Phytoestrogens and the menopause

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Phytoestrogens and the menopause

• G.B.Lockwood,
• School of Pharmacy Pharmaceutical Sciences,
• University of Manchester, Manchester, M13 9PL

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Menopausal Symptoms

• Vasomotor symptoms-mainly hot flushes, insomnia,
  heavy sweating, headaches, mood swings,
  irritability, depression
• Vaginal dryness, soreness, loss of libido?
• Osteoporosis
• Breast cancer
• Cardiovascular disease
• Cognitive effects

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Phytoestrogens

• Defined as plant constituents which bind to
  estrogen receptors, ER? and ER?
• Major classes include
• Isoflavones, sources include soy, red clover and
  Phaseolus beans
• Lignans, sources include flax grains
• Stilbenes, one example is resveratrol
• Coumestans, 3 and 4? methoxycoumesterol

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Major phytoestrogens-widely available

• Phytoestrogens are mainly used instead of HRT due
  to fears of links to breast cancer
• Bind to estrogen receptors 0.001-100 activity of
  estradiol
• Soy isoflavones-50mg/day based on presumed intake
  of Far Eastern populations
• Soy products- soy milk/tofu mainly glycosides,
  miso/tempeh/soy sauce increasing aglycone
  composition
• Red Clover isoflavones- ? 40mg
• Flax Lignans- c40g flaxseed (20mg/day)
• Resveratrol-15-200mg/day

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Soy
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Soy isoflavones
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Soy for menopausal symptoms

• Hot flushes are the major clinical symptom
  investigated
• Epidemiological data-10-20 incidence of hot
  flushes in China/Japan, 70-80 in Western
  countries
• Cause could be Soy factor
• in Japanese diets
• A US survey revealed 7.4 of women used soy
  products for perimenopausal symptoms
• 50-60 success of placebo in trials

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Soy activity

• Some phytoestrogens act as estrogen agonists,
  some antagonists-Concentration dependent?
• Isoflavones have agonist effect in low estrogen
  environments, antagonist effect in high estrogen
  environment
• Estrogen reduced at start of menopause, hence
  isoflavones have agonist effect
• Antagonist effect due to competition with
  endogenous 17?-estradiol

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Rated success of Soy products in treating
menopausal symptoms, mainly hot flushes
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Variability in clinical trials of soy for
menopausal symptoms

• Different products and foods contain varying
  levels of isoflavones
• Optimum dose is not known
• Formulated products may not contain stated levels
• Trial duration ranges from 1-4 months
• Variability and deficiencies in reporting of
  outcomes

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Vaginal symptoms

• No beneficial effects on genital atrophy can be
  expected
• Vaginal dryness variably improved
• Little data from clinical trials

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Osteoporosis

• Reduction in bone density
• Common in menopausal women
• Reduction in estrogen at menopause causes
  increased osteoclastic bone resorption
• Bone loss may continue for 5-10 years after
  menopause

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Possible mechanism of action in osteoporosis

• Prevention of calcium loss
• Beneficial effects on osteoblasts
• Influence on secretion of calcitonin which
  suppresses bone resorption
• Genistein/daidzein suppress osteoblast activity
  in relation to bone turnover
• May affect osteoblasts by mediating cytokine
  production in osteoblasts

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Conventional treatments for osteoporosis

• Women have higher incidence of osteoporotic
  fractures due to lower peak bone mass, and abrupt
  reduction in estrogen at menopause accelerates
  bone loss
• HRT-not recommended for long term treatment
• Inhibitors of bone turnover eg calcitonin,
  biphosphonates
• Bone formation stimulating agents eg fluoride

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Use of soy isoflavones for osteoporosis

• Animal research consistently shows increase in
  bone mineral content (BMC) or bone mineral
  density (BMD)
• Daidzein genistein increase protein synthesis
  alkaline phosphatase release by osteoblast cells
  in vitro
• Epidemiological data show increased consumption
  of fermented products show lower osteoporotic
  bone fractures
• Increased osteocalcin concentrations reported

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Clinical data

• Increased BMD at lumbar spine
• Reduction in excretion of bone resorption markers
  eg pyridinoline
• 54mg/day genistein reduce bone mineral loss at
  femoral neck and lumbar spine, as well as 1mg
  oestrogen
• Lumbar spine BMD increases by 2.4 in equol
  producers (45 of postmenopausal women posses gut
  microflora capable of transformation of daidzein)
• Calcium/Vitamin K2 present in soy products may
  act synergistically in osteoporosis
• 50 reduction of osteoporotic fractures over 4.5
  years in Chinese women (24,000 subjects)
• Trials need to be 2-3 years as bone remodelling
  cycle can last 80 weeks

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Significance of equol

• Infants and germ-free animals do not produce it
• Antibiotics inhibit equol production
• 30-50 of population are equol producers
• Equol is a non-steroidal estrogen
• Equol binds to ER? and ER? similarly to
  genistein, greater than daidzein
• Glycitein is not converted to daidzein, hence not
  to equol
• Equol producers not identified in trials
• S-enantiomer has affinity for ER?

