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What are phytoestrogens?

Phytoestrogens (plant estrogens) are plant compounds with a similar structure to estrogen made naturally in the body.  Some phytoestrogens are able to bind to specific estrogen receptors on cells throughout the body, producing weak estrogenic effects, 100-1000 times weaker than the body’s own estrogen. Other phytoestrogens produce their effect through different mechanisms such as influencing hormones that regulate estrogen.

Estrogen is the hormone responsible for puberty, secondary sexual characteristics and for fertility in females. During menopause the ovaries will lose 95% of their estrogen producing capacity. The adrenal glands and fat tissue are able to convert other hormones to estrogen after menopause, maintaining a small estrogen base.

How do phytoestrogens help during menopause?

There is a growing body of evidence suggesting that phytoestrogens may be effective in reducing the physical and emotional changes associated with menopause. Phytoestrogens are found in hundreds of foods, especially whole unrefined grains, beans, vegetables and fruits and herbal medicines. As estrogen levels decline around menopause, we can harness the weakly stimulating effect of phytoestrogens to level out some of the irregular hormonal ups and downs that are thought to be the cause of hot flushes and night sweats.

In addition, some phytoestrogens may play a role in protecting heart health, slowing osteoporosis, and reducing cognitive decline, although the research is still mixed. However, there are other diet and lifestyle strategies to protect heart and bone health. See my article on osteoporosis for bone health support.

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Where can phytoestrogens be found?

Four groups of phytoestrogens predominate in plants. By harnessing the knowledge of which foods belong in each category, a woman can include sources from each group to optimise her daily dietary intake of phytoestrogens. The most important phytoestrogen sources in foods are isoflavones and lignans. See my article on menopause for more information on herbal medicines and their use during this time.

  • Isoflavones – beans, especially soy beans.

  • Lignans – seeds (especially flax seeds and sesame), whole grains and berries

  • Coumestans – less common, lower amounts – red clover and alfalfa sprouts, split peas, pinto beans, lima beans, sunflower seeds

  • Stilbenes – resveratrol – grapes, peanuts and cranberries, red wine

Isoflavones - Soybeans

The soybean (Glycine max) is the most studied source of isoflavones. Soy has many incarnations however, and is equally touted as both a superfood and a villain food. Some things to bear in mind that can help your choices…

Whole soy foods better preserve the nutritional status of the soybean

  • Fermented soybean (natto, tempeh, miso) – the traditional form of soybeans in Chinese and Japanese culture and most recommended.

  • Edamame – green, whole soy – available frozen for convenience

  • Tofu – soy bean curd, produced in a similar way to cheese. Extra firm is the better choice for general cooking, and the softer silken tofu can be added to smoothies.

  • Soy beverage – the whole bean is used. Fortification with nutrients is optional in Canada, so check the label for added nutrients specifically, calcium vitamin D, vitamin A, riboflavin, zinc.

Processed soybeans

  • Soy protein isolate and textured soy/vegetable protein– these are highly processed, industrially produced forms of soy that are often added to high protein energy bars, and in the production of meat alternatives such as soy hot dogs, soy mince, burgers, etc. Soy protein isolate has not been shown to have the same health benefits or reduction in menopausal symptoms as less processed sources of soy.

  • Genistein and diadzein – a highly refined phytoestrogen concentrated extract sourced mainly from soybeans.

How much do you need?

Research has shown that in the context of a normal diet around 40-70mg of soy isoflavones may be enough to alleviate symptoms. This is equivalent to one third of a cup of edamame or 2 cups of soy beverage or three quarters of a cup of tofu.

Notes On Soy

Organic soy is probably the best choice when you are planning to eat soy regularly.  Organic means that the soybean has not been genetically modified and therefore has not been exposed to increasingly high levels of the pesticide glyphosate. It is only marginally more expensive than non-organic.

Adequate iodine intake is important when increasing dietary soy intake. Soy may impede thyroid function if iodine levels are compromised.  Health Canada recommends 150mcg of iodine per day with a safe upper limit of 1100mcg. See iodine article for further information.

Lignans - Flax Seeds

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  • Flax seeds (Linum usisatissimum) are the richest source of plant lignans,

  • Flax seed has been shown to reduce cholesterol, improve heart health, aid in the prevention of breast cancer and assist with constipation.

  • It is a source of the essential omega-3 fatty acid, alpha-linolenic acid, which research has shown may benefit skin health and have anti-inflammatory activity.

  • Flax seeds can be freshly ground using a coffee grinder and kept sealed in a cool, dark place like the refrigerator for 1-3 months. However, I generally recommend only grinding enough for a week at a time so that the flaxseed oil, which is exposed in the milling process, doesn’t go rancid and remains fresh. The ground flax can be sprinkled on breakfast cereal or added to baking, smoothies, soups etc.

Teaching old bugs new tricks

The gut microbiome is the complex mix of microbes that inhabit our gut and includes bacteria, viruses, fungi and parasite. It appears that the type of microbes we have in our gut influences the extent of the benefits we get from phytoestrogens.

Equol is produced by the action of gut bacteria on the phytoestrogens we eat, providing additional benefits. Equol is a potent antioxidant with estrogenic properties. People can be divided into equol producers and equol non-producers and researchers have found that this difference results from variations in our gut bacteria.

  • The ability of the gut to produce equol can be enhanced by modifying the gut microbes.

  • It has been found that vegetarians produce significantly more equol than non-vegetarians.

  • Asian women eating a more traditional diet of soy and seaweed are more likely to be equol producers. Interestingly, they are reputed to have fewer symptoms during menopause.

Safety of phytoestrogens

There has been concern that if phytoestrogens can mimic our own estrogen can they also have negative effects on breast and uterine tissue leading to cancer? There have been many studies looking at this concern and the consensus appears to be that phytoestrogens are safe and may even assert some protective capacity against breast and other hormone dependent cancers.

A note on Xenoestrogens 

Xenoestrogens are defined as estrogen mimicking compounds that are not produced by the body. Plant estrogens and synthetic estrogens are both xenoestrogens, however, they have very different effects in the body. There is a substantial body of evidence supporting the safety of plant phytoestrogens.

Synthetic xenoestrogens on the other hand, are industrially produced chemical compounds such as petroleum-derived plastics, pesticides, metals, or contaminants in food and personal care products. These have estrogenic effects and act as endocrine disruptors in the body.  The World Health Organisation has called them endocrine disrupting chemicals (EDCs), while recognising their significant negative impact on hormonal health.

Given their ubiquitous presence in daily life it is advisable to wash all vegetables and fruits well, buy organic when your budget allows, source grass fed, organic animal products when possible and read personal care product labels well. The Environmental Working Group have an informative website as a resource. I see an increasing number of women and men with hormonal concerns related to fertility, conception, menstruation, and thyroid and adrenal health.  Avoiding and minimising exposure to synthetic xenoestrogens is always a primary consideration.

If you would like more information on phytoestrogens or menopause I would love to work with you. Please book an appointment online or call 613 233 2040 to book your appointment.

All content provided on this website is for general information purposes only and is not intended to replace medical or specialist advice.

A qualified Medical Herbalist is always your best resource for information related to herbal medicines.

Registered Dietitians are a reliable and trusted resource for nutrition related information, always up to date and always ready to work with you to realise your goals.