E101a riboflavin-5'-phosphate [likely to be from GM
Bacteria]
E102 tartrazine, FD&C Yellow 5 [possible allergic reaction; mice tested
once orally with each additive at up to 0.5xLD50 or the limit
dose (2000mg/kg) develop dose-related DNA damage in the glandular stomach,
colon, and/or urinary bladder, and in the colon even at close to the acceptable
daily intakes (ADIs)ref]
E123 amaranth, FD&C Red 2 [possible allergic reaction; mice tested
once orally with each additive at up to 0.5xLD50 or the limit
dose (2000mg/kg) develop dose-related DNA damage in the glandular stomach,
colon, and/or urinary bladder, and in the colon even at close to the acceptable
daily intakes (ADIs)ref.
The comet assay was positive in the colon of pregnant mice (gestational
day 11) 3 h after oral administration at the limit dose (2000 mg/kg) and
weakly positive in the lung 6 h after the administration : induces DNA
damage in the colon of male mice starting at 10 mg/kgref]
E124 Ponceau 4R, Cochineal Red A, Brilliant Scarlet 4R [possible allergic
reaction]
E125 scarlet GN
E126 Ponceau 6R [colouring]
E127 erythrosine, FD&C red 3 [possible allergic reaction]
E128 red 2G [possible allergic reaction]
E129 allura red AC, FD&C red 40 [possible allergic reaction; mice tested
once orally with each additive at up to 0.5xLD50 or the limit
dose (2000mg/kg) develop dose-related DNA damage in the glandular stomach,
colon (even at close to the acceptable daily intakes (ADIs)), and/or urinary
bladderref.
The comet assay is positive in the colon of pregnant mice (gestational
day 11) 3 h after oral administration of the limit dose (2000 mg/kg) :
induces DNA damage in the colon of male mice starting at 10 mg/kgref;
it inhibits state III mitochondrial respirationref;
few adverse effects in reproductive and neurobehavioral parameters in miceref;
NOAEL for lifetime toxicity/carcinogenicity is 7300 and 8300 mg/kg body
weight/day for male and female mice, respectivelyref;
Red-40 significantly reduces reproductive success, parental and offspring
weight, brain weight, survival, and female vaginal patency development.
Behaviorally, R40 produces substantially decreased running wheel activity,
and slightly increased postweaning open-field rearing activity. Overall,
R40 produces evidence of both physical and behavioral toxicity in developing
rats at doses of up to 10% of the dietref]
[new coccine (food red No. 18) : induces DNA damage in the colon of male
mice starting at 10 mg/kg : 20 ml/kg of soaking liquid from commercial
red ginger pickles, which contains 6.5 mg/10 ml of new coccine, induces
DNA damage in colon, glandular stomach, and bladderref]
E130 indanthrene blue RS
E131 patent blue V [possible allergic reaction]
E132 indigo carmine, indigotine, FD&C blue 2 [possible allergic reaction]
E133 brilliant blue FCF, FD&C Blue 1 [possible allergic reaction]
E140 chlorophylls and chlorophyllins: (i) chlorophylls (ii) chlorophyllins
E141 Cu complexes of chlorophylls and chlorophyllins (i) Cu complexes of
chlorophylls (ii) Cu complexes of chlorophyllins
E142 greens S [possible allergic reaction]
E150a plain caramel [likely to be GM]
E150b caustic sulphite caramel [likely to be GM]
E150c ammonia caramel [likely to be GM]
E150d sulphite ammonia caramel [likely to be GM]
E151 black PN, brilliant black BN [possible allergic reaction]
E152 black 7984 [possible allergic reaction]
E153 carbon black, vegetable carbon [likely to be GM] [possibly of animal
origin]
E154 brown FK, kipper brown [possible allergic reaction]
E155 brown HT, chocolate brown HT [possible allergic reaction]
During the latter half of the twentieth century, inflammatory
bowel disease
and gastrointestinal malignancy
have been major causes of morbidity and mortality in the USA. Even with
improvements in treatment and cancer screening, colorectal cancer remains
the second leading cause of cancer mortality in the United States. The
Western diet has been considered a possible source of inflammatory bowel
disease and colorectal malignancy, and intensive efforts have been undertaken
to study the impact of specific constituents of the Western diet, such
as fiber and fat (1-3). One food additive, carrageenan, has been associated
with induction and promotion of intestinal neoplasms and ulcerations in
numerous animal experiments; however, carrageenan remains a widely used
food additive. In 1982, the International Agency for Research on Cancer
(IARC) (4) designated degraded carrageenan as Group 2B, noting sufficient
evidence for the carcinogenicity of degraded carrageenan in animal models
to infer that "in the absence of adequate data on humans, it is reasonable,
for practical purposes, to regard chemicals for which there is sufficient
evidence of carcinogenicity in animals as if they presented a carcinogenic
risk to humans" (p. 90). The National Research Council has noted this designation
for degraded carrageenan in their 1996 monograph (5). Recognizing the impact
of carrageenan in animal models, several European and British investigators
have advised against the continued use of carrageenan in food (6-11). Several
reports have called attention to the problems associated with carrageenan
consumption (6-11). Extracted from red seaweed, carrageenan has been
used in food products for centuries and was patented as a food additive
for use in the USA in the 1930s. It has been used widely as a food additive,
contributing to the texture of a variety of processed foods. It has also
been used as a laxative,
as treatment for peptic
ulcer disease,
and as a component of pharmaceuticals, toothpaste, aerosol sprays, and
other products (12-15). In 1959, carrageenan was granted GRAS (Generally
Regarded as Safe) status in the USA. GRAS substances are permitted to be
incorporated into food products as long as good manufacturing processes
are used and the substance is used only in sufficient quantity to achieve
the desired effect (16,17). In the USA, the status of carrageenan was reconsidered
by the FDA, and an amendment to the Code of Federal Regulations for the
food additive carrageenan was proposed in 1972 (18). To diminish the
public's exposure to degraded carrageenan, the amendment supported inclusion
of an average molecular weight for carrageenan of 100,000 and a minimum
viscosity of 5 centipoises (cps) under specified conditions. However,
the actual regulation was not amended, although several publications indicated
that it had been modified (7,8,19-23). In 1979, the proposal to include
the average molecular weight requirement of 100,000 and the associated
viscosity requirement in the Code of Federal Regulations was withdrawn.
