Carrageenans are food additives derived from red seaweed such as Chondrus crispus (Irish moss) and other species and are used as a thickening, stabilizing, and texturizing agents in foods and also for reduced-fat meat products (1;2).
They nicely replace animal-based gelatin found in many foods such as soymilk, chocolate milk, yogurts, beers and wines. Lamda-carrageenan, for example, is used to provide a creamy texture to dairy products.
The polymers are high-molecular-weight polysaccharides made up of repeating disaccharide units have a charged nature and their structure gives them their highly reactive properties (2). Concentration and greater molecular weight increases viscosity further (2).
Safety of use of carrageenans in foods has been a matter of controversy and confusion. Leading manufacturers of carrageenan such as FMC corporation have maintained that the use of carrageenan has a centuries-old history of safety in humans that has been confirmed by studies on animals such as dogs and rodents (3). Food-grade carrageenans are not thought to be degraded or absorbed from the gastrointestinal tract of humans (1).
It is known that, when administered systemically, carrageenans are linked to acute liver toxicity (4), are carcinogenic (5) and affect the immune system (6). Also, a substance formed of degraded carrageenan, now known as poligeenan, has long been banned from use in food because of links to fetal toxicity, birth defects, liver toxicity, ulcerative disease, pulmonary lesions and colon cancer in animals (5).
Toxicity concerns of undegraded carrageenans arose when studies in a few experimental animals found that carrageenans were degraded leading to absorption and toxicity (5;6). Another study on rats found that given small quantities of for 90 days, undegraded carrageenans had “penetrated the intestinal barrier degree” in adult rats (7). Low concentrations were also tested on tissue cultures where it was found that lamda-carrageenans entered cells by what appeared to be endocytosis (8).
Despite these data, however, the World Health Organization Expert committee on Food Additives and Joint Food and Agriculture Organization have kept recommendations of allowable daily intake as “not specified” (6).
The groups cited that there was “no credible evidence” to support that food-grade carrageenans were degraded or absorbed in “rodents, dogs, and non-human primates” or that they presented any toxic or carcinogenic effect in these species or in humans long term (6). High doses of carrageenans had been found to lead to cecal enlargement, but the studied amounts were in excess of which humans would consume normally (6).
Reference List
1. Trius A, Sebranek JG. Carrageenans and their use in meat products. Crit Rev Food Sci Nutr 1996;36:69-85.
2. Food and Agriculture Organization. FAO Corporate Document Repository. Training Manual on Gracilaria Culture and Seaweed Processing in China. Available: http://www.fao.org/docrep/field/003/AB730E/AB730E03.htm.
3. Weiner ML. Toxicological properties of carrageenan. Agents Actions 1991;32:46-51.
4. Abe T, Kawamura H, Kawabe S, Watanabe H, Gejyo F, Abo T. Liver injury due to sequential activation of natural killer cells and natural killer T cells by carrageenan. J Hepatol 2002;36:614-23.
5. Watt J, Marcus R. Harmful effects of carrageenan fed to animals. Cancer Detect Prev 1981;4:129-34.
6. Cohen SM, Ito N. A critical review of the toxicological effects of carrageenan and processed eucheuma seaweed on the gastrointestinal tract. Crit Rev Toxicol 2002;32:413-44.
7. Nicklin S, Miller K. Effect of orally administered food-grade carrageenans on antibody-mediated and cell-mediated immunity in the inbred rat. Food Chem Toxicol 1984;22:615-21.
8. Tobacman JK, Walters KS. Carrageenan-induced inclusions in mammary myoepithelial cells. Cancer Detect Prev 2001;25:520-6.
