Alginate: Nutrients, What Research Shows and Safety

Alginate is a gel-forming fiber taken from brown seaweeds such as Laminaria, Macrocystis and Ascophyllum. You may meet it in three very different places: as a food additive that thickens and sets foods (E 400 to E 404), as the active ingredient of Gaviscon-type heartburn medicines, and as an ingredient in diet drinks or supplements. This page keeps those three apart, because the evidence is not the same. We also touch on wound dressings, briefly.

Read this first

• As a food additive, regulators saw no safety concern. EFSA (the EU food safety agency) re-evaluated alginic acid and its salts in 2017 and said no numerical daily limit was needed. It also said infants and young children should not exceed therapeutic doses, and that data were insufficient to judge special medical foods for infants. [1]
• As a heartburn medicine, alginate has real trial support, with limits. A pooled analysis of 14 trials found alginates beat placebo or antacids for reflux symptoms, but they were not clearly better than acid-lowering medicines. [3] The NHS says alginates give short-term relief and should not be taken regularly for long periods. [4] Persistent heartburn needs a clinician.
• For weight loss and blood sugar, the evidence is weak. The main trial of an alginate drink found no weight-loss difference when everyone was counted. [7] This is not a proven weight-loss product.
• Not a nutrient source. There is no USDA entry for alginate, and we did not read a nutrient table for it.

What is in it (USDA values)

No USDA entry for this food. Alginate is an extract (a fiber), not a whole food, and USDA FoodData Central (SR Legacy) has no item for it. We did not read a peer-reviewed nutrient analysis of alginate, so we give no per-100 g table. In trials, alginate was counted as fiber: one preload drink supplied about 15 g of fiber per serving. [7]

The key facts are about its chemistry and uses, not its vitamins:

• Alginic acid and its sodium, potassium, ammonium and calcium salts are the additives E 400 to E 404. [1]


• Propylene glycol alginate (E 405) is assessed separately: EFSA set an acceptable daily intake of 55 mg per kg of body weight a day, based on its propane-1,2-diol part, and estimated exposures did not exceed it. [2]


• The reflux meta-analysis authors say alginates act differently from acid-lowering medicines, by displacing the stomach acid pocket that forms after meals. [3] That is the proposed mechanism; the symptom results below are what was measured in people.

What research says

Funding: the reflux meta-analysis lists grants from US National Institutes of Health programs; the abstract we read has no conflict-of-interest statement. [3] For the weight trial and the others, the abstracts we read did not state funding. [7]

Food, medicine or supplement? As a food additive, alginate is used in small amounts and EFSA found no concern. [1] As a medicine (the Gaviscon type), it is dosed on the label for reflux symptoms. As a supplement or diet drink, the trials used large fiber doses and the results were mixed. Do not carry results from one use to another.

How much is a normal serving

There is no official serving of alginate. EFSA set no numerical daily intake for E 400 to E 404 because it saw no safety concern at the estimated exposures. [1] The research doses (for example 1.5 g before meals in one trial, 15 g of fiber per preload in another) are what the studies gave, not advice. [7] [8] For medicines, follow the label or ask a pharmacist; we give no dose.

Safety, allergy and medicines

• Infants and young children: EFSA said infants and young children should not exceed therapeutic dosages and that data were insufficient to assess alginate in special medical purpose foods for infants and young children. [1] Use infant reflux medicines only as a clinician directs.
• Long-term medicine use: the NHS says alginates and antacids ease symptoms short term and should not be taken regularly for long periods. [4]
• See a doctor if: heartburn is most days, you have food sticking in your throat, repeated vomiting or unexplained weight loss, or symptoms are getting worse. [4]
• Pregnancy: the NHS says a pharmacist can advise pregnant people on suitable heartburn medicines. [4] We did not read an official statement specific to alginate in pregnancy.
• Sodium: alginate medicines are often sodium alginate salts, so they contain sodium. We did not read an official sodium figure, so check the label if you must limit sodium.
• Medicines and interactions: we did not read a source on alginate interactions. Ask a pharmacist, especially if you take several medicines.
• Iodine, thyroid and metals: the alginate extract comes from brown seaweed, which can be rich in iodine and metals in general. We did not find an alginate-specific iodine or metal figure in the sources we read, so we cannot say if it is low or high. See iodine in seaweed.
• Allergy: we did not find alginate allergy reports in the sources we read. Seaweed is not shellfish or fish. For trouble breathing or swelling of the face or throat, call 911 (or your local emergency number).

Choosing, storing and food safety

• On a food label, look for E 400 to E 404 or "alginate", "sodium alginate" or "algin". These are all the same family of additives. [1]
• Heartburn products differ; the label lists the active ingredients and the sodium content. Ask a pharmacist which suits you.
• We did not read a source on storing alginate products, so follow the package.

Related pages

• Kelp noodles
• Agar
• Carrageenan
• Fucoidan
• Iodine in seaweed: how much by type
• Herbal tea, acid reflux, tooth and iron absorption effects