It was anticipated that a new rule-making proposal on carrageenan that
would comprehensively address all food safety aspects of carrageenan and
its salts would be published in about a year, but this has not been forthcoming
(24,25). The proposal withdrawal referred to interim specifications for
food-grade carrageenan using the Food Chemical Codex; these include a viscosity
stipulation, but no average molecular weight requirement (26). In the Food
Chemicals Codex and supplements, carrageenan is described with attention
to specific requirements for its identification and tests of its properties,
including its sulfate content, heavy metal content, solubility in water,
content of acid-insoluble matter, and viscosity [a 1.5% solution is to
have viscosity >= 5 cps at 75°C] (26,27). Although the viscosity is
stipulated, viscosity may not adequately protect food-grade carrageenan
from contamination by the lower molecular weight degraded carrageenans
that IARC has denoted as Group 2B. Because undegraded carrageenan may have
molecular weight in the millions, the actual viscosities of commercial
carrageenans range from about 5 to 800 cps when measured at 1.5% at 75°C
(14). Native carrageenan has molecular weights of 1.5 106-2
107 (28); poligeenan or degraded carrageenan is described as having
average molecular weight of 20,000-30,000 (4). The average molecular weight
of poligeenan has been described elsewhere as 10,000-20,000, but extending
up to 80,000 (29). Food-grade carrageenan has been described as having
average molecular weight of 200,000-400,000 (29), and elsewhere as having
molecular weight of 100,000-800,000 (19). Furcelleran (or furcellaran),
a degraded carrageenan of molecular weight 20,000-80,000, has a sulfate
content of 8-19% (12,17). No viscosity or minimum average molecular weight
was designated for furcelleran in the 1972 or 1979 Federal Register documents
(18,24). In the Food Chemical Codex (fourth edition), a 1.5% solution of
furcelleran at 75°C is described as having minimum viscosity of 5 cps
(27). Today, carrageenan is still included among the food additives designated
GRAS in the Code of Federal Regulations. The stipulations for its use include
the following: a) it is a sulfated polysaccharide, the dominant hexose
units of which are galactose and anhydrogalactose; b) range of sulfate
content is 20-40% on a dry-weight basis; c) the food additive is used or
intended for use in the amount necessary for an emulsifier, stabilizer,
or thickener in foods, except for those standardized foods that do not
provide for such use; d) to assure safe use of the additive, the label
and labeling of the additive shall bear the name of the additive, carrageenan.
Also included are similar standards for carrageenan salts and for furcelleran
and furcelleran salts (30). In 1999-2000, approved uses for carrageenan
were extended to include additional incorporation into food and medicinal
products, including both degraded and undegraded carrageenan in laxatives
(31-33). For use in experimental models, degraded carrageenan (poligeenan)
is derived from carrageenan by acid hydrolysis, frequently by a method
developed by Watt et al. (34). This method is expected to yield a degraded
carrageenan of average molecular weight 20,000-30,000 (35).Experiments
demonstrate that reaction conditions similar to those of normal digestion
can lead to the formation of degraded carrageenan (9-11). In addition,
experimental data have revealed the contamination of food-grade carrageenan
by substantial amounts of degraded carrageenan (10). Also, some bacteria
are known to hydrolyze carrageenan and form low molecular weight derivatives
(36-40).The sections that follow and the accompanying tables
summarize many experimental observations with regard to the intestinal
effects of carrageenan. In addition, I review possible mechanisms for production
of degraded carrageenan from undegraded carrageenan under physiologic conditions,
as well as evidence that provides a basis for the mechanism of carrageenan's
effects and for the reconsideration of the safety of carrageenan in the
human diet.
characteristics of carrageenan : 3 forms of carrageenan predominate, known
as k, i, and l.
All have similar d-galactose backbones (alternating a-1,3
to ß-1,4 linkages), but they differ in degree of sulfation, extent
of branching, solubility, cation binding, and ability to form gels under
different conditions. l-carrageenan is the least
branched and the least gel forming; it is readily soluble at cold temperatures,
in contrast to k- or i-carrageenan.
Some of the basic characteristics of k,
i,
and l carrageenan (4,12-15,20-22,31-33,41-44)
chemical composition : hydrocolloid composed of a-D-1,3-
and b-D-1,4 galactose residues
that are sulfated at up to 40% of the total weight. Strong negative charge
over normal pH range. Associated with ammonium, calcium, magnesium, potassium
or sodium salts.
solubility : l-carrageenan is readily soluble
in cold or hot aqueous solution; k is soluble
in hot solution; treatment of aqueous solution with potassium ion precipitates
k-carrageenan
gel formation : l-does not for gels; l
and i form right-handed helices; potassium chloride
promotes gel formation of k; calcium ion promotes
gel formation of l
metabolism : hydrolysis of glycosidic linkages at lower pH, especially
pH < 3.0; also desulfation by sulfatases.
viscosity : near logarithmic increase in viscosity with increasing concentration.
Viscosity of food-grade carrageenan defined as > 5 cps at 75°C for
a 1.5% solution; viscosity ranges from 5 to 800 cps for a 1.5% solution
at 75°C
source : red algae, predominantly aqueous extraction from Chondrus,
Gigartina,
and various Eucheuma species
molecular weight : discrepancies in definitions. Native carrageenan reported
to have average molecular weight of 1.5 x 106 - 2 x 107; food-grade carrageenan
reported as 100,000-800,000 or 200,000-400,000. Degraded carrageenan (poligeenan)
has average molecular weight of 20,000-30,000; furcellaran has average
molecular weight 20,000-80,000
properties : l and k
combine easily with milk proteins to improve solubility and texture; serve
as thickening agent, emulsifier, stabilizer
synergistic effects : with locust bean gum, increase in gel strength. Other
hydrocolloids may also affect gel strength and cohesiveness
concentration in food products : 0.005-2.0% by weight
In addition to food additive uses, carrageenan has been used in cosmetics,
pesticides, and pharmaceuticals, as well as in toothpaste and room deodorizers.
