Phytoestrogens explained: which foods contain them and how to use them
Phytoestrogens are plant compounds with a shape similar to oestrogen, and they turn up in everyday foods such as soya, flaxseed, chickpeas and sesame seeds. Many women ask me whether they should eat more of them in their forties and fifties. This article explains what phytoestrogens are, why your gut changes what they do, what the research says, which foods contain them, and who should check with their GP first.
What phytoestrogens are
The prefix phyto means plant. A phytoestrogen is a compound made by a plant that can attach to the same receptors in your body as oestrogen, the main female sex hormone. Plants make these compounds for their own reasons, mostly to do with growth and protection against pests and sun damage. They did not evolve for human benefit, and that is worth remembering when you read bold claims on a packet.
Your body has two main types of oestrogen receptor, called alpha and beta. They sit in different tissues. Alpha receptors are common in the breast and the lining of the womb. Beta receptors are common in bone, blood vessels and parts of the brain. Many phytoestrogens bind more readily to beta receptors, and they bind far more weakly than the body's own oestrogen. That is why they are described as having a gentle, modulating influence and not a strong one.
The practical result is that a plate of tofu or a spoonful of ground flaxseed will not behave like a medication. The effect is subtle, it varies from person to person, and it builds only if the food becomes a regular part of how you eat.
The three main families
Knowing the three families helps you find them on a food label, and you can skip the chemistry.
Isoflavones are the best known. They are found in soya beans and everything made from them, and in smaller amounts in chickpeas, lentils, other beans and red clover. The two you will see named most often are genistein and daidzein.
Lignans are found in flaxseed (also called linseed), which is by far the richest source, and in sesame seeds, pumpkin seeds, sunflower seeds, whole grains, berries and many vegetables. Most people in the UK eat more lignans than isoflavones without knowing it.
Coumestans are found in alfalfa and clover sprouts, and in smaller amounts in some beans. They are the least common in a typical diet.
Hops, the herb used to flavour beer, also contain a strongly active phytoestrogen called 8-prenylnaringenin. I mention it because hops appear in several traditional sleep and relaxation herbal blends, and it is one reason a hormone-related medication is worth a conversation with your practitioner before you add a herbal product.
Your gut decides what you get
This is the part that most articles miss, and I think it matters most. Phytoestrogens arrive in your food in a form that your body cannot use well. Bacteria in your large intestine convert them into more active compounds.
The best-studied example is equol. Certain gut bacteria convert the isoflavone daidzein into equol, which binds oestrogen receptors more strongly than daidzein itself. Only some people carry those bacteria. Research suggests roughly a third to a half of adults in Western countries are equol producers, with higher numbers in populations that have eaten soya all their lives. The figures vary between studies, and I would read them as a rough guide.
Lignans follow a similar path. Gut bacteria turn them into compounds called enterolactone and enterodiol. The more varied and well fed your gut bacteria are, the better your chance of making them.
This helps explain a pattern researchers see again and again: two women eat the same food for the same length of time, and one notices a change while the other notices nothing. The difference may sit in the gut. If you would like to read about looking after the bacteria that do this work, I cover it in rewilding your gut and restoring microbial diversity.
What the research says
The research on phytoestrogens is mixed, and I think you deserve to hear that plainly.
Some trials of isoflavones in women with hot flushes have found a modest reduction in how often they happen. Other trials have found no difference from a placebo. Systematic reviews, which pool many trials together, have generally found the evidence inconsistent. Differences in the products studied, the doses, the length of the trial and the women recruited all make comparisons difficult, and the gut question above adds another layer of variation.
Large population studies are more encouraging for general health. Diets rich in whole plant foods, including soya, pulses, seeds and whole grains, tend to be linked with good heart health and a lower risk of several conditions. The difficulty is that people who eat this way usually live differently in other respects as well, so it is hard to pin the benefit on phytoestrogens alone.
