Comment on "Revisiting the carrageenan controversy: do we really understand the digestive fate and safety of carrageenan in our foods?" by S. David, C. S. Levi, L. Fahoum, Y. Ungar, E. G. Meyron-Holtz, A. Shpigelman and U. Lesmes, Food Funct., 2018, 9, 1344-1352.

Carrageenan (CGN) is a polysaccharide that is found in various types of sea weed. It is a common food additive used for its gelling and thickening properties and has been used safely throughout the world for decades. CGN is approved as Generally Recognized as Safe (GRAS) by the United States Food and Drug Administration and is also considered safe for the general population by the World Health Organizations Joint Expert Committee on Food Additive (JECFA) and the European Food Safety Authority. CGN has been tested for safety in various animal models for many years and more recently in an array of in vitro or cell-based models. A recent review published by this journal entitled "Revisiting the Carrageenan controversy: Do we really understand the digestive fate and safety of carrageenan in our foods?" has provided the impetus for this commentary (S. David, et al., Food Funct., 2018, 9(3), 1344-1352). It is important that our food is safe, and clearly there are examples of food additives that were found to be unsafe after years of use, but the issue is the need for accurate interpretation of previously published studies and the need for designing and conducting experiments that can be used to make decisions on safety. It is our hope that this commentary brings to light some of the important physical and chemical properties of CGN and how information can be easily misinterpreted.

Clarifying the confusion between poligeenan, degraded carrageenan, and carrageenan: A review of the chemistry, nomenclature, and in vivo toxicology by the oral route.

Carrageenan (CGN) is a common food additive that has been widely used for decades as a gelling, thickening and stabilizing agent. Carrageenan has been proven safe for human consumption; however, there has been significant confusion in the literature between CGN and the products of intentional acid-hydrolysis of CGN, which are degraded CGN (d-CGN) and poligeenan (PGN). In part, this confusion was due to the nomenclature used in early studies on CGN, where poligeenan was referred to as "degraded carrageenan" (d-CGN) and "degraded carrageenan" was simply referred to as carrageenan. Although this nomenclature has been corrected, confusion still exists resulting in misinterpretation of data and the subsequent dissemination of incorrect information regarding the safe dietary use of CGN. The lack of understanding of the molecular weight distribution of CGN has further exacerbated the issue. The significant differences in chemistry, manufacture, and protein reactivity of CGN versus d-CGN and PGN are reviewed, in addition to the in vivo toxicological profiles of CGN, d-CGN, and PGN. As CGN cannot be hydrolyzed to PGN in vivo, concerns over the use of CGN as a food additive are unfounded, particularly since current studies support the lack of oncogenic and tumorigenic activity of CGN in humans.

Addendum to Weiner, M.L. (2016) Parameters and Pitfalls to Consider in the Conduct of Food Additive Research, Carrageenan as a Case Study. Food Chemical Toxicology 87, 31-44.

This paper is an addendum to a 2016 paper outlining pitfalls and parameters to consider in the conduct of food additive research with carrageenan (Fd. Chem. Tox. 87, 31-44 (2016)). The literature on the food additive, "carrageenan," contains many publications which either erroneously misuse the name, carrageenan, for a sample which is not carrageenan, but "degraded carrageenan" or "poligeenan" and also conduct studies without understanding the physical/chemical properties of carrageenan. Degraded carrageenan and poligeenan are not food additives and have a completely different physical/chemical and toxicological properties from carrageenan. Two recent publication examples, one in vivo and one in vitro, demonstrate the serious misunderstanding promulgated by incorrect sample identity/purity and poor study conduct. These new publication examples reiterate the problems in the literature summarized by the Weiner (2016). It is important to have thorough, rigorous peer review of all studies using carrageenan in vivo or in vitro.

Effects of carrageenan on cell permeability, cytotoxicity, and cytokine gene expression in human intestinal and hepatic cell lines.

