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Lipid metabolism as influenced by dietary protein source and sulfur-amino acids
Abstract
Three studies were conducted to investigate the effects of dietary protein source and sulfur-amino acids on lipid metabolism. In Study I, 60 male, weanling Wistar-Kyoto rats were fed two sources of protein (casein or soy protein isolate) and three variations in sulfur-amino acid supplementation (none, methionine, or cystine). At this level of protein intake (10% by weight), rats fed soy based diets generally had lower serum lipid quantities than did rats fed casein based diets. Overall serum lipid concentrations were greater in rats fed proteins supplemented with methionine while the addition of cystine produced lower lipid levels. Liver lipid concentrations were tremendously increased upon cystine supplementation of soy protein isolate. Protein quality, as determined by Protein Efficiency Ratio, was improved by either sulfur-amino acid; however, methionine had the greatest effect. In Study II, ten human adults were fed four laboratory controlled diets containing either soy protein isolate alone, soy protein isolate supplemented with methionine, soy protein isolate supplemented with cystine, or animal protein. At this level of protein (approximately 16% of total calories), feeding of animal protein based diets produced lower serum lipids than did the soy based diets. Generally, the addition of methionine to soy protein isolate increased blood lipids while cystine supplementation decreased values. Both amino acids improved protein quality as determined by nitrogen balance; however, methionine was more effective. In Study III, a retrospective analysis of the association between animal to vegetable protein intake ratios and serum lipids was performed using adolescent human children as subjects. Negative correlations were found between blood serum lipids and the protein intake ratios. Negative correlations were also found between percent total fat and caloric intakes and serum lipids. These results were not consistent with those obtained from adult populations implying that the physiological demands of growth were probably more influential on serum lipids than were dietary components.
Subject Area
Nutrition
Recommended Citation
Potter, Susan Midland, "Lipid metabolism as influenced by dietary protein source and sulfur-amino acids" (1988). ETD collection for University of Nebraska-Lincoln. AAI8904506.
https://digitalcommons.unl.edu/dissertations/AAI8904506