Soja goed tegen hartproblemen.*
De bioactieve stoffen in soja, zoals genisteïne en daidzeïne, leiden volgens een Chileense studie tot minder bloedstolsels waardoor de kans op een hartaanval of beroerte duidelijk verlaagd wordt. De onderzoekers gaven 29 vrouwen 12 weken lang dagelijks een supplement met 100 milligram soja-flavonoïden, een ander groep vrouwen kreeg een placebo. Na 12 weken bleek dat de rode bloedcellen veranderd waren en minder receptoren aan van het type Tromboxaan A2 hadden aangemaakt. Dat betekent dat de cellen minder makkelijk stolsels vormen. Stolsels zorgen vaak voor het ontstaan van een hartaanval of beroerte.
Study
Sheds Light On Soy And Heart Health
New
research helps explain how soy may contribute to heart health, through a process
scientists refer to as "decreased platelet aggregation." By reducing
the density of platelet receptors, a natural component in soy called isoflavones
may contribute to a reduced risk of blood clotting, which in turn decreases the
risk of heart attack and stroke.
According to the study published in the journal Maturitas, Chilean researchers
recruited post-menopausal women to take part in the double-blind, randomized,
placebo-controlled study. The study randomly assigned the participants to
receive a daily supplement of 100 mg isoflavones or an identical placebo for
three months. At the end of the three-month period, the group receiving the
isoflavone supplement showed a significant decrease in the density of a
particular platelet receptor (known as TxA2), while the placebo group remained
mostly unchanged.
Excessive aggregation of platelets may contribute to cardiovascular diseases,
such as heart attack and stroke. By decreasing the density of platelet receptors,
such as the TxA2, the risk of forming a blood clot that could lead to heart
attack or stroke is also reduced.
Lisa Kelly, MPH, RD commented, "These findings are significant because they
suggest a new understanding of the ways in which soy isoflavones may positively
effect cardiovascular health." Kelly, a dietitian speaking on behalf of the
United Soybean Board, explained further, "Previous research has shown that
soy offers a modest reduction of LDL cholesterol -- the bad cholesterol -- which
may help reduce the risk of heart disease by 10 percent on a population-wide
basis. There are also studies linking soy to lowered blood pressure. This study
uniquely demonstrates that soy may contribute to heart health through a reduced
risk of blood clotting as well, and therefore a reduced risk of heart attack and
stroke."
These findings create a more nuanced understanding of the American Heart
Association (AHA) Nutrition Committee's recent statement in the journal
Circulation that downplayed the degree to which soy can help reduce cholesterol,
pointing to a more modest benefit than previously thought. However, by linking
soy isoflavones to reduced platelet aggregation, the new study suggests the need
for scientists to examine a variety of heart health factors, including but not
limited to cholesterol in order to gain a thorough understanding of the ways in
which soy may contribute to heart health.
The United Soybean Board is a farmer-led organization comprised of 64
farmer-directors. USB oversees the investments of soybean checkoff on behalf of
all U.S. soybean farmers. Working with independent academic researchers
affiliated with the National Institutes of Health (NIH) and academic
institutions, USB has invested millions of dollars into health and nutrition
research related to soy.
OBJECTIVES:
It has been suggested that isoflavones protect the cardiovascular system, in
part by improving lipid profile. The purpose of the present research was to
examine the effect of a 12-week soy isoflavone supplementation on lipoprotein
status and platelet thromboxane A2 receptor density. METHODS: Twenty-nine
healthy postmenopausal women were invited to take part in a randomised study to
receive either 100 mg/day isoflavone supplement (n=15) or identical placebo
capsules (n=14). Blood samples obtained at baseline and after 12 weeks were
analysed for isoflavones, total cholesterol, high density lipoprotein
cholesterol, triglycerides, glucose, insulin, estradiol, testosterone,
gonadotrophins, sex hormone-binding globulin (SHBG) and platelet thromboxane A2
receptor density. Blood pressure measurements, body mass index, subcutaneous fat
at entrance and at the end of treatment were also registered. Changes in
variables between groups were compared by ANOVA for repeated measures. RESULTS:
Blood pressure, body mass index, subcutaneous fat, insulin, serum lipoprotein,
sex hormones and SHBG did not differ among groups. However, platelet thromboxane
A2 receptor density declined significantly (from 181.9+/-30.9 to 115.2+/-16.2
fmol/10(8) platelets) in the experimental group, remaining mostly unchanged in
the placebo group (176.3+/-27.3 to 170.4+/-28.2 fmol/10(8) platelets). The
dissociation constant (Kd) values were unchanged. The change in platelet
thromboxane A2 receptors correlated negatively with isoflavones serum
concentration (r=-0.59, p<0.001). CONCLUSIONS: In this study we demonstrated
that the beneficial effects of isoflavones in menopausal women could be more
related to platelet function than to improving classical cardiovascular risk
factors.
(Nov. 2006)