Carrageenan (CGN) is a common food additive used for its gelling and thickening properties. The present study was done to evaluate intestinal permeability, cytotoxicity, and CGN-mediated induction of proinflammatory cytokines. A standard Caco-2 absorption model showed no CGN permeability or cytotoxicity at concentrations of 100, 500, and 1000 µg/mL. In two human intestinal cell lines (HT-29 and HCT-8) CGN (0.1, 1.0, and 10.0 µg/mL) did not induce IL-8, IL-6, or MCP-1 (CCL2) or produce cellular toxicity after 24 h. The TLR4 agonist LPS produced weak induction of IL-8 in HT-29 cells and no induction in HCT-8 cells. The effects of κ-CGN (0.1, 1.0, and 10 µg/mL) on cellular oxidative stress was assessed in HT-29 cells using CM-H2DCFDA as the probe. No effect on oxidative stress was observed after 24 h. In the human (HepG2) liver cell line, ʎ-CGN (0.1, 1.0, 10.0 and 100.0 µg/mL) had no effect on the expression of IL-8, IL-6, or MCP-1 (CCL2) after 24 h. In conclusion, CGN was not absorbed, and was not cytotoxic. It did not induce oxidative stress, and did not induce proinflammatory proteins.

Parameters and pitfalls to consider in the conduct of food additive research, Carrageenan as a case study.

This paper provides guidance on the conduct of new in vivo and in vitro studies on high molecular weight food additives, with carrageenan, the widely used food additive, as a case study. It is important to understand the physical/chemical properties and to verify the identity/purity, molecular weight and homogeneity/stability of the additive in the vehicle for oral delivery. The strong binding of CGN to protein in rodent chow or infant formula results in no gastrointestinal tract exposure to free CGN. It is recommended that doses of high Mw non-caloric, non-nutritive additives not exceed 5% by weight of total solid diet to avoid potential nutritional effects. Addition of some high Mw additives at high concentrations to liquid nutritional supplements increases viscosity and may affect palatability, caloric intake and body weight gain. In in vitro studies, the use of well-characterized, relevant cell types and the appropriate composition of the culture media are necessary for proper conduct and interpretation. CGN is bound to media protein and not freely accessible to cells in vitro. Interpretation of new studies on food additives should consider the interaction of food additives with the vehicle components and the appropriateness of the animal or cell model and dose-response.

The development and validation of methods for evaluating the immune system in preweaning piglets.

The preweaning piglet has been found to be a valuable research model for testing ingredients used in infant formula. As part of the safety assessment, the neonates' immune system is an important component that has to be evaluated. In this study three concurrent strategies were developed to assess immune system status. The methods included (1) immunophenotying to assess circulating innate immune cell populations, (2) monitoring of circulating cytokines, particularly in response to a positive control agent, and (3) monitoring of localized gastrointestinal tissue cytokines using immunohistochemistry (IHC), particularly in response to a positive control agent. All assays were validated using white papers and regulatory guidance within a GLP environment. To validate the assays precision, accuracy and sample stability were evaluated as needed using a fit for purpose approach. In addition animals were treated with proinflammtory substances to detect a positive versus negative signal. In conclusion, these three methods were confirmed to be robust assays to evaluate the immune system and GIT-specific immune responses of preweaning piglets.

Food additive carrageenan: Part II: A critical review of carrageenan in vivo safety studies.

Carrageenan (CGN) is a seaweed-derived high molecular weight (Mw) hydrocolloid, primarily used as a stabilizer and thickener in food. The safety of CGN regarding its use in food is reviewed. Based on experimental studies in animals, ingested CGN is excreted quantitatively in the feces. Studies have shown that CGN is not significantly degraded by low gastric pH or microflora in the gastrointestinal (GI) tract. Due to its Mw, structure and its stability when bound to protein, CGN is not significantly absorbed or metabolized. CGN also does not significantly affect the absorption of nutrients. Subchronic and chronic feeding studies in rodents indicate that CGN at doses up to 5% in the diet does not induce any toxicological effects other than soft stools or diarrhea, which are a common effect for non-digestible high molecular weight compounds. Review of several studies from numerous species indicates that food grade CGN does not produce intestinal ulceration at doses up to 5% in the diet. Effects of CGN on the immune system following parenteral administration are well known, but not relevant to food additive uses. The majority of the studies evaluating the immunotoxicity potential were conducted with CGN administered in drinking water or by oral gavage where CGN exists in a random, open structured molecular conformation, particularly the lambda form; hence, it has more exposure to the intestinal mucosa than when bound to protein in food. Based on the many animal subchronic and chronic toxicity studies, CGN has not been found to affect the immune system, as judged by lack of effects on organ histopathology, clinical chemistry, hematology, normal health, and the lack of target organ toxicities. In these studies, animals consumed CGN at orders of magnitude above levels of CGN in the human diet: ≥1000 mg/kg/d in animals compared to 18-40 mg/kg/d estimated in the human diet. Dietary CGN has been shown to lack carcinogenic, tumor promoter, genotoxic, developmental, and reproductive effects in animal studies. CGN in infant formula has been shown to be safe in infant baboons and in an epidemiology study on human infants at current use levels.

