Does carrageenan cause gastrointestinal inflammation and higher rates of intestinal lesions, ulcerations, and even malignant tumors in humans?

Question

I came across this article on how to avoid carrageenan on a friend's facebook post.

The "article" starts with this statement:

Carrageenan is a common food additive extracted from red seaweed. For the past four decades, scientists have warned that the use of carrageenan in food is not safe. Animal studies have repeatedly shown that food-grade carrageenan causes gastrointestinal inflammation and higher rates of intestinal lesions, ulcerations, and even malignant tumors.

Despite the evidence showing the risks in eating carrageenan, it’s still approved for use in organic food where it’s most often used as a stabilizer.

Are there conclusive studies showing that carrageenan found in our food is a significant risk for gastrointestinal inflammation, and/or higher rates of intestinal lesions, ulcerations, or malignant tumors in humans?

There are no direct references to research on the article, other than some circular links, resulting in this paper (published by the same website).

I've been looking through some of the references in that paper, but I almost immediately spotted some rather dubious citations.

For example:

15 Marinalg (seaweed-based hydrocolloid industry trade lobby group, representing carrageenan manufacturers) test results show contamination of food-grade carrageenan with degraded carrageenan, classifed as a “possible human carcinogen.” Available online at http://www.marinalg.org/ wp-content/uploads/2012/09/Final-Full-Report.pdf. Last accessed January 30, 2013

However, a review of that cited source shows no mention of the word "carcinogen", and indeed states:

Marinalg believes that there is no toxicological evidence to support the establishment of the specific numerical values in the specification

and

There is neither toxicological evidence from animal studies nor epidemiological evidence from observation of the effects of consumption of carrageenan by a broad segment of the population to indicate that commercial carrageenan for food use is unsafe for human consumption. The effect of the very small amounts of lower molecular weight components in carrageenan is of no significance to human health.

Is the "report" by cornucopia.com complete bunk, or is there real science behind it?

Answer 1

No, it doesn't. Negative effects were seen only on animal models when administered mostly systemically but also orally.

Systemically administered carrageenan has been reported to have a variety of effects, particularly on the immune system, but these are not pertinent to orally administered carrageenan. The lack of carcinogenic, genotoxic, or tumor-promoting activity with carrageenan strongly supports continuing such an ADI (allowable daily intake), and JECFA (Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives), during its most recent review in 2001, continued this recommendation.

Source: 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 Sep;32(5):413-44.

Authorities worldwide have extensively reviewed carrageenan safety. Contrary to Tobacman’s conclusion (1), all of these authorities agree that carrageenan may be used safely in food. As recently as June 2001, the Joint FAO/WHO Expert Committee on Food Additives (JECFA; an independent international panel of expert scientists and government authorities) concluded a multiple year review of all of the relevant safety data on carrageenan (2). This included a specific analysis of the potential for promotion of colon cancer by carrageenan. The JECFA affirmed their earlier conclusion on the safety of carrageenan [e.g., (3)]—that it may be used safely in the diet at amounts only limited by the amount necessary to achieve its technical function. Overall, the carrageenan sold as a food, drug, and cosmetic additive has been tested extensively, and regulatory authorities worldwide have uniformly found carrageenan to be essentially nontoxic and agreed that it may be used safely in food.

Source: P P Kirsch. Carrageenan: a safe additive. Environ Health Perspect. Jun 2002; 110(6): A288.

"Tobacman's conclusion" is based on animal models and there is no evidence to support this in humans:

Because of the acknowledged carcinogenic properties of degraded carrageenan in animal models and the cancer-promoting effects of undegraded carrageenan in experimental models, the widespread use of carrageenan in the Western diet should be reconsidered.

Source: Tobacman JK. Review of harmful gastrointestinal effects of carrageenan in animal experiments. Environ Health Perspect. 2001 Oct;109(10):983-94.

It has also been issued a hypothesis that carrageenan can inhibit papillomavirus infection.

Carrageenan is in widespread commercial use as a thickener in a variety of cosmetic and food products, ranging from sexual lubricants to infant feeding formulas. Some of these products block HPV infectivity in vitro, even when diluted a million-fold. Clinical trials are needed to determine whether carrageenan-based products are effective as topical microbicides against genital HPVs.

Source: Buck CB, Thompson CD, Roberts JN, Müller M, Lowy DR, Schiller JT. Carrageenan is a potent inhibitor of papillomavirus infection. PLoS Pathog. 2006 Jul;2(7):e69.