Date of Award
Doctor of Philosophy
Frances A. Schofield
Jane R. Savage, Ada Marie Campbell, John T. Smith, Samuel R. Tipton
(From the Introduction)
Serum lipid levels of young women are of particular interest because, in a population riddled with atherosclerosis, premenopausal women seem to have a relative immunity both to severe hyperlipidemia and to those diseases thought to be related to it. The diet of this heterogeneous population is characterized by high intakes of animal protein, animal fat, and sugars.
Research has shown that the type and quantity of fat and carbohydrate have varying degrees of influence on serum lipid levels. Various micronutrients are also implicated. Animal experiments using wide ranges of protein intake suggest that under some conditions increased protein consumption lowered serum lipid levels, while under other conditions similar protein intakes raised these levels. The critical conditions have yet to be defined. Metabolic studies with humans have produced contradictory results, causing some authors to declare dietary protein to be hypolipidemic, while others consider it hyperlipidemic, and still others report no effect at all. In several similar studies, young women have responded to lowered protein intakes with lowered serum lipids while young men were unaffected. Because most of these metabolic studies have employed only small groups of subjects, it is possible that their differing results were caused by undiagnosed differences in the health and dietary history of the subjects.
The present study was designed to allow observation of the subjects' non-experimental dietary intakes and serum lipid levels as well as those serum lipid levels occurring during periods of consumption of experimental diets of minimum-adequate to moderate protein content. This experimental design allowed comparison of the subjects' usual dietary intakes with that considered typical of North Americans. The experimental serum lipid levels could be interpreted in terms of the dietary change involved rather than as responses to an absolute dietary intake.
A series of three metabolic studies of premenopausal females consuming diets limited in protein has been conducted in the Department of Nutrition at The University of Tennessee. The protein content of the diets varied from 20 to 48 g. per day, 35 to 65 per cent of the protein coming from animal sources. Variations in fat, sterol, and carbohydrate intakes were kept to the minimum that is possible with ordinary foods. Measurements of serum cholesterol and total esterified fatty acids were made both while the subjects were consuming their freely-selected diets and during the thirty-day experimental periods, thereby permitting at least partial characterization of each individual's serum lipid response. Serum fatty acids were determined during some of the periods in order to observe any qualitative changes in fatty acid patterns when the subjects changed from their usual diets to the experimental fare.
Parham, Ellen Speiden, "The Influence of Dietary Protein on Serum Lipid Levels of Premenopausal Women. " PhD diss., University of Tennessee, 1967.