Xanthan gum was evaluated for acceptable daily intake at the
    eighteenth and twenty-ninth meetings of the Joint FAO/WHO Expert
    Committee on Food Additives (Annex 1, references 35 and 70). A
    toxicological monograph was published after the eighteenth meeting
    (Annex 1, reference 36). An ADI of 0-10 mg/kg b.w. was established at
    the eighteenth meeting and maintained at the twenty-ninth meeting,
    Since the last evaluation, new information has become available, which
    was evaluated by the present Committee. The previously-published
    monograph has been expanded and is reproduced in its entirety below.


    Biochemical aspects

         Caloric availability and digestibility studies indicated that
    xanthan gum is not utilized by the body. This conclusion was
    substantiated by finding that practically all of the gum fed during a
    7-day period could be accounted for in the faeces (Booth et al.,

         When 14C-labelled xanthan gum prepared by fermentation of
    uniformly-labelled glucose with Xanthomonas campestris was fed to
    rats at a level of 2% (50 mg total) in the diet, a maximum of 15% of
    the label was metabolized to carbon dioxide in 100 hours. In vitro
    tests showed that the acetate content was labile at gastric pH.
    Acetate and pyruvate accounted for only 9.8% of the label in the gum
    used. The finding that 15% of the label was metabolized to carbon
    dioxide indicated that the hexoses were used to a certain extent also.
    No accumulation in tissues was found, and the observed metabolism of
    labelled material and distribution of 14C in tissues was that
    expected from feeding a simple 14C-labelled molecule such as acetate
    or a hexose. Analysis of faecal material showed no accumulation of the
    five polysaccharide constituents, except acetate. Some 98% of the
    radioactivity in the faeces could be attributed to unchanged or only
    slightly modified polysaccharide. In vitro tests indicated that
    nonenzymatic hydrolysis and the action of faecal micro-organisms are
    responsible for the initial breakdown of polysaccharide in vivo
    (Gumbmann, 1964).

    Toxicological studies

    Special study on reproduction


         A three-generation reproduction study was carried out using
    groups of 10 male and 20 female rats in the first generation and 20
    male and 20 female rats in subsequent generations. Dosage levels of 0,
    0.25, and 0.5 g/kg/day were administered in the diet. Criteria
    evaluated were survival, body weight, general appearance, behaviour,
    the number of litters produced, number of live births and still
    births, physical condition of the young, weight at birth and weaning,
    and survival of the young. Females that had fewer than two litters
    were examined to determine whether there was fetal resorption.
    Malformations in offspring were recorded and gross and
    micropathological examinations were made on the offspring of the
    second and third generations. No adverse effects attributable to
    xanthan gum were found in this study (Woodard et al., 1973).

    Acute toxicity


    Animal     Route     (mg/kg b.w.)     Reference

    Mouse      oral      > 1000           Booth et al., 1963
               i.p.      > 50             Booth et al., 1963
               i.v.      100-250          Hendrickson & Booth (sine data)

    Rat        oral      > 45,000         Jackson et al. (sine data a)

    Dog        oral      > 20,000         Jackson et al. (sine data b)

         Daily application of a 1% solution for 15 days to rat skin
    produced no signs of irritation. Daily application of a 1% solution
    for five days to rabbit conjunctiva produced no signs of irritation.
    Intradermal challenge tests in guinea-pigs did not produce evidence of
    sensitization (Hendrickson & Booth, sine data).

         Five albino rats received single doses of xanthan gum. The
    material was administered by inhalation for one hour using a stainless
    steel inhalation chamber. A total of 19 g of the test material was
    used during the one-hour exposure, which gave a calculated chamber
    concentration of approximately 21 mg/liter. Following exposure all
    rats were observed periodically for one hour for pharmacologic and
    toxicologic signs over a period of 14 days. No signs of toxicity were
    seen and the rats retained good physical appearance throughout. No
    gross changes were seen at autopsy (Knott & Johnston, 1973).

    Short-term studies


         A study was carried out on an unspecified number of rats fed
    diets containing 7.5 or 10% xanthan gum for 99-110 days. No adverse
    effects were observed in extensive investigatins on these animals
    (Booth et al., 1963).

         In a 91-day feeding study, a reduced rate of weight gain was
    found in groups of rats receiving 7.5 or 15% xanthan gum in the diet.
    Diets containing 3 or 6% gum did not reduce weight gain. No
    significant alterations in haemoglobin, red or white cell counts, or
    organ weights were observed in these rats. Histological examination of
    tissues from rats at the 15% level showed no pathological effects. At
    the highest-dose level the animals produced abnormally large faecal
    pellets, but diarrhoea did not occur. A paired-feeding test was used

    to compare the growth of rats ingesting a diet containing 7.5% xanthan
    gum and comparable rats restricted to the same intake of control diet.
    No differences in weight gain were found at the end of 18 days,
    indicating the absence of a growth-inhibiting factor (Booth et al.,

         Groups of 5 male and female weanling rats were fed 0, 2.5, 5.0,
    or 10.0% commercial xanthan gum product, which consisted of drum-dried
    whole fermentation medium (beer) in which Xanthomas campestris
    B-1459 was cultured, for 110 days. A laboratory-prepared whole-dried
    ferment was tested at a single dietary level of 7.5%, substituted at
    the expense of the entire basal diet, for 99 days. No significant
    pathological changes associated with feeding either B-1459
    fermentation medium were detected (Booth et al., 1968).

