Boost Your Digestive Health with Fiber, Fermented Foods, and Lifestyle Changes

Maintaining healthy digestion is crucial for overall well-being, and incorporating fiber and fermented foods into your meals can significantly aid this. These dietary components positively impact the gut microbiome, a key player in digestive health. Explore the importance of fiber and fermented foods, along with lifestyle changes, to support a healthy digestive system and enhance quality of life.

How — and why — to fit more fiber and fermented food into your meals 

Fiber and fermented foods are top priorities to help maintain healthy digestion.

Fiber, fermented foods, and the gut microbiome  

The gut microbiome is composed of bacteria, viruses, fungi, and other microorganisms living in the colon (large intestine). What you eat, the air you breathe, where you live, and many other factors affect the makeup of the gut microbiome. Some experts think of it as a hidden organ because it has a role in many important functions of the body — for example, helping the immune system function optimally, reducing chronic inflammation, keeping intestinal cells healthy, and providing some essential micronutrients that may not be included in a regular diet. 

Your gut communicates with your brain through pathways in the gut-brain axis. Changes in the gut microbiome have been linked with mood and mental health disorders, such as depression and anxiety. However, it’s not yet clear that these changes directly cause these types of problems. 

We do know that a healthy diet low in processed foods is key to a healthy gut microbiome. And increasing evidence suggests that fiber and fermented foods can play important parts here. 

Fiber 101  

Fiber’s main job is to make digestion smoother by softening and adding bulk to stool, making it pass quickly through the intestines. 

But fiber has other benefits for your microbiome and overall health. A high-fiber diet helps keep body weight under control and lowers LDL (bad) cholesterol levels. Research has found that eating enough fiber reduces the risk of heart disease, type 2 diabetes, and some cancers. 

What to know about fiber

There are two types of fiber: insoluble (which helps you feel full and encourages regular bowel movements) and soluble (which helps lower cholesterol and blood sugar). However, recent research suggests people should focus on the total amount of fiber in their diet, rather than type of fiber. 

If you’re trying to add more foods with fiber to your diet, make sure you ease into new fiber-rich habits and drink plenty of water. Your digestive system must adapt slowly to avoid gas, bloating, diarrhea, and stomach cramps caused by eating too much too soon. Your body will gradually adjust to increasing fiber after a week or so. 

How much fiber do you need?  

The fiber formula is 14 grams for every 1,000 calories consumed. Your specific calorie intake can vary depending on your activity levels. 

But instead of tracking daily fiber, focus on adding more servings of fiber-rich foods to your diet. Fruits, vegetables, legumes, nuts, seeds, and whole grains are all high in fiber. 

What about over-the-counter fiber supplements that come in capsules, powders that you mix with water, and chewable tablets?  

If you have trouble eating enough fiber-rich foods, then these occasionally can be used, and there is no evidence they are harmful. But they should not serve as your primary source of dietary fiber. 

Fermented foods 101  

Fermented foods contain both prebiotics — ingredients that create healthy changes in the microbiome — and beneficial live bacteria called probiotics. Both prebiotics and probiotics help maintain a healthy gut microbiome. 

What to know about fermented foods  

Besides helping with digestion and absorbing vital nutrients from food, a healthy gut supports your immune system to help fight infections and protect against inflammation. Some research suggests that certain probiotics help relieve symptoms of gut-related conditions like inflammatory bowel disease and irritable bowel syndrome, though not all experts agree with this. 

Many foods that are fermented undergo lacto-fermentation, in which natural bacteria feed on the sugar and starch in the food, creating lactic acid. Not only does this process remove simple sugars, it creates various species of good bacteria, such as Lactobacillus or Bifidobacterium. (Keep in mind that some foods undergo steps that remove probiotics and other healthful microbes, as with beer or wine, or make them inactive, like baking and canning.) 

The exact amounts and specific strains of bacteria in fermented foods vary depending on how they are made. In addition to probiotics, fermented foods may contain other valuable nutrients like enzymes, B vitamins, and omega-3 fatty acids. 

How often should you eat fermented foods? There is no recommended daily allowance for prebiotics or probiotics, so it is impossible to know precisely which fermented foods or quantities are best. The general guideline is to add more to your daily diet. 

