WORLD HEALTH ORGANIZATION
Toxicological evaluation of some food colours, thickening
agents, and certain other substancse
WHO FOOD ADDITIVES SERIES NO. 8
The evaluations contained in this publication were prepared
by the Joint FAO/WHO Expert Committee on Food Additives which
met in Geneva, 14-23 April 19751
World Health Organization, Geneva 1975
1 Nineteenth Report of the Joint FAO/WHO Expert Committee on Food
Additives, Wld Hlth Org. techn. Rep. Ser., 1975, No. 576;
FAO Nutrition Meetings Report Series, 1975, No. 55.
The monographs contained in the present volume are
also issued by the Food and Agriculture Organization
of the United Nations, Rome, as
FAO Nutrition Meetings Report Series, No. 55A
ISBN 92 4 166008 2
(C) FAO and WHO 1975
MICROCRYSTALLINE CELLULOSE
Explanation
This substance was evaluated for acceptable daily intake for man
by the Joint FAO/WHO Expert Committee on Food Additives (see Annex 1,
Refs No. 27 and No. 33) in 1971 and 1973.
Since the previous evaluation, additional data have become
available and are summarized and discussed in the following monograph.
The previously published monographs have been expanded and are
reproduced in their entirety below.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
Four rats were fed 14C-labelled microcrystalline cellulose at
10 and 20% of their diet. No evidence of degradation or digestion was
noted. Faecal recoveries of radioactivity ranged from 96-104% and were
complete for all labelled material. No radioactivity appeared in the
urine (Baker, 1966). One human subject received 150 g of 14C-labelled
microcrystalline cellulose (47.6 µc) in two portions on one day and
unlabelled 150 g microcrystalline cellulose daily for the subsequent
10 days. Twenty-four hour faecal and urine collections were examined
for radioactivity. No radioactivity appeared in the urine or in the
expired CO2. All administered radioactivity was recovered from the
faeces within two days (Baker, 1968). Examination of the stools of one
male and one female patient given 30 g micro-crystalline cellulose as
dry flour or gel for five-and-one-half weeks showed the presence of
undegraded material of the same birefringence as the original
microcrystalline cellulose administered. No significant effects on the
human gastro-intestinal tract were noted during the administration
(Tusing et al., 1964).
TOXICOLOGICAL STUDIES
Special studies on reproduction
Rat
Groups of eight male and 16 female rats were used to produce a P,
F1a, F1b, F2 and F3 generation after having been fed on diets
containing 30% of microcrystalline cellulose flour or gel or ordinary
cellulose as a control. The presence in the diet of such an amount of
non-nutritious material, which contributed no calories had an adverse
effect on reproduction. Fertility and numbers of live pups were
relatively depressed and lactation performance in all three
generations, as well as survival and the physical condition of the
pups, were unsatisfactory throughout the study. The new-born pups
appeared smaller, weak and showed evidence of disturbed motor
coordination. Liver weights were increased in the group receiving
microcrystalline cellulose gel in all generations but other organ
weights showed no consistent patterns. Gross and histopathology
revealed renal changes similar to those seen in the feeding study in
females of all generations. Other organs showed no consistent changes.
No teratological deformities were seen (Anonymous, 1964).
Special studies on teratogenicity
Rat
Seventy-two test rats (Sprague-Dawley CD) divided into eight
groups were fed a mixture of four types of Elceme in the ratio of
1:1:1:1. (Elceme is a microcystalline cellulose, and the four types
are identified by particle size, namely, 1-50 µ (powder), 1-100 µ
(powder), 1-150 µ (fibrillar), 90-250 µ (granulate)), in the diet at a
level of 0, 2.5, 5 or 10% for 10 days, between the sixth and fifteenth
day of pregnancy. Rats of four test groups were killed on the twenty-
first day of pregnancy and the following parameters studied: number of
foetuses and resorption sites, litter size and average weight of rats,
average weight of foetuses, average backbone length. Foetuses were
also examined for soft tissue of skeletal defects. The remaining
groups were allowed to bear young, which were maintained to weaning
(21 days). The following parameters were studied: litter size, weight
of pup at days seven and 21, as well as a histological study of the
offspring. Although there is some suggestion that administration of
dietary Elceme resulted in a dose dependent increase in resorption
sites, as well as a change in sex ratio, and possible defects such as
opaque crystalline lenses, the data has not been presented in a manner
which permits a meaningful interpretation. However, the authors
conclude that Elceme is non-teratogenic (Ferch, 1973a).
