and consistency. It slows the separation of oil and water in emulsions, prevents ice crystals from growing in frozen products, and holds moisture in baked goods. Because it is largely indigestible, it passes through the gut as dietary fibre rather than being absorbed.
Used in ice cream and frozen desserts, dairy-based puddings and mousses, salad dressings, fruit yoghurts, bakery fillings, and some processed cheese products. It also appears in certain diet and meal-replacement products where its water-absorbing bulk is used to promote a feeling of fullness. On a UK ingredient label it appears as 'alginic acid' or 'E400'.
Alginic acid is not digested or absorbed in the small intestine and reaches the colon largely intact, where it behaves as a soluble dietary fibre. It can be partially fermented by colonic bacteria. At the quantities present in food, this is not considered a physiological concern, and the fibre contribution is minor compared with whole food sources.
EFSA's Panel on Food Additives and Nutrient Sources (ANS) concluded that alginic acid and its salts (alginates E401-E404) are not absorbed from the gastrointestinal tract and are metabolised as dietary fibre, with no nutritional or toxicological concern at permitted use levels.
At doses considerably above those found in food, alginic acid's water-absorbing capacity can have a mild laxative effect. The amounts used as a food additive are far below those used therapeutically. No adverse effects have been reported at food-use levels in the regulatory literature.
The Joint FAO/WHO Expert Committee on Food Additives (JECFA) established that alginic acid has not established a numerical ADI, as the substance was considered to present no toxicological hazard at levels consistent with good manufacturing practice.
Alginic acid is derived from seaweed and is not derived from any of the 14 major declarable allergens under UK food law. It is not derived from animals, dairy or gluten-containing grains. People with known seaweed or iodine sensitivities occasionally report reactions, but this is not recognised as a declarable allergy under current UK regulations.
Alginic acid is not listed among the 14 allergens that must be declared under UK Regulation (EU) No 1169/2011 (retained in UK law). Seaweed sensitivity is not a recognised declarable allergen category.
People with a known sensitivity to seaweed should check ingredient labels for 'alginic acid' or 'E400', though seaweed sensitivity is uncommon and not a declarable allergen category under UK law. There is no requirement for any population group to limit intake at normal food levels.
Alginic acid has been used in food manufacturing for over a century and has been through formal regulatory review by both EFSA (2017) and JECFA. The available evidence, including animal and human studies at doses far above food-use levels, has not produced signals of toxicity, carcinogenicity or endocrine disruption. Its main effect in the body is as a bulk dietary fibre. The science here is well-settled and the substance is among the least controversial food additives in routine use.
No. Alginic acid is approved for use in the UK under the UK FSA approved-additives list and in the EU under Regulation 1333/2008. It has no bans or restrictions imposed in either jurisdiction.
Alginic acid is a carbohydrate extracted from seaweed, not the whole seaweed, so it does not carry meaningful levels of iodine. People managing their iodine intake for medical reasons do not generally need to consider alginic acid in food.
Alginic acid appears in ice cream, frozen desserts, dairy puddings and mousses, salad dressings, processed cheese, bakery fillings, diet meal-replacement products and some beers. Look for 'alginic acid' or 'E400' in the ingredients list.
Yes. Alginic acid is extracted from brown seaweed and contains no animal-derived ingredients. It is suitable for vegans and vegetarians.
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