Which fermented foods should you choose? Fermented foods have a range of tastes and textures because of the particular bacteria they produce during fermentation or that are added to foods. Yogurt is one of the most popular fermented foods (look for the words “live and active cultures” on the label). Still, many options are available if you are not a yogurt fan or want to expand your fermented choices. Kimchi, sauerkraut, kombucha, and pickles are a few examples. Probiotic supplements do not require FDA approval, so there is no guarantee that the types of bacteria listed on a label can provide the promised benefits — or are even in the bottle. Therefore, it is best to get your probiotics from fermented foods.

How a healthy gut benefits your blood pressure

Your gut microbiota — the trillions of tiny bacteria, viruses, and fungi dwelling deep within your intestinal tract — play a big role in your health. Beyond helping with digestion, these microbes also make certain nutrients and release substances that have wide-ranging effects throughout the body, including on the cardiovascular system.

A wealth of evidence shows a strong connection between the gut microbiota and blood pressure, according to a science advisory published recently in Hypertension. Over all, the findings support what nutrition experts have long advocated: eat a diet rich in whole, plant-based foods, which are naturally low in sodium and high in fiber, says Dr. Frank Hu, professor of nutrition and epidemiology at the Harvard T.H. Chan School of Public Health.

“A high-sodium diet is an important cause of high blood pressure, and one possible mechanism may be mediated through the gut microbiome,” says Dr. Hu. Research shows that a salty diet increases the prevalence of bad microbes and reduces the number of beneficial microbes. When bad microbes accumulate in the gut, they form breakdown products and toxins that promote inflammation.

Prebiotics

But when beneficial microbes prevail, they need to feed on fiber, especially prebiotic fiber, which is not digested by your body but instead broken down in your lower intestine. That’s why a diet that provides a mix of healthy fiber from vegetables, fruits, whole grains, beans, nuts, and seeds is so important, says Dr. Hu, who serves on the advisory committee of the Harvard Chan Microbiome in Public Health Center.

Another good source of prebiotic fiber is resistant starch, which forms in starchy foods like potatoes, rice, and pasta when they’re cooked and cooled overnight, he adds. The cooling process converts some of the starch that would normally be broken down in your small intestine into a form that instead feeds the bacteria in your large intestine.

Well-nourished beneficial bacteria in your gut churn out short-chain fatty acids, including acetate, propionate, and butyrate. These compounds then circulate through the bloodstream, where they’re thought to interact with specific receptors on cells that help regulate blood pressure, Dr. Hu explains.

The power of polyphenols

Many plant-based foods — especially berries, tea, coffee, cocoa, and extra-virgin olive oil — are rich in compounds known as polyphenols. “These compounds also have a positive influence on the composition and function of your microbiome,” says Dr. Hu. When polyphenols are metabolized in the gut, they create all kinds of small molecules that affect the function of your immune and nervous systems. The result is a decrease in inflammation and better blood vessel function, both of which can improve blood pressure control.

Probiotics

Probiotics found in fermented foods and drinks can also support a healthy microbiota. Try adding a variety of the following products to your diet, Dr. Hu suggests.

Yogurt and kefir. Look for the words “contains live cultures” when choosing yogurt or kefir (a yogurtlike drink with a tart flavor and a thinner consistency).

Kombucha. This fizzy, tart, slightly sweet drink is made from fermented tea and often flavored with fruits and herbs. Look for brands without added sugar.

Pickles and sauerkraut. Find these in the refrigerated section of the supermarket and check for the words “naturally fermented” on the label.

Kimchi. This spicy, reddish fermented cabbage dish from Korea is made with a mix of garlic, salt, vinegar, and chili peppers.

Miso. A strong, salty paste made from soybeans fermented with brown rice, miso is popular in Japanese cuisine.

Tempeh. This firm, chewy product made from fermented soybeans has a firmer texture than tofu.

Skip the supplements

What about probiotic supplements sold over-the-counter as pills, capsules, or powders? They are not carefully regulated, and the amount of live bacteria can vary substantially from one product to another, says Dr. Hu. “While some probiotic supplements have modest benefits for specific gastrointestinal conditions, there is little evidence that they are effective in preventing chronic diseases like hypertension. I’d recommend spending your money instead on a healthy diet that’s naturally rich in prebiotics and probiotics,” he says.

Help prevent symptoms from some common digestive diseases and conditions 

Not all digestive diseases can be prevented. But nearly all can be impacted by your lifestyle habits and choices. 

