Limited lipid-lowering effects of regular consumption of whole soybean foods.
OBJECTIVE
To examine cardiovascular health benefits of foods containing a whole soybean extract.


METHODS
The study design was a randomized, placebo-controlled crossover trial of consuming soy-based milk and yoghurt (treatment) or equivalent dairy products (control) for 5 weeks each. Twenty-six mildly hypercholesterolaemic and/or hypertensive volunteers were recruited from the community as study volunteers, of which 23 completed. Main outcome measures included clinic and ambulatory blood pressure, arterial compliance, lipids, fatty acids and isoflavones in fasted blood and 24-hour urinary isoflavone excretion. Nutrient intakes were assessed initially and after each 5-week period. Multiple regression analyses were used to determine predictor variables in statistical models; order effects were tested by repeated measures ANOVA. Changes in Lp(a) were determined by Wilcoxon signed ranks tests; other differences between treatment and control were assessed by t tests.


RESULTS
Plasma and urinary isoflavones were markedly increased by whole soy supplementation but there were no overall differences in plasma lipids, blood pressure or arterial compliance between the soy and dairy diets. However, in 8 equol-positive subjects (equol detected in either plasma or urine), retrospective analysis revealed significant reductions in total cholesterol (8.5%), LDL cholesterol (10%), LDL:HDL ratio (13.5%), plasma triglycerides (21%) and lipoprotein(a) (11%) with the soy diet. These reductions were independent of changes in polyunsaturated fat and other macronutrient intakes.


CONCLUSIONS
Regular consumption of whole soybean milk and yogurt products had no effect on plasma lipids, blood pressure or arterial compliance in at-risk subjects, despite substantially increasing isoflavone levels in blood and urine. Retrospective analysis suggests that improvement of plasma lipids may have been limited to equol-positive subjects.
Meyer
Barbara J
BJ
Department of Biomedical Science and Smart Foods Centre, University of Wollongong, NSW, Australia. barbara_meyer@uow.edu.au
Larkin
Theresa A
TA
Owen
Alice J
AJ
Astheimer
Lee B
LB
Tapsell
Linda C
LC
Howe
Peter R C
PR
D000924:Anticholesteremic Agents / Q000008:administration & dosage*; D001794:Blood Pressure / Q000187:drug effects; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D018592:Cross-Over Studies; D003611:Dairy Products; D005227:Fatty Acids / Q000097:blood; D005260:Female; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood / Q000178:diet therapy* / Q000652:urine; D006973:Hypertension / Q000097:blood / Q000178:diet therapy* / Q000652:urine; D007529:Isoflavones / Q000008:administration & dosage / Q000097:blood / Q000652:urine*; D008055:Lipids / Q000097:blood*; D008297:Male; D008875:Middle Aged; D013025:Glycine max / Q000737:chemistry
D000924:Anticholesteremic Agents; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D005227:Fatty Acids; D007529:Isoflavones; D008055:Lipids