         Diets containing a nutritionally adequate, high-maltose nutrient
    mixture and either 4% xanthan gum or 4% cellulose were fed
    ad libitum to male Wistar rats for 7 days. The feeding of this gum
    increased the combined weight of the small intestine and its contents
    by 110%. This effect was partially due to an enlarged cell mass and to
    extra dry matter in the contents; however, it was chiefly due to a
    400% increase in intraluminal water. Xanthan feeding enhanced greatly
    the persistence of sugars beyond the proximal quarter of the small
    intestine and increased their total recovery in the first
    three-quarters of that organ by 150%. The xanthan-induced increase in
    intraluminal water in the small intestine was partially due to a
    slowed absorption of osmotically-active substances from the gut
    (Trout et al., 1983).

         Rats were fed a stock diet for at least 3 days. They were then
    starved for 2 days and divided into 4 groups of 6 animals each. The
    starved rats served as a model for differentiating effects of various
    dietary carbohydrates. (The feeding of nutritionally-adequate
    high-carbohydrate diets to starved rats causes an elevation of total
    liver lipid and of hepatic enzymes associated with lipogenesis.) In
    experiment 1, rats were fed nutritionally-adequate diets; the
    carbohydrate was starch or glucose with or without xanthan gel
    (a suspension containing 4% xanthan gum). Experiment 2 had the same
    design as experiment 1, but the diets were fat-free. In experiment 3,
    the dose-response relationship was examined by feeding 0.8, 1.4, or
    2.0% xanthan gum. In all experiments relative liver size, final body
    weight, weight gain, total food intake, utilizable nutrient intake,
    glucose-6-phosphate (G-6-P) dehydrogenase activity, malic enzyme
    activity, and total liver lipid were measured. Xanthan gel lowered
    relative liver size, total liver lipid, G-6-P dehydrogenase, and malic
    enzyme activity. In the dose-response experiment xanthan gum, at less
    than 2% of the dry diet ingredients, lowered nutrient intake
    (Putney et al., 1978).


         Eighteen young adult male guinea-pigs were injected
    intracutaneously with a 0.1% solution of xanthan gum 3 times per week
    for a total of 10 injections. Ten days after the last injection, each
    guinea-pig received a challenge injection. The injection sites were
    evaluated at 24 hours for size of the erythematous spot and for the
    intensity of the color produced. Body weights were recorded at 0, 15,
    and 30 days. Xanthan gum did not produce sensitization in the
    guinea-pig under the conditions of the experiment (Durloo & Johnston,


         Two ml of a 1% solution (W/w) of xanthan gum was applied to the
    skin of a group of 3 rabbits for 6 weeks. After macroscopic and
    histological evaluation, the cumulative cutaneous irritation index was
    zero, indicating that the substance was very well tolerated
    (Guillot et al., 1982).


         Four groups of 2 male and 2 female young adult beagle dogs were
    fed for 2 weeks on diets providing 0, 1, or 2 g/kg b.w./day xanthan
    gum or 2 g/kg b.w./day of cellulose powder. Persistent diarrhoea
    occurred in the high-dose dogs, and occasional diarrhoea occurred in
    dogs in the low-dose group. All dogs, including controls, lost weight
    but the weight loss was most marked in animals receiving xanthan gum.
    Red blood cell counts, haemoglobin concentrations, and serum
    cholesterol concentrations were lowered and the relative adrenal
    weight increased in dogs receiving 2 g/kg b.w./day xanthan gum. These
    effects were considered to be due to the persistent diarrhoea in this
    group. Liver and kidney function tests indicated no disturbance in the
    function of these organs. Extensive gross and histopathological
    examination failed to detect lesions which could be attributed to
    ingestion of the gum (Robbins et al., 1964).

         Groups of 3 male and 3 female beagle dogs were fed diets
    supplying 0, 0.25, or 0.5 g/kg b.w./day xanthan gum for 12 weeks.
    Animals in the high-dose group had softer stools than normal, but no
    diarrhoea. Growth was slightly retarded in the males and the serum
    cholesterol level was lowered in both sexes of the high-dose group. No
    other adverse effects were seen. The no-adverse-effect-level in this
    test was considered to be 0.25 g/kg b.w./day (USDA, 1964).

