D. M. Hegsted

The Composition of Human Adipose Tissue from Several Parts of the World

T HAT the composition of the fat of adipose tissue in animals may be varied by the kind of dietary fat fed has long been known although the quantitative aspects, the extent to which specific fatty acids change under various dietary loads and conditions, remains to be determined. Hirsch et ‘ have demonstrated changes in the adipose tissue of man when fed diets high in corn oil. These findings become of considerable interest with the intensive study of the effect of dietary fat upon atherosclerosis and coronary heart disease. This paper reports data upon the fatty acid composition of adipose tissues collected from autopsy material or at surgery from several areas of the world where the diets differ considerably in the amount and kind of fat.

COMPARATIVE LIPID RESPONSE OF FOUR PRIMATE SPECIES TO DIETARY CHANGES IN FAT AND CARBOHYDRATE

Abstract The serum lipid response to long-term feeding of saturated or unsaturated fat with or without dietary cholesterol was compared during three experiments using four species of juvenile monkeys (squirrel, cynomolgus, cebus and spider) born and raised in captivity. When diets containing 10% safflower oil, 10% coconut oil, or high in carbohydrate (48.6 %) with or without 0.1 % cholesterol were fed to cebus and squirrel monkeys for alternate 6 week periods, coconut oil was hypercholesterolemic in both species, but dietary cholesterol further enhanced the hypercholesterolemia only in squirrel monkeys. The effect of the nature of the dietary carbohydrate on serum lipids was examined by feeding these diets continuously to spider monkeys for 36 months while varying the source of the carbohydrate. The results indicated that only coconut oil with sucrose was hyperlipidemic in this species. When cynomolgus and cebus monkeys were fed coconut or safflower oil with or without 0.2% cholesterol, the cynomolgus monkey demonstrated a marked hypercholesterolemia in response to dietary cholesterol and a more moderate response to saturated fat, while the cebus again proved more sensitive to dietary saturated fat than to dietary cholesterol. These data emphasize the interspecies variation between primates with respect to their serum lipid responses to dietary saturated fat, carbohydrate and cholesterol, and identify potential models for study of control mechanisms involved in the regulation of circulating lipids.

Response of adult rats to deficiencies of different essential amino acids

I. Adult rats were fed on diets free of either lysine, methionine, threonine or protein. The threonine- and protein-deficient animals lost weight at approximately the same rate, about IOO g in 14 weeks, at which time several were moribund. In contrast, lysine-deficient animals lost only about 30 g in 14 weeks and had lost only46 g after zz weeks, when they were killed. Methioninedeficient animals showed an intermediate response. Losses in weight of several tissues - kidney, heart and two muscles - were related to, but not necessarily proportional to, the loss of bodyweight. Liver weights relative to body-weights were large in lysine- and threonine-deficient animals and smallest in methionine-deficient animals. 2. Adult rats were fed on diets containing zero, a moderate amount (about twice the estimated minimal requirement) or an excess (about four times the estimated requirement) of lysine or threonine in all combinations (3 x 3 design). Analysis of variance of the body-weights, tissue weights and tissue nitrogen contents indicated, in general, a significant effect of each amino acid, as expected, but also, in most instances, a significant interaction. Plasma concentrations of lysine and threonine were affected by the intakes of the respective amino acids, but plasma lysine concentrations were also affected by the threonine intake. 3. Liver histology also suggestedsignificant interactions between the two amino acids. Animals given no lysine but moderate amounts of threonine developed severely fatty livers; next most severely affected were animals receiving excess of both amino acids. Threonine deficiency, in the presence or absence of lysine, produced moderately fatty livers similar to those seen in protein-deficient animals. 4. Since animals have varying ability to conserve body nitrogen when they are fed on diets limiting in different essential amino acids, mcasuremcnts of biological value (BV) and net protein utilization by conventional methods, over a short period of time, over-estimate nutritive value rclative to amino acid score and probably over-estimate the true nutritive value of poor-quality proteins, particularly those limiting in lysine. If so, this is a serious error, since it leads to underestimates of the protein requirements if BV is used. The fact that certain tissues, particularly the liver, do not necessarily lose nitrogen in proportion to total body nitrogen and may show specific pathological effects depending on the limiting amino acid or the proportions of amino acids in the diet also indicates that general measures of nitrogen economy may not be sufficiently discriminating tests of the nutritive value of proteins. It is abundantly clear that the nutritional quality of dietary proteins is dependent on, if not entirely determined by, the essential amino acid content of the protein. The concept of an amino acid score has been strongly supported by the observation that there is a significant correlation between the calculated score (the adequacy of the most limiting amino acid relative to a protein or amino acid mixture assumed to be ‘ideal’) and observed biological value (BV) or net protein utilization (NPU) (Block & Mitchell, 1946-7; FAO, 1957; WHO, 1965). This concept thus assumes that the nutritional quality of a protein will be compromised to an equal degree by equivalent degrees of deficiency of any essential amino acid or that protein synthesis will be equally impaired by a lack of any essential amino acid.

