Scoping review of research on gastrointestinal effects of selected emulsifiers, stabilisers, and thickeners

None of the included studies were suitable for assessing long-term effects in humans, and the uncertainty related to the results and conclusions of the studies were high.

Emulsifiers, stabilisers and thickeners (EST)

Emulsifiers, stabilisers and thickeners are additives used in food to improve and preserve consistency. Emulsifiers are used to mix water and fats, thickeners are used to make food more viscous, and stabilisers can be used to prevent the precipitation. Substances that do not meet the criteria in the EU regulations for food additives, which are also followed in Norway, may have different biological properties than the approved additives. Studies of emulsifiers, stabilisers and thickeners that do not describe the substances in such a way that they unambiguously satisfied the criteria could, therefore, not be included in the overview.

The emulsifiers, stabilisers and thickeners included in this scoping review were carrageenan (E 407), sodium carboxymethyl cellulose (E 466), sodium alginate (E 401), agar (E 406), processed Eucheuma seaweed (E 407a), guar gum (E 412), xanthan gum (E 415), and gellan gum (E 418).

Few new studies were included in the updated scoping review

In 2023, VKM mapped the research on what types of effects had been studied in the gastrointestinal tract in animals, humans or in organ models after exposure to the above-mentioned eight EST. VKM found that there was insufficient information about the substances in 214 studies, and therefore we could not assess whether the reported effects in these studies were due to the approved EST or to similar substances with other properties.

"In this updated scoping review, VKM sent requests by email to the corresponding authors of the publications, whenever such contact information was available," says Trine Husøy, who was the chair of the project group. "Following receipt of the requested information, six of these studies were included. It was also confirmed that in some studies, the substance tested did not fulfill the criteria for use as food additives in Norway/EU. This shows the importance of including specific eligibility criteria also for the substances. The literature search was updated, but no new studies fulfilling all eligibility criteria were identified."

In total, from the previous scoping review (VKM, 2023) and the present update, 21 studies fulfilling the eligibility criteria were identified: five studies in humans and 16 in animals. The study durations were between 1 day and 1 week (acute) for human studies.

"The risk of bias, i.e. the potential for systematic errors or flaws in the design, conduct, or reporting of individual studies, were assessed for the 21 studies," says Trine Husøy. "The risk of bias was assessed to be high in human studies and as moderate or high in animal studies."

Conclusion

The conclusion in the present updated scoping review, after inclusion of six additional studies, remains the same as in the previous scoping review (VKM, 2023). The included studies on the effects of agar (E 406), sodium alginate (E 401), carrageenan (E 407), processed Eucheuma seaweed (E 407a), sodium carboxymethyl cellulose (E 466), guar gum (E 412) and xanthan gum (E 415) on the gastrointestinal tract were few, and in most of the studies the potential for systematic errors in the results or findings was high. None of the studies lasted long enough to evaluate long-term exposure in humans. Thus, the evidence base will be weak for assessment of risk for any negative effects on the gastrointestinal tract in humans.