It has been used as a treatment of ulcers and as an emulsifier in mineral
oil laxatives, liquid petrolatum, and cod liver oil. However, its predominant
role has been in food preparations, in which it is used across a wide variety
of food groups because of its ability to substitute for fat and its ability
to combine easily with milk proteins to increase solubility and improve
texture. Hence, it is used in low-calorie formulations of dietetic beverages,
infant formula, processed low-fat meats, whipped cream, cottage cheese,
ice cream, and yogurt, as well as in other products. From its original
use several centuries ago as a thickener in Irish pudding and its incorporation
into blancmange, the food additive use has extended widely and cuts across
both low-fat and high-fat diets. It is often combined with other gums,
such as locust bean gum, to improve the texture of foods (12-14,22,41,42).
In 1977, data obtained by the survey of industry on the use of food additives
produced an estimate of daily carrageenan intake of 100 mg for individuals
older than 2 years. The 1971 survey of industry had indicated that formula-fed
infants in the first 5 months of life had an intake of 108 mg/day (21,43).
Informatics, Inc., in a report prepared for the Food and Drug Administration,
cited daily carrageenan consumption of 45 mg (19); this is similar to the
reported intake of 50 mg/day of carrageenan in France (45). Nicklin and
Miller (20) reported intake of 0-1.5 g/day, depending on choice of diet
and total food consumed. Although the Food and Nutrition Board of the National
Research Council of the National Academy of Sciences of the United States
in 1971 initially estimated 367 mg/day for carrageenan intake for individuals
older than 2 years in the United States, this was subsequently revised
to 11 mg/day. The wide range of estimates may be attributed to inconsistencies
in how industry has reported carrageenan production and consumption data,
variation in processed food formulations with regard to extent of incorporation
of carrageenan, and changes in use of carrageenan in nonfood products.
Daily individual consumption of between 50 mg/day and 100 mg/day is consistent
with total consumption in the United States of 7,700 metric tons, as estimated
for 1997 (46). The content of carrageenan in several commonly consumed
food products is summarized in Table 2. Because manufacturing practices
vary and change over time and the food formulae are proprietary, carrageenan
content is indicated by a range (12,13,47-49). The content is expressed
as the percent by weight of carrageenan used in the production of the food.
experimental results in animal models : intestinal lesions after exposure
to carrageenan in animal models. Table 3 summarizes the laboratory investigations
that associate exposure to carrageenan with the occurrence of intestinal
lesions (50-93). Several animals were tested, including guinea pig, rat,
monkey, mouse, rabbit, and ferret. The guinea pig seemed most susceptible
to ulceration and the rat most susceptible to malignancy. Many studies
used exposure to carrageenan in a drinking fluid, at concentrations generally
of 1%. Some were feeding studies, in which carrageenan was added to a solid
diet. Some studies used gastric or duodenal intubation to ensure intake
at a specified level; however, this method may have affected the way that
carrageenan was metabolized by gastric acid (74,82-84,91). Feeding of carrageenan
with milk may also have affected study results, because carrageenan binds
tightly to milk proteins (caseins), affecting its metabolism (12-15,22,41,42,47).
The degraded carrageenan used in most of the experiments had molecular
weight from 20,000 to 40,000. Several major findings in relation to neoplasia
and ulceration were observed in these animal studies. All of these studies
observed the effects of carrageenan in comparison to appropriate control
animals.
[skip Table 3]
In the footnote to Table 3, several subdivisions of the table are indicated
with citation of the entries from the table. The subdivisions include:
a) studies in which carrageenan alone induces abnormal proliferation or
malignancy, b) studies in which carrageenan alone induces intestinal ulcerations,
c) studies in which carrageenan appears to be a promoter of malignancy
in association with another agent, d) studies using a rat model, e) studies
using a guinea pig model, f) studies using degraded carrageenan, g) studies
using undegraded carrageenan, h) studies indicating uptake of carrageenan
into an extraintestinal site(s), i) studies indicating intestinal breakdown
of carrageenan into lower molecular weight forms, and j) studies demonstrating
ulcerations in rats using degraded carrageenan. In the table, the classification
of the carrageenan used in the experiments as , , or is indicated
when this information is clear from the original report.
neoplasia. Wakabayashi and associates (72) demonstrated the appearance
of colonic tumors in 32% of rats fed 10% degraded carrageenan in the diet
for less than 24 months. The lesions included squamous cell carcinomas,
adenocarcinomas, and adenomas. With exposure to 5% degraded carrageenan
in drinking water, there was a 100% incidence of colonic metaplasia after
15 months. Metastatic squamous cell carcinoma was observed in retroperitoneal
lymph nodes in this experiment. In addition, macrophages that had metachromatic
staining consistent with carrageenan uptake were observed in liver and
spleen. Other studies have demonstrated the development of polypoidal lesions
and marked, irreversible squamous metaplasia of the rectal mucosa, the
extent of which was associated with duration and concentration of carrageenan
exposure (67,70). Oohashi et al. (67) observed a 100% incidence of colorectal
squamous metaplasia that progressed even after degraded carrageenan intake
was discontinued in rats fed 10% degraded carrageenan for 2, 6, or 9 months
and sacrificed at 18 months. Fabian et al. (84) observed adenomatous and
hyperplastic polyps as well as squamous metaplasia of the anorectal region
and the distal colon in rats given 5% carrageenan as a drinking fluid.
