Common signs of poor gut health

Common digestive signs of an unhappy gut

Upset stomach, gas, and bloating

Passing wind and some bloating is normal and often indicates the fermentation of fibre – which acts as food for your gut microbes. However, if gas or stomach bloating become excessive, uncomfortable or start to affect quality of life, this may indicate dysbiosis; a term used to describe an imbalance in the ‘good’ and ‘bad’ bacteria in the gut microbiome

Bloating, excessive gas and abdominal discomfort are among the most common digestive complaints (Mearin et al 2016).  These symptoms can occur when food is not fully broken down, absorbed or eliminated efficiently, with some foods leading to increased fermentation by gut bacteria.

Constipation and diarrhoea

Bowel habits are a key indicator of gut health. Chronic constipation, persistent diarrhoea, or alternating between the two may indicate disrupted gut motility or an altered balance of microorganisms in the gut. 

Normal bowel frequency varies widely - anywhere from three times per day to three times per week can be healthy. However, stools that are consistently hard, loose, difficult to pass (often resulting in incomplete evacuation or unsatisfactory evacuation), or urgent may signal a problem. 

Constipation and diarrhoea can often be improved with simple dietary and lifestyle adjustments, although persistent symptoms should always be assessed by a healthcare professional such as a GP.

For constipation, increasing fluid intake can help soften stools and support bowel movements. Gradually increasing dietary fibre, particularly from foods such as oats, vegetables, fruit, beans and wholegrains, may also improve stool frequency and consistency by adding bulk and helping stimulate gut motility. It’s important to increase fibre gradually and alongside adequate hydration, as a sudden increase may worsen bloating or discomfort (NICE 2025).

For diarrhoea, maintaining hydration is essential because the body loses significant fluid and electrolytes through frequent loose stools. Drinking water, oral rehydration solutions or diluted fruit juices can help replace these losses. In the short term, it can help to choose gentler, easily digested foods that are lower in fibre (such as white rice, bananas, toast or plain potatoes) while symptoms settle. It may also be helpful to temporarily avoid potential triggers such as alcohol, caffeine, very fatty foods or very high-fibre foods, which can stimulate the gut and worsen symptoms (NICE 2024).

Food intolerances

Food intolerances occur when the digestive system struggles to process certain components of food. Unlike food allergies, which involve the immune system, intolerances do not trigger an immune response and are not severe , but they can significantly affect quality of life.

Food intolerance symptoms are usually mild, and can include:

• bloating
• gas
• abdominal pain
• diarrhoea
• nausea

However, symptoms for both food intolerances and food allergies can be similar, so it is important that you speak to a doctor or qualified health professional so that they can investigate your symptoms.

Alterations in gut microbes may influence the growth of other microorganisms, ability to digest certain foods comfortably and alteration to your gut environment. A change in these factors could  contribute to symptoms such as bloating, gas, abdominal pain or diarrhoea (Valdes et al 2018). Lactose intolerance is a well-established example, which is a difficulty in digesting lactose – the sugar found in dairy products. Lactose intolerance means that your body does not make enough of the enzyme ‘lactase ‘which breaks down the lactose found in dairy products. There are two types of lactose intolerance: primary and  secondary: Primary lactose intolerance indicates an inherited decrease in lactase production, often due to genetics, with lactase levels decreasing as you move into adulthood. Secondary lactose intolerance occurs because of a gut-related illness or damage to your gut lining, leading to a decreased production of lactase. Secondary lactose intolerance symptoms often  recover with time.

If you have a lactose intolerance you may still be able to manage some lactose in your diet in smaller amounts. Yogurt for example, will often contain lower levels of lactose than milk, due to the presence of bacteria, which has the ability to break down lactose. However please speak to a healthcare professional on the best way to approach foods containing lactose.  

Food tolerance can also change over time. Restricting foods without proper assessment may sometimes worsen symptoms by reducing dietary variety and, in turn, gut microbial diversity. Online/home food intolerance tests are not recommended by health care professionals – please speak to a doctor or dietitian for personalised advice.

