The effect of isoflavone supplement intake on gene-expression in postmenopausal women

Alleged benefits experienced by the consumption of soy in Asian countries have
been attributed to the isoflavone content of soy products. Amongst other
benefits, isoflavones are believed to relieve menopausal symptoms and are
therefore often consumed in supplement form in Western countries. These
supplements contain relatively high amounts of isoflavones, and the question is
if these concentrations still exert beneficial effects or whether negative
effects become dominant. At the moment, the European Food Safety Authority
(EFSA) is also taking a better look at the potential health effects of
isoflavones.

Primary objective: to determine the effect of intake of one dose of
isoflavones, as compared to placebo, for eight weeks on gene-expression in
Peripheral Blood Mononuclear Cells (PBMCs) in post-menopausal, equol-producing
women.
Secondary Objectives: to determine the association between isoflavone plasma
levels and gene-expression in PBMCs;
to determine the variation of isoflavone plasma levels between subjects after
intake of isoflavones for four and eight weeks;
to explore whether PBMC gene-expression markers identified after 8 weeks
isoflavone intervention are already present after 4 weeks intervention;
to explore whether the severity of previous menopausal complaints is related to
the effect of isoflavones on PBMC gene-expression;
and
to explore the association between isoflavone levels in plasma and spot urine.

Double-blind placebo controlled crossover intervention study

Two intervention periods of eight weeks with a isoflavone supplement or a
placebo and a washout period of 8 weeks in between.

The subjects have to fill in a short screening questionnaire, a questionnaire
regarding their menopausal complaints, and twice a food frequency questionnaire.
The subjects have to visit the research centre 6 times, with their morning
urine, to give a blood sample, to measure their arterial stiffness and to be
weighed. In total the subjects spend, actively, around 9 hours in the study.
On the basis of the existing material there is no evidence that these
supplements are unsafe. There are indications of concern in the scope of
effects on hormone-sensitive breast cancer and for babies fed with soy infant
formula, based on in vitro and animal studies and not supported by clinical and
epidemiological studies. In the present study, however, persons with history of
cancer are excluded.
At present, there is not enough human data to draw firm conclusions about the
safety of isoflavones. Therefore the present study is important. Isoflavones
can exert, after long-term usage of high doses, positive as well as negative
effects. In the present study we will explore the effects of isoflavone intake
on a broad scale with the use of micro-arrays. The supplements that will be
used are commercially available and the dose is equal to the dose that
producers subscribe. In literature we found 14 studies that use a dosage higher
than 100 mg/day for a longer exposure time than in the present study. These
studies did not report adverse effects
Venapunctures can occasionally cause a local hematoma or bruise and some
participants may report pain or discomfort.