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.
SALTS OF MYRISTIC, PALMITIC, AND STEARIC ACIDS
Explanation
These compounds have been evaluated for acceptable daily intake
by the Joint FAO/WHO Expert Committee on Food Additives (see Annex 1,
Ref. No. 20) 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
Myristic, palmitic and stearic acid are the naturally occurring
fatty acid component of tallow and other animal fats and oils as well
as some vegetable oils. Most of the commercial and pharmaceutical
preparations also contain mixed acids. Myristic acid has been shown to
decrease the incorporation of acetyl Co-A into fatty acids by liver
homogenates (Korchak & Masoro, 1964). Giving 1-C14 labelled stearic
acid to two groups of four male rats resulted in the formation of
labelled cholesterol which was widely distributed within 24 hours
after administration (De Leo & Foti, 1961). Diets containing 20 to 40%
glycerylmonostearate depress the growth and cause high mortality in
young and adult mice. This is preventable by 4% oleate or linoleate.
Depot fat levels of stearate do not increase. The mechanism of
toxicity is unknown (Tove, 1964). Stearic acid is only 24% digestible
as measured by fat ingested and excreted in male rats fed seven to
eight days 10% of stearic acid in their diet (Carroll & Richards,
1958). Stearic acid decreases the incorporation of acetyl Co-A into
fatty acids by liver homogenate fractions (Korchak & Masoro, 1964).
Using 14C-labelled palmitic acid i.v. in rats it was shown that
30% entered the liver within five minutes where it was present almost
wholly in the esterified form. More 14C appeared in the hepatic
neutral fats than in the phospholipid fraction and it disappeared more
rapidly from neutral fat. Similar relations were found for plasma
fats. After 80 minutes the levels of 14C in plasma and liver lipids
were similar, however the carcass lipids were not equilibrated even
after 24 hours (Olivecrona, 1962). The in vitro uptake of tritium-
labelled palmitic acid by the lipid fraction of rat pancreas was not
affected by non-opmoc detergents, but was increased by cationic and
anionic detergents. Only anionic lauryl sulfate stimulated the
incorporation into neutral lipids of palmitic acid but not into the
phospholipid fraction (Oett, 1965).
Comments:
Myristic, palmitic and stearic acid and their salts are normal
products of the metabolism of fats and their metabolic fate is well
established. Provided the contribution of the cations does not add
excessively to the normal body load there is no need to consider the
use of these substances in any different light to that of dietary
fatty acids.
EVALUATION
Estimate of acceptable daily intake for man
Not limited.*
REFERENCES
Carroll, K. K. & Richards, J. F. (1958) J. Nutr., 64, 411
De Leo, T. & Foti, L. (1961) Drugs affecting lipid metabolism Proc.
Symp., Milan, pp. 83-88
Korchak, H. M. & Masoro, E. J. (1964) Biochim. biophy. Acta., 84, 750
Oett, K. (1965) Experientia, 21, 253
Olivecrona, T. (1962) Acta physiol, scand., 54, 295
Tove, S. B. (1964) J. Nutr., 84, 237
* See relevant paragraph in the seventeenth report (pages 10-11).