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
Geneva
1974
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.
GUAR GUM
Explanation
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 expanded and is reproduced
in its entirety below.
BIOLOGICAL DATA
BIOCHEMICAL ASPECTS
The digestibility of guar gum in rats fed 0.4 g/day was estimated
to be 76% (Booths et al., 1963). The rat can use guar gum as precursor
for liver glycogen but at a much reduced efficiency (Krantz et al.,
1948). Feeding chicks for four weeks on a diet containing 3%
cholesterol, 3% guar gum and 3% cholesterol plus 3% guar gum reduced
the serum cholesterol levels, especially if both cholesterol and guar
gum were ingested. Liver cholesterol was only depressed if cholesterol
and guar gum were fed (Couch et al., 1966). The caloric value was
determined in groups of 10 rats fed for one week a 5 g basal diet
supplemented with either 1 g or 3 g corn starch or 1 g and 3 g guar
gum. At 1 g level guar gum was equivalent to corn starch but at the
3 g level there was a lower equivalence. All animals had large
intestines but normal faeces (Wisconsin Alumni Research Foundation
Laboratory, 1964).
TOXICOLOGICAL STUDIES
Acute toxicity
No data available.
Short-term studies
Rat
Five male rats were fed 0 and 5% guar gum for 91 days in their
diet. No differences were observed between the two groups in weight
gain and food efficiency (Booths et al., 1963). Five rats were fed a
diet containing 0.5% guar gum and varying amounts of water. Weight
gain and protein efficiency increased with higher water content (Keane
et al., 1962).
Fifteen male and 15 female rats were fed a diet containing 5% of
guar flour. Thirty rats served as control. Animals were sacrificed for
autopsy studies at two to three month intervals. Seven male and eight
female animals were carried to termination at 104 weeks. There were no
adverse effects on growth, and gross and microscopic pathology
(Krantz, 1947).
A 90-day feeding study with groups of 10 male and 10 female rats
at levels of 0, 1, 2 and 5% is in progress (Til & Spanjers, 1973).
Monkey
Two monkeys (no duration animals) received 1 g of guar flour in
their diet per day. Wellbeing, growth and haematology (RBC, WBC, HP
and urea N2) remained normal (Krantz, 1947).
Chicken
Groups of 20 chicks, one-day-old, maintained on diets containing
2% guar gum for 21 days showed depressed growth, reduced nitrogen
retention, fat absorption. Pancreatic weight was significantly
increased when diets contained guar gum in a high protein (30%) diet
(Kratzer et al., 1967).
Long-term studies
None available.
OBSERVATIONS IN MAN
Five volunteers ingested 1 g of guar flour in a capsule per day
for 10 days without any apparent effect (Krantz, 1947).
Comments:
Guar gum is consumed in some parts of the world as a component of
guar flour. When it comprises less than 15% of the diet it is
calorically equivalent to corn starch. A short-term and a long-term
study in rats, though both not adequate by present standards, revealed
no adverse effects at the 5% level. A new adequate short-term study is
under way to check the reliability of the older studies. Further work
would be desirable on the potential effects of macromolecules storage
in the body.
EVALUATION
Estimate of acceptable daily intake for man
Not limited.*
FURTHER WORK OR INFORMATION
Desirable
Results on the short-term study which is in progress to check the
reliability of the older studies.
REFERENCES
Booths, A. N., Hendrickson, A. P. & De Eds, F. (1963) Toxic appl.
Pharmacd., 5, 478
Couch, J. R., Bakski, Y. K. & Farr, F. M. (1966) VII International
Congress of Nutrition, Abstracts, p. 195
Keane, K. W. et al. (1962) J. Nutr., 77, 18
Krantz, J. C. (1947) Unpublished report by General Mills Inc.
Krantz, J. C., Carr, C. J. & Farson, C. B. (1948) J. Amer. diet. Ass.,
24, 212
Kratzer, F. H., Rajaguru, R. W. A. S. B. & Vohra, P. (1967) Poultry
Sci., 46(6), 1489-1493
Til, H. P. & Spanjer, M. T. H. (1973) Report No. 4093, TNO
Wisconsin Alumni Research Foundation Lab. (1964) Unpublished report
No. 3110860/1 to Stein, Hall & Co.
* See relevant paragraph in the seventeenth report, pages 10-11.