Similarly, Watt and Marcus (90) observed hyperplastic mucosal changes and
polypoidal lesions in rabbits given carrageenan as drinking fluid for 6-12
weeks at a concentration of 0.1-5%. Focal and severe dysplasia of the mucosal
epithelium was observed in rabbits after 28 months of 1% degraded carrageenan
in their drinking fluid (58).
promotion of neoplasia. Several studies demonstrated an increased occurrence
of neoplasia in relation to exposure to undegraded or degraded carrageenan
and associated exposure to a known carcinogen. Experimental data with undegraded
carrageenan included enhanced incidence of colonic tumors in rats treated
with azoxymethane (AOM) and nitrosomethylurea (NMU), when carrageenan was
added to the diet. Groups of rats received control diet; control diet with
15% carrageenan; 15% carrageenan plus 10 injections of AOM given weekly;
carrageenan plus NMU; NMU alone; and AOM alone. AOM or NMU with carrageenan
led to 100% incidence of tumors, versus 57% with AOM alone and 69% with
NMU alone (p < 0.01). Controls had 0%, and carrageenan alone led to
an incidence of 7%. In addition, when undegraded carrageenan was combined
with AOM, there was a 10-fold increase in the number of tumors per rat
(73). (Figure 1)
Figure 1. Carrageenan and promotion of neoplasms. No tumors were found
in the control animals. With AOM and undegraded carrageenan, there was
a 10-fold increase in the number of tumors per rat. See text for exposure
regimens (73). 1,2-Dimethylhydrazine (1,2-DMH) alone caused neoplams in
40% of animals tested; with addition of undegraded carrageenan, 75% of
exposed animals had tumors that were larger and occurred more frequently
proximal (57). The combination of 1,2-DMH and degraded carrageenan was
associated with an increase in small intestinal tumors from 20% to 50%
of exposed animals and with an increase from 45% to 60% in large intestinal
tumors (64).
Using undegraded carrageenan as a solid gel at concentration 2.5% for
100 days, Corpet et al. (50) found that after exposure to azoxymethane,
there was promotion of aberrant crypt foci by 15% (p = 0.019). Exposure
of rats to 6% undegraded carrageenan in the diet for 24 weeks, with 1,2-dimethylhydrazine
(1,2-DMH) injections weekly, was associated with an increase in tumors
from 40% to 75% and with the more frequent occurrence of larger and proximal
tumors (57). Degraded carrageenan in the diet of rats at a 10% concentration
in association with exposure to 1,2-DMH weekly for 15 weeks was associated
with an increase in small intestinal tumors from 20% to 50% and in colonic
tumors from 45% to 60% (64). Iatropoulos et al. (77) found that in rats
given 5% degraded carrageenan in the drinking water for less than 30 weeks
in association with injections of 1,2-DMH weekly, there were increases
in poorly differentiated adenocarcinomas and in tumors of the ascending
and transverse colon, as well as increased proliferation of cells in the
deep glandular areas. Several investigators have measured the effect of
carrageenan on thymidine incorporation and colonic cell proliferation.
Wilcox et al. (51) observed a 5-fold increase in thymidine kinase activity
in colon cells with 5% undegraded or 5% degraded carrageenan. There was
an associated 35-fold increase in proliferating cells in the upper third
of crypts with degraded carrageenan and an 8-fold increase with undegraded
carrageenan (51). With 5% -undegraded carrageenan fed to rats for 4 weeks,
Calvert and Reicks (55) observed a 4-fold increase in thymidine kinase
activity in the distal 12 cm of the colon (p < 0.001). Fath et al. (59)
observed a 2-fold increase in colonic epithelial cell proliferation, with
increase in labeling indices in both proximal and distal colon and extensive
increase of the proliferative compartment in the proximal colon to the
upper third of the intestinal crypt, after exposure of mice to 10% degraded
carrageenan in drinking water for 10 days.
ulceration. Many studies have demonstrated significant ulceration of the
cecum and/or large intestine after oral exposure to carrageenan in guinea
pigs, rabbits, mice, rats, and rhesus monkeys (34,35,53,56,58,59,62,63,65,68,70,71,75,
78-80,82,83,86-93). Ulcerations arose in association with exposure to either
degraded or undegraded carrageenan. Lesions occurred initially in the cecum
of guinea pigs and rabbits, but could be induced in more distal parts of
the colon of the guinea pig, as in an experiment in which carrageenan was
introduced directly into the colon after ileotransversostomy (63). In rats,
the ulcerative lesions appeared initially in distal colon and rectum (8).
Undegraded and degraded carrageenan have been associated with epithelial
cell loss and erosions in rats (51,65,70,87,93). Watt et al. (34) first
observed ulcerations in response to carrageenan exposure in animal models
more than three decades ago. They noted that 100% of guinea pigs given
2% degraded carrageenan as liquid for 20-30 days had colonic ulcerations
and that 75% of the animals > 200 ulcers (34). When guinea pigs were given
1% undegraded carrageenan as liquid for 20-30 days, 80% developed colonic
ulcerations (92). The lesions were routinely produced with carrageenan
concentrations of 0.1-1%, which is similar to the concentration in a variety
of food products (7,12-14). Grasso et al. (83) demonstrated pinpoint cecal
and colonic ulcerations in guinea pigs and rabbits given 5% undegraded,
as well as degraded, carrageenan in the diet for 3-5 weeks. Lesions were
not observed in ferrets and squirrel monkeys given degraded carrageenan
by gastric intubation (83). Other investigators have also observed ulcerations
after exposure to either degraded or undegraded carrageenan (75,88). Engster
and Abraham (75) observed ulceration of cecum in guinea pigs given -carrageenan
of molecular weight 21,000-107,000, demonstrating ulcerations were also
caused by higher molecular weight carrageenan. Cecal ulcerations were not
found with exposures to or carrageenan of molecular weight
varying from 8,500-314,000. Investigators have noted that carrageenan-induced
ulcerations of the colon are dose dependent and related to duration of
exposure (52,53,67,68,70,89,90). Kitsukawa et al. (52) observed small epithelial
ulcerations in guinea pigs who received carrageenan in their drinking fluid
at two days. Olsen and Paulsen (68) observed cecal lesions after 24 hr
and confluent ulcerations after 7 days in guinea pigs that ingested a 5%
carrageenan solution. In rats, superficial erosions were observed at the
anorectal junction at 24 hr after 10% dietary carrageenan (70); these extended
more proximally over time. In 5 days of feeding with a 5% carrageenan solution,
Jensen et al. (62) observed as many as 111 ulcerations/cm2 over the mucosal
surface of the cecum in the guinea pig. Benitz et al. (82) observed a dose
effect when degraded carrageenan was given at concentrations of 0.5-2%
in drinking fluid to rhesus monkeys for 7-14 weeks. Watt and Marcus (89)
observed that in rabbits given 0.1% degraded carrageenan as drinking fluid,
60% of the animals developed ulcerations, whereas 100% of those given 1%
carrageenan had ulcerations when exposed for 6-12 weeks.
