Why your gut is also responsible for your mood

Intense focus and easy, sociable conversation one week – followed by irritation, insecurity and uncontrollable anger the next. For many women, their mood feels random or unpredictable. And worse still: the outside world often dismisses it as being “hormonal” or simply the way things are.

Yet research shows that these mood swings are linked to how your body functions throughout your cycle. And more importantly, what happens in your gut plays a far greater role than was long assumed. In this article, you’ll learn all about the cycle–mood–gut triangle, how these elements influence each other, and what you can do to support your mood.

The gut–brain axis explained

Your gut and brain are in constant communication. Through nerve pathways, the immune system and signalling molecules, they exchange information about your energy levels, stress and mood. This two-way communication is known as the gut–brain axis, or the brain–gut connection. Your gut is even referred to as the “second brain” because of its influence on emotions and mood.

For example: serotonin plays an important role in mood, calmness and emotional stability, and a significant proportion of the substances required to produce serotonin are influenced in the gut. That doesn’t mean your mood lives in your stomach, but it does mean your gut helps determine how stable or vulnerable you may feel.

The gut–brain axis helps explain symptoms such as:

Irritability: when the gut is under extra strain, for example due to stress or a busy schedule, the body can shift more quickly into a state of alertness. As a result, stimuli are experienced more intensely.

Low mood: fluctuations in neurotransmitters (the substances that transmit signals in the brain) can contribute to a heavier mental state. The gut plays a supporting role here because it influences how these neurotransmitters are produced and regulated.

Brain fog: when the body requires a lot of energy for regulation and recovery, there is less capacity left for mental sharpness. Inflammatory processes and communication between the gut and brain both play a role.

More and more research shows that hormonal fluctuations also influence the composition and activity of your gut microbiome (the collection of microorganisms living in your intestines). These changes are therefore also linked to mood and sensitivity to stress.

Gut–brain axis and your cycle

The gut–brain axis is not separate from your cycle. Hormonal fluctuations change how the communication system between your gut and brain is calibrated.

Here’s how it works: during your cycle, hormones such as oestrogen and progesterone fluctuate. Your gut responds to these hormonal changes by processing food more easily or with more difficulty, and by sending signals related to energy, satiety and safety. These signals travel directly to your brain.

Your brain uses this information to determine how much capacity there is for focus, emotional stability and recovery. When your body needs a lot of energy to maintain balance, there is less room left for mental clarity or resilience.

Your system functions as a continuous feedback loop: hormonal shifts influence your gut and stress system → these affect your brain and mood → which then shapes how resilient you feel in the next phase of your cycle.

In some phases, your body can process more stimuli at once, making it easier to feel active and alert. In other phases, your body responds more quickly to stress or pressure, meaning fatigue and overstimulation can occur sooner.

Your gut–brain axis and the phases of your cycle

The way hormones and gut responses interact differs across each phase of the cycle. In some phases you may feel more stable, while in others you may be more sensitive to stress and stimuli:

Menstruation (winter, 3 to 7 days)

During menstruation, both oestrogen and progesterone drop to their lowest levels. This can result in less mental noise, but also reduced energy. Rest and simplicity are often supportive during this phase.

Follicular phase (spring, 7 to 10 days)

After your period, oestrogen levels rise. This hormone supports energy, focus and mental clarity, among other functions. Many women feel lighter and sharper during this phase. The gut often responds more steadily as well: food is processed more evenly and the body is less prone to overstimulation. This contributes to a more balanced mood.

Ovulation (summer, 3 to 4 days)

Around ovulation, the hormones linked to energy and alertness peak. You may feel sociable, focused and resilient. At the same time, this heightened alertness places greater demands on the body. The stress system is more active, while recovery takes a back seat. As a result, a build-up of long days, social stimuli or insufficient rest can more quickly lead to fatigue or a sudden dip in energy.

Luteal phase (autumn, 10 to 14 days)

After ovulation, the hormonal balance shifts. Progesterone increases, while oestrogen first declines and then briefly rises again. These fluctuations require ongoing adaptation from the body. During this phase, the gut often becomes more sensitive to stress, food and other stimuli.

As the luteal phase progresses and both progesterone and oestrogen drop sharply just before menstruation, the inflammatory balance in the body also changes. This drop is accompanied by a temporary increase in inflammatory activity – a normal biological process that prepares the body for menstruation.

This mild inflammatory response can amplify existing sensitivities and affect energy, focus, mood and digestion. It is therefore often during this phase that symptoms such as irritability, low mood, brain fog or bloating become more noticeable.

Three simple tips to support your mood

You can’t control everything, and work pressure, caregiving responsibilities, deadlines or poor sleep don’t always align neatly with your cycle. This section is therefore not about eliminating all triggers from your life, but about creating conditions that help your body cope better with the load.

Rhythm and recovery through nutrition

A regular eating pattern helps your body experience predictability, especially during phases when you are more sensitive. This gives your system a sense of stability, even when the rest of your day is busy.

Eat in line with your cycle, as consistently as possible

It’s not what you eat on a single day, but how you approach food throughout your entire cycle that makes the difference. Variety and regularity support your gut and, in turn, your mood.

Stress and sleep

Stress and disrupted sleep increase the sensitivity of the gut–brain axis. Especially in the second half of your cycle, paying extra attention to recovery can help make mood swings feel less intense.

Finally

Mood swings throughout the month are not a sign that your body isn’t functioning properly. But if they significantly affect you, you don’t have to simply accept them. They reflect how your body responds to hormonal changes, daily demands and internal signals.

By viewing your mood, your gut and your cycle as an interconnected whole, you gain a realistic understanding of what’s going on – allowing you to make choices that support you rather than work against you.

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