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Breast cancer

• HRT increases risk of breast cancer (1.3-2.4
  times) over 5 years
• Epidemiological evidence from Japan shows no link
  between isoflavone intake and breast cancer
• In Australian women, increased urinary excretion
  of equol associated with reduced risk of breast
  cancer
• Early and routine consumption is most beneficial
• Soy isoflavones possibly stimulate breast
  cancers, particularly postmenopausally,
  correlations have been shown between oestrogenic
  effect, plasma prolactin levels, and breast
  cancer risk

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Anti-cancer activity

• Inhibition of DNA topoisomerase
• Suppression of angiogenesis
• Induction of differentiation in cancer cell lines
• Induction of apoptosis
• Genistein is a potent estrogen agonist and has
  cell growth inhibitory actions

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Cardiovascular disease

• Strong epidemiological evidence supports
  benefits, but diet may contribute
• Soy protein reduces total cholesterol, LDL
  cholesterol and triglycerides
• A meta analysis revealed that 34 out of 38
  studies showed cholesterol reduction, but the
  roles of soy protein and isoflavones is not clear
  
• Reduction in systolic blood pressure has been
  reported
• Soy isoflavones have produced negative findings
• Combinations of soy protein and isoflavones
  produce modest improvements
• 45,694 Chinese women found systolic and diastolic
  BP reduced with 25g soy over 2-3 years

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Cognitive function

• Probably decreases due to decreased estrogen
  levels
• Increased incidence of Alzheimers in
  postmenopausal women
• One trial reported increase in verbal memory, but
  no effect in other indicators
• 60mg/daily over 12 weeks was reported to increase
  memory, pattern recognition and mental
  flexibility
• Significant improvements occur in males young
  women taking 100mg/day over 10 weeks

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Mode of action of soy isoflavones

• Phytoestrogens require a flavonoid with 2-4 OH
  groups, methylation of these reduces oestrogenic
  activity.
• Phytoestrogens bind to the oestrogen receptor
  (ER), predominantly ER? and exert a weak
  oestrogenic effect, or anti-oestrogenic effect
• Phytoestrogens may affect transcription of
  estrogen-regulated gene products
• Phytoestrogens are antioxidants

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Soy isoflavone distribution

• Occur as glycosides, and hydrolysis, in the oral
  cavity and intestine, which allows absorption
• 20 fold inter-individual variation in hydrolysis
  rate
• 50mg isoflavone leads to 50-800 ng/ml in the
  plasma
• Peak concentration 6-8 hours after 100mg dose
• These levels are higher than normal plasma
  oestradiol levels
• Isoflavones show less serum protein binding than
  oestradiol
• Effects of the food matrix likely to be important

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Ipriflavonesemi-synthetic isoflavone

• Non-oestrogenic, mainly used in osteoporosis
• Metabolised to daidzein and others
• 200mg tds have been shown to produce
  statistically significant increases in BMD, and
  markers of bone metabolism
• Increased calcium uptake in the duodenum
• Some trials show no benefits
• In one trial 13 developed subclinical
  lymphocytopenia

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Red Clover
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Red Clover

• Lower isoflavone level than soy
• 80mg isoflavone/day produced 44 reduction in hot
  flushes
• Similar benefits to soy in osteoporosis
• Reduced breast cancer, prostate cancer and
  ovarian cancer risks
• Insignificant effects on lipoprotein levels

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Red Clover isoflavones
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Red Clover isoflavone distribution

• Formononetin and biochanin A are efficiently
  demethylated to daidzein and genistein
  respectively
• Peak concentrations of daidzein and genistein are
  12 and 2 hours after a 40 mg dose of isoflavones
• Formononetin is also converted to equol via
  demethylation to daidzein
• Levels reported are c10 of those reported for
  equivalent doses of soy isoflavones

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Flaxseed
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Flaxseed

• 40g flaxseed is as effective as HRT for mild
  menopausal symptoms (25g ineffective)
• 25g Flax has a greater effect on estrogen
  metabolism than the same dose of soy
• Urinary enterolactone positively correlated with
  BMD in Korean postmenopausal women
• Urinary enterolactone was higher in Dutch women
  with greatest bone loss
• Variable results in work on flaxseed
  supplementation on biochemical markers of bone
  metabolism

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Flax lignans
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Flaxseed

• Reduction in LDL/HDL cholesterol levels
• n-3-PUFAs, particularly ?-linolenic acid, in flax
  may have activity
• 1.5g flax lignan/day gives a higher probability
  of intact cognitive function
• Increased vascular compliance and induction of
  synaptogenesis in the hippocampus may be
  responsible

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Flaxseed lignan metabolism

• The importance of the metabolites, enterolactone
  and enterodiol have yet to be elucidated
• No pharmacokinetic data available

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Trans-Resveratrol
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trans-Resveratrol

• Physiological levels obtained from wine, up to
  15mg/L
• 10-200mg dosage forms available, no specified
  dosage
• Antioxidant
• Anticancer activity
• Cardioprotective
• Oestrogenic- binds to ER? and ER? receptors
  17000 activity of estradiol
• Increases in bone density in postmenopausal women
  have been reported

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Quality

• Soy isoflavones-10/15 failed, levels 30-99
• 300 variability between different soy food
  product types ie raw, soaked, cooked, drink, tofu
• Soy infant formulas-up to 25 variability
• Soy milk-70 variability
• Tofu-50 variability
• Phytoestrogens-28/32 failed, levels 0 and 383,
  all products claiming genistein/daidxein failed
• Red clover-Promensil passed
• A number of products do not state levels of named
  constituents
• No data on flax lignans or resveratrol

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Adverse effects

• Soy-gastrointestinal problems, supplement
  unpalatability (particularly soy drinks), nausea,
  allergy in one trial
• In vitro genotoxicity with isoflavones
• High level male tofu consumers suffered poor
  cognitive performance, lower brain weight!
• High intake in animal studies suggests they may
  affect fertility
• Adverse effects of HRT not reported in any of the
  trials (breast tenderness, vaginal bleeding)
• Vaginal spotting
• No reported adverse effects-Red clover/Flax

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Conclusions

• Soy, red clover, and flax are the main sources of
  dietary estrogens
• Phytoestrogens may have oestrogenic or
  anti-oestrogenic activity depending on
  circulating levels of sex hormones, and may
  stimulate breast cancer
• Generally safe-much epidemiological evidence
• Other components may interfere with
  activity/bioavailability