resemblance to ulcerative colitis. Several investigators have noted the
resemblance between the ulcerative lesions and accompanying inflammatory
changes induced by carrageenan and the clinical spectrum of ulcerative
colitis (56,94-99). Since the development of the carrageenan-induced model
of ulcerative disease of the colon in 1969, carrageenan exposure has been
used to model ulcerative colitis and to test for response to different
treatments (52,62,100,101). Clinical features in the experimental animals
exposed to carrageenan have included weight loss, anemia, diarrhea, mucous
in stools, and visible or occult blood in stools. The absence of small
intestinal lesions and the lack of remission and exacerbation are also
characteristic features of the carrageenan model (99,102). Onderdonk (94)
discussed the similarity between the carrageenan model of colitis and ulcerative
colitis in humans and considered whether animal models for inflammatory
bowel disease were also models for intestinal cancer because of the increased
risk of colon cancer in individuals with ulcerative colitis. He reviewed
the findings from carrageenan-treated animals, including loss of haustral
folds, mucosal granularity, crypt abscesses, lymphocytic infiltration,
capillary congestion, pseudopolyps, and strictures. Other observations
have demonstrated an apparent sequence from colitis to squamous metaplasia
and then to tumors of the colorectum (67,72,102). Atypical epithelial hyperplasia
in the vicinity of carrageenan-induced ulcerations resembled findings from
human ulcerative colitis that provide a link to intestinal neoplasia (86,98).
proposed mechanism of development of lesions. A common feature observed
in the animal models of ulceration in association with carrageenan exposure
is macrophage infiltration (35,56,63,65,68,75,76,78-81, 83,84,88,92,102-104).
Fibrillar material and metachromatic staining of the macrophages were observed.
Notably, the macrophage lysosomes appeared to take up the fibrillar material
and to become distorted and vacuolated. It appeared that colonic ulcerations
developed as a result of macrophage lysosomal disruption, with release
of intracellular enzymes, subsequent macrophage lysis, and release of intracellular
contents that provoked epithelial ulceration (75,76,79,84,85,88,105,106).
In the rhesus monkey, Mankes and Abraham (76) observed vacuolated macrophages
with fibrillar material when the animals were given undegraded carrageenan
of molecular weight 800,000 as a 1% solution in their drinking fluid, demonstrating
the occurrence of these changes after exposure to undegraded as well as
to degraded carrageenan. In an effort to clarify further the precise pathogenic
changes that occurred, Marcus et al. (35) evaluated pre-ulcerative lesions
after exposure of guinea pigs to degraded carrageenan for only 2-3 days.
The animals received 3% drinking solution of carrageenan, with an average
daily carrageenan intake of 5.8 g/kg. Early focal lesions were observed
macroscopically in the cecum in only one animal with this brief exposure.
However, in all test animals, a diffuse cellular infiltrate, with macrophages
and polymorphonuclear leukocytes, was apparent microscopically. Inflammatory
changes in the cecum and ascending colon were present in all animals, and
in the distal colon and rectum in three of four animals. Metachromatic
staining material was noted in the lamina propria of the colon and surface
epithelial cells from cecum to rectum, as well as in colonic macrophages.
The surface epithelial cells and the macrophages contained vacuoles filled
with the metachromatic material, which was not found in the controls and
not seen in more advanced lesions in previous studies. These early lesions
suggested that the presence of degraded carrageenan within surface epithelial
cells might be associated with the subsequent breakdown of the mucosa and
to ulceration by a direct toxic effect on the epithelial cells (35). Hence,
a model of mechanical cellular destruction by disruption of lysosomes from
carrageenan exposure arises from review of the experimental studies in
animals. The observed changes in the lysosomes resemble the characteristic
changes observed in some lysosomal storage diseases, in which there is
accumulation of sulfated metabolites that cannot be processed further due
to sulfatase enzyme deficiency (107-110). Table 4 presents a proposed mechanism
of the effects of carrageenan.
possible role of intestinal bacteria. The relationship between the intestinal
microflora and the biologic activity of carrageenan has been reviewed (111,112).
Investigators have examined the impact of antibiotics and alteration of
the resident microbial flora on the activity of carrageenan. Grasso et
al. (83) studied the impact of neomycin treatment on the development of
ulcerations by carrageenan. Pretreatment against coliforms failed to attenuate
the course of carrageenan-associated ulcerations (80,83). Pretreatment
with metronidazole was effective in preventing carrageenan-induced colitis
in another experiment, although there was no benefit in established colitis
(71). Aminoglycosides administered after carrageenan exposure were associated
with reduced mortality, but not with reduction in the number of colonic
ulcerations (94). Hirono et al. (65) found increased ulcerations and squamous
metaplasia from the anorectal junction to the distal colon in germ-free
rats fed 10% carrageenan for less than 63 days. Additional considerations
about the mechanism of action of carrageenan involved the role of production
of hydrogen sulfide gas from metabolism of carrageenan in the digestive
tract. Because carrageenan is heavily sulfated (up to 40% by weight), bacterial
sulfatases and sulfate reductases can produce hydrogen sulfide gas or HS-
from carrageenan. Carrageenan, as well as other sulfated polysaccharides,
has been shown to stimulate H2S production from fecal slurries (113). Sulfide
has been implicated in the development of ulcerative colitis, perhaps attributable
to interference with butyrate oxidation by colonic epithelial cells (114,115).