    Long-term studies


         Groups of 30 male and 30 female Charles River CD strain rats were
    fed diets for 104 weeks supplying O, 0.25, 0.5, or 1.0 g/kg b.w./day
    xanthan gum. No abnormalities which could be attributed to ingestion
    of these experimental diets were found with regard to survival,
    body-weight gain, food consumption, behaviour, or appearance.
    Ophthalmic and haematologic examination yielded normal results.
    Analysis of blood for glucose, SGOT, and prothrombin time showed no
    abnormalities in test groups. Organ weights were within normal limits
    and no lesions attributable to xanthan gum were found on gross and
    histopathological examination (Woodard et al., 1973).


         Xanthan gum was administered in the diet at levels supplying
    0, 0.25, 0.37, or 1.0 g/kg b.w./day to groups of 4 male and 4 female
    beagle dogs for 107 weeks. No effects attributable to administration
    of the gum were seen in the treated animals with regard to survival,
    food intake, body-weight gain, electrocardiograms, blood pressure,
    heart rate, body temperature, or ophthalmic and neurological
    examinations. Haemoglobin, total and differential white cell counts,
    coagulation and prothrombin times, thrombocyte counts, serum alkaline
    phosphatase, blood urea nitrogen, blood glucose, SGOT, and SPGT were
    the same in control and treated animals. Urine pH, glucose
    concentrations, and sediment contents were comparable between test and
    control groups, but there was a dose-related increase in urine SG and
    a more frequent appearance of urinary albumin in dogs consuming
    1.0 g/kg b.w./day of gum than in the other groups. Stool consistency
    was normal at the 0.37 g/kg level, but stools were loose at the
    top-dose level. The weight of the faeces showed a dose-related
    increase, as would be expected from feeding a non-absorbed hydrophilic
    gum at high-dose levels. The increased urinary SG is consistent with
    physiological adjustment for the extra water excreted in the faeces.
    Examination of the appearance and weights of organs and
    histopathological examinations failed to detect any adverse effects of
    treatment with xanthan gum at any dose level (Woodward et al.,

    Observations in man

         A study group of 30 individuals who had expressed a commitment to
    lose weight in a pre-study interview were medically examined and found
    to be psychologically suited for a weight-reduction program. Twenty
    participants were given capsules containing 550 milligrams of xanthan
    gum (2 capsules 20-30 minutes before meals). These participants were
    divided into two groups of 10 each; those in group A were placed on a
    fixed low calorie diet (1000-1200 calories per day), while those in

    group B were given no numerical dietary caloric restriction, but they
    were encouraged to limit their caloric intake. Participants in group C
    (control group of 10) were given a placebo and requested to limit
    caloric intake to 1000-1200 calories per day. The test was performed
    over an 8-week period. Group B did better in terms of the number of
    successes and the amount of weight lost than did the A group. Both
    groups given capsules containing xanthan gum did better than the
    control group (Wong et al., 1974).

         Over-weight patients were given capsules for 3 weeks in a
    double-blind study. Each capsule contained either 0.25 g xanthan gum
    or 0.5 g paraffin oil (placebo). The patients were told to take 4
    capsules 30 minutes before each meal together with a glass of water
    (12 capsules/day). No significant changes in plasma lipid levels were
    observed. The patients tolerated the capsules well. There were no
    clear side-effects reported and there was not a tendency toward more
    frequent stools. The authors concluded that xanthan gum can effect a
    slow but significant weight loss in individuals with varying degrees
    of overweight (Ockerman et al., 1983).

         Five healthy men (aged 26-50 years) consumed for 23 days
    10.4-12.9 g xanthan gum each day in three portions. The daily
    ingestion of xanthan gum at this high level had no significant effect
    on plasma biochemistry, haematological indices, urinalysis parameters,
    glucose and insulin tests, serum immunoglobulins, triglycerides,
    phospholipids, HDL cholesterol, or breath hydrogen or methane
    concentrations. There was a 10% reduction in serum cholesterol, and a
    significant increase in faecal bile acid concentrations following the
    ingestion of xanthan gum. The xanthan gum also acted, as expected from
    a dose-ranging study, as a bulking agent in terms of its effects on
    faecal dry and wet weight and on transit time (Eastwood et al.,


         In response to the request of the twenty-ninth meeting of the
    Committee, information was provided on the nature of the nitrogenous
    constituents of xanthan gum. About half of the nitrogenous matter is
    proteinaceous and contains amino acid residues in the same relative
    proportions as are present in other food grade gums. The rest is
    present as amino sugars, nucleic acids, and nucleotides (personal
    communication from W.J. Sander, Marinalg International, Paris, France,
    to A.W. Randell, FAO, Rome, May 21, 1986; submitted to WHO by Marinalg

         A two-year study in rats failed to show any carcinogenic or other
    toxic effects attributable to the gum. A reproduction study in rats
    was negative. In addition, the results of several short-term studies
    in rats, rabbits, guinea-pigs, and dogs were also available. No toxic
    effects were observed in these studies. Several recent studies in
    humans indicated no adverse effects at levels up to 10-13 grams daily.


