Why your IBS gets worse every month - and what your hormones have to do with it

We’re talking IBS and hormones this April, which marks IBS awareness month!  If you've ever noticed your IBS flaring up in sync with your menstrual cycle, you're not imagining it and you're not alone. Research consistently shows that women are diagnosed with IBS at nearly twice the rate of men, and a significant proportion report that their symptoms such as bloating, cramping, diarrhoea, or constipation, change noticeably across the month.

The connection between IBS and hormones is one of the most undert-alked areas in gut health and understanding it could change how you manage your symptoms entirely.

The oestrogen and progesterone effect

Oestrogen and progesterone both directly influence gut motility - the speed at which food moves through your digestive system. In the lead-up to menstruation, progesterone levels drop sharply. This drop is associated with faster gut transit, which can trigger diarrhoea-dominant IBS symptoms. Conversely, higher progesterone during the luteal phase (the week or two before your period) slows motility, contributing to bloating and constipation. For those living with IBS, these hormonal shifts can amplify symptoms that are already difficult to predict.

Prostaglandins, the hidden driver

During menstruation, the body releases prostaglandins, hormone-like compounds that trigger uterine contractions. The problem is they don't stay localised. Prostaglandins can also stimulate contractions in the bowel, leading to cramping, urgency, and loose stools that mirror  or worsen, IBS symptoms. This is why period-related gut upset is so common, even in people without a formal IBS diagnosis.

What to eat across your cycle

• Follicular phase (days 1–13). Rising oestrogen often means better tolerance. Use this window to reintroduce variety - try gentle higher-fibre foods like oats and cooked legumes in small portions to support microbiome diversity.
• Luteal phase (days 14–28). Prioritise magnesium-rich foods and fibre diveristy (pumpkin seeds, ground flaxseed, kiwi fruit, raspberries, dark chocolate, tofu) to support muscle relaxation and ease constipation. Reduce high-FODMAP foods and ultra-processed snacks, which can worsen bloating when progesterone is high.
• During menstruation. Focus on anti-inflammatory foods such as oily fish, walnuts, ginger, and turmeric, to help counteract prostaglandin activity. Keep meals smaller and more frequent to reduce gut load.

Cortisol and the stress loop

Hormones extend beyond the reproductive system. Cortisol — your primary stress hormone — also plays a significant role in gut function. Elevated cortisol increases gut permeability and can alter the balance of gut bacteria, both of which are implicated in IBS. For many people, hormonal fluctuations and life stress compound each other, creating a cycle that's hard to break without addressing both simultaneously. Prioritising sleep, blood sugar balance and stress management are as much a part of IBS nutrition as food choices themselves.

Tracking your symptoms alongside your cycle, even simply with a notes app, can reveal patterns that make your IBS feel far less random. If you notice consistent hormonal flares, speak to a registered dietitian or GP who can help you build a cycle-friendly nutrition plan. Your hormones and your gut are in constant conversation. It's time to listen in.

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