CAROB BEAN GUM*
(Locust Bean Gum)
Explanation
This substance was evaluated for acceptable daily intake for man
by the Joint FAO/WHO Expert Committee on Food Additives in 1969, 1973
and 1975 (see Annex I, Refs. 19, 32 and 37). Toxicological monographs
were issued in 1969, 1973 and 1975 (see Annex I, Refs. 20, 33 and 38).
Since the previous evaluation, additional data have become
available and are summarized and discussed in the following monograph.
The previously issued monographs have been expanded and are reproduced
in their entirety below.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
In a bioavailable calorie assay, groups of 10 male weanling rats
(Sprague-Dawley) were given 5 g basal diet or basal diet plus 0.5, 1,
2 g sucrose or 0.5, 1, 2 g gum for 10 days. Comparison of the carcass
weight gain showed that carob bean gum was not a source of
bioavailable calories (Robaislek, 1974).
Fifteen controls and 18 male test rats, after three days on
normal diet followed by a 12 hour fast, received two-and-one-half days
in their diet either 67% cocoa butter with wheat flour or 67% cocoa
butter with 33% carob bean gum. Glycogen accumulated in the liver but
far less efficiently than with wheat flour (Krantz et al., 1948).
A digestibility study in groups of five male and five female rats
(Purdue strain) on a mannose-free diet showed that 85-100% of mannose
fed as 1% carob bean gum in the diet for 18 hours was excreted in the
faeces over a total of 30 hours. Some decrease in chain length of
galactomannan may have occurred, probably through the action of the
microflora as mammals are not known to possess mannosidase. Liberation
of galactose units was not determined (Tsai & Whistler, 1975).
* Carob bean gum (also called locust bean gum) is the material
separated and variously refined from the endosperm of the seed of
the carob tree, Ceratonia siliqua, a large leguminous evergreen
that is widely cultivated in the Mediterranean area. The
carbohydrate component of carob bean gum is considered to be a
neutral galactomannan polymer consisting of a main chain of 1,4-
linked D-mannose units with a side chain of D-galactose on every
fourth or fifth unit, attached through 1,6-glycosidic linkages to
the polymannose chain. (FASEB/LSRO/SCOGS-3)
Incubation of solutions or suspensions with human gastric juice,
duodenal juice + bile, pancreatic juice and succus entericus with or
without added rabbit small gut membrane enzymes produced no evidence
of hydrolysis (Semenza, 1975). Rat large gut microflora partially
hydrolysed carob bean gum in vitro (Towle & Schranz, 1975) after
conditioning to 1% carob bean gum in the diet for three weeks.
Groups each of eight male Holtzman rats were maintained on a
purified synthetic diet, or the diet plus 1% cholesterol, or the diet
+ 1% cholesterol + 10% carob bean gum for 28 days. The increased liver
cholesterol and liver total lipid induced by cholesterol feeding was
largely counteracted by concurrent feeding of carob bean gum (Ershoff
& Wells, 1962).
Groups each of 12 chicks, one day old were fed a casein sucrose
basel diet supplement with 3% cholesterol and either 10%, 6%, 3%, 2%,
1.5% or 1.0% locust bean gum for 27 days. At the end of the test
period, plasma cholesterol was determined. At the 10% level, there was
a 35% reduction of plasma cholesterol, no significant effect in body
weight or food consumption. At the 6% level, there was a moderate
reduction in cholesterol level. There was a wide variation in the
hypocholesterolemic activity of the carob bean gums tested with some
preparation being totally inactive (Fahrenbach et al., 1966).
The effect of carob or locust bean gum on nitrogen (N) balance
and dry matter digestibility was studied in rats. Seventy-two weanling
male Sprague-Dawley rats were divided into a control and five
experimental groups of 12 animals each. Various gums including locust
bean gum were fed at the 10% level in a casein-saccharose-corn starch
diet. Following a three-day adaptation period, feed remnants, urine
and faeces were collected during an eight-day balance period. Trypsin
inhibitory activity was measured in each diet. Carob bean gum caused a
significant rise in faecal N loss, resulting in a marked reduction of
apparent protein digestibility from 87.8% in the controls to 75%.