    Estimate of acceptable daily intake for man

    ADI "not specified".

    Further work or information


         An adequate long-term study in a second rodent species, because
    of the potential high exposure levels of this substance and the fact
    that xanthan gum is prepared from a microbial source not normally used
    in food.


    Booth, A.N., Hendrickson, A.P., & De Eds, F. (1963). Physiologic
         effects of three microbial polysaccharides on rats.
         Toxicol. Appl. Pharmacol., 5, 478-484.

    Booth, A.N., Hendrickson, A.P., & De Eds, F. (1968). Rat feeding study
         of whole dried ferment containing polysaccharide B-1459 (xanthan
         gum). Unpublished report from Western Regional Research
         Laboratory, United States Department of Agriculture, Albany, CA,
         USA. Submitted to WHO by Marinalg International, Paris, France.

    Durloo, R.S. & Johnston, C.P. (1973). Keltrol(R), intracutaneous
         sensitization potential in the guinea pig. Unpublished report
         from Woodard Research Corporation, Herndon, VA, USA. Submitted to
         WHO by Marinalg International, Paris, France.

    Eastwood, M.A., Brydon, W.G., & Anderson, D.M.W. (1986). The dietary
         effects of xanthan gum in man. Unpublished report submitted to
         WHO by Marinalg International.

    Guillot, J.P., Giauffret, J.Y., Martini, M.C., Gonnet, J.F., &
         Soule, G. (1982). Safety evaluation of gum and thickeners used in
         cosmetic formulation. Int. J. Cosmetic Sci., 4, 53-66.

    Gumbmann, M.R. (1964). Metabolism of 14C polysaccharide B-1459
         (xanthan gum) by the rat. Unpublished report from Western
         Regional Research Laboratory, United States Department of
         Agriculture, Albany, CA, USA. Submitted to WHO by Marinalg
         International, Paris, France.

    Hendrickson, A.P. & Booth, A.N. (sine data). Supplementary acute
         toxicological studies of polysaccharide B-1459 (xanthan gum).
         Unpublished report from Western Regional Research Laboratory,
         United States Department of Agriculture, Albany, CA, USA.

    Jackson, N.N., Woodard, M.W., & Woodard, G. (sine data a). Xanthan
         gum acute oral toxicity to rats. Unpublished report from Woodard
         Research Corporation, Herndon, VA, USA.

    Jackson, N.N., Woodard, M.W., & Woodard, G. (sine data b). Xanthan
         gum acute oral toxicity to dogs. Unpublished report from Woodard
         Research Corporation, Herndon, VA, USA.

    Knott, W.B. & Johnston, C.D. (1973). Keltrol(R), acute inhalation
         toxicity to rats. Woodard Research Corporation, Herndon, VA, USA.

    Ockerman, P.A. (1983). Untitled unpublished report discussing clinical
         study of xanthan gum used for weight control. Department of
         Clinical Chemistry, University Hospital, Lund, Sweden. Submitted
         to WHO by Marinalg International, Paris, France.

    Putney, J.D., Trout, D.L., Johnson, D.A., Moy, N.L., & Michaelis, O.E.
         (1978). Effect of xanthan gel on hepatic lipogenesis in
         starved-refed rats. Nutr. Rep. Internatl., 18, 659-669.

    Robbins, D.J., Moulton, J.E. & Booth, A.B. (1964). Subacute toxicity
         study of a microbial polysaccharide fed to dogs. Food Cosmet.
         Toxicol., 2, 545-550.

    Trout, D.L., Ryan, R.O., & Bickard, N.C. (1983). The amount and
         distribution of water, dry matter and sugars in the digestive
         tract of rats fed xanthan gum. Proc. Soc. Exp. Biol. Med.,
         172, 340-345.

    USDA (1964). Safety evaluation of polysaccharide B-1459 (xanthan gum)
         in laboratory animals - effects of feeding to dogs. Unpublished
         report from Western Regional Research Laboratory, United States
         Department of Agriculture, Albany, CA, USA,

    Wong, G.O. (1974). Method of controlling human appetite. United States
         Patent No. 3,843,786.

    Woodard, G., Woodard, M.W., McNeely, W.H., Kovacs, P., & Cronin,
         M.T.I. (1973). Xanthan gum: safety evaluation by two-year
         feeding studies in rats and dogs and a three-generation
         reproduction study in rats. Toxicol. Appl. Pharmacol.,
         24, 30-36.

    See Also:
       Toxicological Abbreviations
       XANTHAN GUM (JECFA Evaluation)