Research Investigation of Soy and Estrogen

Recent research suggests that in addition to playing a role in disease prevention and
menopausal symptom reduction, phytoestrogens can reduce anxiety-related behaviors in animals
and improve memory in both animals and humans. This project seeks to investigate the
potential anxiolytic (anti-anxiety) and cognition-enhancing effects of phytoestrogen
treatment, in comparison to another popular treatment, estradiol, and placebo, for
perimenopausal women. Given the detrimental effects of stress on memory performance, a
widely used laboratory stressor will be implemented to investigate whether phytoestrogens
and/or estradiol enhance memory by counteracting the negative effects of stress on memory
processes.

Estrogen and Anxiety Recent animal studies suggest that estrogen can play an important role
in modulating anxiety, yet there has been little human research on this topic. Research
suggests that the anxiolytic effects of estrogens are mediated by estrogen receptor-beta 1
(ER-beta), one of two known estrogen receptors in the brain 2. ER-beta agonists decreased
the release of stress hormones after immobilization stress in rats compared to no treatment
and treatment with ER-alpha agonists 3. Additionally, transgenic female mice lacking ER-beta
exhibited increased anxiety and decreased serotonin in several brain areas, including the
hippocampus 4. The regulation of anxiety by ER-beta is likely to be related to the effects
of ER-beta on serotonin transmission 5. The inhibition of anxiety-related behaviors in
female rats is mediated by ER-beta in the hippocampus 6. Whereas ER-beta agonists decrease
anxiety-related behaviors in female rats, ER-alpha agonists may work in an opposite fashion
3,7.

Phytoestrogens and Anxiety Unlike estrogen, which binds equally to ER-alpha and ER-beta,
phytoestrogens have a much greater affinity for ER-beta than ER-alpha 8. Phytoestrogens are
plant compounds that are structurally and functionally similar to endogenous estrogens and
are currently being widely investigated to determine their potential role in disease
prevention. Phytoestrogens have been shown to have anxiolytic effects in female rats.
Specifically, female rats fed soy diets or soy supplements exhibited less anxiety-related
behavior in a well-validated behavioral maze task compared to control-fed counterparts 9.
Though the animal literature supports a role for phytoestrogens in reducing anxiety and/or
stress responses following an acute stressor, current research in humans is inconclusive and
is based on self-report measures of day-to-day stress rather than responses to acute
stressors. Trials examining the effects of different soy-based preparations and diets on
cognition and menopausal complaints have yielded inconsistent results. To date, three trials
have found improved overall mood, depressive symptoms, anxiety symptoms or better reaction
to the stress of testing 10,11 while five trials have shown no changes in these outcomes
12-15. No human studies have examined the potential anxiolytic effects of phytoestrogens on
stress and anxiety following a laboratory stressor. Past studies have shown mixed evidence
for whether phytoestrogens are beneficial in regards to menopausal symptoms. A recent study
has shown that women who have a specific intestinal microflora, and thus are able to produce
the isoflavan equol, are the ones who receive the benefit from the phytoestrogens, such as
reduced anxiety, as equol has a greater estrogenic activity and affinity for both estrogen
receptors (Ishiwata et al., 2009).

Stress and Anxiety in Midlife Women Recent studies demonstrate notable age and sex
differences in stress responsivity. Postmenopausal women have larger increases in salivary
cortisol after psychosocial laboratory stressors compared to premenopausal women 16. This
finding was corroborated by a recent meta-analysis which indicated that the effect of aging
on cortisol response to pharmacological or psychological challenge was about three times
greater in women compared to men 17. A community-based study of adults in their 70s found
greater 12-hour free cortisol excretion to be associated with poorer delayed verbal recall
for women only 18. Women in this study who exhibited increases in cortisol excretion two and
a half years later were more likely to show declines in memory performance at that time
compared to women without increased cortisol excretion. Using a well-validated psychosocial
laboratory stressor, Wolf and colleagues found a stronger detrimental effect of psychosocial
stress on visual-verbal memory (pictorial memory for common items) for older women compared
to older men 19. These data suggest that interventions that lower cortisol, particularly in
women, may lower age-related memory declines.

