This substance was evaluated for acceptable daily intake for man
    (ADI) by the Joint FAO/WHO Expert Committee on Food Additives in 1975
    (see Annex, Ref. 37). A toxicological monograph was issued in 1975
    (see Annex, Ref. 38).

         Since the previous evaluation, additional data have become
    available and are summarized and discussed in the following monograph.
    The previously published monograph has been expanded and is reproduced
    in its entirety below.



         The principal component of this gum is a galactomannan with a
    linear chain of (1--->4) linked ß-D-mannopyranose units with
    alpha-D-glactopyranose units attached by (1--->6) linkages to every
    third mannose unite on average. In a bioavailable calorie assay,
    groups of 10 male weanling rats (Sprague-Dawley) were given 5 g basal
    diet alone or with 0.5, 1, 2 g sucrose or 0.5, 1, 2 g tara gum for
    10 days. Comparison of the carcass weight gain showed that tara
    gum was not a source of bioavailable calories (Robaislek, 1974). A
    digestibility study in groups of five male and five female rats
    (Purdue strain) on a mannose-free diet showed that 88-100% of mannose
    fed as 1% tara gum in the diet for 18 hours were 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).
    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 tara gum in vitro (Towle & Schranz, 1975) after
    conditioning to 1% tara gum in the diet for three weeks.


    Special studies on reproduction


         A three generation reproduction study was carried out in CD
    strain Charles River albino rats. Groups of 10 male and 20 female
    animals were fed a diet containing 5% alpha cellulose (control) or 5%
    tara gum. The same dose and animal numbers were employed for

    successive generations throughout the study. In each generation the
    parental animals received the test diets for 11 weeks prior to mating
    and then through mating, gestation and weaning. The females of the F0
    and F2 generation were mated to produce two litters. Females of the
    F1 generation produced three litters. Ten males and 20 females were
    retained at weaning from the second litter of each dietary group as
    parental animals for the next generation. Ten weanlings per sex per
    dietary group from the F3b litters were selected for histopathologic
    examination of 12 tissues and organs, and organ weight values were
    also obtained. All other animals were subjected to gross necropsy.

         At several weeks during the study, there were instances of
    statistically lower body weight in the tara gum F2 parental males and
    the F0 and F1 parental females.

         There was a statistically significant reduction in the number of
    pups viable at lactation days 12 and 21 in the tara gum group. There
    were significant lower pup weights in the tara gum groups at days 4,
    12, and 21 in the F1 generation and days 1, 4, 12 and 21 of the F3
    generation. There were no other significant between group differences
    in reproductive performance.

         No significant between group differences were noted in parental
    premating food consumption, mortality and gross or microscopic

         The following statistically significant differences in organ
    weights and organ weight ratios were observed for tara gum group as
    opposed to the control group: lower absolute liver and brain weights
    and greater kidney, testes, heart, and brain to body weight ratios.
    These differences were ascribed to the lower body weight of the tara
    gum F2 weanlings from whom the values were obtained (Domanski et al.,

    Acute toxicity

         No data available.

    Short-term studies


         A 90-day feeding study was carried out in groups of 10 male and
    10 female rats at dietary levels of 0, 1, 2 or 5% of the diet. No
    abnormalities were observed in general appearance, behaviour, and
    survival in any of the groups. Growth, food intake and food efficiency
    were slightly decreased at the 5% dietary level in both sexes. A
    relative lowering of the body weight was found in the males in the 2%
    group, but no effect on food intake and efficiency. Haematology and
    urinalysis showed no treatment-related differences. A significant

    increase in blood urea nitrogen was observed in males at the 5%
    dietary level. At the 2% and 5% levels, an increase was found in the
    relative weight of the caecum. An increase in the relative weight of
    the thyroids at the 2% and 5% levels and a slight increase in the
    relative weight of the kidneys at the 5% level was observed in males
    only. No lesions were found on gross and histopathological examination
    attributable to the ingestion of the gum (Til et al., 1974).


         Three groups of three male and three female beagles received
    either 0, 1, or 5% tara gum in their diet for 90 days. No
    abnormalities were noted as regards behaviour, mortality, haematology,
    urinalysis, clinical chemistry, organ weights, gross histopathology
    (Oshita et al., 1975).

    Long-term studies


         Groups of 50 male and 50 female Charles River Strain albino rats
    were fed diets containing 5% alpha cellulose (control) or 5% tara gum
    for up to two years. An interim sacrifice of 10 animals/sex/group was
    carried out after 12 months.

