Toxicological evaluation of some food
    additives including anticaking agents,
    antimicrobials, antioxidants, emulsifiers
    and thickening agents


    The evaluations contained in this publication
    were prepared by the Joint FAO/WHO Expert
    Committee on Food Additives which met in Geneva,
    25 June - 4 July 19731

    World Health Organization


    1    Seventeenth Report of the Joint FAO/WHO Expert Committee on
    Food Additives, Wld Hlth Org. techn. Rep. Ser., 1974, No. 539;
    FAO Nutrition Meetings Report Series, 1974, No. 53.



         This substance has been evaluated for acceptable daily intake by
    the Joint FAO/WHO Expert Committee on Food Additives (see Annex 1,
    Ref. No. 19) in 1969.

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



         Karaya gum does not disintegrate appreciably in the alimentary
    tract. In a study of 10 dogs 95% of the orally administered gum was
    recovered in the faeces. It absorbs a large quantity of water and
    therefore acts as a mechanical laxative. It tends to increase faecal
    nitrogen excretion, does not affect starch digestion in the dog and
    does not inhibit the utilization of vitamin A in rats (Ivy & Isaacs,
    1938). The caloric value was determined in groups of 10 rats fed for
    one week 5 g basal diet with either 1 g and 3 g corn starch or 1 g and
    3 g karaya gum supplements. At the 1 g level karaya gum only had 30%
    of the caloric value of corn starch. At the 2 g level growth was very
    depressed. The intestines were enlarged in all rats on gum (Wisconsin
    Alumni Research Foundation Laboratory, 1964).


    Acute toxicity

         No data available.

    Short-term studies


         Examination of the intestines of rats fed 1 g of karaya gum per
    day for 91 days showed no gross abnormalities. There was no
    interference with normal growth (Ivy & Isaacs, 1938).


         Three dogs were fed 5 g unprocessed karaya daily for 30 days.
    Defaecations were more frequent, faecal bulk and moisture were
    increased but there was no obvious gastrointestinal irritation (Ivy &
    Isaacs, 1938).

    Long-term studies


         Five rats were fed 20% karaya gum in the diet for two years.
    Three developed enlarged colon and ulceration (Hoelzel et al., 1941).
    In another experiment groups of three rats were fed karaya gum at
    first at 10%, gradually increasing to 25% in the diet over their life
    span. Controls of five and seven animals received low residue diets.
    No caecal ulceration was found in this experiment (Carlson & Hoelzel,


         Forty-six female and 43 male subjects took karaya gum granules
    for one week at levels equivalent to 7 g per day. Seven subjects had
    abdominal discomfort (Ivy & Isaacs, 1938). Ingestion or inhalation was
    reported to have caused allergy (Figley, 1950).

         Sixteen cases of allergic sensitivity to inhalation of the gum
    used as a wave set, and to oral ingestion as a laxative were reported.
    Symptoms included hay fever, asthma, dermatitis and gastrointestinal
    distress (Figley, 1950).

         In a comparison with carob bean gum as a laxative in 10 human
    subjects karaya gum was found to be transformed to a gelatinous state
    at a higher level in the intestine and to be transported more rapidly
    through the intestinal tract (Holbrook, 1951).


         Karaya gum has a long history of human use as a laxative agent
    and has also been consumed as food though being of less calorie value.
    There is evidence in a few species that the gum might irritate the
    bowel. In a few cases allergic responses in man have been recorded.
    The long-term tests reveal only enlargement of the colon but are
    inadequate. Metabolic studies in several species, preferably including
    man, and adequate 90-day studies in several species are required
    before an evaluation can be done.


         Not possible on the data available.


    Carlson, A. J. & Hoelzel, F. (1948) J. Nutr., 36, 27

    Figley, K. D. (1950) J. Amer. med. Ass., 114, 747

    Hoelzel, F., Costel, E. & Carlson, A. J. (1941) Amer. J. dig. Dis., 8,

    Holbrook, A. A. (1951) Amer. J. dig. Dis., 18, 24

    Ivy, A. C. & Isaacs, B. L. (1938) Amer. J. dig. Dis., 5, 315

    Wisconsin Alumni Research Foundation Lab. (1964) Unpublished report
         No. 3110860/1 to Stein, Hall & Co.

    See Also:
       Toxicological Abbreviations
       Karaya gum (FAO Nutrition Meetings Report Series 46a)
       Karaya gum (WHO Food Additives Series 18)
       Karaya gum (WHO Food Additives Series 24)
       KARAYA GUM (JECFA Evaluation)