Gut microbiota modulation by carboxymethyl cellulose and carrageenan: current evidence and health implications

The gut microbiota plays a central role in digestion, metabolism, immune regulation, and inflammatory processes, and is highly responsive to dietary factors, including food additives. With the increasing consumption of ultra-processed foods, growing attention has been directed toward the long-term effects of commonly used additives on gut health. This review examines the interactions between food additives and the gut microbiota, with a specific focus on the emulsifiers carboxymethyl cellulose (CMC) and carrageenan (CGN), which are widely used in processed foods. Evidence from in vitro, animal, and limited human studies indicates that both CMC and CGN can alter gut microbiota composition, disrupt intestinal barrier integrity, and promote pro-inflammatory responses, although their mechanisms of action differ. CGN has been more consistently associated with direct activation of inflammatory signalling pathways and epithelial stress, whereas CMC primarily induces microbiota-mediated effects, including altered microbial spatial organisation and mucus barrier disruption, leading to low-grade inflammation. The magnitude of these effects appears to depend on dosage, duration of exposure, and the experimental model employed. Overall, the findings summarised in this review suggest that chronic exposure to CMC and CGN may contribute to gut dysbiosis and increased inflammatory susceptibility, particularly within dietary patterns rich in ultra-processed foods. These observations highlight the need for harmonised research methodologies, more human-relevant long-term studies, and reconsideration of current food safety assessment frameworks to better account for microbiota-related outcomes.