SummaryThe influence of a purified rat diet containing 20 or 33% of the saturated medium chain‐length triglycerides (MCT) with and without linoleic acid supplements on growth, caloric requirements for weight maintenance and weight increase, fertility, lactation performance, and serum cholesterol levels was compared with that of similar diets containing lard, coconut oil, or no fat.Among male rats maintained on diets containing 20% lard or 20% MCT and .09% linoleic acid for 18 months no differences were observed between the groups other than the depressed body weight and lowered serum cholesterol levels of the group fed MCT. When groups of male rats were kept at constant weight by the daily restricted feeding of diets containing lard, MCT, or coconut oil or no fat plus 2% linoleic acid, the weight‐maintenance requirements of the group fed MCT were higher than of those on lard and coconut oil and even somewhat higher than the requirements of the animals fed the fat‐free diet. The requirements for weight increase over those for maintenance were 0.9 g. per gram increase for all diets. Additional linoleic acid in the MCT diet decreased the weight and maintenance differences between groups fed MCT and lard.The lactation performance of mothers on MCT plus .09% linoleic acid was poor. The second generation animals initially showed signs of more severe linoleic acid deficiency which however disaappeared without linoleic acid supplements.Some cholesterol levels of animals on MCT were significantly below those of groups on lard. Addition of linoleic acid to the MCT diet did not change the results.
Summary
There is increasing evidence that the abnormal nutritional properties of highly autoxidized fats are related to the polymers which develop during autoxidation. Lard and cottonseed oil were aerated at 95°C. for 200 hrs. and molecularly distilled; and the residue fractions, non‐volatile at 275 to 300°C., were studied.
Diets containing 20% of autoxidatively produced polymeric residue, fed to albino rats, led to diarrhea and rapid death, but when this residue was reduced to 10%, most of the animals were gradually able to tolerate it. At the 4 or 7% level it was well tolerated, but growth was reduced. There were no distinctive histological lesions, and withdrawal of the polymer permitted immediate realimentation without evidence of subsequent injuries.
The polymeric residue from autoxidized cottonseed oil exerted a greater growth‐depressant effect than that from lard, and the latter, more than that from a hydrogenated vegetable oil used for deep‐fat frying for 80 hrs. at 190°C. Addition of fresh fat to the polymeric residues decreased their growth‐depressant effect.
When rats were fed a measured amount of diet sufficient to maintain their weight, the caloric requirement necessary for weight maintenance gradually decreased. When the dietary fat source consisted of polymeric residue to the extent of 4 to 10%, the caloric requirement for weight maintenance decreased relatively little, if at all. The polymeric residue from autoxidized lard was, in this respect, as effective as that from autoxidized cottonseed oil.
Summary
Lard and cottonseed oil which had been autoxidized at about 100°C. for 210 hrs. were fractionated by a technique involving molecular distillation, conversion to ethyl esters, urea‐complex formation, and redistillation. The ethyl esters were then fed to rats for three weeks at a level of 8% in a purified diet. Growth, water intake, organ weights, total liver lipids, and serum and liver cholesterol levels were determined. Groups fed 8% lard served as controls.
Growth was severely depressed by the residue fractions of the urea‐complex‐ and noncomplex‐forming portions of the original molecular distillates. Of the three fractions from the original molecular distillation residues, the dimeric and polymeric fractions were the most active. The relative liver and kidney weights were usually increased by feeding the growth‐depressing fractions. However there were a number of exceptions indicating more specific effects from some of the fractions. Water intakes were lower with the fractions derived from the original molecular distillates than with those from the original molecular distillation residues. Testicular fat body weights suggested that feeding of autoxidized CSO fractions led to less neutral fat deposition than feeding of corresponding autoxidized lard fractions. Dry weight of the enlarged livers was higher, and the total lipid lower than of the control livers. Total liver cholesterol was higher in animals with smaller livers, but there was no difference in the cholesterol content of the total liver lipids. Serum cholesterol levels were lower in animals with large livers.
Further study of those fractions having pharmacological properties is suggested.
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