[PHNUTR-L] Daidzein from soy linked to heart health benefits
Kathrynne Holden, MS, RD
fivestar at nutritionucanlivewith.com
Fri Jun 23 08:09:54 PDT 2006
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Daidzein from soy linked to heart health benefits
By Stephen Daniells
23/06/2006 - Increasing levels of daidzein, an isoflavone found in soy,
have been linked to significant improvements in cholesterol levels and
could boost heart health, says a new study.
“These results are the first to demonstrate a beneficial association
between blood levels of the phytoestrogen daidzein and lipoproteins in
human subjects,” wrote lead author Noel Bairey Merz from the University
of Pittsburgh Graduate School of Public Health.
A recent scientific statement by the American Heart Association (AHA) in
the journal Circulation concluded that soy had little effect on
cholesterol levels, and raised doubts about health claims associated
Dr Frank Sacks, a member of the AHA panel, said in January: “It's really
clear that isoflavones don't contribute anything to cardiovascular
But the new study, published in The Journal of Clinical Endocrinology
and Metabolism (Vol. 91, pp. 2209-2213), reports that high blood levels
of daidzein were associated with favourable lipoprotein profiles.
If its findings are reproduced in future studies, they might lead to a
re-evaluation of the science that led AHA to its conclusion.
Half of the women recruited for the Women's Ischemia Syndrome Evaluation
(WISE) study (483 subjects; BMI 29.4; average age 58; 79 per cent
post-menopausal) were chosen for this research. All the volunteers had
at least one coronary risk factor. Blood samples were taken and levels
of the soy isoflavones daidzein and genistein were measured.
Blood levels of total cholesterol (TC), triglyceride (TG) and
HDL-cholesterol (HDL-C) were determined by an enzymatic assay.
LDL-cholesterol (LDL-C) levels were calculated using the Friedewald formula.
The researchers found that increasing levels of daidzein were associated
with decreasing levels of TG and increasing HDL-C levels. Women with the
highest blood daidzein levels (more than 13.2 nanograms per millilitre)
had 17 per cent lower TG levels and 5 per cent higher HDL-C levels than
women with the lowest levels (less than 3.2 nanograms per millilitre).
When the researchers examined the data taking into account levels of the
female hormone estradiol, they found that the link between daidzein
blood levels and lipid profiles was stronger in women with low estradiol
levels. The relationship between daidzein and blood lipids was not
significant for women with high estradiol levels.
“Our findings of the beneficial association between daidzein and
lipoproteins being dominantly evident among women with low blood
oestrogen levels supports the idea that daidzein may operate, in part at
least, via an oestrogen receptor mechanism,” said the researchers.
No relationship between blood levels of the isoflavone genistein and
blood lipoprotein levels was found.
“These and prior studies suggest that cardiovascular risk reduction
strategies in women should consider dietary intake of food products,
such as soy, which elevate blood daidzein levels, consistent with recent
recommendations,” concluded Bairey Merz.
This study has several limitations, most notably that other dietary
factors such as dietary fibre or fat intake were not evaluated by the
researchers. Also, the design of the study prevented the researchers
from proving causality.
“These results require replication in future prospective, randomised
trials using a dietary source of daidzein in women with low oestrogen
levels, as well as correlative dietary studies to link them to dietary
habits, including supplement use,” concluded the authors.
CVD causes almost 50 per cent of deaths in Europe, and is reported to
cost the EU economy an estimated €169bn ($202bn) per year. According to
the American Heart Association, 34.2 per cent of Americans (70.1m
people) suffered from some form of cardiovascular disease (CVD) in 2002.
Kathrynne Holden, MS, RD < fivestar at nutritionucanlivewith.com >
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