The connection between the gut and hormones
When women suffer from hormonal complaints — think mood swings, fatigue, bloating, weight gain or irregular cycles — the first thought is often: it must be menopause. And that's partly true. But what many women (and many doctors) overlook is the enormous influence your gut has on your hormonal system.
In your gut live trillions of micro-organisms: bacteria, fungi and viruses that together form your microbiome. This microbiome is not a passive collection, but an active organ that produces, breaks down and recycles hormones. Scientists now speak of the gut as the ‘second endocrine organ’ of your body.
The connection works in both directions. On the one hand, your gut flora directly influences your hormone levels: how well oestrogen is broken down, how much serotonin is produced and how your body handles insulin and cortisol. On the other hand, your hormones influence the composition of your gut flora. Declining oestrogen levels, as during perimenopause, change your gut flora, which can in turn lead to digestive complaints you never had before.
This explains why so many women around their 40s suddenly suffer from bloating, constipation, flatulence or irritable bowel syndrome. These are not simply ‘stomach complaints’. They are signals that your hormonal and gut systems are struggling with each other.
The estrobolome: gut bacteria that recycle oestrogen
One of the most fascinating discoveries of recent years is the estrobolome. This is a specific group of gut bacteria that produce the enzyme beta-glucuronidase. This enzyme plays a key role in your body's oestrogen metabolism.
Here is how it works: after oestrogen has done its job in your body, it is sent to the liver for breakdown. The liver attaches oestrogen to another substance (glucuronic acid) so that it is transported via bile into your intestines and eventually leaves the body with your stool. So far so good.
But this is where the estrobolome comes into play. The bacteria in this group produce the enzyme beta-glucuronidase, which breaks the bond between oestrogen and glucuronic acid. This allows oestrogen to be reabsorbed into your bloodstream. In a healthy situation, this creates a fine balance: not too much oestrogen is excreted, not too much is recycled.
But if your gut flora is out of balance — for example through poor diet, chronic stress, antibiotic use or too little fibre — the estrobolome can become dysregulated. There are two scenarios:
- Too much beta-glucuronidase: too much oestrogen is sent back into the bloodstream. This leads to oestrogen dominance, with complaints such as sore breasts, heavy periods, mood swings, weight gain around the hips and an increased risk of hormone-sensitive conditions.
- Too little beta-glucuronidase: too much oestrogen is excreted. This can lead to symptoms of oestrogen deficiency, such as dry skin, joint pain, osteoporosis and hot flushes.
The estrobolome in brief
Your gut bacteria partly determine how much oestrogen circulates in your body. A healthy, diverse gut flora provides the right balance. Dysbiosis (disturbed gut flora) can lead to both oestrogen dominance and oestrogen deficiency — two extremes with their own distinct complaints.
The good news: you can positively influence your estrobolome by adjusting your diet. More fibre, more diversity in plant-based foods and fermented products help feed the right bacteria. More on that below.
The gut-brain axis: serotonin and mood
Did you know that around 90 to 95 percent of your serotonin is produced in your gut? Serotonin is the hormone that regulates your mood, sleep, appetite and pain perception. It is often called the ‘happiness hormone’, and the largest part of it is not in your brain, but in your gut.
Your gut and brain communicate constantly via the vagus nerve, a long nerve that runs from your brainstem to your abdomen. We call this communication system the gut-brain axis. Through this axis, your gut bacteria send signals to your brain that influence your mood, stress sensitivity and even your cognitive function.
As a woman over 40, this is especially relevant. Oestrogen stimulates the production of serotonin. When your oestrogen level drops during perimenopause, your serotonin production often drops too. If a disturbed gut flora is added to this, you get a double blow: less serotonin from declining oestrogen and less serotonin from an unhealthy gut.
This explains why so many women in perimenopause suffer from low mood, irritability, anxiety and sleep problems. It is not ‘in your head’. It is literally in your gut.
Moreover, your gut bacteria also produce other neurotransmitters such as GABA (the calming hormone) and dopamine (motivation and reward). A healthy gut flora therefore contributes to emotional stability, better sleep and greater mental resilience.
Cortisol and the gut-stress cycle
Stress damages your gut flora, and a damaged gut flora makes you more susceptible to stress. This is a vicious cycle that many women recognise: you have stress, your gut acts up, you feel worse, your stress level rises further. Chronically elevated cortisol — your stress hormone — reduces the diversity of your gut flora and weakens your gut wall. Stress management is therefore just as important for your gut as good nutrition.
