The association of dietary fat with serum cholesterol in vegetarians: the effect of dietary assessment on the correlation coefficient.

The biologic relation between dietary fats and serum cholesterol established in controlled dietary studies usually has not been found in cross-sectional studies of the general population. In vegetarian groups, dietary variables and serum cholesterol have been correlated significantly. To examine the role of technique of dietary assessment versus the dietary pattern of vegetarians, the authors studied the relation of diet with total serum cholesterol in 46 predominantly vegetarian adults in the Boston, Massachusetts, area in 1973-1974. The basis of the dietary information was 10-day diet records. Total serum cholesterol was positively associated with dietary cholesterol (r = 0.53) and saturated fatty acids (r = 0.50) in partial correlation analysis adjusted for age, sex, and triceps skinfold. The use of one-day dietary records lowered these correlation coefficients to about 0.3. Analysis of the components of variation of nutrient intake demonstrated that the vegetarians had a lower within-person variance, a higher between-person variance, or both compared with nonvegetarian study groups. Biologic responsiveness to dietary fat in the vegetarians was similar to that predicted by the Keys equation derived from nonvegetarians. Therefore, multiple-day averaging of dietary records and relatively smaller ratio of within-person to between-person variation in intake favor the detection of cross-sectional associations of diet with serum cholesterol.

Ingestion of egg raises plasma low density lipoproteins in free-living subjects.

In addition to their usual diet, 17 lactovegetarian college students consumed 400 kcal of test foods per day containing one extra-large egg for three weeks and similar isocaloric eggless foods for an additional three weeks in a randomised double-blind crossover trial. Ingestion of the egg increased dietary cholesterol from 97 to 418 mg per day. Mean plasma low density lipoprotein (LDL) cholesterol was 12% higher (p = 0.005) and mean plasma apolipoprotein B was 9% higher (p = 0.007) when eggs were being consumed than during the eggless period. Mean plasma high density lipoprotein cholesterol, apolipoproteins A-I and A-II, very low density lipoprotein cholesterol, and total triglycerides did not change significantly. Thus, ingestion of egg seems selectively to raise cholesterol and protein in LDL particles in the plasma of free-living normal people. Plasma LDL may be more sensitive to cholesterol at low intakes than at moderate to high intakes.

Assessment of the efficiency of protein utilization in young squirrel and macaque monkeys.

The efficiency of protein utilization was assessed in three groups of infant squirrel monkeys fed diets containing restricted amounts of lactalbumin, casein, and soy protein isolate as the sole nitrogen source for 3-week periods. Lactalbumin was fed in similar conditions to a group of macaques for comparison. The regression of weight gain on protein intake was calculated for each dietary protein yielding an estimate of protein needs for weight maintenance and an estimate of the efficiency of utilization of protein for growth (slope X percentage protein in tissue). Mean requirements for weight maintenance of infant squirrel monkeys for lactalbumin, casein and soy protein isolate were 3.43, 3.63, and 7.96 g/kg per day and growth was accomplished with an efficiency of 27.8, 32.1, and 22.2%, respectively. In contrast, the macaques utilized lactalbumin with an efficiency of 65%, similar to that of the infant cebus monkey and adult man. The low efficiency found in young squirrel monkeys was altered neither when the habitual feeding schedule was prolonged from 16 to 24 hr per day in a group of casein-fed animals nor when sulfur amino acids were added to casein.

Protein utilization and lysine metabolism in obese and non-obese growing rats.

Efficiency of protein utilization and lysine metabolism were studied in growing rats of the Zucker 13M strain, both obese and lean, and in the Charles River CD strain. When graded levels of wheat gluten or wheat gluten supplemented with lysine were fed to these three types of rats, no significant differences in the efficiency of protein utilization were found. However, under these dietary conditions, the Zucker obese rats appeared to be about 167% more efficient in energy utilization than the Zucker lean rats or the Charles River strain. The response of liver lysine-ketoglutarate reductase to the dietary treatment was similar in these three types of growing rats. The enzyme activity was induced by dietary lysine. Rats fed a lysine-deficient purified diet had a significantly lower enzyme activity than those fed a protein-free diet indicating that the same adaptive mechanism for lysine conservation as previously observed in adult rats also occurred in the growing animal. Interaction between dietary and genetic factors on fatty liver was found in this study. The most severe fatty liver was observed in the Zucker obese rats fed the most lysine-deficient diet containing 8% wheat gluten protein.

