Gut health guide

Your digestive system breaks down what you eat into parts small enough for your body to absorb; your body uses these nutrients for energy, growth and repair. The large intestine absorbs water and turns undigested waste into stool. The bacteria that live in your digestive tract, called gut flora or the microbiota, help with digestion.^[1]

About 100 trillion microorganisms, most of them bacteria, live in the human digestive tract. Studies in twins show that the makeup of the microbiota is shaped more by environmental factors such as diet, medicines and body measurements than by genetics.^[2]

• Gut bacteria ferment fiber that cannot be digested and produce short-chain fatty acids. One of these, butyrate, is the main energy source for the cells of the large intestine.^[2]
• The gut microbiota is linked to many traits related to immunity, metabolism and behavior.^[2]
• Eating fiber has been linked to positive effects in many conditions.^[2]

Some of the findings in this field come from animal studies or from observational studies that cannot show cause and effect. Randomized controlled trials provide the strongest evidence.^[2]

• Gas: It enters your digestive tract when you swallow air and when bacteria in your large intestine break down some undigested carbohydrates.^[9]
• Constipation: Fewer than three bowel movements a week; hard, dry or lumpy stools; stools that are difficult or painful to pass; or a feeling that your bowels have not fully emptied. In the US, about 16 in every 100 adults have symptoms of constipation, and about 33 in every 100 adults aged 60 and older.^[6]
• Diarrhea: Loose, watery stools three or more times a day, or more often than is usual for you. Acute diarrhea usually lasts less than a week and goes away on its own; diarrhea that lasts at least 4 weeks is called chronic diarrhea.^[8]

The most common symptom of irritable bowel syndrome (IBS) is abdominal pain, often related to bowel movements. Depending on the type of IBS, bowel habits can shift toward diarrhea, constipation or both; bloating, a feeling that your bowels have not fully emptied, and white mucus in the stool can also occur. IBS is a long-term condition and symptoms can come and go; it does not damage the digestive tract.^[3]

The cause of IBS is not fully known. Factors such as problems in the interaction between the brain and the gut, stressful events early in life, bacterial infections of the digestive tract, bacterial overgrowth in the small intestine, food intolerances and genetics are thought to play a role together.^[3]

Alcohol, caffeine, spicy or fatty foods, stress and anxiety can trigger IBS symptoms.^[12]

Your doctor may suggest a low FODMAP diet for a few weeks to see whether it helps your symptoms. In Monash University's three-step approach, the first step lasts 2–6 weeks; after that, each FODMAP group is added back one at a time, each tried over 3 days. The aim is a more flexible, balanced way of eating that, in the long term, limits only the foods that trigger your symptoms.^{[5, 11]}

A low FODMAP diet should be followed with the guidance of a dietitian experienced in IBS. Some people with IBS can eat some foods that contain FODMAPs without having symptoms.^{[5, 10, 11]}

Adults are advised to get 22–34 grams of fiber a day; how much you need depends on your age and sex. Add high-fiber foods a little at a time so your body can get used to them.^[7]

Eating plenty of fiber is linked to a lower risk of heart disease, stroke, type 2 diabetes and bowel cancer. High-fiber foods also help digestion and help prevent constipation.^[14]

Some research suggests that soluble fiber may be more helpful for easing IBS symptoms.^[5]

Some of these foods (for example apples, pears, peas and most legumes) are high in FODMAPs. If you have IBS, make your choices together with your dietitian.^[10]

Fluids such as water, fruit and vegetable juices with no added sugar, and clear soups help fiber work better and make stools softer. The Turkish Dietary Guidelines recommend that adults drink no less than 8–10 glasses of water and other drinks a day.^{[7, 15]}

• Eat three main meals a day, and in particular don't skip breakfast. Chew your food well and eat slowly.^[15]
• If you have IBS, don't delay or skip meals, and don't eat too quickly.^[13]
• Keep a diary of what you eat and your symptoms; this makes it easier to notice the foods that trigger you.^[13]
• If you have IBS, limit very fatty, spicy or processed foods, alcohol and carbonated drinks; don't drink more than 3 cups of tea, coffee or other caffeinated drinks a day.^[13]
• Look for ways to relax, and stay active on a regular basis.^[13]

These symptoms may point to a health problem other than IBS.^[4]

I offer my clients nutrition counseling in person and online, from a functional medicine perspective. Alongside your symptoms, I also look at your diet and lifestyle to try to understand the causes behind your complaints. My priority throughout is supporting gut health.

My services in this area include nutrition for digestive diseases, the low FODMAP diet, elimination diets, nutrition for allergies and intolerances, and food intolerance testing. In an elimination diet, foods suspected of causing a sensitivity are removed from your diet for a set period. I prepare a medical nutrition protocol tailored to you and help you make healthy habits part of your daily life.

A nutrition plan does not replace the treatment your doctor recommends; it works alongside it. Talk to your doctor about any change to the medicines you take.