Phytoestrogens are plant-derived polyphenols that mimic the natural endocrine system chemical oestrogen / estrogen. 

The definition has been extended in recent years to include chemicals that both mimic oestrogen and thus bind to the oestrogen receptor sites and also those that are capable of blocking activity at a site – agonists AND antagonists. 

They do this via the brain-pituitary-gonad axis (a principal endocrine system involving in reproductive regulation) and peripheral reproductive organs.

Oestrogen and progesterone control the female reproductive cycle.  Estrogens or oestrogens control menstruation.  Progesterone has an enormous number of functions besides that of reproduction, but in this context when eggs release progesterone, for example, the sperm use progesterone as a homing signal to swim toward eggs.  It also regulates many processes during pregnancy.

It is thus possible, by manipulating the balance of estrogen and progesterone, to control the fertility of a woman, enhancing it or reducing it, in effect ensuring no babies result.  Thus even if one does not use plants to do this, it is important to know that they can.  If you want a baby for example, it may be that one of the possible reasons you haven’t had one is the food you eat.

In addition to this overdosing on phytoestrogens can have an effect on men, quite a significant effect.  A man who has abandoned dairy products for soy milk and one who also loves his flaxseed, beans, oats and porridge, muesli, barley beer, lentils and rice, is getting a pretty hefty dose of phytoestrogens. 

One of the most exciting things about phytoestrogens is that we may have found in them the first safe effective male contraceptive. 

The chemicals

 

Phytoestrogens belong to a heterogenous group with their structure similar to estradiol-17β (E2). They are called estrogen-like molecules or nonsteroidal estrogens structurally similar to E2.

Systematically, the group of phytoestrogens includes over 100 molecules, divided according to their chemical structure into:

• isoflavones  - eg genistein, daidzein, glycitein, and formononetin
• flavones  - eg  luteolin
• coumestans – eg coumestrol
• stilbenes – eg resveratrol
• lignans  - eg secoisolariciresinol, matairesinol, pinoresinol, and lariciresinol

Isoflavones are found at high concentrations in soybean products, for example, whereas lignans are found in flax seed, coumestans are found in clover, and stilbenes are found in cocoa- and grape-containing products, particularly red wine.

Each chemical may have what is called estrogenic action or antiestrogenic action. THIS IS KEY.

• An antiestrogenic – either blocks the production or utilization of estrogens, or inhibits their effects.  What are called aromatase inhibitors are a special type of antiestrogen because they reduce the production of estrogen.  Hot flashes, osteoporosis, breast atrophy, and vaginal dryness can be side effects of antiestrogens in those women whose estrogen levels were previously in balance.
• An estrogenic - is any natural substance that mimics the effects of the natural hormone estrogen.  In effect, Once inside the cell, they bind to and activate estrogen receptors (ERs).  The steroid 17β-estradiol is the most potent and prevalent endogenous estrogen.  In those whose estrogen was in balance, these natural products can produce – according to the Greeks anyway - feminine desire! Estrogen comes from the Greek οἶστρος (oistros), literally meaning "verve or inspiration" but figuratively sexual passion, and the suffix -gen, meaning "producer of".  In those out of balance – such as post menopausal women it can bring them back to balance even though they may be infertile.

 

Some chemicals rather confusingly can be both depending on how much there is in the plant.

Synthetic estrogens are used as part of some oral contraceptives, as if estrogen is constantly in the system, a baby cannot be conceived. 

There is no reason why natural products should not have the same effect. 

As such one can look at this two ways, estrogenics are natural contraceptives and produce a form of infertility – two sides of the same coin.

The following table is derived from Dr Duke’s phytochemical database.