Other special studies
Rats, pigs and dogs
Rats, pigs and dogs were used to study the persorption of
microcrystalline cellulose. The animals were not fed 12 hours prior to
oral administration of the test compound. Rats, dogs and pigs were
given 0.5, 140 and 200 g respectively, of the test compound. Venous
blood was taken from the animals one to two hours after administration
of the test compound, and examined for particles. Persorbed particles
were demonstrated in the blood of all three species. The average
maximum diameter for persorbed particles was greater for rats than for
dogs and pigs (Pahlke & Friedrich, 1974).
Other studies have been carried out to demonstrate the
relationship between persorbability and size and consistency of
granules. Using quartz sand, the upper limits for persorbability was
shown to be 150 µ. Starch granules must be structurally largely intact
to possess the property of persorbability. Persorbed starch granules
may be eliminated in the urine, pulmonary alveoli, peritoneal cavity,
cerebrospinal fluid, via lactating milk and transplancental
(Volkheimer et al., 1968).
In another study dyed plant foods (oatmeal, creamed corn) were
fed to human subjects, and blood and urine examined for coloured
fibres. Dyed fibres were shown to be present (Schreiber, 1974).
Lycopodium spores and pollen grains have also been shown to be
persorbed by humans (Linskens & Jorde, 1974).
Acute toxicity
Rat
Groups of five male rats received a single oral dose, by stomach
tube of 10.0, 31.6, 100, 316, 1000 or 3160 mg/kg body weight of a
suspension of Cellan 300 (refined alpha-cellulose) in distilled water
or Mazola maize oil. The animals were observed for seven days
following administration. No differences were observed among the
groups as regards the average body weight, appearance and behaviour
compared to normal rats. No abnormal histopathological findings were
reported in any animals with either formulation. Therefore the acute
oral LD50 is >3160 mg/kg (Pallotta, 1959).
Similar single doses of refined alpha-cellulose were given
intraperitoneally in distilled water suspension to five male rats.
During seven days observation there were no abnormalities in the rats
given 316 mg/kg or less. At the 1000 and 3160 mg/kg level there was
inactivity, laboured respiration and ataxia, 10 minutes after
administration and at 3160 mg/kg ptosis and sprawling of the limbs.
These animals appeared normal after 24 hours and for the remainder of
the observation period. At sacrifice body weights were higher than
normal and gross autopsy revealed adhesions between the liver,
diaphragm and peritoneal wall and congestion of the kidneys. Masses
resembling unabsorbed compound were also observed and these were
found to a small extent in the mesentary of the animals administered
316 mg/kg. Histologically all other organs appeared normal. There were
no mortalities and therefore the acute intraperitoneal LD50 is
>3160 mg/kg body weight (Pallotta, 1959).
Short-term studies
Rat
Groups of four male rats were kept on diets containing 0.25, 2.5
or 25% of various edible celluloses for three months. No differences
were observed among the groups with regard to growth and faecal
output. Histopathology of the gastro-intestinal tract revealed no
treatment-related abnormalities (Frey et al., 1928).
Three groups of five male rats received 0.5% or 10%
microcrystalline cellulose in their diet for eight weeks. Growth was
comparable to controls but the 10% group showed slightly lower body
weights. Haematology, serum chemistry and vitamin B1 levels in blood
and faeces showed no differences from controls (Anonymous, 1966).
