Gastrointestinal Tract Digestion and Carrageenan: How Misconceptions have influenced the Understanding of Carrageenan Safety

Carrageenan (CGN) is a naturally occurring fiber isolated from various species of red seaweeds (class Rhodophyceae). It has been safely consumed for hundreds of years and today is approved for use in the food industry as a food additive by regulatory agencies around the world. Unfortunately, some researchers have used misleading and incorrect interpretations of early studies to suggest that food-grade CGN (Mw = 200,000 to 800,000 Da.) is not safe for human consumption. These researchers reference studies conducted with the acid-hydrolysis products of CGN, which include degraded carrageenan (d-CGN; Mw = 20,000 to 40,000 Da.) and poligeenan (PGN; Mw = 10,000 to 20,000 Da.), as evidence of the potential adverse health effects of high Mw CGN. While PGN and d-CGN have been shown to have adverse effects in vivo, the same is not true for CGN. Both PGN and d-CGN are made in the laboratory under harsh conditions of low pH (< 2.0) and high temperature (80°C), and have distinctly different physical, chemical and toxicological profiles than CGN. Studies have shown that d-CGN and PGN are not formed in vivo after ingesting CGN, nor are d-CGN and PGN used as food additives. Yet these differences between d-CGN/PGN and CGN are either not understood or are ignored by many authors in the published literature and the adverse effects observed with d-CGN and PGN are being used to question the safety of CGN. This has caused significant confusion in the literature and with regulators. Here we review the physical, chemical and toxicological properties of CGN, d-CGN and PGN. We then review the ingestion of CGN, how the formation of d-CGN and PGN does not occur in vivo. Finally, we discuss recent review providing a prime example of how some publications use misinformation to suggest CGN is unsafe for ingestion.