My view as a naturopath is that these foods earn their place on your plate because they are nutritious, high in fibre, rich in minerals and kind to your gut. Any gentle hormonal influence is a welcome extra, and I would not rest a whole plan on it.
Foods to put on your plate
Here is where I would start. Choose whole, minimally processed forms.
Ground flaxseed. Grind the seeds fresh, or buy them ground and keep them in the fridge, because the oils spoil. Stir a tablespoon into porridge, yoghurt or a smoothie. Whole seeds often pass through undigested, which is why grinding matters. Drink extra water when you increase seeds, because the fibre needs fluid.
Tofu, tempeh and edamame beans. Tempeh is fermented, which many people find easier to digest. Edamame make a quick snack or side.
Miso. A spoonful stirred into warm (not boiling) water or soup gives you a fermented soya food. Miso is salty, so keep an eye on the amount if you watch your blood pressure.
Soya milk and soya yoghurt. Choose unsweetened versions with a short ingredient list.
Chickpeas, lentils and other beans. Hummus, dahl and bean stews all count.
Sesame seeds and tahini. Sprinkle seeds on salads and use tahini as a dressing or spread.
Pumpkin and sunflower seeds. A small handful adds minerals as well as lignans.
Whole grains such as oats, rye and barley. They add fibre alongside the lignans.
Broccoli, cabbage, kale and other brassica vegetables. They are weak phytoestrogens, and they belong in the same conversation about how your body handles and clears hormones. They are very good for you in any case.
A word on soya
Soya has attracted more worry than almost any other food, so I want to give it some space.
Traditional soya foods such as tofu, tempeh, miso and natto have been eaten in parts of Asia for centuries, often daily and from childhood. Whole soya foods are a good source of protein, fibre and minerals. In my practice I am happy for most women to eat them regularly.
The picture changes with heavily processed products. Soya protein isolates and textured soya protein are added to many meat alternatives, protein bars and shakes. They deliver a concentrated dose of isoflavones in a form that is a long way from a bowl of edamame. If you eat a lot of these products, look at the label and consider mixing them with whole foods.
If you prefer to avoid soya, you lose very little. Flaxseed, pulses, seeds and whole grains give you plenty.
How long to try it, and how to shop
Give a change in food at least eight to twelve weeks before you judge it. Hormone-related symptoms shift slowly, and they also rise and fall with stress, sleep and the time of the month, so a single good or bad week tells you very little. A simple diary helps. Note your sleep, your temperature at night and your mood once a week, and look back after a couple of months.
When you shop, read the ingredient list before the front of the pack. Choose tofu made from soya beans and a coagulant such as calcium sulphate, tempeh made from whole beans, and soya milk that lists soya beans and water near the top. Buy flaxseed whole or ground in a sealed pack, and store it somewhere cool and dark. Organic soya is a good choice where you can find it, because most soya grown worldwide is genetically modified, and some people prefer to avoid that.
What a day might look like
You do not need a special diet. A day that includes phytoestrogens could look like this:
Breakfast: porridge made with oats, topped with a tablespoon of ground flaxseed, berries and a few pumpkin seeds.
Lunch: a large salad with chickpeas, grated carrot, leaves and a tahini dressing, with a slice of rye bread.
Snack: a small handful of nuts and seeds, or edamame beans with a pinch of salt.
Dinner: a stir-fry with tofu or tempeh, broccoli, ginger and brown rice, or a lentil dahl with vegetables.
Notice that every meal also carries protein and fibre. That helps your blood sugar stay steadier through the day, and steady blood sugar is one of the foundations I return to again and again. I explain why in hormone support: why I look at stress, blood sugar and the gut first.
Fibre and the way your body clears used hormones
Your liver prepares used oestrogen for removal, and much of it travels out of the body through the bile and the gut. Fibre in the bowel helps carry it on its way. When digestion is sluggish, some of that oestrogen can be reabsorbed. This is one reason I pay attention to regular bowel movements, plenty of plant fibre and enough water in any conversation about hormones.
