From Carrageenan County, Ireland, emerges a red algae extract called carrageenan that has been used in foods and medications for many centuries. The U.S. Food and Drug Administration, European Food Safety Authority, and World Health Organization support the safety of food-grade carrageenan for its intended use, including in infant formula and follow-on products, at levels consistent with good manufacturing practices. Some of those approved uses leverage an array of functional properties, such as thickener, gelling, and stabilizing agent, and emulsifier in a variety of foods and household products, and as an excipient in and production aid for pharmaceutical products, including some antibiotics (McKim, 2014; Weiner, 2014; Necas & Bartosikova, 2013).
Carrageenan is an alkaline aqueous extract from red seaweed (WHO, 2007). This extraction process avoids the production of low molecular weight polymers (<5%), which are the focus of recent scrutiny. The most common forms of carrageenan in the food supply are kappa, iota, and lambda. These forms vary in their degree of sulfation (20%–40%) and linkage of highly flexible hexose units of galactose and anhydrogalactose. The molecular weight of food-grade carrageenan typically ranges between 200K and 800K Da with average >100K Da although a molecular weight range is not stipulated in any food regulations (Campo et al., 2009).
Poligeenan, formerly known as “degraded carrageenan,” is the product of acid hydrolysis (pH 0.9–1.3) conducted at high temperatures (>80°C) for extended periods of time. This product has a molecular weight of approximately 10K to 30K Da. Poligeenan is not a food additive or found in the food supply. Current evidence indicates dietary carrageenan is not absorbed, hydrolyzed, or converted to poligeenan following ingestion by rodents, dogs, and nonhuman primates, or by intestinal microflora (McKim, 2014; Cohen & Ito, 2002). The absence of intestinal degradation of carrageenan is supported by the lack of endogenous enzymes, such as carrageenases and galactosidases that recognize the unique structure of carrageenan (Weiner, 2014; Panaras & Martin, 1985). However, it should be noted that some species of marine organisms, not components of human microflora, produce κ-carrageenase (Potin et al., 1991).
The degradation of carrageenan to poligeenan has not been demonstrated in in vivo studies. A review of animal studies with poligeenan, a surrogate of carrageenan exposure, indicates this product can elicit inflammatory responses in the small bowel and in in vitro studies with various human cell lines (Tobacman, 2001).
Another assessment of inflammatory potential of carrageenan was demonstrated when it was injected into the footpad of rats (Harmuth-Hoene & Schwerdtfeger, 1979). On the other hand, topical administration of carrageenan suggested this polysaccharide may function as a microbicide by inhibiting herpes simplex virus, human papillomavirus, and human immunodeficiency virus (Marais et al., 2010; Marais et al., 2011). These findings emphasize and clearly indicate the route of administration is a critical and fundamental variable in assessing the potential toxicity and safety of any substance, whether that substance is a possible food ingredient or prospective component in a pharmaceutical mixture.
Several early studies assessed the potential carcinogenicity of carrageenan when fed to rodents. These studies, following the subcutaneous injection of three different colon tumor initiators and co-administration of diets containing 6% or15% of various forms of carrageenan, indicated an increase in colon cancer based on tumor burden (Arakawa et al., 1986; Watanabe et al., 1978). Careful examination of these studies indicates the diets were nutritionally insufficient. In addition, high carrageenan concentration (>5%) was inappropriate to assess safety based on contemporary research protocols. Follow-up studies on the possible genotoxicity of carrageenan indicated this food additive was not mutagenic (IRAC, 1983; JECFA, 1999).
A comprehensive review on the potential impact of food-grade carrageenan on the immune system system indicated the absence of any adverse effect (Cohen & Ito, 2002). As suggested by other investigators, poligeenan does exhibit toxicological properties at high doses (>10%), levels that do not occur in the food supply.
Clearly, the physical and toxicological properties of carrageenan and poligeenan differ considerably. From a practical perspective, evidence indicates poligeenan does not have any functional properties in aqueous food matrices, whereas carrageenan is typically used at concentrations of 0.10% or less.
The spectrum of scientific literature over more than three decades of research and food applications indicates carrageenan is a food additive that is safe for consumers of all ages and has broad applications in the food industry.
Roger Clemens, Dr.P.H., CFS,
Chief Scientific Officer,
Horn Company, La Mirada, Calif.