         Statistically significant lower body weight and body weight
    changes were noted at a number of weeks in both male and female
    animals in the tara gum group. There were also statistically
    significant reductions in food consumption in the tara gum groups both
    males and females - at a number of weeks. This may have been due to
    the physical characteristics of the control diet (alpha cellulose
    added) which may have accounted for greater spillage and therefore
    greater apparent food consumption in the control animals.

         Some changes in haematological measurements were noted in rats in
    the tara gum groups. These included a statistically significant
    decrease in haematocrit values at 12 months in male rats, in total
    erythrocyte count and leukocyte count in male rats at 99 weeks, in
    monocyte count in female rats at 12 months and in reticulocyte counts
    in females at 18 months. Statistically significant increases were
    reported in the haemoglobin concentration at 99 weeks, in the
    monocytes at 12 months and reticulocyte count in female rats given
    tara gum.

         With respect to clinical chemistry, statistically significant
    increases in animals given tara gum were noted for the following
    measurements: SGPT activity in males at 12 months; fasting serum
    glucose, and BUN at 12 months in females and SGOT activity in females
    at three months. A significant decrease was noted in total cholesterol
    levels at six and 12 months in females given tara gum.

         At the 12-month interim sacrifice the following statistically
    significant changes were noted in males fed 5% tara gum: significantly
    greater brain to body weight, testes to body weight and heart to body
    weight ratios and significantly lower liver to brain weight ratio. At
    the final sacrifice the following statistically significant changes
    were noted in animals given tara gum; lower adrenal gland to body
    weight ratios in males and lower absolute brain weight in females.

         No significant differences were reported in between the tara gum
    and control groups with respect to gross or microscopic pathology
    (Carlson & Domanski, 1980).


         The studies in rats on the in vivo digestibility and calorie
    bioavailability show that this gum is not digested by mammalian
    intestinal enzymes but is partially attacked by rat gut flora. Human
    gut enzymes do not hydrolyse this gum in vitro. Short-term studies
    in rats and dogs showed no evidence of adverse effects at the 5%
    level. The observed effects on caecal weight were discussed in a
    previous report and were not considered significant for man. The
    effect on thyroid weight without concomitant histopathological changes
    was also considered to be of doubtful significance. The previous
    report indicated the need for adequate long-term studies on rodent
    species, as well as reproduction and embryotoxicity (including
    teratogenicity) studies. A long-term study in rats demonstrated no
    significant toxicity. The reproduction study indicated a possible
    effect of 5% tara gum on lactation since pup body weights and
    viability tended to be lower in the pups in the tara gum groups as
    compared to the controls given cellulose. No studies on teratogenicity
    are available.


    Level causing no toxicological effects

    Rat: 5% in the diet equivalent to 2500 mg/kg bw.

    Estimate of temporary daily intake for man

    0-12.5 mg/kg bw.


    Required by 1984

         Multigeneration reproduction study in rats at several dose

         Teratogenic study.


    Carlson, W. A. & Domanski, J. (1980) Two-year chronic oral toxicity
         study with tara gum in albino rats. Unpublished data. Industrial
         Bio-Test, Northbrook, Illinois, United States of America

    Domanski, J., Carlson, W. & Frawley, J. (1980) Three generation
         reproduction study with tara gum in albino rats. Unpublished
         data. Industrial Bio-Test, Northbrook, Illinois, United States of

    Oshita, G. et al. (1975) 90-day subacute oral toxicity study with tara
         gum in beagle dogs. Unpublished report from Industrial Bio-Test
         Labs, Inc. submitted to the World Health Organization by Hercules

    Robaislek, E. (1974) Bioavailable calorie assay of guar gum.
         Unpublished report from WARF Institute, Inc. submitted to the
         World Health Organization by Institut Européen des Industries de
         la Gomme de Caroube

    Semenza, G. (1975) 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 Européen des Industries de la Gomme de Caroube

    Til, H. P., Spanjers, M. Th. & De Greet, A. P. (1974) Sub-chronic
         toxicity study with tara gum in rats. Unpublished report from
         Centraal Instituut voor Voedingsonderzoek TNO submitted to the
         World Health Organization by Hercules B.V. and Institut Européen
         des Industries de la Gomme de Caroube

    Towle, G. A. & Schranz, R. E. (1975) 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

    Tsai, L. B. & Whistler, R. L. (1975) Digestibility of galactomannans.
         Unpublished report submitted to the World Health Organization by
         Professor H. Neukom, Chairman of the Technical Committee of
         Institut Européen des Industries de la Gomme de Caroube

    See Also:
       Toxicological Abbreviations
       Tara gum (WHO Food Additives Series 21)
       TARA GUM (JECFA Evaluation)