Leaky gut and hormonal disruption
The wall of your small intestine is only one cell layer thick. This cell layer forms a selective barrier: nutrients are allowed through, but harmful substances such as bacteria, toxins and undigested food particles are kept out. The cells are held together by so-called tight junctions: protein connections that function like locks on a gate.
With a leaky gut (increased intestinal permeability), these tight junctions are damaged. The ‘locks’ open, and substances that normally stay outside the bloodstream leak through the gut wall. Your immune system responds with an inflammatory reaction.
This chronic low-grade inflammation has far-reaching consequences for your hormones:
- Insulin resistance: chronic inflammation reduces your cells' sensitivity to insulin. This leads to higher insulin levels, more fat storage (especially around the belly) and an increased risk of type 2 diabetes.
- Thyroid problems: inflammation can attack your thyroid and disrupt the conversion of the inactive thyroid hormone T4 to the active T3. Many women with a sluggish thyroid also have gut problems.
- Elevated cortisol: a leaky gut keeps your immune system continuously on high alert, causing your cortisol levels to remain chronically elevated. This disrupts your sleep, your oestrogen-progesterone balance and your metabolism.
- Disrupted oestrogen metabolism: inflammation in the gut disrupts the estrobolome, causing oestrogen metabolism to become unregulated.
What causes a leaky gut? The most common culprits are chronic stress, excessive alcohol consumption, insufficient fibre, ultra-processed food, prolonged use of anti-inflammatories (NSAIDs) and repeated antibiotic use. The good news: your gut wall can recover, provided you choose the right nutrition and lifestyle.
Nutrition that strengthens your gut flora
The composition of your gut flora is largely determined by what you eat. This means that with targeted food choices you can improve your microbiome — and thereby your hormone balance. These are the most important food groups:
Fibre-rich foods
Fibre is the food of your good gut bacteria. They ferment fibre into short-chain fatty acids such as butyrate, propionate and acetate. These substances feed your intestinal cells, strengthen the gut barrier and have an anti-inflammatory effect. Aim for at least 25 to 30 grams of fibre per day.
Good sources: vegetables (broccoli, Brussels sprouts, artichokes, chicory), fruit (berries, apples with skin, pears), legumes (lentils, chickpeas, white beans), whole grains (oats, quinoa, buckwheat) and nuts and seeds.
Fermented foods
Fermented products contain live bacteria that replenish and diversify your gut flora. Research shows that people who regularly eat fermented food have a more diverse gut flora and lower inflammation markers in their blood.
Good sources: unpasteurised sauerkraut, kimchi, kefir, natural yoghurt (unsweetened), kombucha, miso and tempeh. Note: choose unpasteurised varieties, as pasteurisation kills the good bacteria.
Cruciferous vegetables
Broccoli, cauliflower, Brussels sprouts, kale and cabbage deserve special mention. They contain not only fibre, but also indole-3-carbinol, a substance that helps your liver break down oestrogen healthily. They therefore directly support both your gut and your hormones.
Polyphenol-rich foods
Polyphenols are plant-based antioxidants that act as prebiotics: they specifically feed the good bacteria in your gut. They also have an anti-inflammatory effect.
Good sources: berries (blueberries, raspberries, blackberries), green tea, dark chocolate (at least 70% cacao), extra virgin olive oil, pomegranate and turmeric.
Bone broth and collagen
Bone broth contains amino acids such as glutamine, glycine and proline that help repair the gut wall. Glutamine is the primary energy source for your intestinal cells. If you have a sensitive gut or suspect increased intestinal permeability, bone broth can be a valuable addition to your diet.
The 30-plant rule
Research from the American Gut Project shows that people who eat 30 or more different plant-based products per week have a significantly more diverse gut flora. Count everything: vegetables, fruit, herbs, spices, nuts, seeds, legumes and whole grains. Variety is the key word for a healthy microbiome.
Nutrition that damages your gut
Just as important as what you add is what you limit. Certain foods and substances can damage your gut flora and the gut barrier:
Refined sugars
Sugar feeds the wrong gut bacteria and yeasts (such as Candida). A sugar-rich diet reduces the diversity of your gut flora, promotes inflammation and increases intestinal permeability. Moreover, sugar spikes cause insulin spikes, which disrupts your entire hormone system. Limit added sugars to a maximum of 25 grams per day. Always read labels too, as sugar is hidden in many products.
Ultra-processed foods
Ready-made meals, crisps, biscuits and other ultra-processed products contain emulsifiers, preservatives and artificial sweeteners that can damage the gut barrier. Research shows that emulsifiers such as polysorbate 80 and carboxymethylcellulose attack the mucus layer of your gut — precisely the layer that protects you against leaky gut.