Butyrate has been shown to induce intestinal cellular differentiation,
suppress intestinal cell growth, and decrease expression of c-myc, among
other functions in colonic epithelial cells (116-118). No fermentation
of carrageenan was reported after testing with 14 strains of intestinal
bacteria. The increase in sulfide production observed arising from incubation
of -carrageenan with colonic bacteria demonstrates that intestinal metabolism
of carrageenan does occur. However, data pertaining to breakdown of carrageenan
by fecal organisms are limited (112,113)
extraintestinal manifestations of carrageenan exposure. Trace amounts of
un-degraded carrageenan have been reported to cross the intestinal barrier,
with accumulation of label in intestinal lymph nodes (61,74). Several investigators
have noted uptake of carrageenan by intestinal macrophages with subsequent
migration of these macrophages to lymph nodes, spleen, and liver (61,67,74,78,82,84,85).
In association with carrageenan-induced intestinal ulcerations, Delahunty
et al. (56) observed an increased permeability to large molecules, such
as [3H]PEG (polyethylene glycol)-900. This finding suggested that the intestinal
changes induced by carrageenan may be a factor in subsequent absorption
of carrageenan or other large molecules.
other experimental data. Because it can induce acute inflammation, carrageenan
has been widely used in experimental models of inflammation to assess activity
of anti-inflammatory drugs and to study mediators of inflammation (4,61,106,119,120).
Injected into an experimental site, such as the plantar surface of a rat's
paw, pleural cavity, or subcutaneous air bleb, carrageenan induces an inflammatory
response, with edema, migration of inflammatory cells, predominantly PMN
leukocytes, and possibly granuloma formation (61,120). Undegraded carrageenans
in vitro can inhibit binding of bFGF, TGF-ß1, and
PDGF but not IGF-1 or TGF-a (121). Macrophage
injury and destruction caused by carrageenan may be a factor in the reduced
cytotoxic lymphocytic response associated with carrageenan exposure
in vivo (122). In addition to depression of cell-mediated immunity,
impairment of complement activity and of humoral responses have been reported.
Prolongation of graft survival and potentiation of tumor growth have been
attributed to the cytopathic effect on macrophages (96,123). Because of
its
effect on T-cells, carrageenan has been studied for its impact on viral
infections with herpes simplex virus types 1 and 2 (124) and HIV-1 (125,126),
as well as infections with Chlamydia trachomatis (127). In experimental
systems, undegraded carrageenan has produced destruction of several different
cell types in addition to macrophages, including small intestine epithelial
cell monolayers (54), androgen-dependent malignant prostatic cells (128),
bFGF-dependent endothelial cell line (128), rat mammary adenocarcinoma
13762 MAT cells (129), and human mammary myoepithelial cells (130). Lysosomal
inclusions and vacuolation have been observed in macrophages, intestinal
epithelial cells, and myoepithelial cells exposed to carrageenan (79,85,131).
Injections of carrageenan were noted to induce sarcomas, as well as mammary
tumors in animal models, in an early study (132). In other experiments,
mammary and testicular tumors have been observed (69,133). Carrageenan
has also been noted to have anticoagulant activity, and large systemic
doses have been fatal through nephrotoxicity (4).
mechanisms for production of degraded carrageenan from undegraded carrageenan
:
gastrointestinal metabolism of carrageenan to
form smaller molecular weight components has been observed by several investigators,
who reported that carrageenan of high molecular weight changed during intestinal
passage, compatible with hydrolysis yielding lower molecular weight components
(9,10,74,75). Under conditions such as might occur in digestion, 17% of
food-grade carrageenan degraded to molecular weight < 20,000 in 1 hr
at pH 1.2 at 37°C. At pH 1.9 for 2 hr at 37°C, 10% of the carrageenan
had molecular weight < 20,000 (9). These data suggest that substantial
fractions of lower molecular weight carrageenan are likely to arise during
normal digestion.
Table 5 presents data with regard to contamination of food-grade carrageenan
by lower molecular weight carrageenan. 25% of
total carrageenans in 8 food-grade carrageenans were found to have molecular
weight < 100,000, with 9% having molecular weight < 50,000 (9)
in addition, several bacteria have been identified that are able to hydrolyze
carrageenan into smaller products, including tetracarrabiose. These bacteria,
including Cytophaga species and Pseudomonas carrageenovora,
are of marine origin; it is unknown whether the human microbial flora can
perform similar hydrolysis reactions (36-40,134).
extent of human exposure to carrageenan : indirect evidence relating exposure
to carrageenan and the occurrence of ulcerative colitis and intestinal
neoplasms consists of the similar geographic distribution between higher
consumption of carrageenan and higher incidence of inflammatory bowel disease
and colorectal cancer. Ulcerative colitis is more common in North America,
the United Kingdom, and Scandinavia, and less common in Central and Southern
Europe, Asia, and Africa (135). This incidence distribution is similar
to distributions for colorectal malignancy and for carrageenan consumption,
providing some ecologic evidence to support a potential etiologic role
of carrageenan in human disease (46,136). The reported TD50
(tumorigenic dose 50% = the dose rate, in milligrams per kilogram body
weight per day, which will halve the probability of remaining tumorless
over the life span of the exposed animal) by the Carcinogenic Potency Database
for degraded carrageenan is 2,310 mg/kg body weight/day, based on rodent
experiments (137,138). This extrapolates to 138.6 grams for a 60-kg individual.
