Emulsifiers, stabilisers, and thickeners -- effects on the gastrointestinal tract

This scoping review was commissioned by the Norwegian Food Safety Authority. The aim was to map the scientific literature investigating effects on the gastrointestinal (GI) tract after intake of emulsifiers, stabilisers, and thickeners (ESTs). The background for the assignment was that certain published studies indicated that the ESTs carrageenan and sodium carboxymethyl cellulose may have negative effects on the GI tract. Eight ESTs are included in this scoping review: carrageenan (E 407) and sodium carboxymethyl cellulose (E 466), and six ESTs that may be used as their substitutes, namely 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).

Fourteen studies of which one was a study on humans and 13 were studies on animals, fulfilled the eligibility criteria. The studies were conducted between 1977 and 2022. VKM evaluated whether the design and conduct of the included studies prevented bias (systematic errors), as bias may cause misleading results and wrong conclusions. Ten of the included studies had high risk of bias and none had low risk of bias.

None of the included studies investigated GI tract effects of sodium alginate (E 401) or gellan gum (E 418). GI tract effects were investigated in one animal study of agar (E 406) and Eucheuma seaweed (E 407a), in one human and one animal study of xanthan gum (E 415), two animal studies of sodium carboxymethyl cellulose (E 466), in four animal studies of guar gum (E 412), and in seven animal studies of carrageenan (E 407). The number of studies addressing GI tract effects of substitution ESTs for carrageenan was limited, and none of these substances were included in the studies addressing gut inflammation or gut permeability.

GI tract effects of ESTs were addressed in 14 eligible studies. GI tract effects were not investigated for two of the ESTs included in the scoping review. GI tract effects were investigated in studies of agar (E 406), sodium alginate (E 401), carrageenan (E 407), processed Eucheuma seaweed (E 407a), sodium carboxymethyl cellulose (E 466), gellan gum (E 418), guar gum (E 412), and xanthan gum (E 415). None of the studies addressed chronic exposures. Animal models were used in 13 of the included studies, and the risk of bias was high in ten studies. Thus, the available research literature on GI tract effects, according to our inclusion criteria, is limited in quantity and has limited relevance for long-term exposure in humans and is encumbered with high risk of bias. These weaknesses limit the use of the results of the scoping review in a future risk assessment.