It also explains why a food-first approach makes sense. A diet full of the foods listed above delivers phytoestrogens and the fibre that helps clear used hormones at the same time.
Who should check first
Most people can eat these foods without any concerns. A few situations deserve a conversation with your GP or specialist first.
A history of breast cancer, or another hormone-sensitive condition. Advice on soya and phytoestrogens varies with the type of cancer and the care you have had, and it changes as research develops. Please speak to your oncology team or GP before you increase soya, flaxseed or phytoestrogen herbs, and follow their guidance.
If you take tamoxifen or an aromatase inhibitor. The same applies. Ask before you change what you eat in a major way.
If you take thyroid medication. Soya can interfere with the absorption of levothyroxine. Many practitioners suggest leaving about four hours between the tablet and a soya food. Check with your GP or pharmacist about your own timing.
If you have a thyroid condition and a very high soya intake. Mention it at your next review.
If you are pregnant or breastfeeding. Normal food amounts are fine, but high-dose supplements and herbal products are not advised.
If you have a soya, sesame or seed allergy. Choose a different food from the list.
If breast cancer runs in your family. Mention your diet to your GP, who can tell you whether anything changes for you.
Herbs with a long history at this stage of life
Herbal medicine has worked with women through midlife for a very long time. These herbs are traditionally used to support women's wellbeing at this stage, and their traditional use does not amount to proof that they work for any individual.
Red clover contains isoflavones and is traditionally taken as a tea during the menopause transition. Sage is traditionally used for night sweats, and is usually taken as a tea. Hops and lime flower are traditionally used in blends for relaxation and a settled evening. Shatavari is an Ayurvedic herb traditionally used to support women's health through the life stages. Chaste tree (Vitex) has a long history of use for women's cycle wellbeing.
Herbs with hormonal activity are more active than foods, so the safety rules are stricter. Avoid them in pregnancy and while breastfeeding, and speak to your GP or practitioner first if you have a hormone-sensitive condition or take hormonal contraception, HRT or any fertility or hormone-related medication.
I formulated Hormone Harmony around this tradition. It combines ashwagandha, shatavari, chaste tree and holy basil, with three Australian Bush Flower Essences: She Oak, Mulla Mulla and Bush Fuchsia. A tonic works best as one ally alongside the foods and habits above, taken consistently for several weeks. The product page carries the full safety information, and please read it before you start.
Food, medication and your GP
Food and herbs can sit alongside medical care, and I never suggest them as an alternative. If your symptoms are affecting your sleep, your mood or your work, HRT may be worth discussing. Your GP can explain the benefits and risks for your own health history, and what I describe in this article can continue at the same time. If you are in the early forties and wondering whether your sleep changes are linked to hormones, I look at that closely in perimenopause and sleep: why your nights change in your 40s.
When to see your GP
Phytoestrogen foods are gentle, and they suit a gradual approach. Please see your GP if:
your periods become very heavy, you pass large clots, or you bleed between periods or after sex
you have any bleeding more than 12 months after your last period
your symptoms start before the age of 45
you notice a new breast lump, a change in the skin or nipple, or persistent pelvic pain
your mood is low or anxious most of the time, or you feel overwhelmed. If you feel unsafe, call NHS 111, or 999 in an emergency
you take prescribed medication and plan to add herbs or high-dose supplements
Where this fits
Phytoestrogens work best as part of a wider pattern: whole food, steady blood sugar, a gut that is well fed, and a nervous system that gets to rest. If you would like to understand the monthly rhythm underneath all of this, the female hormonal cycle explained is a good place to begin. If you would like to see where your own starting point might be, the EarthWise health quiz is a good place to start.
Sarah Burt is a registered naturopath, medical herbalist and iridologist with 25+ years of clinical experience. All EarthWise tonics are formulated by Sarah based on her clinical protocols.
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This article is for informational purposes only and is not intended to diagnose, treat or cure any health condition. Always consult a qualified health practitioner before making changes to your health regimen.
