Relation between soy-associated isoflavones and LDL and HDL cholesterol concentrations in humans: a meta-analysis.
BACKGROUND
Differences in isoflavone content of soy protein may explain the absence of a dose-response relation between soy protein intake and blood cholesterol concentrations.


OBJECTIVE
To study specifically the effect of soy-associated isoflavones on cholesterol concentrations in well-controlled trials substituting soy protein with dairy or animal protein.


METHODS
Studies were identified by MEDLINE searches (1995 - 6 June 2002) and reviewing reference lists. Studies were included if they had a control group or treatment, experimental diets only differed in the amounts of soy protein and isoflavones and were each fed for at least 14 days. A total of 10 studies met these criteria, providing 21 dietary comparisons.


METHODS
: Studies comprised 959 subjects (336 men and 623 women), average age ranged from 41 to 67 y and baseline cholesterol concentration from 5.42 to 6.60 mmol/l.


METHODS
The intake of soy-associated isoflavones increased by 1-95 mg/day and the intake of soy protein increased by 19-60 g/day.


RESULTS
Feeding daily 36 g soy protein with 52 mg soy-associated isoflavones on average decreased low-density lipoprotein (LDL) cholesterol by -0.17+/-0.04 mmol/l (mean+/-s.e.) and increased high-density lipoprotein (HDL) cholesterol by 0.03+/-0.01 mmol/l. There was no dose-response relation between soy-associated isoflavones and changes in LDL cholesterol (R=-0.33, P=0.14) (Pearson correlation coefficient) or HDL cholesterol (R=-0.07, P=0.76) or their ratio.


CONCLUSIONS
Consumption of soy-associated isoflavones is not related to changes in LDL or HDL cholesterol.
Weggemans
R M
RM
Unilever Health Institute, Unilever Research and Development Vlaardingen, Vlaardingen, The Netherlands.
Trautwein
E A
EA
D000328:Adult; D000368:Aged; D008076:Cholesterol, HDL / Q000097:blood*; D008078:Cholesterol, LDL / Q000097:blood*; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D006937:Hypercholesterolemia / Q000097:blood / Q000178:diet therapy*; D007529:Isoflavones / Q000008:administration & dosage* / Q000378:metabolism; D016239:MEDLINE; D008297:Male; D008875:Middle Aged; D030262:Soybean Proteins / Q000008:administration & dosage / Q000737:chemistry
D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D004044:Dietary Proteins; D007529:Isoflavones; D030262:Soybean Proteins