PROCESSED EUCHEUMA SEAWEED
First draft prepared by
Ms E. Vavasour
Toxicological Evaluation Division
Bureau of Chemical Safety, Food Directorate
Health and Welfare Canada
Ottawa, Ontario, Canada
Processed Eucheuma seaweed (PES) was previously considered by
the Committee at its thirtieth and thirty-ninth meetings (Annex 1,
references 73 and 101) but it could not be evaluated for use in
foods because no relevant toxicological data were available. At its
present meeting the Committee reviewed a 90-day feeding study in
rats on a processed Eucheuma seaweed from E. cottonii and a
series of genotoxicity studies on a processed Eucheuma seaweed
from E. cottonii were available. Complete details of the 90-day
study were not provided.
2. BIOLOGICAL DATA
2.1 Biochemical Aspects
No information available.
2.2 Toxicological Studies
2.2.1 Acute toxicity studies
No new information available
2.2.2 Short-term toxicity studies
Groups of 10 male and 10 female Sprague-Dawley rats, 6 weeks
old, were fed diets which contained 0, 0.5, 1.5 or 5.0% PES, or 5.0%
refined carrageenan derived from Eucheuma cottoni for 3 months.
The rats were observed twice daily and the gross appearance of the
stools was checked in the morning. Individual body weights and food
consumption were measured weekly throughout the study. Standard
haematological and clinical chemistry parameters were measured in
blood samples taken from all animals at sacrifice. Urinalysis was
also conducted on fresh urine and 24-hour urine samples at week 13
of the study. Faecal samples were analyzed for gross appearance and
occult blood. Necropsy was performed on all animals at sacrifice,
selected organs weighed (brain, pituitary gland, submandibular
glands, thymus, lungs, thyroid, heart, liver, caecum, spleen,
kidneys, adrenal glands, testes, epididymides, prostate, ovaries and
uterus) and 40 tissues and organs preserved for histopathological
examination. No individual data were provided.
No deaths were observed during the study. The average daily
intakes for each of the dose levels of PES were 382, 1140 and
3887 mg/kg bw/day for males, and 410, 1292 and 4170 mg/kg bw/day for
females. A dose-related trend in the incidence of altered stool
quality was noted, in particular soft, big-size and fragmented
stool. This effect was most apparent (earlier onset, higher
frequency of occurrence and larger number of animals affected) in
the groups receiving 5% PES or refined carrageenan, especially the
latter. Faecal occult blood was not noted in any of the groups. In
addition, a higher urine volume and lower urine specific gravity was
observed in the 5% PES groups. Toluidine blue staining of the
liver, spleen, mesenteric lymph nodes and gastrointestinal tract did
not reveal deposition of metachromatic material at microscopic
examination. It was concluded that absorption of carrageenan did
not occur. No other effects attributable to treatment were evident
from the summary of the histopathological results (Philippine Bureau
of Food and Drugs 1992).
2.2.3 Long-term/carcinogenicity studies
No new information available
2.2.4 Reproduction studies
No new information available
2.2.5 Special studies on genotoxicity
The results of genotoxicity assays on PES are summarized in
2.3 Observations in humans
No information was available.
Table 1. Results of genotoxicity assays on PES
Test System Test Object Concentration of Results Reference
Rec assay B. subtilis 25-100 mg/ml Negative Sylianco et al. 1992
Ames test1,2 S. typhimurium TA100 25-100 mg/ml Negative Sylianco et al. 1992
Host-mediated Swiss Webster mice/ 625-2 500 mg/kg bw Negative Sylianco et al. 1992
assay S. typhimurium
Micronucleus Swiss Webster mice 625-2 500 mg/kg bw Negative Sylianco et al. 1992
1 Without S9 metabolic activation.
2 Only one strain of S. typhimurium was used for the Ames assay, though it is standard
practice to use 4 strains.
Analytical data provided on the commercial product and on the
material used in the toxicity studies were reported to conform to
the specifications that were prepared at the present meeting. The
viscosity specification indicated that the carrageenan component was
not degraded. Analytical data showed that the relative molecular
mass of processed E. cottonii was well above that of degraded
carrageenan and similar to that of traditionally refined
carrageenan, and that the acid-insoluble component of PES was
similar to cellulose. The crude protein content of the commercial
batches ranged from 0.1 to 1.5%, with a mean value of 1%. The
product did not contain heavy metals at levels of toxicological
In the 90-day feeding study in rats PES was administered at
0.5%, 1.5%, and 5% in the diet, in addition a comparison group was
fed traditionally-refined carrageenan at a level of 5%. The most
notable effect from this study was an alteration of stool
characteristics in both the groups fed PES and those fed
traditionally-refined carrageenan at the 5% level, which was more
pronounced in the group receiving traditionally-refined carrageenan.
This effect is to be expected from this kind of poorly absorbed
material and was not considered to be of toxicological significance.
No deposits of metachromatic material were observed in the livers of
these rats, and no traces of blood were detected in the faeces as
would have been expected if the PES had been degraded. No effects
of toxicological significance were observed.
No genotoxic effects were observed in in vitro bacterial
assays or in an in vivo mammalian assay.
The Committee allocated a temporary ADI of 0-20 mg/kg bw to
processed Eucheuma seaweed, based on the application of a 200-fold
safety factor to the intake associated with the 5% dose level
(equivalent to 3890 mg/kg bw/day) in the 90-day study in rats. The
ADI was made temporary, pending submission of the complete details
from this study, including histopathological data for individual
animals. The Committee was informed that additional
characterization data on processed Eucheuma seaweed existed, and
requested that that these data and the individual data from the
90-day rat study should be submitted for review by 1995.
PHILIPPINE BUREAU OF FOOD AND DRUGS. 1992. Three months subchronic
oral toxicity test of dietary Philippine Natural Grade carrageenan
in rats. Interim report. BFAD protocol no. 91-5. Unpublished
report submitted to WHO by the Government of the Philippines.
SYLIANCO, C.Y.L., BALBOA, J., SERRAME, E. AND GUANTES, E. 1992.
Mutagenicity, clastogenicity and antimutagenicity potential of
carrageenan. Unpublished report submitted to WHO by the Government
of the Philippines.