New perspectives on dietary soybean effects on serum cholesterol and thyroxin

A series of experiments were conducted in mildly hypercholesterolemic men, rats and hamsters to determine the effects of non-protein components from soy on serum cholesterol and thyroid hormones. In mildly hypercholesterolemic males, 20 g soy cotyledon fiber with or without soy protein was not effective in lowering serum cholesterol levels. Individuals consuming soy/cellulose containing muffins had significantly higher free thyroxin index values than when a low-fat, low-cholesterol diet was consumed. In rats, soy isoflavanoids when added to dietary casein caused a significant lowering of LDL cholesterol relative to casein without isoflavanoids. Animals fed casein that had been supplemented with the crude soybean isoflavanoid extract had significantly higher serum total thyroxin and free thyroxin index values than animals that were given non-supplemented casein. The effects by the exogenous isoflavanoids appeared to be modified by the type of dietary protein. Rats fed soybean diets from which isoflavanoids had been removed showed similar cholesterol and thyroid hormone levels to those observed in animals fed soy diets that contained isoflavanoids. In hamsters, animals fed casein diets that were supplemented with a crude soybean isoflavanoid extract at the level normally found in soy isolate had significantly lower total and LDL+VLDL cholesterol concentrations than animals fed casein without isoflavanoids. When the amount of isoflavanoids added to casein was doubled, both total and LDL+VLDL cholesterol concentrations increased and became intermediate between those observed for casein alone and casein plus isoflavanoids added at the level normally found in soy isolate. This pattern of changes in serum cholesterol was not observed for the thyroid hormones. Serum total thyroxin appeared to increase linearly when increasing levels of isoflavanoids were added to either casein or soy. Results from these studies indicate that while dietary soybeans can cause an increased plasma thyroxin, this does not appear to be related to their effects on serum cholesterol.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Biology, Animal Physiology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Balmir, Frantzie

Contributors dc:contributor

• Potter, S.M.

• Biology, Animal Physiology
• Chemistry, Biochemistry
• Health Sciences, Nutrition

Statement dc:rights

• Copyright 1994 Balmir, Frantzie

Language dc:language

eng

Identifier

AAI9512294
(UMI)AAI9512294

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/23699