If the total carrageenan intake per person in the United States is about
100 mg a day (43), about 9 mg of carrageenan with molecular weight <
50,000 is likely to be ingested through contamination of food-grade carrageenan
by degraded carrageenan, and at least 8 mg with molecular weight < 20,000
is likely to arise during normal digestion (simulated by exposure to pH
1.9 with pepsin for 1 hr at 37°C). This suggests an average intake
of about 10 mg/day of degraded carrageenan for an individual older than
2 years of age in the United States. An important issue is whether 10 mg/day
degraded carrageenan is safe to ingest. By the Delaney clause, no carcinogen
should be permitted in food. The Food Quality Protection Act (FQPA) established
a usage level for negligible risk associated with pesticide residue in
food at 1 ppm (139,140). Applying this standard to the extrapolated TD50
for degraded carrageenan for a 60-kg person, the anticipated average intake
of 10 mg/day is 70-fold greater than this standard (138.6 g/106/day). These
calculations do not take into consideration possible exposure to furcellaran
(molecular weight 20,000-80,000), or the wide range of possible intakes
of carrageenan.
Conclusion : inflammatory bowel disease and colorectal malignancy represent
major sources of morbidity and mortality in the USA. A possible factor
in the etiology of these pathologies is exposure to carrageenan. Several
investigators have expressed their concerns about the use of undegraded
carrageenan in food products (6-10), yet no legislative protection to restrict
incorporation of low molecular weight fractions has been enacted. In fact,
there has been no substantive review by the Food and Drug Administration
of carrageenan since the studies undertaken more than two decades ago.
However, there has been increased evidence regarding the cancer-promoting
activity of undegraded carrageenan and further confirmation of the carcinogenic
potential of degraded carrageenan. Evidence for the role in carcinogenesis
of carrageenan appears to support a nongenotoxic
model based on direct toxic effects, for carrageenan has been nonmutagenic
in Salmonella mutagenicity testing and nongenotoxic by DNA repair
tests (60,102). A model of cellular destruction--from disruption of lysosomes
by accumulation of carrageenan by-products or by interference with normal
cellular oxidation-reduction processes from sulfate metabolites--emerges
from review of the experimental studies. The impact of sulfatases, of either
bacterial or human origin, on the metabolism of carrageenan requires further
investigation. By interference with the normal intracellular feedback mechanisms
associated with arylsulfatase activity, including steroid sulfatase, the
highly sulfated carrageenan may have an impact on the availability of active,
unsulfated hormones, such as dehydroepiandrosterone, derived from dehydroepiandrosterone-sulfate,
and estrone-1, derived from estrone-1 sulfate. Genetic characteristics
that affect sulfatase and hydrolysis reactions as well as the individual
intestinal microflora may influence how carrageenan is metabolized and
how its effects are manifested. These factors may determine how carrageenan
is metabolized differently by different individuals, but these characteristics
may not be accessible to manipulation. A basic factor that can be controlled
is the intake of carrageenan, which is amenable to dietary modification
or food additive regulation. Although carrageenan is widely used as a food
additive for its texture-enhancing properties, other gums, some of which
are used in combination with carrageenan, such as locust bean gum, gum
arabic, alginate, guar gum, or xanthan gum, potentially can be used alone
or in different combinations as substitutes for carrageenan (41,46). Alternatively,
higher fat composition can lead to changes in food properties that may
compensate for exclusion of carrageenan. Other hydrocolloids that are used
as stabilizers and thickeners have not been associated with harmful gastrointestinal
effects, and it is reasonable to expect that they could replace carrageenan
in many food products. Although the dietary fibers pectin and psyllium
affect intestinal motility, ulcerations or neoplasms have not been induced
with either these or the other water-soluble polymers used as food additives.
In contrast, other highly sulfated polysaccharides, amylopectin sulfate
and dextran sulfate sodium, have induced ulcerations and neoplasia, suggesting
that the degree of sulfation and polysaccharide molecular weight may be
critical for induction of the observed effects (102). The major pieces
of evidence that support an argument to reconsider the advisability of
use of carrageenan as a GRAS food additive are:
degraded carrageenan is a known carcinogen in animal models
undegraded carrageenan is a known co-carcinogen in animal models of carcinogenesis
in animal models, both degraded and undegraded carrageenan have been associated
with development of intestinal ulcerations that resemble ulcerative colitis
hydrolysis such as may occur by exposure to gastric acid in the human stomach
can lead to the depolymerization of undegraded carrageenan and the availability
of degraded carrageenan
food-grade carrageenan may be contaminated with low molecular weight, degraded
carrageenan that may arise during food processing
the use of a viscosity measurement to characterize a carrageenan sample
is insufficient because the presence of a small number of large molecules
(and undegraded carrageenan may have molecular weight in the millions)
may obscure a significant low molecular weight fraction.
The potential role of carrageenan in the development of gastrointestinal
malignancy and inflammatory bowel disease requires careful reconsideration
of the advisability of its continued use as a food additive
A recent review of the toxicology of carrageenan by Tobacman (1) raised
questions about the safety of carageenan-containing foods. Intact carageenan
is a high molecular weight hydrocolloid (molecular weight 1.5-20
106). One concern has focused on the potential for degraded (low molecular
weight) carageenan to be formed by acid hydrolysis in the stomach and the
possibility that this material could promote cancer of the colon (1). Rats
fed degraded carrageenan have been shown to develop colorectal tumors (2).
Studies involving initiation with the genotoxic carcinogen azoxymethane,
followed by quantitation of the number of aberrant intestinal crypts formed
in response to subsequent carrageenan exposure, have also suggested that
degraded carageenan has the potential to promote colon cancer in rats (3).
These findings have led to degraded carrageenan being classified by the
International Agency for Research on Cancer (IARC) as 2B, a possible human
carcinogen, based on animal study data. Native carrageenan has been classified
by IARC as 3, unclassifiable with respect to carcinogenicity in humans.