Protein deficiency and energy restriction in young cebus monkeys.

Infant cebus monkeys (Cebus albifrons) were fed liquid formulas that were limited in protein, energy, or a combination of the two restrictions. Weight gain, food intake, hematological development, and plasma protein and cholesterol levels were monitored over a 20-week period. The animals restricted in protein developed the classical signs of protein deficiency--reductions in plasma albumin, a mild anemia, accumulation of fat in the liver, and, in a few cases, facial edema. These animals maintained a relatively high energy intake, and apparently wasted energy when compared to similarly non-growing energy-restricted animals. Energy-restricted animals did not exhibit these symptoms, even when their daily protein intake was reduced to match that of protein-restricted monkeys. It is concluded that an energy restriction superimposed upon a limited protein intake did not increase protein requirements or precipitate protein deficiency.

Protein and calorie malnutrition in infant cebus monkeys: growth and behavioral development during deprivation and rehabilitation.

The growth and development of 32 cebus monkeys were studied during a period of insult in nutritional or rearing conditions and after rehabilitation. Eight experimental groups of four animals each were subjected to one of four diets--control, protein restricted, calorie restricted, and protein-calorie restricted, and one of two rearing conditions-partial isolation or a comparatively enriched condition-in a 4 x 2 factorial design. The period of insult from 2 to 6 months of age was followed by 6 months of rehabilitation in both diet and rearing conditions. It was found that only diet affected physical growth, but both diet and rearing affected behavioral development and exploratory behavior. Whereas calorie deficiency produced a direct effect on behavior independent of rearing conditions, protein deficiency produced an effect only in combination with rearing restriction. The effect of protein-calorie deficiency had some characteristics in common with each of the other deficiencies. Retardation in rate of behavioral development was less severe than retardation in growth, most notably in the protein-restricted, enriched-rearing group, producing animals who were behaviorally mature for their size. All groups caught up in physical growth during rehabilitation but the protein-calorie restricted groups failed to recuperate completely in exploratory behavior.

The effects of a 20-week nutritional insult on the skeletal development of Cebus albifrons during the 1st year of life.

Using an atlas constructed from records of a group of normal monkeys in the same colony, the effects of a 20-week low-calorie or low-protein nutritional insult on skeletal development were determined. The most significantly retarded sites were the late-forming ossifications (epiphyses, sesamoids, and tuberosites). A general increase in ossification anomalies and in individual variation was evident. The similarity of these findings to studies previously reported for man indicates the utility of nonhuman primate models for the further study of nutritional deficiency.

Physical growth of cebus monkeys, Cebus albifrons, during protein or calorie deficiency.

Infant cebus monkey (Cebus albifrons) on experimental diets providing low-protein (2.8% of calories) or low-calorie (67% of ad libitum intake) levels for 20 weeks beginning at 8 weeks of age showed marked changes in their patterns of physical growth. Significant size differences between the malnourished animals and the control group appeared within 4 weeks. Although rates of growth were significantly reduced in all measurements, all of the malnourished monkeys, including low-protein animals showing zero weight gain, continued skeletal growth (except in skull measurements) at low levels for the duration of experiment. Both the protein- and calorie-restricted animals developed a thin, emaciated appearance often associated with marasmus, not by the continuous loss of tissue byt by the redistribution of the tissue over a slowly expanding skeleton. For many skeletal proportions, the pattern and shape development in the malnourished animals differed from that of the control animals. Growth during malnutrition was most affected in those parts of the skeleton which were more advanced in relative size.

Physical growth of cebus monkeys (Cebus albifrons) during the first year of life.

Infannt cebus monkeys, removed from their mothers shortly after birth, were reared in a primate nursery on diets of controlled nutritional quality. At regular intervals between birth and one year of age, each monkey was anesthetized, measured, and radiographed. Measurements were fitted to functions of the animal's age in days; a linear function for the first 6 to 8 weeks and a logarithmic function for the remainder of the first year. Mean constant curves have been calculated for each measure and estimates of animal variability have been obtained by interpolating sizes at given ages from regression lines fitted to the data for each animal. The maximum rate of growth was attained soon after birth. Cranial-caudal and distal-proximal maturity gradients in size attainment were observed.