Is Fibre Good for Diarrhea? A Guide to Choosing the Right Type

December 20, 2025 •

4 min read

While many Americans get only about 15 grams of fiber per day, the effect of fibre on our gut can be surprisingly fast and varied. Depending on the type, the answer to 'Is fibre good for diarrhea?' can be either a helpful yes or a cautionary no.

Quick Summary

Soluble fiber can effectively help manage diarrhea by absorbing excess water and bulking up stool, while insoluble fiber may aggravate symptoms. The key lies in understanding which type to consume and how to introduce it safely.

Key Points

Soluble fibre is generally good for diarrhea: It absorbs excess water, forming a gel that slows digestion and firms up loose stools.
Insoluble fibre can make diarrhea worse: It adds bulk and accelerates bowel movements, which is often counterproductive during a bout of diarrhea.
Increase fibre gradually: A sudden, large increase in fibre can cause bloating, gas, and cramping, so introduce it slowly.
Stay well-hydrated: Drinking plenty of water is crucial when increasing fibre intake, as fibre needs water to work effectively.
Prioritise soluble-rich foods: Focus on gentle foods like bananas, applesauce, oats, and peeled, cooked vegetables.
Know when to limit fibre: In cases of acute, severe diarrhea or during an inflammatory bowel disease flare-up, a temporary low-fibre diet is often necessary.
Consult a healthcare professional: Always seek medical advice for chronic or severe diarrhea to identify the cause and receive appropriate treatment guidance.

Understanding the Two Types of Fibre

Fibre, or roughage, is a carbohydrate found in plant foods that the body cannot digest. It passes through the digestive system mostly intact, and its specific properties are determined by whether it is soluble or insoluble.

Soluble Fibre: The Diarrhea-Friendly Option

Soluble fibre dissolves in water, forming a gel-like substance. This gel helps slow down the digestive process and bulks up the stool by absorbing excess water in the intestines. For individuals experiencing diarrhea, this action is highly beneficial as it can reduce the frequency of bowel movements and improve stool consistency, making them more formed. Excellent food sources include oats, beans, applesauce, bananas, and psyllium husks. Fiber supplements like psyllium are particularly effective due to their high soluble fiber content.

Insoluble Fibre: Proceed with Caution

Insoluble fibre, by contrast, does not dissolve in water. It acts as a bulk-forming agent, speeding up the passage of waste through the digestive tract. While this is ideal for relieving constipation, it can potentially worsen diarrhea symptoms by further accelerating bowel movements. Insoluble fibre is found in foods like whole grains, nuts, seeds, and the skins of many fruits and vegetables. In cases of severe diarrhea, or for individuals with conditions like diarrhea-predominant Irritable Bowel Syndrome (IBS), it is often recommended to limit insoluble fibre intake.

Safely Incorporating Fibre During Diarrhea

Introducing fibre into your diet while experiencing diarrhea requires a cautious and gradual approach. A sudden increase can lead to unwanted side effects such as bloating, gas, and cramping, which is the opposite of what you want.

Start Slowly and Stay Hydrated

To avoid overwhelming your sensitive digestive system, increase your fibre intake gradually over several weeks. Start by adding just one new soluble fibre-rich food a day to see how your body reacts. Equally important is to significantly increase your fluid intake alongside the fibre. Fibre works best when it absorbs water, and adequate hydration prevents potential constipation and dehydration, which are risks of excessive fibre without enough fluids.

Prioritize Soluble-Rich Foods

Focus on incorporating foods known to be gentle on the stomach and high in soluble fibre. The classic BRAT diet (Bananas, Rice, Applesauce, Toast) is a good starting point, as these foods are bland and low in insoluble fibre, but can be adjusted to include more soluble fibre sources.

