Digestive fate of dietary carrageenan: Linking biopolymer physicochemical characteristics to effects on digestive proteolysis, gut functions and human microbiome

Carrageenan (E407) (CGN) is an increasingly consumed food additive¹ whose safety is at the heart of considerable debate^2-4. There are three commercial CGNs that mainly differ in the MW and sulphation degree and termed: kappa(k), iota(i) and lambda(λ)-CGN. This study sought to underpin CGN macromolecular characteristics directing its implications on digestive proteolysis, gut functions and the human microbiome.

Although CGNs may possess similar techno-functionality (e.g. flow behavior), they have different biopolymer characteristics, as determined by SEC-MALS and DLS. Such differentiating attributes govern CGN electrostatic binding to food proteins, which in turn alter the scarcity of bioaccessible bioactive peptides upon digestion (determined by LC-MS/MS peptide profiling coupled to in vitro human digestion models). This effect has been correlated to CGN sulphation degree/zeta potential. In co-cultures, CGNs were found to disrupt zonula occuludens-1 and F-actin structures as well as enhance epithelial permeability to macromolecules². In addition, physiologically digested CGN (pdCGN) has been found to induce recruitment of TH1 immune cells to the luminal side of the epithelium. In human colonic models (from 10 healthy male volunteers, age 25.7±4.2), pdCGN has been found to alter colon microbiota composition. Illumina Miseq 16S rRNA sequencing show a marked increase in the Firmicutes/Bacteroidetes ratio from 3 for controls to 94, 126 and 42 for cultures fed with k, i & λ-CGN (p-value<0.15,p<0.15,p<0.05, respectively). Such changes have been related to the development of obesity. Again, CGN biopolymer charge is linked to its effect on microbiota diversity, richness and evenness.

Overall, this work provides much needed evidence on the possible implications of CGN to human health and establishing CGN charge and electrostatic biopolymer interactions as determinants of CGN anti-nutritional effects.

1. David.S. et al.(2019). FOOD FUNCT,10

2. Fahoum,L. et al. (2017). MOL NUTR FOOD RES,61(3)

3. David,S. et al. (2018). FOOD FUNCT,9(3).

4.Younes,M. et al. (2018). EFSA Journals,16(4)