Gastroesophageal Reflux Disease (GERD) prevention 

There are a lot of things you can do to prevent the symptoms of GERD. Some simple lifestyle changes include: 

Elevating your head and shoulders while sleeping by using foam wedges or extra pillows. Lying on your left side also can help reduce acid reflux. 

Avoid foods that cause the esophageal sphincter to relax during their digestion.

These include:

• coffee 
• chocolate 
• fatty foods 
• whole milk 
• peppermint 
• spearmint. 

Limit acidic foods that make the irritation worse when they are regurgitated. These include citrus fruits and tomatoes. 

Avoid carbonated beverages. Burps of gas force the esophageal sphincter to open and can promote reflux. 

Eat smaller, more frequent meals. 

Do not lie down after eating. 

Do not eat during the three to four hours before you go to bed. 

If you smoke, quit. 

Limit or avoid drinking alcohol. It loosens the esophageal sphincter. 

Lose weight if you are obese. Obesity can make it harder for the esophageal sphincter to stay closed. 

Avoid wearing tight-fitting garments. Increased pressure on the abdomen can open the esophageal sphincter. 

Use lozenges or gum to keep producing saliva. 

Preventing celiac disease symptoms

Because celiac disease is a genetic disorder and because gluten is encountered in almost everyone's diet, there is no practical way to prevent it. If you do have it, you can stop intestinal damage and eliminate your symptoms by following a strict, gluten-free diet. Although it is not proven, some experts suspect that if celiac disease runs in your family, you may be able to delay the disease for your own children or reduce the likelihood that they will get the disease by breast-feeding, so that you delay the introduction of other foods to your infant's diet. 

Preventing diverticulosis and diverticulitis 

People whose diets contain large amounts of fiber are less likely to develop diverticulosis, or pouches that form in the wall of the large intestine. The recommended daily fiber intake is at least 20 grams per day, but a healthier goal is 35 grams of fiber daily, preferably from fruits, vegetables, and grains.

Your doctor also may recommend unprocessed bran or a fiber product. It is important to increase fiber intake gradually and to drink more water to increase the bulk of the bowel movements, which reduces pressure inside the bowel. Physical activity also may lower the risk of diverticulosis. By increasing your fiber intake, staying well hydrated and engaging in regular physical activity, you will develop fewer diverticula. These steps also help avoid diverticulitis, an inflamed diverticulum usually caused by an infection.

Help for Crohn's disease 

There is no way to prevent Crohn's disease. 

But you can keep the condition from taking a heavy toll on your body. Maintain a well-balanced, nutritious diet to store up vitamins and nutrients between episodes or flare-ups. By doing so, you can decrease complications from poor nutrition, such as weight loss or anemia. 

Also, do not smoke. Along with many other harmful health effects, smoking is a risk factor for developing Crohn's disease and is also linked to complications such as fistulas. 

Crohn's disease can increase your risk of getting colon cancer. Have your colon checked regularly for early cancerous or precancerous changes. Check with your doctor regarding which types of tests to have and how frequently to repeat them. 

Limiting ulcerative colitis symptoms

There is no way to prevent ulcerative colitis. 

However, some people are able to decrease the frequency of symptoms. They do this by avoiding foods that seem to provoke flare-ups. For some people with ulcerative colitis, this includes spicy foods and milk products. 

If you have ulcerative colitis, you can decrease the toll it takes on your body. To do this, eat a well-balanced, nutritious diet — especially when you are not having symptoms such as poor appetite and nausea that make it hard to eat. By doing so, you can decrease complications from malnutrition, such as weight loss or a low blood count. 

Managing Irritable Bowel Syndrome (IBS) 

Because no one knows what causes IBS, it is impossible to prevent the disorder. Once diagnosed with IBS, a person may be able to reduce the frequency and severity of symptoms by reducing stress and changing the diet. 

Enhancing your diet with fiber and fermented foods, alongside mindful lifestyle changes, boosts digestive health and reduces the risk of disorders. Embrace these habits for improved overall well-being.

This article is part of our collaboration with Harvard Health Publishing, a trusted source of medical expertise from Harvard Medical School. Content has been adapted for local audiences.

Copyright © 2025 by Harvard University. Original work prepared by Harvard Health Publishing. This content is for informational purposes only and does not replace professional medical advice, and do not represent the views of Manulife (Singapore) Pte. Ltd.