Phytoestrogens are natural hormonal compounds found in plants and plant-based foods. When eaten, they may affect a person in the same way as human Estrogen. 

Because these hormones are described as ‘natural’ many confuse this word with ’healthy’ and believe them to be healthier than other hormones, where in fact they should be viewed as an external (endogenous) hormone with potential modulating / disrupting effects, both beneficial and the opposite.

This article explores the health benefits and risks of phytoestrogens. It also lists foods that are high in phytoestrogens.

What are phytoestrogens?

Phytoestrogens or plant Estrogen are naturally occurring compounds found in plants, often found in a person’s diet.

The hormone Estrogen is classically known as the female hormone responsible for female characteristics, such as increased fat storage, buttocks, thighs, hips and breasts and the menstrual cycle, etc.

Eating plant-based foods that contain phytoestrogens such as some vegetables, fruits, grains, and legumes may disturb the effects of the body’s own Estrogen, both in an increasing and decreasing manner. Phytoestrogens can also be taken as supplements. 

There are several types of phytoestrogens, e.g. Genistein and Daidzein both of which are found in soy. 

How do phytoestrogens work?

Phytoestrogens have a similar though not identical biochemical structure to that of the body’s natural Estrogen, and as such don’t bind as firmly to Estrogen receptors, meaning their effects may be weaker. The fact that they are non-bioidentical also increases the risk of side effects.

When phytoestrogens enter the body, they attach to the cells Estrogen receptors where they can have a blocking or an excitatory effect, i.e. decrease or increase the effects of Estrogen. Estrogen receptors are found in cell walls and DNA. Phytoestrogens are considered to be a type of SERM – Selective Estrogen Receptor Modulator, much like the medication Tamoxifen used in breast cancer.

Phytoestrogens should therefore be viewed as potential endocrine (hormone) disruptors which ‘disrupt’ normal hormonal function, much like other external hormonal compounds, such as those found in plastics, pesticides, dyes, creams, etc.

There are 2 types of Estrogen receptors Alpha and Beta, where phytoestrogens primarily attach to Beta receptors. 


Related to peri-menopause and menopause where the body’s Estrogen levels naturally fall and fluctuate causing a variety of symptoms, can the use of phytoestrogens be beneficial for some women.

Perimenopause usually starts around the beginning of the 40s, where menopause is official when 1 year has passed since the last menstrual bleed. Symptoms of perimenopause can include:

  • hot flashes
  • tender breasts
  • low libido
  • poor sleep / tiredness
  • irregular periods
  • mood swings
  • personality changes

Some women suffer greatly and others less, there is no ‘standard’ perimenopause. Supporting some of the effects of Estrogen with some kind of replacement can be enormously beneficial.

Phytoestrogens are seen as a ‘natural’ alternative to the bioidentical Estrogen used in the more standard hormone replacement therapies, but because they are non-bioidentical and bind less firmly their effects can be less predictable and less stable.

But with that said phytoestrogens as supplements have been clinically proven to have an effect on relieving hot flushes. 

Other potential benefits include:

1. Clinically proven to increase / maintain bone density in postmenopausal women. Fermented red clover is excellent as this trial demonstrate

2. Can slow tumour growth in breast / prostate cancers, possibly by blocking receptor sites for Estrogen and / or increasing activation of Beta receptors that may have anti-cancer effects. This area still needs more research to fully understand whether or not phytoestrogens play a useful role in cancer prevention and treatment.

3. Promotes heart health in postmenopausal women by effecting health of blood vessel walls.

Risks and side effects

When using any type of non-bioidentical hormone modulator there will be side effects, so although there can be benefits similar to Estrogen replacement therapy in peri-menopausal and post-menopausal women eating phytoestrogens during fertile years can have negative effects, such as:

1.Can lengthen menstrual cycle causing menstrual irregularities 

2. Can supress fertility hormones FSH and LH causing fertility problems 

3. Can increase SHBG a protein which binds to Estrogen and Testosterone in the blood making them inactive, thus decreasing their effects creating hormone imbalances

4. Can disrupt the enzymes responsible for converting Androgens (the male hormones such as Testosterone) to Estradiol and Estrone Estrogens and the reciprocal conversion of Estrone to Estradiol.

5. Can decrease libido by effecting the production of Oxytocin in the brain

6. Some animal studies demonstrate increased aggression and less social behaviour 

7. May disrupt the development of the brain and reproductive organs in children

More research is needed to fully understand how phytoestrogens work, as it is not clear whether consuming them in higher levels carries similar health risks as with the exposure to other external Estrogens, the so called xenoestrogens found in plastics, creams, pesticides, dyes, etc.

While it is believed to be healthful to eat a plant-based diet, many of these plant foods contain phytoestrogens, so if you are not peri-menopausal or later it may be wise to avoid a higher intake, especially in supplement form and especially if you’re a man.

Foods containing phytoestrogens

Soy beans and their products – tofu, tempeh, miso, soy sauce, soy yoghurt, ice cream, protein powders, etc.

  • Beans
  • Lentils
  • Flax seeds and sesame seeds
  • Some grains – wheat, oats and barley 
  • Fenugreek
  • Red clover

Fermentation of the above foods increases bioavailability, which is important for the effective treatment of peri-menopausal symptoms and as a support after menopause. 

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