Phytoestrogens and Cognition Soy isoflavones have been shown to enhance hippocampal (memory)
and frontal lobe (executive) functioning in both clinical trials and animal studies.
Research indicates that the neuroprotective properties of phytoestrogens include a positive
impact on choline acetyltransferase and nerve growth factor in the hippocampus and frontal
cortex of female rats 20 and a weakening of tau phosphorylations associated with Alzheimer's
disease in primates 21. Cognitive improvements such as enhanced working memory and
visual-spatial memory have been noted for female rats fed phytoestrogen-rich diets or
supplements 22. Clinical trials have revealed a consistent improvement in mental flexibility
and planning abilities (complex executive tasks) in samples of postmenopausal women (17, 18)
as well as younger men and women (16). Further research examining the effects of
phytoestrogens on executive tasks is warranted, as many trials, including a large recently
published trial have not adequately tested this cognitive domain (15, 19-21, Ho et al.,
2007). To date, seven randomized trials in humans have been published which examine the
effects of phytoestrogens on verbal memory. Results indicated significant verbal memory
improvements with phytoestrogens in young men and women 11 and non-significant trends toward
improved verbal memory in four additional trials of younger postmenopausal women 12,13.
Phytoestrogen treatment did not benefit verbal memory in the one trial involving only older
postmenopausal women 14 and a recent trial of women aged 55-76 (Ho et al., 2007).
Interestingly, these findings are largely consistent with the "critical period hypothesis"
that proposes estrogen therapy benefits cognitive functioning only when initiated during the
menopausal transition or shortly thereafter 23. Accumulating evidence suggests that
phytoestrogen treatment may also specifically enhance cognition in the early menopause.

Inclusion Criteria:

- Female

- Perimenopausal as defined by the Stages of Reproductive Aging Workshop (STRAW)
criteria, specifically in either of the two following stages: a) early transition
defined as changes in cycle length of seven days or more in either direction in
consecutive cycles or b) late transition defined as > 60 days amenorrhea and FSH > 40
IU/mL

- Intact uterus/ovaries (i.e. no surgical menopause)

- at least 1 self-reported hot flash per week

- Estrogen therapy not contraindicated

- Able to give informed consent

- Age between 40 and 65 years

- English as first and primary language

Exclusion Criteria:

- Positive pregnancy test or breastfeeding (pregnancy tests will be given to all women)

- Obesity > 35 BMI

- Previous history of endometrial hyperplasia/neoplasia

- Previous history of cancers of the breast or reproductive tract

- History of presence of myocardial infarction (MI) or stroke

- Current clinical diagnosis or a diagnosis within the past year of an anxiety
disorder, severe recurrent depression, or severe psychiatric disturbance

- History of head injury with more than 60 minutes loss of consciousness

- History of neurological condition affecting cognitive function (e.g., brain tumor,
multiple sclerosis)

- History of developmental disability affecting cognitive function (e.g., mental
retardation, attention deficit)

- Current use of CNS-acting medication (e.g., antidepressants, anxiolytics,
diphenhydramine)

- History or presence of cerebrovascular accident, sickle cell anemia

- History of alcohol or drug abuse as defined by DSM criteria

- Abnormal vaginal bleeding of undetermined cause

- Untreated or uncontrolled hypertension defined as systolic blood pressure greater
than 165 mm hg or diastolic blood pressure greater than 95 mm hg

- Concurrent administration of medication containing estrogen, progestin, SERM within
four months of enrollment

- Concurrent administration of medication containing St. John's wort, bisphosphonates,
or dietary phytoestrogens within one month of enrollment

- History of migraine associated with hormone use

- History or presence of deep vein thrombosis, thrombophlebitis or thromboembolic
disorder

- Current participation in any other clinical trial within 30 days of enrollment

- Smoker

- Diabetes

- Premature ovarian failure (defined as having last menstrual period before age 40)

- Abnormal PAP smear in previous year

- Abnormal mammogram in previous year

- Vegans (vegetarians who tend to consume greater than average doses of phytoestrogens)

- Allergy to soy (affects ~1% of people in the United States; reactions are typically
mild)

- Symptomatic fibroids (significant size or significant menstrual changes)

- Menorrhagia

- Lactose intolerant