Urinary N was significantly lower than controls. Faecal dry matter was
also significantly increased by carob bean gum. There was only slight
trypsin inhibition caused by carob bean gum (Harmuth-Hoene &
Schwerdtfeger, 1979).
Carob bean gum has been noted to contain tannins, which depress
appetite and growth and trypsin inhibitors, which are also growth
inhibitory (LSRO/FASEB/SCOGS-3, 1972).
TOXICOLOGICAL STUDIES
Special studies on teratogenicity
Teratogenical experiments with four species of animals (rats,
mice, hamsters and rabbits) did not indicate that the test material
was a teratogen to mice at 280 mg/kg bw and 1300 mg/kg, although 5/21
dams died at the latter dose. Up to 1300 mg/kg in rats, up to
1000 mg/kg in hamsters and at 196 mg/kg in rabbits no teratological
effects were seen. At 910 mg/kg in rabbits, most of the pregnant dams
died (Morgareidge, 1972).
In one study, carob bean gum was injected via the air cell and
yolk or albumen routes into fertile eggs prior to and after 96 hours
of incubation. Eggs were candied at 48-hour intervals and dead embryos
were examined for stage of development and defects. At hatching, all
chicks were examined for gross defects and samples were taken for
gross skeletal staining and histopathological examination. Although
the authors do not state levels of carob bean gum injected, they note
anophthalmia, phocomelia, micromelia and torticollis occurring with
carob bean gum (Naber & Smothers, 1975).
Special studies on mutagenicity
Mutagenic tests on rats and mice using three different methods
gave negative results. There was no measurable mutagenic response in
recombination frequency for Sacc. cerev. in host-mediated assay at
5 g/kg or in vitro. No adverse effects were seen on chromosomes in rat
bone marrow or human lung cell cultures. The dominant lethal test in
rats was negative (Maxwell & Newell, 1972).
Carob (locust) bean gum was evaluated for genetic activity in
microbial assays with and without the addition of mammalian metabolic
activation preparations. Indicator organisms used were Saccharomyces
cerevisiae and Salmonella typhimurium, strains TA-1535, TA-1537
and TA-1538. Mammalian metabolic activation preparations were from
mouse (ICR adult), rat (Sprague-Dawley adult) and monkey (Macaca
mulatta adult). Carob (locust) bean gum did not exhibit genetic
activity in any of the assays employed (Brusick, 1975).
Acute toxicity
LD50
Species Route mg/kg bw Reference
Rat Oral >5000 Maxwell & Newell, 1972
Short-term studies
Rat
Groups of 10 males and 10 females were fed in their diet carob
bean gum at levels of 0%, 1%, 2% or 5% for 90 days. General condition,
behaviour, survival, growth, food intake, haematology, blood
biochemistry and urinalysis showed no treatment-related differences
between test and control groups at any dietary level except that the
last glucose level was slightly increased in the 5% group. Gross and
microscopic examination did not reveal any pathological changes
attributable to ingestion of the gum. The increase in the relative
weight of the caecum at the 2% level is not considered to be of
toxicological importance (Til et al., 1974).
Groups each of newly weaned Sprague-Dawley rats (10/group) were
fed a soybean-corn meal diet containing 2% locust (carob) bean gum for
36 days. Locust bean gum had no effect in the digestibility of the
diet, nor was there any significant effect on growth (Vohra et al.,
1979).
Dog
Four groups of five male and five female Beagles were fed 0%, 1%
5% or 10% of a precooked mixture of carob bean and guar gum
(proportions unknown) for 30 weeks. Only at the 10% level were
hypermotility and soft, bulky stools observed, probably of not
toxicological significance. Also at the 10% level digestibility was
reduced. No adverse haematological, urinary, gross and
histopathological and ophthalmological findings were noted (Cox et
al., 1974).