 

As a little extra to add to this table, progesterone is also a key part of a woman’s fertility and the edible plants that contain the Antiprogesterone chemical GOSSYPOL include

• Abelmoschus esculentus (L.) MOENCH -- Okra; found in Seed
• Glycine max (L.) MERR. -- Soybean; found in Seed
• Helianthus annuus L. -- Girasol, Sunflower; found in Seed

In contrast the plants that promote [as opposed to contain] progesteronic activity are

• Avena sativa L. -- Oats; found in Plant, Seed
• Glycine max (L.) MERR. -- Soybean; found in Seed
• Hordeum vulgare L. -- Barley, Barleygrass; found in Seed
• Ilex paraguariensis ST. HIL. -- Mate, Paraguay Tea, South American Holly; found in Leaf
• Lens culinaris MEDIK. -- Lentil; found in Seed
• Medicago sativa subsp. sativa -- Alfalfa, Lucerne; found in Plant
• Oryza sativa L. -- Rice; found in Seed
• Persea americana MILLER -- Avocado; found in Fruit
• Pisum sativum L. -- Pea; found in Seed
• Sesamum indicum L. -- Sesame Seed
• Tamarindus indica L. -- Indian Tamarind, found in Fruit
• Theobroma cacao L. -- Cacao; found in Seed
• Trigonella foenum-graecum L. -- Fenugreek, found in Plant
• Triticum aestivum L. -- Wheat; found in Seed
• Vigna radiata (L.) WILCZEK -- Green Gram, Mungbean; found in Seed
• Zea mays L. -- Corn; found in Cob

 Plants and phytoestrogens – the ‘sometimes there sometimes not’ dichotomy

Phytoestrogens may not always be present in a plant.  One year it may have a prolific supply and the next it may have nothing.  In order to understand why we have to look at it from the plant’s point of view, for example

 

Phytoestrogens, largely formononetin and genistein, are produced in the leaves of stunted desert annuals in a dry year. When ingested by California quail, these compounds apparently inhibit reproduction and prevent the production of young that will not have adequate food. In a wet year, forbs grow vigorously and phytoestrogenic substances are largely absent. Quail then breed prolifically and the abundant seed crop carries the enlarged population through the winter.  PMID:  1246602

Thus plants regulate the wildlife they depend on to spread seed by altering their reproductive cycles via these chemicals.  The plant always has the same chemicals in its make-up, but it adjusts the quantities of them to achieve the balance it needs.  So some may be increased and some decreased. 

It is possible that far more plants we are unaware of, actually have this ability, but because we irrigate them and fill them full of fertiliser, we never notice the change.

It is thus an explanation for the varying effects of various foods.  One group of women may be gorging themselves on flaxseed, soybeans, oat cakes and muesli, but getting no effect. Another group may be nibbling on a tofu sandwich [I jest] and it hits them like a steam train. And the reason may be that the plants were either produced in conditions in which the plant would down grade the estrogenic effect, or were grown in conditions in which the estrogenic effect would be produced in abundance.

One of the plants used medically to help with female hormonal problems, for example,  is red clover.  In the 1940s and early 1950s, it was noticed that some pastures of red clover had estrogenic [and anti-estrogenic] effects.  The plants that had anti-estrogenic activity, had an adverse effects on the fecundity of grazing sheep.  In other words it was definitely proved for mammals and not just birds.  Plants manipulate us all.

Phytoestrogens and health

 

The effects that phytoestrogens have depend on where you are to start with – what your hormone levels are

• In balance - If you are in balance hormonally and you eat phytoestrogen rich plants, they can act like a form of birth control – particularly in men.  If you reduce them or cut them out, then presumably one’s fertility increases, although the studies on this are almost non existent
• Lacking - If you are very low on estrogen as a consequence of the menopause, for example, they may help to balance out the hormone levels of those who are lacking the hormone and restore them to balance.  The problems of the menopause are the extreme fluctuations as the body tries to readjust to a new life of infertility, these chemicals may help to smoothe out the fluctuations.  Similarly if you are female and low on estrogen, then they may help to bring you back into balance and may even improve your fertility. 
• Too much – by cutting out or lowering the number of phytoestrogen rich foods one eats, then one brings oneself back into balance [male or female]

There are positives and negatives to phytoestrogens.  Although American studies, sponsored by powdered baby food manufacturers, have come up with the rather inevitable conclusion that soymilk based feed for babies has no effect on their growth or sexual development, unsponsored studies outside of America appear to show it does have an effect.

They key with all chemicals is balance, balance, balance.  And overdosing a very small baby or child on hormones, is fairly obviously not going to do it any good at all.