Usually, men are at a higher risk than women of developing cardiovascular
disease; however, once women go through menopause, their risk of
cardiovascular disease increases to that of men.
Since it is known that postmenopausal women are at high risk of
cardiovascular disease, researchers set out to learn if soy protein
could lower that risk. Specifically, researchers hoped to discover
if soy isoflavones (which exert weak estrogenic activity in the
body and are structurally similar to estrogens) would positively
alter blood lipid concentrations and if phytate (a chemical occurring
in plants, capable of combining with calcium, zinc, iron, and other
nutrients and interfering with their absorption by the body) would
decrease oxidative stress indexes.
The study was a six-week double-blind
study that involved 55 postmenopausal women, aged 47-72. Subjects
were randomly assigned to one of four soy protein isolate treatments:
- Low-phytate/low-isoflavone
- Normal-phytate/low-isoflavone
- Low-phytate/normal-isoflavone
- Normal-phytate/normal-isoflavone
Beginning two weeks before the study and continuing through, subjects
were required to avoid all supplements, as well as foods that were
phytate-rich (cereals, legumes and nuts) and isoflavone-rich (primarily
legumes) during the intervention. They were given 40-gram packets
of soy protein they could use to make smoothies or add to their
daily meals.
Results of the study directly contradicted that of previous studies:
Researchers found that there was no considerable, beneficial effect
of isoflavones or phytate in reducing oxidative damage or favorably
changing blood lipids in postmenopausal women. Also, total and HDL
cholesterol levels weren't much different between normal- and low-isoflavone
groups either.
American
Journal of Clinical Nutrition March 2005;81(3):590-596
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