Carrageenan has been the subject of significant investigation for several decades, and the complexity pertaining to it may have impeded our ability to form a clear impression about its harmful effects. In rodent models, there is clear evidence that degraded carrageenan can induce ulcerations and neoplasms. Also, there is clear evidence that food-grade carrageenan can be broken down to degraded food thickener carrageenan by acid hydrolysis and by bacteria, and degraded carrageenan is likely to contaminate food-grade carrageenan.

Although most of our concerns about carcinogenic exposures arise in relation to the unmetabolized product, the situation with carrageenan requires some extension of our perspective to recognize that exposure to undegraded carrageenan is inevitably accompanied by exposure to degraded carrageenan. If we accept the Delaney standard of no known carcinogens in food or the pesticide standard of no more than one in part in a million, the use of carrageenan in food is clearly in excess.

When the Food and Drug Administration considered the status of carrageenan in the early 1970s, their review included a study of 24 rhesus monkeys with appropriate controls (4,5). Investigators observed that monkeys fed 2% degraded carrageenan did not gain weight, had an immediate change in stool consistency, and consistently had blood in their stools, which was associated with a decline in hemoglobin, until approximately 10 weeks after the withdrawal of the carrageenan. In addition, they developed mucosal erosions and ulceration and multiple crypt abscessescrypt abscesses. Abscesses that are characteristic of ulcerative colitis, and are located in the mucosa of the large intestine. Pathologic changes were dose and duration dependent. Thus, these data indicate that degraded carrageenan can induce colitis in primates.

It is unfortunate that the June 2001 meeting of the FAO Expert Committee on Food Additives rated the acceptable daily intake of carrageenan as "not specified," as they had done previously, including at the 28th meeting in 1984, rather than establishing a different position. In the 1999 report on carrageenan prepared as part of the World Health Organization Food Additives Series, Greig stated that the JECFA ADI of "not specified" for carrageenan was temporary, pending review in 2001. Also, Greig pointed out that degraded carrageenans and processed Eucheuma seaweed were not included by the JECFA in the specifications of food-grade carrageenan in 1984. Subsequently, a review of carrageenan was undertaken for the 2001 meeting.

I hope that the recommendations pertaining to carrageenan will be revised by regulatory groups. Clearly, there are significant economic issues and interests for the food industry and for populations involved in farming red seaweeds. In the United States, the FDA has ignored the harmful potential of carrageenan for over 20 years, but now is the time to reevaluate carrageenan and its potential harmful effects.