Toxicological evaluation of some food
additives including anticaking agents,
antimicrobials, antioxidants, emulsifiers
and thickening agents
WHO FOOD ADDITIVES SERIES NO. 5
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).
No data available.
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 &
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,
OBSERVATIONS IN MAN
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.