Lactose and Calcium Transport in Gut Sacs

The effects of glucose and lactose upon calcium absorption in rats were investigated using the inverted gut sac technique with Ca45.In weanling animals calcium transport was stimulated by lactose both in the duodenum where calcium is absorbed against a concentration gradient and in the lower intestine where absorption is by passive diffusion. The ability of lactose to stimulate transport was lost as the animals became older, and was not clearly demonstrable after the animals were 6 weeks of age. The active transport of calcium against a concentration gradient in the upper intestine is partially dependent upon the amount of calcium in the diet the animals receive. Only a slight and insignificant effect of dietary calcium upon calcium transport in the lower intestine could be shown.

Hematological Development of the Infant Squirrel Monkey (Saimiri sciureus)

Hematologic developmental norms from infant squirrel monkeys indicate a relative maturation of the hematopoietic system by 16 weeks. The elevated hemoglobin, hematocrit, red blood cell count, MCV and MCH at birth are followed by a decreasing hemoglobin (decreasing red blood cell count and MCV) until 4 weeks of age. A reticulocytosis then occurs until the hemoglobin level approximates adult concentrations by 16 weeks of age with gradual changes in this as well as hematocrit, red blood cell count, MCV and MCH thereafter. Total leukocytes and segmented neutrophils are elevated at birth and decrease rapidly in the first 2 weeks, reaching stabile values by 16 weeks. An opposite trend is seen with the lymphocyte population. Plasma protein and albumin concentrations show a nadir at 2 weeks of age with the albumin levels stabilizing by 10 weeks and the total protein concentration continuing to increase throughout the 1st year.

Recommended dietary intakes of elderly subjects

Various authors have criticized the Recommended Dietary Allowances (RDA) because they do not include values for elderly subjects. It is argued here that such values would not be useful. The large majority of elderly subjects have one or more diagnosed diseases, drug consumption is high, etc, and it is unlikely that specific dietary standards for such a group could be developed or would be useful. More importantly, I argue that the RDA do not and cannot do most of the things which dietary standards ought to do, and their use generates considerable misinformation. It is time to reconsider the whole issue of dietary standards. It is not clear that elderly subjects who do not require therapeutic diets need to consume a diet which differs from that of the rest of the population.

Hematological Development of the Cebus Monkey (Cebus albifrons and apella)

Data from the analysis of 352 blood samples from 77 cebus monkeys, ranging in age from birth through 1 year of age, and 54 samples from 29 adult animals were compiled to establish hematological norms.

Protein-Energy Interrelationships during Dietary Restriction: Effects on Tissue Nitrogen and Protein Turnover

Young adult female rats were fed diets containing either 50 or 0% lactalbumin at levels of 2, 4 or 6 g diet/day for 2, 8, and 16 days. There was no other protein in the diet. Tissue nitrogen and loss of radioactivity from tissues labeled with 14C- and 3H-glutamate were measured. In a second study, similar rats were fed graded levels of lactalbumin at food intake levels of 3, 5, or 7 g/day. Change in tissue nitrogen varied with the tissue, the time of observation, and the severity of the food restriction. After 8 days, animals fed high levels of protein at the most severe food restriction showed increases in gastrocnemius nitrogen and losses in liver nitrogen, while after 16 days both tissues had marked nitrogen losses. Nitrogen losses at the lowest level of food intake increased with the dietary protein level, whereas dietary protein was protective of tissue nitrogen at higher food intakes. Severity of energy restriction had no effect on loss of tissue radioactivity and the apparently longer tissue protein half-lives from animals fed protein-free diets are attributed to increased amino acid recycling. Such results indicate that short-term studies and overall nitrogen balance experiments will fail to identify changes occurring in different tissues and may yield misleading results.