A mixture of four types of Elceme (in the ratio of 1:1:1:1)
was fed to groups of Wistar rats for 30 days at a dietary level of
50%, and for 90 days at a dietary level of 10% (Elceme is a
microcrystalline cellulose, and the four types are identified by
particle size, namely, 1-50 µ (powder), 1-100 µ (powder), 1-150 µ
(fibrillar), 90-250 µ (granulate)). All test animals were observed for
food intake and weight gain. For animals in the 10% group urinalysis,
haematologic tests and serum biochemical tests were carried out at
weeks six and 13 of the test. A complete autopsy including
histopathology was carried out at the end of the study. Animals in the
50% level were subjected to a persorption test, and the last day of
the study, by addition of a cellulose staining dye (Remal, Wine-red)
to the food of the test animals at a level equivalent to 5% of the
Elceme. The animals were sacrificed 24 hours after administration of
the diet, and a careful histological examination was made of the
gastro-intestinal tract, spleen, liver, kidney and heart for stained
particles.
Animals in 10% level gained significantly less weight than those
in the control group; the marked decrease commenced in the third or
fourth week of the study. Food intake was similar in test and control
group. Urinalysis, haematologic values and biochemical values for test
and control groups were similar for test and control group 1. At
autopsy some of the rats on the test died had distended stomachs which
often contained considerable amounts of the test diet. The absolute
liver and kidney weight and the ratio of the weight of these organs to
brain weight was increased in test animals when compared with control
animals. No compound related pathology was reported. Animals in the
50% group, showed considerable less weight gain than control animals
in spite of a marked increase in food consumption. No persorption of
dyed fibres was observed (Ferch, 1973).
Long-term studies
Rat
Three groups of 50 male and 50 female rats received in their diet
for 72 weeks either 30% ordinary cellulose or dry microcrystalline
cellulose or microcrystalline cellulose gel. Appearance and behaviour
was comparable in all groups. No adverse effects were noted. The body
weights of males given microcrystalline cellulose gel were higher than
those of the controls. Food efficiency, survival and haematology were
comparable in all groups. The liver and kidney weights of males
receiving microcrystalline cellulose gel were higher than the
controls. Gross and histopathology showed some dystrophic
calcification of renal tubules in females on microcrystalline
cellulose but all other organs appeared unremarkable. Tumour incidence
did not differ between the groups (Anonymous, 1963).
OBSERVATIONS IN MAN
A number of clinical studies using refined cellulose as roughage
in the human diet for the treatment of constipation showed no
deleterious effects. Groups of 18 children received regular amounts of
edible cellulose instead of normal cereal for three months. The only
effect noted was an increase in bowel movements but no diarrhoea or
other gastro-intestinal disturbances were seen (Frey et al., 1928).
Eight male and eight female volunteers supplemented their normal
diet with 30 g microcrystalline cellulose per day either as dry powder
or gel (15% aqueous) for six weeks followed by two weeks without
supplementation. No adverse findings were reported regarding
acceptance or body weight but most subjects complained of fullness and
mild constipation. Haematology was normal in all subjects. Biochemical
blood values showed no differences between treatment and control
periods, nor was there evidence of liver or kidney function
disturbance. Urinalysis produced normal findings. The faecal flora
remained unchanged. The cellulose content of faeces increase five to
eight times during the test period. Microscopy revealed the presence
of microcrystalline cellulose (Anonymous, 1962).
In another study eight healthy males received 30 g
microcrystalline cellulose daily as supplement to their diet for
15 days. D-xylose absorption varied between pretest, test and post-
test periods being lower during microcrystalline cellulose ingestion.
The absorption of I131 triolein was unaffected by microcrystalline
cellulose ingestion. No change was noted in the faecal flora nor was
there any significant effect on blood chemistry during ingestion of
microcrystalline cellulose. Examination of urine, blood and faecal
levels of vitamin B1 during microcrystalline cellulose ingestion
showed no difference from control periods (Anonymous, 1966).
