Ms. Anthony et al., SOYBEAN ISOFLAVONES IMPROVE CARDIOVASCULAR RISK-FACTORS WITHOUT AFFECTING THE REPRODUCTIVE-SYSTEM OF PERIPUBERTAL RHESUS-MONKEYS, The Journal of nutrition, 126(1), 1996, pp. 43-50
Although the beneficial effects of dietary soybean protein compared wi
th animal proteins on plasma lipids, lipoproteins and atherosclerosis
have been known for about 50 years, it has been uncertain whether thes
e effects are due to its amino acid concentrations or other components
in soybeans. To assess the effect of soybean protein's alcohol-extrac
table components (including the isoflavonic phytoestrogens genistein a
nd daidzein) on plasma lipid and lipoprotein concentrations and to est
ablish its lack of effect on the reproductive system, we fed 27 peripu
bertal male and female rhesus monkeys moderately atherogenic diets in
which the source of dietary protein was a soy isolate (20% by weight),
either containing phytoestrogens (also termed isoflavones) or with th
e phytoestrogens removed by alcohol extraction. The study was a crosso
ver design with each period lasting for 6 mo. The phytoestrogen-intact
soy protein (compared with the alcohol-extracted soy protein) had fav
orable effects on plasma lipid and lipoprotein concentrations, specifi
cally by significantly reducing LDL + VLDL cholesterol concentrations
in both males and females (similar to 30-40% lower), significantly inc
reasing high density lipoprotein cholesterol (HDLC) concentrations for
females (similar to 15% higher) and significantly lowering total plas
ma cholesterol (TPC):HDLC ratios (similar to 20% lower for males and 5
0% lower for females). The phytoestrogens had no adverse effects on th
e reproductive systems of either the males or females, as evaluated by
reproductive hormone concentrations and organ weights at necropsy. Th
us, the isoflavones in soy protein improve cardiovascular disease risk
factors without apparent deleterious effects on the reproductive syst
em of peripubertal rhesus monkeys.