Chicken
Groups of 20-day-old chickens were fed diets containing 0.25%,
0.52%, 12% and 22% carob bean gum for three weeks. Growth depression
was dose related and marked at the 2% level of intake (Kratzer et al.,
1967; Vohra & Kratzer, 1964).
Groups of day-old broiler chickens (seven per group, breed not
specified) were fed a soybean protein-corn based diet containing 2%
carob (locust) bean gum for 24 days. The dietary intake of the
chickens was measured daily for the last week of the experimental
period; digestibility of the test diet was calculated from the dry
weights of the feed and excreta. The average body weight of chickens
and the digestibility of the diet was reduced significantly by the
inclusion of locust (carob) bean gum in the diet (Vohra et al., 1979).
Japanese quail
Groups of day-old Japanese quail (10 per group) were fed a
soybean-meal-corn based diet containing 2% locust (carob) bean gum for
either 35 or 37 days. The dietary intake of the quail was measured
daily for the last week of their experimental period; the
digestibility of the diet was calculated from the day weights of the
feed and excreta. Average body weight and digestibility of the diet
was significantly reduced by inclusion of locust (carob) bean gum in
the diet (Vohra et al., 1979).
Long-term studies
None available.
OBSERVATIONS IN MAN
A clinical study of a commercial preparation of carob bean grain
as a laxative in doses of "two heaping teaspoonfuls" in 56 patients,
some of whom took the preparation regularly for two years, resulted in
no untoward effects related to the gastrointestinal tract, and no
allergenic reaction (Holbrook, 1951).
Eight infants between the ages of 2.5-5 months were fed meals of
sugared milk or sugared milk plus a 1% powder extract from carob bean.
Addition of the carob supplement did not alter the duration of the
gastrointestinal transit time of the meal. Physiological aerophagy was
markedly suppressed by the supplement (Rivier, 1952).
In patients with renal failure, ingestion of 25 g of locust bean
gum/day had a laxative effect, decreased high blood pressure, and
caused a fall in serum urea, creatinine, and phosphorus by the second
week of treatment (Yatzidis et al., 1979).
Comments
In vitro tests with human enzyme preparations show little
utilization by the gut. Carob bean gut was not teratogenic in several
mammalian species although it did produce terata in the chick embryo
assay. The available short-term studies in the rat and dog showed no
evidence of adverse effects at the 5% level. The effects noted in
feeding trials are those expected of a non-metabolized polymeric
substance acting as a bulking agent. Carob bean gum is used in
pharmaceutical preparations.
The previously requested long-term feeding and reproduction
studies are not yet available.
EVALUATION
Estimate of acceptable daily intake for man
Acceptable daily intake not specified.*,**
FURTHER WORK OR INFORMATION
Required by 1984
(1) An adequate long-term study in a rodent species.
(2) Reproduction studies.
* 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.
** Temporary.
REFERENCES
Brusick, D. Mutagenic evaluation of compound FDA 71-14 PM9000-40-2.
Locust bean gum. Unpublished report from Litton Bionetics, Inc.
Submitted to the World Health Organization by the US Food and
Drug Administration, 1975
Cox, G. E., Baily, D. E. & Morgareidge, K. Subacute feeding in dogs
with a precooked gum blend. Unpublished report from the Food and
Drugs Labs, Inc., submitted to the World Health Organization by
Hercules B. V., 1974
Ershoff, B. H. & Wells, A. G. Effects of gum guar, locust bean gum and
carrageenan on liver cholesterol of cholesterol-fed rats. Proc.
