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PLANT OESTROGENS

Plant oestrogens (also known as phytoestrogens) are substances that occur naturally in plants. It’s thought that plants may use them as part of their natural defence against the overpopulation of herbivore animals by controlling female fertility. Plant oestrogens have a similar chemical structure to human oestrogen (one of the main female hormones), and are able to bind to some of the same receptors as your own oestrogens. This means they have an oestrogenic effect on your body, although it’s weaker.

This article was included in issue 88 (spring 2021) of The Menopause Exchange newsletter.

Sources
There are three different types of plant oestrogens:
Isoflavones are primarily found in soy beans and soy products, chickpeas and other legumes. They include genistein, daidzein, glycitein and equol.
Lignans include enterolactone and enterodiol. They are found in oilseeds (primarily linseed), cereal bran, legumes, grains and some vegetables.
Coumestans include alfalfa and red clover.

Many plant sources contain a mixture of all three types of plant oestrogens. Soybeans are the richest source of plant oestrogens. Other good sources include soya milk and soya milk products (such as yogurts), soya flour, linseeds, tofu, pumpkin seeds, sesame seeds, edamame beans, miso soup, tempeh, chickpeas, fava beans, pistachios, peanuts, and other fruits and nuts. Plants containing plant oestrogens contain many other health-enhancing substances, so these can form a healthy part of your diet.

How do they work?
Both oestrogens and plant oestrogens fit like a lock and key to certain sites in your body (called receptors) and this causes certain actions to happen. However, your own body’s oestrogens have a much stronger effect than plant oestrogens.

When lots of your own oestrogens are around (e.g. before the menopause), these fit to the receptors and have oestrogenic effects around the body. At the perimenopause, when there is less and less of your own body’s oestrogen around, you start to feel the effects of lower oestrogen levels in the form of hot flushes etc. At this stage, if you take plant oestrogens, these will bind to increasingly free oestrogen receptors and exert their weak oestrogenic effect.

Some researchers claim that this added oestrogen boost, even though not as strong as the effect of HRT, does have some positive effects and can go a little way to replace your lost oestrogen at the menopause. However, controversy exists on how well these plant oestrogens can perform when your own oestrogen is failing. Research seems to throw up mixed results; some showing very definite positive results on hot flushes, bone health, cardiovascular disease and cognitive function, while others show little or no effect.

Some experts believe that plant oestrogens aren’t well absorbed and others believe that some people aren’t so good at converting plant oestrogens into the active substances in their gut (to then be absorbed into their body). There is some evidence that consuming plant oestrogens several times a day appears to be more effective than having one larger dose each day.

Soy products can take several weeks or more to reach their maximal potential in your body if they’re going to work at all. For example, soy isoflavones take more than 13 weeks to reach just half of their maximum effect, unlike HRT which takes only three weeks to show benefits.

Supplements
The effectiveness of plant oestrogen supplements seems to vary. In addition, the NHS advises that complementary and alternative treatments, such as herbal remedies and bioidentical (‘natural’) hormones, aren’t recommended for menopausal symptoms, because it’s generally unclear how safe and effective they are.

Some remedies can interact with medicines and cause side effects. If you are thinking about using a complementary therapy or taking a supplement, it’s highly recommended that you ask your GP or pharmacist for advice first. Be assured that there are no known health risks from eating more plant foods; you should be safe getting plant oestrogens from food by eating a varied diet. Make sure to eat fruits, vegetables, grains, nuts, seeds and legumes to experience the benefits.

How much do you need?
Pinning down exactly how much plant oestrogen (isoflavones) you need each day is quite hard. For osteoporosis and hot flushes, studies have used doses of between 45mg and 90mg of soy isoflavones, which also translates to about two to three servings of soya foods per day. One study showed around 29mg of
the isoflavone genistein, as a supplement, had a significant effect on hot flushes; which can also be obtained by drinking two 200ml glasses of soya milk or 80g soya mince a day.

A note on breast cancer
It’s believed that Asian women who eat a traditional Asian diet have less breast cancer when they reach the menopause because all their life their diet will have been high in plant oestrogens (getting about 30g a day). However, most women in the western world won’t have consumed such a diet. The effect is different when you only start to eat these foods once you hit the menopause.

Many breast cancers are oestrogen positive. The treatment usually involves giving a drug that removes any remaining oestrogen in the body, so that the cancer doesn’t develop again. For this reason, cancer experts such as Macmillan Cancer Support and the World Cancer Research Fund advise menopausal women who have had oestrogen-positive breast cancer to not take plant oestrogen supplements. However, most experts believe that eating some plant oestrogens as part of a heathy diet is fine.

About the author
Gaynor Bussell is a freelance dietitian and nutritionist. She sees private patients and also writes articles about diet and nutrition.

Created Spring 2021

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