Comments:
The human studies including the use of radiolabelled
microcrystalline cellulose show complete absence of digestion or
absorption. Doses up to 30 g per day appear to be tolerated
therapeutically as a bulk laxative. While long-term animal studies
reported for microcrystalline cellulose do not permit the
establishment of a no-effect level, the adverse effects produced are
probably attributable to the inadequacies of a diet containing a large
amount of indigestible, non-absorbable, non-caloric material. Detailed
studies on the persorption of particulate matter suggest that
infinitesimally small amounts of ingested microcystalline cellulose
may be absorbed, in a manner similar to other naturally occurring
plant particulate matter, e.g. cellulosic material. However, any
persorbed microcystalline cellulose is likely to be excreted in the
urine or bile as has been observed with other particulate matter, and
is not likely to accumulate in hazardous amounts in tissues and
organs. The general inertness of this material strongly suggests that
microcrystalline cellulose is biologically similar to other cellulose
derivatives which have already been considered by Joint FAO/WHO Expert
Committees on Food Additives and for which ADIs have been established
on the basis of long-term studies in several animal species.
EVALUATION
Acceptable daily intake not specified.*
REFERENCES
Anonymous (1962) Microcystalline cellulose; oral administration -
Human. Unpublished report from Hazleton Labs, Inc. submitted to
the World Health Organization by FMC Corporation
Anonymous (1963) Long-term nutritional balance study - Rats.
Unpublished report from Hazleton Labs, Inc. submitted to the
World Health Organization by FMC Corporation
Anonymous (1964) Microcystalline cellulose: reproduction study - Rats.
Unpublished report from Hazleton Labs, Inc. submitted to the
World Health Organization by FMC Corporation
* The statement "ADI not specified" means that, on the basis of the
available data (toxicological, biochemical, and other), the total
daily intake of the substance, arising from its use or uses at the
levels necessary to achieve the desired effect and from its acceptable
background in food, does not, in the opinion of the Committee,
represent a hazard to health. For this reason, and for the reasons
stated in individual evaluations, the establishment of an acceptable
daily intake (ADI) in mg/kg bw is not deemed necessary.
Anonymous (1966) Effect of ingestion of avicel-contained foods on
living organisms. Unpublished report from Yoshitoshi Internal
Seminar submitted to the World Health Organization by Asahi
Chemical Industry Co., Ltd.
Baker, E. M. (1966) Microcystalline cellulose: oral administration -
Rats. Unpublished report from Fitzsimmons General Hospital
submitted to the World Health Organization by FMC Corporation
Baker, E. M. (1968) Microcrystalline cellulose: oral administration -
Humans. Unpublished report from Fitzsimmons General Hospital
submitted to the World Health Organization by FMC Corporation
Frey, J. W., Harding, E. R. & Helmbold, T. R. (1928) Dietetic
investigations of edible pure cellulose, Med. J. Record, 127,
585-589
Ferch, H. (1973a) Innocuity of Elceme(R). Part I, Pharm. Ind., 35, (9),
578-583
Ferch, H. (1973b) Innocuity of Elceme(R). Part II, Pharm. Ind., 35,
(9), 658-661
Linskens, H. F. & Jorde, W. (1974) Persorption of lycopodium spores.
and pollen grains, Naturwissenschaften, 61, 35
Pahlke, G. & Friedrich, R. (1974) Persorption of microcystalline
cellulose, Naturwissenschaften, 61, 35
Pallotta, A. J. (1959) Acute oral administration - Rats; and acute
intraperitoneal administration - Rats, of microcrystalline
cellulose. Unpublished report from Hazleton Labs, Inc. submitted
to the World Health Organization by FMC Corporation
Schreiber, G. (1974) Ingested dyed cellulose in the blood and urine
of man, Arch. environ. Health, 29, 39
Tusing, T. W., Paynter, O. E. & Battista, O. A. (1964) Birefringence
of plant fibrous cellulose and microcrystalline cellulose in
human stools freezer-stored immediately after evacuation,
Agric. Fd. Chem., 12, (3), 284-287
Volkheimer, G., Schultz, F. H., Lehmann, H., Aurich, I., Hubner, R.,
Hubner, M., Hallmayer, A., Munch, H., Opperman, H. & Strauch,
S. (1968) Primary portal transport of persorbed starch granules
from the intestinal wall, Medicine Experimentalis, 18,
103-108
See Also:
Toxicological Abbreviations