Susan M. Potter

Soy protein and isoflavones: their effects on blood lipids and bone density in postmenopausal women.

The effects of soy protein (40 g/d) containing moderate and higher concentrations of isoflavones on blood lipid profiles, mononuclear cell LDL receptor messenger RNA, and bone mineral density and content were investigated in 66 free-living, hypercholesterolemic, postmenopausal women during a 6-mo, parallel-group, double-blind trial with 3 interventions. After a control period of 14 d, during which subjects followed a National Cholesterol Education Program Step I low-fat, low-cholesterol diet, all subjects were randomly assigned to 1 of 3 dietary groups: Step I diet with 40 g protein/d obtained from casein and nonfat dry milk (CNFDM), Step I diet with 40 g protein/d from isolated soy protein containing 1.39 mg isoflavones/g protein (ISP56), or Step I diet with 40 g protein/d from isolated soy protein containing 2.25 mg isoflavones/g protein (ISP90). Total and regional bone mineral content and density were assessed. Non-HDL cholesterol for both ISP56 and ISP90 groups was reduced compared with the CNFDM group (P < 0.05). HDL cholesterol increased in both ISP56 and ISP90 groups (P < 0.05). Mononuclear cell LDL receptor mRNA was increased in subjects consuming ISP56 or ISP90 compared with those consuming CNFDM (P < 0.05). Significant increases occurred in both bone mineral content and density in the lumbar spine but not elsewhere for the ISP90 group compared with the control group (P < 0.05). Intake of soy protein at both isoflavone concentrations for 6 mo may decrease the risk factors associated with cardiovascular disease in postmenopausal women. However, only the higher isoflavone-containing product protected against spinal bone loss.

Endocrinological response to soy protein and fiber in mildly hypercholesterolemic men

Abstract Soy protein and soy fiber may affect hormones involved in cholesterol metabolism. Therefore, plasma insulin, total thyroxine (T4), free thyroxine index (FTI), triiodothyronine (T3), and thyroid stimulating hormone (TSH) were measured in 17 hypercholesterolemic men consuming baked products containing 50 g/d of protein and 20 g/d of fiber from either soy flour (SF), soy protein isolate (ISP)/soy fiber (ISP/SCF), ISP/cellulose (ISP/Cell), or nonfat dry milk/cellulose (NFDM/Cell). A latin square design was used and included all four dietary treatments, each lasting four weeks. Hormones were analyzed at the end of each experimental period and after an initial baseline period of 10 days. Although the mean values of T4 showed an increase in all treatments relative to baseline, significant differences ( p p p

Effects of dietary protein source on cholesterol metabolism in neonatal pigs

Abstract The purposes of this study were to determine the effects of dietary protein sources used in human infant formulas on cholesterol metabolism, and to examine several hormones as potential mediators of a cholesterolemic response. Thirty (15 male/15 female), two day old piglets were removed from sows and fed diets differing only in casein:whey ratios of either 100% casein, 80% casein:20% whey, or 40% casein:60% whey for three weeks. Piglets fed diets containing increasing amounts of casein had increased total and free (unesterified) serum cholesterol (p

The role of dietary protein source in the development of cholesterol metabolism in rabbits

Twenty-one male 4-week-old New Zealand white rabbits were assigned to one of three dietary treatments (seven rabbits/treatment) in which protein source was derived from varying casein to whey ratios (100:0, 80:20, 40:60). Blood was collected at 10, 14, 18, and 20 weeks and animals were killed at 24 weeks and blood, livers, and aortas were removed. From weeks 20 to 24, a 0.4% cholesterol diet was fed. Results showed that animals fed the 40:60 diet had highest blood cholesterol concentrations prior to the cholesterol challenge (P < 0.05). After the challenge, differences disappeared. Low density lipoprotein and high density lipoprotein cholesterol concentrations in 40:60 animals were also higher than in 80:20 animals until 20 weeks of age (P < 0.05). Total triglycerides were highest in 100:0 fed animals at 10 and 14 weeks of age (P < 0.05) and stayed highest in this group after the challenge (P < 0.05). Rabbits fed 40:60 diet had higher 3-hydroxy-3-methylglutaryl coenzyme. A reductase activities than the 100:0 rabbits (P < 0.05). Total liver lipids were also higher in the 40:60 than 100:0 group (P < 0.01), and fecal cholesterol content was higher in the 80:20 than 100:0 group (P < 0.05). Bile acid excretion and atherosclerotic plaque formation were not affected by dietary treatment. These results indicate that plasma lipids are influenced by dietary protein source during the postweanling period, but the mechanism for this response remains to be defined.