In a recent paper, Taché et al (4) used a well-established and highly
sensitive aberrant crypt assay to examined the potential for carrageenan
to promote azoxymethane-induced colonic cancer; they found no promoting
effect when a humanized gut flora was used. Because the carrageenan was
administered in the drinking water, it was available for degradation in
the acidic environment of the stomach. The use of normal rodent microbiologic
flora produced a promoting effect of carrageenan in this model system (4),
confirming positive results of previous studies, in contrast with the negative
effect that occurred using humanized intestinal flora in the rat. Thus,
the conclusion must be that this colon cancer-promoting effect is a rodent-specific
phenomenon, requiring a rodent intestinal microbiologic flora, and that
carrageenan would not promote colon cancer in humans. The concerns with
regard to the induction of ulcerative colitis expressed by Tobacman (1)
are also inappropriately extrapolated from animal data with regard to human
risk. There have been many studies carried out with carrageenan in animals,
and carrageenan has been used to induce inflammation in susceptible species
and to test the anti-inflammatory properties of new candidate drugs. Although
guinea pigs are very sensitive to the induction of colitis by carrageenan,
primates--a more appropriate species for comparison to humans--are resistant
to the induction of colitis by carrageenan. The safety of carrageenan for
use in foods was confirmed at the 57th meeting of the Joint Food and Agriculture
Organization of the United Nations/World Health Organization Expert Committee
on Food Additives (JECFA) in Rome in June 2001 (5). The JECFA recommended
an acceptable daily intake (ADI) of "not specified," the most favorable
ADI for a food additive. This recommendation was made after a review of
all of the current toxicology and carcinogenicity studies on carrageenan
by two world experts in this field, S. Cohen (University of Nebraska Medical
Center, Omaha, NE, USA) and N. Ito (Nagoya City University Medical School,
Nagoya, Japan). It included consideration of studies not cited by Tobacman
(1) in her evaluation
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 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 (1), the use of carrageenan in
food is clearly in excess. Carthew has raised issues pertaining to the
role of human intestinal flora on the effects related to carrageenan and
the possibility of interspecies variation in the toxicity of carrageenan.
The paper by Taché et al. (2) referred to by Carthew actually supports
concerns about the availability of degraded carrageenan after exposure
to food-grade carrageenan and human microflora. The authors report data
on the average molecular weight of carrageenan recovered from stool samples
in feeding experiments with rats in which human intestinal microflora had
been introduced. The average molecular weight of the carrageenan extracted
from feces was 346,000 ± 18,000 in the rats with the conventional
intestinal flora and was slightly lower (307,000 ± 37,000) in the
rats exposed to human intestinal microflora. This strongly suggests that
metabolism of dietary carrageenan does not depend on the presence of rodent
microflora. Interpretation of Taché et al.'s (2) data on the number
of crypt foci and the numbers of aberrant crypts is confounded by lack
of a comparable control group, as noted by the authors. When they sought
to expose a control population to similar conditions (life in an isolator,
sawdust bedding), they found that the rats developed only 20 aberrant crypt
foci per colon; this was far less than the previously reported controls
that developed 86 ± 23 aberrant crypt foci per colon or the experimental
animals with human intestinal microflora that developed 55 ± 18
aberrant crypt foci per colon (3), suggesting unresolved experimental issues
pertaining to initiation. This confounds interpretation of the data about
promotion. Also, Taché et al. (2) did not provide details about
the actual composition of the microflora in their experimental rats, and
we do not know if it was consistent throughout the experiment. Hence, these
data cannot be used to declare that the colon cancer-promoting effect of
food-grade carrageenan is a "rodent-specific phenomenon" and that it requires
a rodent intestinal microbiologic flora. When the Food and Drug Administration
(FDA) 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
abscesses. 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/WHO Expert Committee
on Food Additives (JECFA) (6) rated the acceptable daily intake (ADI) of
carrageenan as "not specified," as they had done previously, including
at the 28th meeting in 1984 (7), rather than establishing a different position.
In the 1999 report on carrageenan prepared as part of the World Health
Organization Food Additives Series, Greig (8) stated that the JECFA ADI
of "not specified" for carrageenan was temporary, pending review in 2001.
Also, Greig (8) 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. Greig (8; p. 16) noted that "Maintenance of a restriction
on the relative mass distribution in the specifications of carrageenan
for food use provides protection against the adverse effects of carageenans
(sp) of low relative molecular mass." However, in 2001 the JECFA apparently
did not endorse any specific restriction on the molecular weight of food-grade
carrageenan. The report of Cohen and Ito to which Carthew refers and the
full report of JECFA 2001 are not yet published. 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.
Premier Foods has found itself
at the centre of a potentially damaging cancer scare in February 2005 after
using in its products chilli powder contaminated with Sudan 1 / 1-phenylazo-2-naphthol
-- an illegal red dye used for colouring non-edible items such as solvents,
oils waxes, petrol, gasoline and shoe and floor polishes. The dye, used
in a batch of Worcester sauce flavouring, was consequently used as an ingredient
in > 480 processed foods which were withdrawn from sale (the biggest food
recall in the UK’s food history). Premier, maker of British household brands
including Branston Pickle, Typhoo Tea and Ambrosia custard, said Wednesday
that a number of its customers intended to claim for the costs related
to the recall of products. The European Commission revealed on Feb 25 that
the batch of Sudan 1 dye at the root of the food scare came from India.
Europe-wide rules introduced in June 2003 controlling products like the
Sudan 1 dye were not being enforced. On March 7 2005 the health department
of east China's Shandong Province hunted down and seized a number of spicy
seasoning containing the cancer-causing Sudan I Monday in its capital Jinan.
The 164 boxes of spicy seasoning food, produced by the Guangzhou-based
Heize Meiweiyuan Food Co. Ltd., were seized in thestorehouse of the company's
Jinan agent, after the provincial health department found more than 100
bottles of the seasoning in a hotel. The agent said the seasoning did not
sell well in Jinan becauseof a high price and "a peculiar taste to many
locals". The provincial health department immediately ordered another round
of checkup in all the shops and supermarkets in Shandong, but found no
other food containing the cancer-causing colorant. The Heize Meiweiyuan
Food Co. Ltd was ordered to halt production for Sudan I checkup by the
Ministry of Health on March 5. All Kentucky Fried Chicken (KFC) outlets
in China have stopped selling New Orleans roast chicken wings and chicken
hamburgers after the cancer-causing food colourant, Sudan I, was found
in the sauce