Calcium alginate
A natural thickener and gelling agent made from brown seaweed, used to set, stabilise and thicken a wide range of foods.
What is it?
Calcium alginate is the calcium salt of alginic acid, a naturally occurring polysaccharide extracted from brown seaweed (kelp). It forms firm, heat-stable gels in the presence of calcium ions, distinguishing it from sodium alginate which produces softer, more soluble gels.
What does it do?
When added to food, calcium alginate creates a gel network by cross-linking alginate chains through calcium ions. This makes it useful as a thickener, gelling agent and stabiliser. It can hold water, prevent ingredients separating and maintain texture across a range of temperatures. In food manufacturing it is also used to encapsulate flavours or form thin edible coatings.
Where you will see it
Found in restructured or formed fish and meat products (such as formed fish fillets and sliced meat), canned or jarred fruit and vegetables, coatings on fresh-cut produce, bakery fillings, dairy desserts and some processed cheeses. It appears on ingredient labels as 'calcium alginate' or 'E404'.
What the science says
Digestibility and systemic absorption
Alginates are dietary fibres that humans lack the enzymes to digest. Calcium alginate passes largely intact through the small intestine and is fermented to a limited degree by gut bacteria in the colon. Very little reaches the bloodstream. EFSA's 2017 re-evaluation group concluded that systemic exposure is negligible at the levels used in food.
EFSA concluded that alginic acid and its salts (E 400 to E 404), including calcium alginate, are not absorbed to any meaningful extent from the gastrointestinal tract at food-use levels.
Acceptable daily intake and exposure
Regulators did not set a numerical acceptable daily intake for calcium alginate because the toxicological data did not identify a level of concern. EFSA's refined dietary exposure assessment found no safety concern at reported food-use levels for any age group, including children.
No numerical ADI was established for E 400 to E 404. The panel found no safety concern at the levels of refined exposure reported for food additive uses.
Long-term and animal toxicology
Feeding studies in rodents at high doses did not produce organ toxicity or carcinogenic effects attributable to alginate. The substance is not genotoxic in standard battery tests. Findings at very high experimental doses relate to the bulking and mineral-binding properties of the fibre rather than any chemical toxicity.
Standard subchronic and chronic rodent studies found no adverse effects attributable to alginate at dietary concentrations up to approximately 5% of diet, aside from reduced calcium absorption at very high doses linked to fibre binding, not systemic toxicity.
Where it stands with the regulators
Who should be careful
No specific population group needs to avoid calcium alginate based on current evidence. People on very low-calcium diets should be aware that alginate fibre can bind dietary calcium in the gut at high intakes, though this is not a concern at normal food-use levels. Look for 'calcium alginate' or 'E404' on the label.
The honest read
Calcium alginate is a well-established food hydrocolloid derived from seaweed, used in processed foods for decades. The science base on alginates is substantial, and EFSA carried out a thorough re-evaluation in 2017 covering the full family. No concerning signals emerged at normal dietary exposure levels. The main regulatory discussions have centred on mineral binding at very high experimental doses, a property inherent to all dietary fibres, not a specific hazard of alginate. There is no active scientific controversy about its use in food.
Related additives
Common questions
Is E404 banned in the UK?
No. Calcium alginate (E404) is an approved food additive in the UK and EU, permitted in a wide range of food categories under the UK's assimilated food additive regulations.
Does E404 have any effect on mineral absorption?
At very high experimental doses, alginate fibre can bind calcium and other minerals in the gut, reducing their absorption. At the levels present in food this effect is not considered significant. People on medically supervised very-low-calcium diets who eat large quantities of alginate-thickened products may wish to note this, but it is not a concern at typical intakes.
What foods contain E404?
E404 is used in formed or restructured fish and meat products, canned and jarred fruit and vegetables, bakery fillings, dairy desserts and some processed cheeses. It may also be used as an edible coating on fresh-cut produce. Check the ingredients list for 'calcium alginate' or 'E404'.
Is E404 vegan?
Yes. Calcium alginate is derived from brown seaweed and contains no animal-derived ingredients. It is suitable for vegans and vegetarians.
Sources
- EFSA ANS Panel - Re-evaluation of alginic acid and its sodium, potassium, ammonium and calcium salts (E 400-E 404) as food additives, EFSA Journal 15(11):5049
- PMC full text of the EFSA 2017 re-evaluation (E 400-E 404)
- UK Food Standards Agency - Approved additives and E numbers (E400-E499 section)
- EU Regulation (EC) No 1333/2008 on food additives (consolidated text)
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