Nutritional Studies on Rats on Diets Containing High Levels of Partial Ester Emulsifiers

Abstract

The external appearance and behavior of the rats at all levels of partial ester emulsifier were quite normal throughout the two-year feeding test, except for those whose diarrheal condition resulted in inflammation and unthrifty appearance around the anal region. The animals thus affected were in the 20% Myrj 52 and Tween groups. No evidence of anemia, cachexia, or of abnormal neurological behavior was seen in any of the animals, particularly nothing to indicate the existence of any of the recognized nutritional deficiencies. Attention was directed to symptoms of thiamine shortage in view of the report that Myrj 45 at a 2% level caused destruction of dietary thiamine (National Research Council, '53); no such evidence was found in any of the emulsifier diets even at the 20% feeding level. Six-week storage tests at room temperature with diets containing up to 20% of Myrj 45 showed thiamine retention of 90% or better. The laxative action was seen at the 20% level of Myrj 52 and the Tweens, and to a lesser extent at the 10% level, but not at all in the Myrj 45 or Span 60 groups. The emulsifiers responsible for this effect were those with long-chain polyoxyethylene groups (20 or 40 ethylene oxide moieties) whereas those which did not induce this response were the sorbitan stearate Span 60 and the polyoxyethylene (8) stearate Myrj 45. Laxation could be induced equally well by the longer chain polyols themselves. Hematological tests at 12 weeks, one, one-and-a-half, and two years in all F₀ groups and at 12 weeks in 3 succeeding generations yielded consistently negative results. Blood chemical tests performed on representative rats at these periods included determinations of blood sugar and non-protein nitrogen and (in F₂ and F₃ generation rats) plasma cholesterol. A tendency toward an increase in blood sugar level was noted as the rats reached old age but the values were nevertheless within normal limits as, indeed, were all other blood chemical values. A transient albuminuria was seen in all groups (including the controls) at one year and sporadic positive tests for reducing substances were obtained especially at two years, but the distribution of these findings among the groups, and the normal blood sugar and non-protein nitrogen values, suggest that they had no significance attributable to the emulsifiers. Microscopic examination of urine sediment at one year revealed the presence of occasional oxalate crystals in some of the emulsifier groups but in general fewer were found at the 20% levels than at 10%. Except possibly for the Span 60 group, the presence of oxalates in the two-year urine specimens was not significantly increased. These findings will be discussed in a subsequent report in connection with renal and bladder pathology. Coefficients of digestibility of the fatty acid moieties of the partial ester emulsifiers were determined and used in computing the caloric value of the supplemented diets described in the first paper of this series (Oser and Oser, '56). The mean values found for Myrj 45, Myrj 52, Span 60, Tween 60, Tween 65, Tween 80, and Primex were 80.4, 96.0, 53.5, 97.7, 84.1, 100.0, and 93.5, respectively. These coefficients appeared to be correlated with the melting points of the emulsifiers except in the case of Myrj 52 which contains only 14% of fatty acid.