I work with a lot of clients with gut issues. I know first-hand the benefit of improving your diet to support good gut health, and how enjoyable life can be when you aren’t running to the loo all the time!

Firstly, if diarrhoea is a new or persistent symptom for you it’s really important that you see your GP to have it checked out. In some cases it can be a sign of something more serious like inflammatory bowel disease, or even colon cancer, so please make sure you’ve had these ruled out. You may also have a bacterial or viral infection that requires a course of medication to clear it, and in acute and severe cases diarrhoea can cause severe dehydration which may require intravenous fluids and a hospital stay.

Diarrhoea is defined as passing looser or more frequent watery stools (bowel movements) than is normal for you. This can be acute (sudden onset and lasting 2-3 days) but it can also occur less frequently and last longer (weeks or even months). I thought I would provide some insights into the reasons why you might experience diarrhoea, so read on to find out more.


This could be viral such as Norovirus, bacterial such as Salmonella or E.Coil, or parasitic like Giardiasis. These pathogens can be passed through poor hygiene practices and are usually from contaminated food. These can be quite acute in their onset and dehydration is a danger. They will often clear up on their own by resting, keeping hydration up with plenty of fluids and avoiding eating until you feel well enough or have stopped having other symptoms such as stomach cramps or vomiting. In some cases antibiotics for bacterial infections or anti-parasitic drugs may be needed to clear them up.

Coeliac disease

Coeliac disease is a condition where your immune system attacks your own tissues when you eat gluten. This causes damage to your small intestine so you are unable to take in nutrients. Coeliac disease can cause a range of symptoms, including diarrhoea, abdominal pain and bloating. It affects around 1 in 100 people and can often go undiagnosed or misdiagnosed as IBS for a long time. The only way to manage Coeliac disease is a lifelong gluten free diet. It’s important that it is properly diagnosed and you get professional help as resulting nutrient deficiencies are common.

Non-coeliac gluten sensitivity

Whilst you may not have Coeliac disease I do see many people in clinic who find their gut symptoms rapidly improve when they remove gluten-containing grains from their diet. Some people are sensitive to the amount they consume (so small amounts infrequently are ok), and others find that they can’t cope with lots of wheat (wheat contains gluten) but are ok with grains like spelt (which contains less gluten). The best way to tell if gluten is causing an issue is to take it out of your diet for 30 days, and importantly don’t just replace foods with highly processed gluten free alternatives. Swapping everything over to gluten free cereals, bread, pasta and biscuits is unlikely to be helpful to your digestion. I usually recommend people opt for rice, potato, quinoa and root vegetables and other less refined alternatives during this time.

Lactose intolerance

Lactose is a type of milk sugar found in the milk of most mammals. Some people lack the ability to produce enough of an enzyme called lactase in the small intestine, and therefore cannot break these milk products down. Lactose is found in cows, sheep, goats and other mammals milk. Lactose free or low lactose dairy products are good options for these people, providing it’s only lactose that they have an issue with.

Non IgE mediated food allergy

Non IgE mediated food allergies are caused by a reaction involving other components of the immune system apart from IgE antibodies. The reactions do not appear immediately after the ingestion of the food and usually relate to reactions in the gastrointestinal tract such as vomiting, bloating and diarrhoea. I see these frequently in clients, but please note there is no reliable form of non IgE food allergy or intolerance testing. An exclusion diet and working with a professional who can review a food and symptom diary is the best way to figure this out. You can have a non IgE mediated food allergy to almost any food but some of the most common include: wheat, egg, cows milk products, soy, citrus fruits, tomatoes, shellfish, white fish, nuts, kiwi, avocado and coconut.


FODMAPS are a bit of a mouthful but stand for fermentable oligo-, di-, mono-saccharides and polyols”. These are short-chain carbohydrates that are resistant to digestion. Instead of being absorbed into your bloodstream, they reach your large intestine where most of your gut bacteria live. Your gut bacteria then use these carbohydrates for fuel, producing gas and causing digestive symptoms in sensitive individuals. FODMAPs also draw liquid into your intestine, which may cause diarrhoea. Although not everyone is sensitive to FODMAPs, people with irritable bowel syndrome (IBS) can be. It is worth working with a professional if you want to undertake a low FODMAP diet so they can support you. It is a restrictive diet and is designed to be used only short-term until symptoms improve, before you reintroduce FODMAPs in a controlled way to see which FODMAPs cause you issues.

Small Intestinal Bacterial Overgrowth (SIBO)

Small intestinal bacterial overgrowth (SIBO) is a condition affecting the small intestine. It occurs when bacteria that normally grow in other parts of the gut start growing in the small intestine. Symptoms can include diarrhoea, bloating, wind, abdominal pain. It is well worth working with a professional to support you if you do have SIBO as a combination of diet, lifestyle and supplemental support is required to address a bacterial imbalance.

Supplemental vitamin C and/or magnesium

Whilst I might recommend a short-term course of magnesium citrate for clients with constipation, high doses of either magnesium or vitamin C can cause loose stools. As with most supplements, it is worth getting a professional opinion about whether the forms and dose you are using are working for you.

Sugar alcohols

Sugar alcohols are sweeteners that have about half the calories of regular sugar. They occur naturally in certain fruits and vegetables, but some are man-made and are often added to processed foods. Mannitol, sorbitol, xylitol, erythritol are types of sugar alcohol. Products labelled “sugar free” or “no sugar added” have sugar alcohols in them. Chewing gum, diabetic foods, low carb and keto products often use them. Some people are very sensitive to them, and for others it’s the amount they consume that is the problem.


Alcohol is a known gut irritant, certain types can be quite triggering for some people. Red wine, beer and cider I find are the worst culprits, but all alcohol consumed in excess can cause problems. Often people blame the food and not the alcohol they consume for their diarrhoea. Get diarrhoea every time you drink or the day after? It’s better to cut the alcohol out first before you start stripping your diet back. I find spirits like gin, vodka and rum better for people in small quantities (one or two drinks in one sitting).

Certain food additives

Especially the ‘gums’. Carageenan, guar gum, xantham gum, locust bean gum, agar, acacia gum (also called gum arabic), arrowroot powder. These gums are commonly added to foods to help thicken them, improve texture and increase shelf life. Interestingly they are often added to a lot of gluten free foods, as gluten itself is quite sticky and helps products hold together, without gluten products like guar gum and xantham gum may be required to get the food to hold together. I find some of my clients are very sensitive to these gums and do better without them.


Never underestimate the powder of stress and anxiety. I see this so often in clinic. Work stress, relationship stress and financial stress will all activate the body’s stress response – commonly termed as the ‘fight, flight or freeze’ state, which is the sympathetic nervous system kicking in. This causes blood flow to divert away from the gut and other areas of the body, to the heart and muscles in order for you to fight or take flight easily! This can wreak havoc with your gut. Diarrhoea is often a common side effect as your body will literally want to clear any food in your digestive system out that it can. Long-term persistent stress can negatively affect your beneficial bacteria population, reduce levels of stomach acid (required to kill off unwanted bugs you consume and start the process of digestion) and alter peristalsis (the muscular contractions that occur in the gut to push food through). The good news is that resolving ongoing stress, and helping your body by implementing breathing exercises, meditation, mindfulness, yoga, and herbal adaptogens can all help support the body to deal with the effects of stress better.


I hope this list is helpful for you when considering the many different factors that can play a role in causing diarrhoea. If you would like personalised support to explore any of the areas above in more detail please book an appointment.