Other factors that could be impacting your gut health

Fatigue and poor sleep

The gut plays an important role in sleep regulation.

When the balance of microorganisms in the gut is disrupted, it may affect how the gut and brain communicate with each other, which can play a role in sleep. The gut helps send messages that influence immune responses, inflammation, and the production of hormones, like melatonin, the sleep hormone. If the balance of gut microorganisms is disrupted, this could affect how effectively melatonin is produced and how well the body prepares for sleep. Changes in gut microorganisms may also affect how the body responds to stress and regulates daily rhythms, potentially making it harder to switch off and sleep well. This growing area of research highlights the close connection between gut balance and healthy sleep patterns (Sejbuk et al 2024).

Fatigue that persists despite adequate rest, particularly when it occurs alongside digestive symptoms, may warrant further investigation, so it's important you get this checked out with a doctor.

Skin irritation (eczema, acne)

The “gut-skin axis” describes the connection between gut health and skin conditions. Inflammation originating in the gut may influence immune responses that manifest on the skin such as eczema, acne and rosacea.

Research has shown associations between gut dysbiosis and inflammatory skin conditions. Skin conditions are multifactorial though and influenced by many factors such as genetics, hormones and environmental factors, but digestive symptoms occurring alongside skin flare-ups may suggest a shared underlying pathway  (O’Neill et al 2016).

Mood changes and the Gut-Brain axis

The gut and brain are closely connected and constantly communicate with each other through what scientists call the gut–brain axis. This communication happens through nerves, hormones and signals from the immune system. One important pathway is the vagus nerve, which acts like a communication highway, carrying messages back and forth between the gut and the brain (Cryan et al 2019).

Changes in the balance of microorganisms in the gut may affect how the body produces certain chemical messengers linked to mood, as well as signals involved in inflammation. Research suggests that differences in gut microorganisms are associated with feelings of anxiety and low mood, although scientists are still working to fully understand the mechanisms.

However, this relationship is bidirectional - psychological stress can also alter gut function, creating a feedback loop in which gut symptoms and mood changes reinforce one another.

Unintentional weight changes

The gut microbiome plays a role in how energy is extracted from food, how blood glucose is regulated, appetite and how fat is stored  (Turnbaugh et al 2006). An imbalance may impair nutrient absorption, affect hunger or alter metabolic signalling pathways.

A study found that the mix of bacteria in the gut may play a role in how the body uses and stores energy. In animal studies, differences in gut bacteria were linked to body weight, even when calorie intake and physical activity were similar  (Turnbaugh et al 2006).

Weight changes linked to gut health are often subtle and gradual. Weight alone is not a reliable indicator of gut health, but unexplained gain or loss should always be investigated medically.

When to seek medical advice

While mild digestive symptoms are common, medical advice should be sought if you experience:

• Persistent bloating or abdominal pain
• Chronic diarrhoea or constipation (or a change in bowel habit)
• Blood in stools
• Unexplained weight loss
• Ongoing fatigue
• Symptoms that interfere with daily life or sleep

In some cases, small dietary or lifestyle changes may help support gut health. You can read more general information below:

Summary

Take-home message: Gut symptoms are often normalised, but persistent discomfort is not something to simply “put up with”. Listening to your body and seeking appropriate support early can make a meaningful difference.

My top tip for supporting gut health: Focus on everyday habits that nourish the gut. Aim to eat a wide variety of plant foods including oats and linseeds (to help with bloating) and kiwis* if constipation is an issue, to provide different types of fibre that support microbial diversity. Ensure adequate fluid intake to aid digestion and bowel function, and consider including fermented foods such as yoghurt or kefir regularly as part of a balanced diet (BDA 2025).

*The British Dietetic Association (BDA) guidelines recommend eating 2-3 kiwifruits a day for at least four weeks to help improve chronic constipation (Dimidi et al 2025).