Comparative functional observational battery study of twelve commercial pyrethroid insecticides in male rats following acute oral exposure.

Twelve commercial pyrethroid insecticides (technical-grade active ingredients) were evaluated individually for acute neurobehavioral manifestations of toxicity under conditions suited to assist with determining whether they act by a common mechanism of toxicity. The pyrethroids that were tested reflect a diversity of structures, including six with an alpha-cyano phenoxybenzyl moiety (beta-cyfluthrin, lambda-cyhalothrin, cypermethrin, deltamethrin, esfenvalerate and fenpropathrin) and six without this moiety (bifenthrin, S-bioallethrin, permethrin, pyrethrins, resmethrin and tefluthrin). These chemicals also present a variety of behavioral effects, including ones that are historically classified as causing a T (tremor), CS (choreoathetosis with salivation) or intermediate syndrome of intoxication, and others that have not previously been classified. Each pyrethroid that was tested consisted of the complement of isomers that occur in commercial products--a key factor for relevance for environmental and human exposure and for comparisons, since the biological activity of the individual isomers can vary tremendously. Young-adult male Sprague-Dawley rats (10 per dose group) were administered a single dose of pyrethroid by oral gavage, in corn oil, at a volume of 5 ml/kg. Each was tested at a range of two or three dose levels, including a minimally toxic dose, to establish the more sensitive manifestations of toxicity, and a more toxic dose, to establish a more complete spectrum of neurobehavioral manifestations. Animals were evaluated using a functional observational battery (FOB) that was designed to characterize and distinguish effects classically associated with T or CS syndromes of intoxication. The FOB was performed when manifestations of toxicity were most apparent at the time of peak effect (2, 4, or 8 h post-dosing) by observers who were blinded to dose group assignment, thus avoiding possible bias. The results from this study indicate that some pyrethroids clearly exhibit the historic classification symptoms of the T and CS syndromes while others do so less obviously. Use of the statistical technique of Principal Component Analysis (PCA) further helped interpret the study findings, as described in the accompanying paper (Breckenridge et al., 2009). These results establish manifestations of neurotoxicity in vivo that can be used as weight of evidence to determine whether pyrethroid insecticides act through a common mechanism of toxicity in mammals. Based on a review of the FOB data, analyzed by PCA, and other published data, two common mechanism groups are proposed. Group 1 would include pyrethrins, bifenthrin, resmethrin, permethrin, S-bioallethrin and tefluthrin. Group 2 would include cypermethrin, deltamethrin, esfenvalerate, beta-cyfluthrin and lambda-cyhalothrin. Fenpropathrin exhibited features of both groups.

A 90-day dietary study on kappa carrageenan with emphasis on the gastrointestinal tract.

Groups of Fischer 344 rats (20/sex/group) received control or treated diets at levels of 0, 25,000 or 50,000 ppm kappa carrageenan with a molecular weight range (Mw) of 196,000-257,000 Da for 90 days. The Low Molecular Weight Tail (LMT) ranged between 1.9% and 12.0%<50 kDa (mean 7%) based on the results of a program initiated to develop a validated analytical method to measure the LMT. This is the first GLP dietary study in which carrageenan is characterized by percentage LMT. Clinical examinations were performed daily. Individual food consumption/body weight measurements were made weekly. Ophthalmic exam was conducted prior to and at the end of treatment. Hematology/serum chemistry and urinalysis evaluations were done at necropsy, as were organ weight determinations for adrenals, brain, heart, kidneys, liver, ovaries, spleen, testes and thyroid with parathyroids. Full histopathological evaluation of organs was conducted on the control and 50,000 ppm groups, including hematoxylin-eosin-stained cross sections of paraffin-embedded rolled colon. Clinical signs were limited to soft feces in high dose rats and to a lesser extent in low dose rats. There were no treatment-related effects on body weights, urinalysis, hematology or clinical chemistry parameters, or on organ weights or ophthalmic, macroscopic or microscopic findings. The gastrointestinal tract appeared normal in detailed histopathological evaluation using the Swiss roll technique. The NOAEL is 50,000 ppm in the diet (mean calculated test material consumption of 3394+/-706 mg/kg/day in males, 3867+/-647 mg/kg/day in females). The results of the study provide evidence that it is not necessary to characterize carrageenan by a specification for LMT (less than 5% below 50 kDa) as has been done in Commission Directive 2004/45/EC of 16 April 2004 (Commission Directive, 2004/45/EC of 16 April 2004 amending Directive 96/77/EC laying down specific purity criteria on food additives other than colors and sweeteners. Official Journal of European Union 20 April, 2004, L113/19-L113/21).

