Does Progesterone Cause Bloating? What the Studies Show

Your belly is swollen in the evening, even though you have not eaten anything different. Maybe you recently started taking progesterone. Maybe you are in the middle of menopause. Everywhere you read the same explanation: progesterone relaxes the gut muscles, the bowel becomes sluggish, and that causes the bloating.

I looked at the studies. The short answer: bloating around menopause is real. But in humans there is little evidence that progesterone causes it by slowing digestion. And for the belly that visibly sticks out, there is a different explanation, one you can work on yourself.

Does progesterone cause bloating?

Some women get stomach or bowel complaints on progesterone. The common explanation for this is wrong, though. Progesterone does not make digestion slower. Two studies show this. In both, women were randomly assigned to progesterone or a placebo.

In the first study, 49 women after menopause took 400 mg of progesterone or a placebo every day for a week. The researchers measured how fast the contents of the bowel moved along. On progesterone they moved faster, and stools became softer.⁸ That does not look like a sluggish bowel.

In the second study, 189 women in perimenopause, the years before the last period, took 300 mg of progesterone in the evening against hot flushes, or a placebo. 8 in 100 women on progesterone reported nausea or other stomach and bowel complaints, compared with 1 in 100 on the placebo.¹⁷

Fig. 1: What was measured when women took progesterone

So progesterone can upset your stomach. Nobody knows why. According to these data, slower digestion is not the reason. Both studies were small and short. If your bloating started when you began taking progesterone, talk to your doctor.

Where does the idea come from that progesterone slows digestion?

Mainly from animal studies. In rats and mice, progesterone clearly slows the gut. In humans the effect is much smaller, if it exists at all. Experts from the Mayo Clinic say the same in a review.¹⁶

In humans, researchers tested it using the menstrual cycle. Progesterone is high in the second half of the cycle and low in the first. If progesterone slowed the gut, food should take longer in the second half. Seven studies measured this. Two found slower digestion, five found no clear difference.^{2,5,9,11,12,18,21}

Fig. 2: Seven studies on digestion and the menstrual cycle

The most careful of these studies confirmed ovulation with a blood test in 18 women and measured each woman in both halves of the cycle. Food took 45 hours on average to pass through the whole gut in the first half and 51 hours in the second.¹² The difference was so small that it could be chance.

One review that looks at animal and human studies together still considers a slowing effect of progesterone likely.⁴ Looking at human studies alone, the evidence is weak.

What does menopause have to do with it?

Menopause does bring more bloating. It just cannot be pinned on progesterone. An American study followed 291 women through menopause over many years. The women kept a diary of their symptoms and regularly gave urine samples.

Bloating increased in two phases: when cycles became irregular, and later, when periods stopped for two months or longer. Tension was also linked to more bloating.¹³

The study does not show which hormone is behind this. Progesterone was not even measured. For constipation and diarrhoea, the same researchers found no link with menopause, but they did find one with tension.³

Why does the belly visibly stick out?

How big your belly looks depends less on the gas than on your diaphragm. That is the muscle below the lungs that separates the chest from the belly.

A Spanish research group put the same amount of gas into the gut of 20 people with bloating and 15 people without. They measured what the diaphragm and the belly muscles did. In people without bloating, the diaphragm moved upwards and the belly wall tightened. That made room for the gas without the belly sticking out much. In people with bloating, the diaphragm pushed downwards and the belly wall gave way. With the same amount of gas, their belly stuck out much more.²⁰

Fig. 3: How the diaphragm pushes the belly forward

Whether hormones play a role here has not been studied. But it is the part of bloating where you can do something yourself.

Can you train your diaphragm?

One study suggests you can. The same research group randomly split 42 people whose belly sticks out after meals into two groups. 36 of them were women aged 17 to 64.

The first group practised at three sessions in front of a screen that showed the movement of their chest and belly. First, participants learned to lift the chest and pull the belly in at the same time. This moves the diaphragm upwards. Then they practised switching between the two: chest down and belly out, then chest up and belly in again. At home they did this every day, for five minutes before and after each main meal.

The second group got a placebo capsule. This showed whether the training does more than simply expecting something to help.

After four weeks, the belly in the training group stuck out much less after meals. Participants rated their bloated belly two thirds lower than before. In the placebo group, little changed.¹

So far only this one research group has tested the training. European experts therefore rate the evidence as weak.¹⁴ Those who kept practising still had fewer symptoms after six months. At that point, however, there was no comparison group any more.¹

What you can do

1. If you take progesterone, bring it up. If the bloating started when you began taking it, tell your doctor. The dose, the time of day and the form can be adjusted.

2. Practise releasing your diaphragm. This helps if the belly sticking out after meals bothers you most. Lift your chest and pull your belly in at the same time, then let go and switch calmly back and forth. Do this for five minutes before and after each main meal. It is easier to learn with guidance: ask a gastroenterology practice about biofeedback.

3. Increase fibre slowly and drink enough. This helps mainly with constipation. Psyllium husk is the best studied.¹⁹ With 10 grams of acacia fibre a day, people with constipation went to the toilet about once a week more often after four weeks.¹⁰ They did not get more bloating from it. More water mainly helps if you were drinking too little before.¹⁵

4. Move. In studies, exercise helped with constipation. How much is unclear, because the studies differed a lot.⁷

5. Have your pelvic floor checked. If constipation does not go away, the cause is sometimes a pelvic floor that does not relax properly during a bowel movement. In one study, pelvic floor training with biofeedback helped women after menopause more than dietary advice alone.²²

6. Take warning signs seriously. Weight loss, blood in the stool, anaemia or symptoms that wake you at night need to be seen by a doctor.

What comes next

Bloating around menopause is real. Progesterone is probably not the main reason, even if it upsets the stomach in some women. Which part of the hormonal change is behind it, research does not know yet. You can still do something: with your diaphragm, with fibre and in a conversation with your doctor.

If you would like to look at hormones, digestion, sleep and stress together, I am happy to support you. In hormone coaching for perimenopause we look for the starting points that fit your everyday life. Anything that needs a medical check stays with your doctor. The easiest way to start is a free initial consultation, online and without obligation.

You can read more about the gut in menopause in Does perimenopause change your gut?.