Comparison: Soluble vs. Insoluble Fibre for Diarrhea


Feature	Soluble Fibre	Insoluble Fibre
Effect on Stool	Absorbs water, making stools firmer and more formed.	Adds bulk and speeds up movement, which can worsen diarrhea.
Action in Gut	Forms a gel that slows digestion.	Acts like a "broom," pushing waste through faster.
Best For Diarrhea?	Yes, helps to slow things down and normalize consistency.	Generally no, can aggravate a sensitive digestive system.
Good Food Sources	Oats, applesauce, bananas, psyllium, beans, carrots.	Whole grains, nuts, seeds, leafy greens, skins of fruits and vegetables.

Sample Meal Ideas for Diarrhea Management

Breakfast: Oatmeal with sliced banana for extra soluble fibre. Avoid adding nuts or seeds initially.
Lunch: White rice with well-cooked, peeled carrots. Add a small portion of lentils for more soluble fibre.
Dinner: Broiled chicken or fish with mashed potatoes. The BRAT diet elements are easy to digest.
Snacks: Applesauce, ripe bananas, or a small handful of plain, cooked beans.

When Fiber Isn't the Answer

While soluble fibre is a powerful tool for managing some types of diarrhea, it is not a universal solution. For certain conditions or severe cases, a high-fiber diet is not recommended and can be detrimental.

Acute vs. Chronic Diarrhea

In cases of acute, severe diarrhea (e.g., from an infection), medical professionals often recommend a bland, low-fibre diet initially to let the bowel rest and heal. Once symptoms begin to improve, you can slowly reintroduce soluble fibre. For chronic diarrhea, increasing soluble fibre can be very helpful, but you should always consult a doctor to determine the underlying cause.

Special Health Considerations

People with underlying digestive conditions like Inflammatory Bowel Disease (IBD) or severe IBS may need to significantly adjust their fibre intake. During a flare-up of Crohn's disease or ulcerative colitis, a low-fibre or fibre-restricted diet may be necessary. This is to give the inflamed bowel time to heal by reducing the amount of work it has to do. For these reasons, personalised medical advice is crucial.

Conclusion

For those asking "Is fibre good for diarrhea?", the answer depends on the type of fibre and the severity of the symptoms. Soluble fibre, found in foods like oats and bananas, helps solidify loose stools by absorbing water and slowing down digestion. In contrast, insoluble fibre, present in whole grains and seeds, may worsen symptoms by speeding up intestinal transit. When managing diarrhea with fibre, it is vital to increase intake gradually, prioritise soluble sources, and maintain excellent hydration. For severe or chronic conditions, always consult a healthcare provider for personalised advice, as low-fibre diets may be temporarily required to allow the digestive system to rest and recover. For more in-depth information, you can also consult resources like the Mayo Clinic's guide on dietary fiber.

Frequently Asked Questions

Soluble fiber is best for diarrhea because it dissolves in water to form a gel-like substance. This helps to slow down digestion, absorb excess water, and firm up loose, watery stools.

Good food sources of soluble fiber include oats, bananas, applesauce, psyllium husks, cooked beans, and peeled carrots. These are gentle on the digestive system and help to bulk up stool.

Yes, insoluble fiber can sometimes worsen diarrhea. It adds bulk and speeds up the movement of waste through the digestive tract, which can be counterproductive when you are already experiencing loose stools.

Yes, a fiber supplement like psyllium (e.g., Metamucil), which is a source of soluble fiber, can be helpful for diarrhea. However, it's best to start with a small dose and increase it slowly, and always consult a doctor before starting a new supplement.

There is no single recommended amount, as individual tolerance varies. For good bowel health, generally 25-35 grams is advised, but during diarrhea, focus on increasing soluble fiber gradually. For severe diarrhea, a temporary low-fiber diet may be recommended by a doctor.

For some with diarrhea-predominant IBS, increasing soluble fiber can be effective. However, some types of fibre or a sudden increase can worsen symptoms like bloating and gas. A dietitian can help tailor a plan.

During a severe flare-up of a digestive illness like Inflammatory Bowel Disease (IBD) or in cases of acute, infectious diarrhea, a low-fiber or fibre-restricted diet may be necessary to allow the bowel to rest and heal.