Subchronic and developmental toxicity studies in rats with Ac-Di-Sol croscarmellose sodium.

Studies were conducted to evaluate the subchronic and developmental toxicity of Ac-Di-Sol (croscarmellose sodium). In the subchronic study, groups of Sprague-Dawley rats (20/sex/group) received 0 (control), 10000, or 50000 ppm Ac-Di-Sol in the diet for 90 consecutive days (equivalent to 757 and 893 mg/kg/day for males and females fed 10000 ppm, respectively, and to 3922 and 4721 mg/kg/day for males and females fed 50000 ppm, respectively). No mortality, clinical signs of toxicity, or adverse toxicological effects on hematology or serum chemistry parameters, feed consumption, or ophthalmologic examinations were noted in any treatment group. Body weight gain was depressed in high-dose males during the final 3 weeks. The only treatment-related histological lesion noted was moderate renal mineralization at the corticomedullary junction in one high-dose female. This lesion was not considered a specific effect of Ac-Di-Sol, but rather a secondary effect resulting from a potential increase in urinary pH and renal excretion of sodium due to the high intake of sodium associated with Ac-Di-Sol. In the developmental toxicity study, groups of pregnant Sprague-Dawley rats (25/group) received 0 (control), 10000, or 50000 ppm Ac-Di-Sol in the diet on gestational days 6 to 15. No evidence of maternal, fetal, or embryo toxicity was noted. The no-observed-adverse-effect level (NOAEL) for Ac-Di-Sol in both studies exceeds 50000 ppm in the diet, which represents doses of 3922 and 4712 mg/kg/day, for males and females, respectively. The results of these studies demonstrate the low subchronic oral toxicity and developmental toxicity of Ac-Di-Sol, and support the safe use of Ac-Di-Sol in oral applications such as pharmaceuticals, dietary supplements, and sweetener tablets.

Mechanisms of pyrethroid neurotoxicity: implications for cumulative risk assessment.

The Food Quality Protection Act (FQPA) of 1996 requires the United States Environmental Protection Agency to consider the cumulative effects of exposure to pesticides having a 'common mechanism of toxicity.' This paper reviews the information available on the acute neurotoxicity and mechanisms of toxic action of pyrethroid insecticides in mammals from the perspective of the 'common mechanism' statute of the FQPA. The principal effects of pyrethroids as a class are various signs of excitatory neurotoxicity. Historically, pyrethroids were grouped into two subclasses (Types I and II) based on chemical structure and the production of either the T (tremor) or CS (choreoathetosis with salivation) intoxication syndrome following intravenous or intracerebral administration to rodents. Although this classification system is widely employed, it has several shortcomings for the identification of common toxic effects. In particular, it does not reflect the diversity of intoxication signs found following oral administration of various pyrethroids. Pyrethroids act in vitro on a variety of putative biochemical and physiological target sites, four of which merit consideration as sites of toxic action. Voltage-sensitive sodium channels, the sites of insecticidal action, are also important target sites in mammals. Unlike insects, mammals have multiple sodium channel isoforms that vary in their biophysical and pharmacological properties, including their differential sensitivity to pyrethroids. Pyrethroids also act on some isoforms of voltage-sensitive calcium and chloride channels, and these effects may contribute to the toxicity of some compounds. Effects on peripheral-type benzodiazepine receptors are unlikely to be a principal cause of pyrethroid intoxication but may contribute to or enhance convulsions caused by actions at other target sites. In contrast, other putative target sites that have been identified in vitro do not appear to play a major role in pyrethroid intoxication. The diverse toxic actions and pharmacological effects of pyrethroids suggest that simple additivity models based on combined actions at a single target are not appropriate to assess the risks of cumulative exposure to multiple pyrethroids.