The effects of carrageenan on drug-metabolizing enzyme system activities in the guinea-pig

Evidence and hypotheses on adverse effects of the food additives carrageenan (E 407)/processed Eucheuma seaweed (E 407a) and carboxymethylcellulose (E 466) on the intestines: a scoping review

This scoping review provides an overview of publications reporting adverse effects on the intestines of the food additives carrageenan (CGN) (E 407)/processed Eucheuma seaweed (PES) (E 407a) and carboxymethylcellulose (CMC) (E 466). It includes evidence from human, experimental mammal and in vitro research publications, and other evidence. The databases Medline, Embase, Scopus, Web of Science Core Collection, Cochrane Database of Systematic Reviews and Epistemonikos were searched without time limits, in addition to grey literature. The publications retrieved were screened against predefined criteria. From two literature searches, 2572 records were screened, of which 224 records were included, as well as 38 records from grey literature, making a total of 262 included publications, 196 on CGN and 101 on CMC. These publications were coded and analyzed in Eppi-Reviewer and data gaps presented in interactive maps. For CGN, five, 69 and 33 research publications on humans, experimental mammals and in vitro experiments were found, further separated as degraded or native (non-degraded) CGN. For CMC, three human, 20 animal and 14 in vitro research publications were obtained. The most studied adverse effects on the intestines were for both additives inflammation, the gut microbiome, including fermentation, intestinal permeability, and cancer and metabolic effects, and immune effects for CGN. Further studies should focus on native CGN, in the form and molecular weight used as food additive. For both additives, randomized controlled trials of sufficient power and with realistic dietary exposure levels of single additives, performed in persons of all ages, including potentially vulnerable groups, are needed.

Structure and function of non-digestible carbohydrates in the gut microbiome

Together with proteins and fats, carbohydrates are one of the macronutrients in the human diet. Digestible carbohydrates, such as starch, starch-based products, sucrose, lactose, glucose and some sugar alcohols and unusual (and fairly rare) α-linked glucans, directly provide us with energy while other carbohydrates including high molecular weight polysaccharides, mainly from plant cell walls, provide us with dietary fibre. Carbohydrates which are efficiently digested in the small intestine are not available in appreciable quantities to act as substrates for gut bacteria. Some oligo- and polysaccharides, many of which are also dietary fibres, are resistant to digestion in the small intestines and enter the colon where they provide substrates for the complex bacterial ecosystem that resides there. This review will focus on these non-digestible carbohydrates (NDC) and examine their impact on the gut microbiota and their physiological impact. Of particular focus will be the potential of non-digestible carbohydrates to act as prebiotics, but the review will also evaluate direct effects of NDC on human cells and systems.

Review of harmful gastrointestinal effects of carrageenan in animal experiments

In this article I review the association between exposure to carrageenan and the occurrence of colonic ulcerations and gastrointestinal neoplasms in animal models. Although the International Agency for Research on Cancer in 1982 identified sufficient evidence for the carcinogenicity of degraded carrageenan in animals to regard it as posing a carcinogenic risk to humans, carrageenan is still used widely as a thickener, stabilizer, and texturizer in a variety of processed foods prevalent in the Western diet. I reviewed experimental data pertaining to carrageenan's effects with particular attention to the occurrence of ulcerations and neoplasms in association with exposure to carrageenan. In addition, I reviewed from established sources mechanisms for production of degraded carrageenan from undegraded or native carrageenan and data with regard to carrageenan intake. Review of these data demonstrated that exposure to undegraded as well as to degraded carrageenan was associated with the occurrence of intestinal ulcerations and neoplasms. This association may be attributed to contamination of undegraded carrageenan by components of low molecular weight, spontaneous metabolism of undegraded carrageenan by acid hydrolysis under conditions of normal digestion, or the interactions with intestinal bacteria. Although in 1972, the U.S. Food and Drug Administration considered restricting dietary carrageenan to an average molecular weight > 100,000, this resolution did not prevail, and no subsequent regulation has restricted use. Because of the acknowledged carcinogenic properties of degraded carrageenan in animal models and the cancer-promoting effects of undegraded carrageenan in experimental models, the widespread use of carrageenan in the Western diet should be reconsidered.