Soc. exp. Biol. Med., 110, (3), 580-582, 1962
Fahrenbach, M. J., Riccardi, B. A. & Grant, W. E. Hypocholesterolemic
activity of mucilaginous polysaccharides in White Leghorn
cockerels. Proc. Soc. exp. Biol. Med., 13(2), 321-6, 1966
Harmuth-Hoene, A. & Schwerdtfeger, E. Effect of indigestible
polysaccharrides on protein digestibility and nitrogen retention
in growing rats. Nut. Metab., 23, 399-407, 1979
Holbrook, A. A. The behaviour of carob bean in the gastrointestinal
tract of man. A. J. Dig. Dis., 18, 24-28, 1951
Krantz, J. C., Jr., Carr, C. J. & de Farson, C. B. Guar polysaccharide
as a precursor of glycogen. J. Amer. diet. Ass., 24, 212,
1948
Kratzer, F. H., Rajaguru, R. W. A. S. B. & Vohra, P. The effect of
polysaccharides on energy utilization, nitrogen retention and fat
absorption in chickens. Poultry Sci., 48, 1489-1493, 1967
LRSO/FASEB. Evaluation of the health aspects of carob bean gum as a
food - SCOGS-3, 1972
Maxwell, W. A. & Newell, G. W. Study of the mutagenic effects of FDA
71-14 (Locust bean gum). Unpublished report from the Stanford
Research Institute submitted to the World Health Organization by
Hercules B. V., 1972
Morgareidge, K. Teratological evaluation of FDA-71-14 (Locust bean
gum). Unpublished report from the Food and Drug Research Labs,
Inc. submitted to the World Health Organization by Hercules B.
V., 1972
Naber, E. C. & Smothers, S. E. Patterns of toxicity and teratogenicity
in the chick embryo resulting from the administration of certain
nutrients and food additives. Poultry Sci., 54(5), 1806, 1975
Rivier, C. Recherches sur le mode d'action du Nestargel. Schweiz.
Mediz., 82, 256, 1952
Robaislek, E. Bioavailable calorie assay of Guar gum. Unpublished
report from WARF Institute, Inc. submitted to the World Health
Organization by Institut Europeen des Industries de la Gomme de
Caroube, 1974
Semenza, G. Report on the possible digestion of locust bean gum in the
stomach and/or in the small intestine in an in vitro study.
Unpublished report from the Eidgenossische Technische Hochschule
Zurich submitted to the World Health Organization by the Institut
Europeen des Industries de la Gomme de Caroube, 1975
Til, H. P., Spanjers, M. Th. & de Groot, A. P. Subchronic toxicity
study with locust bean gum in rats. Unpublished report from
Centraal Instituut voor Voedingsonderzoek TNO submitted to the
World Health Organization by Hercules B.V. and Institut Europeen
des Industries de la Gomme de Caroube, 1974
Towle, G. A. & Schranz, R. E. The action of rat microflora on carob
bean gum solutions in vitro. Unpublished report from Hercules
Research Center submitted to the World Health Organization by
Hercules Incorporated, 1975
Tsai, L. B. & Whistler, R. L. Digestibility of galactomannans.
Unpublished report submitted to the World Health Organization by
Professor H. Neukom, Chairman of the Technical Committee of
Institut Europeen des Industries de la Gomme de Caroube, 1975
Vohra, P. & Kratzer, F. H. Growth inhibitory effects of certain
polysaccharides for chickens. Poultry Sci., 43, 1164-1170,
1964
Vohra, P., Shariff, G. & Kratzer, F. H. Growth inhibitory effect of
some gums and pectin for Tribolium castaneum larvae, chickens
and Japanese quail. Nutr. Rep. Internatl., 19(4), 463-469,
1979
Yatzidis, H., Koutsicos, D. & Digenis, P. Newer oral sorbents in
uremia. Clin. Nephrol., 11(2), 105-106, 1979
See Also:
Toxicological Abbreviations
Carob bean gum (FAO Nutrition Meetings Report Series 46a)
Carob bean gum (WHO Food Additives Series 5)
CAROB BEAN GUM (JECFA Evaluation)