Excessive alcohol
Alcohol is one of the greatest enemies of your gut. It disrupts the composition of your gut flora, increases intestinal permeability and burdens your liver — the organ responsible for breaking down hormones. Even two glasses of alcohol per day can cause measurable damage to your gut barrier.
Prolonged antibiotic use
Antibiotics are sometimes necessary, but they don't only kill pathogens — they also decimate your good gut bacteria. Research shows that a single course of antibiotics can disturb your gut flora for up to twelve months. If you need to use antibiotics, support your gut extra with probiotics and fibre-rich food.
Too little variety
Eating the same thing every day is one of the most underestimated causes of a disrupted gut flora. Your gut bacteria thrive on variety. If you always eat the same vegetables, the same grains and the same proteins, your gut flora becomes monotonous — and thereby more vulnerable.
Prebiotics and probiotics: what really works?
You hear these terms often, but what is the difference? And what really works for your hormone balance?
Prebiotics: food for your good bacteria
Prebiotics are indigestible fibres that serve as food for the beneficial bacteria in your gut. You eat them not for yourself, but for your microbiome. Prebiotics stimulate the growth of bacteria that produce short-chain fatty acids, suppress inflammation and strengthen your gut barrier.
The best prebiotic foods:
- Onion and garlic: contain inulin and fructo-oligosaccharides (FOS)
- Leek and asparagus: rich in inulin
- Chicory: one of the richest sources of inulin
- Green banana: contains resistant starch that feeds your good bacteria
- Oats: contain beta-glucans that support your gut flora
- Flaxseed: prebiotic fibre plus lignans that help regulate oestrogen
Probiotics: adding live bacteria
Probiotics are live micro-organisms that supplement your gut flora. You get them through fermented food or supplements. For hormone balance in women, several strains are particularly interesting:
- Lactobacillus rhamnosus: supports the gut barrier and reduces inflammation
- Lactobacillus gasseri: associated with less belly fat and better insulin sensitivity
- Bifidobacterium longum: helps with stress reduction via the gut-brain axis
- Lactobacillus acidophilus: supports the estrobolome and oestrogen balance
Food or supplement? Always start with food. Fermented products contain not only probiotic bacteria, but also prebiotic fibre, vitamins and minerals. A supplement can be a good addition, but does not replace a healthy diet. Choose a supplement with at least 10 billion CFU (colony forming units) and multiple strains. Keep it refrigerated and preferably take it with a meal.
Practical rule of thumb
Eat at least one portion of fermented food daily (sauerkraut, kefir, yoghurt or kimchi) and at least three different prebiotic foods (onion, garlic, leek, oats, flaxseed). This is the easiest way to support your gut flora every day — without supplements or complicated schedules.
Your action plan for healthy gut and hormones
Knowledge is valuable, but what matters is what you do with it. Below you'll find a concrete step-by-step plan to improve your gut health and hormone balance. Start with week 1 and build up gradually.
Week 1: Laying the foundation
- Add one portion of fermented food to your meals daily (a spoonful of sauerkraut at lunch, a glass of kefir as a snack)
- Replace refined carbohydrates with wholesome alternatives (oats, wholegrain, quinoa)
- Drink at least 1.5 to 2 litres of water per day
- Cut out sugary drinks and limit alcohol
Week 2: More variety
- Count how many different plant-based products you eat per week, and try adding two new ones each week
- Eat cruciferous vegetables daily (broccoli, cauliflower, Brussels sprouts or kale)
- Add prebiotic foods: onion, garlic, leek and flaxseed
- Build an evening routine for stress reduction (breathing exercises, walking, journaling)
Week 3: Deepening and persisting
- Aim for 25 to 30 grams of fibre per day. Use an app to track it if needed
- Experiment with new fermented products (kimchi, miso, kombucha, tempeh)
- Limit ultra-processed food to a maximum of two occasions per week
- Consider a probiotic supplement if you notice your gut needs extra support
Week 4 and beyond: Your new normal
- Make the above habits your standard — not as a diet, but as a lifestyle
- Listen to your body: less bloating, better bowel movements and more energy are signs that your gut is recovering
- Keep a food diary to identify patterns
- Give yourself patience — your gut flora needs four to six weeks to change noticeably
A disturbed gut flora doesn't build up in a day, and it won't recover in a day either. But every meal is an opportunity to support your gut — and thereby your hormones. Small, consistent steps lead to big changes.
Do you want to get serious about this, but don't know where to start? In the FEM Rebalance programme you'll receive a six-week nutrition plan specifically developed to support your gut and hormones. With personal guidance, concrete recipes and a community of women making the same journey.