Can Too Much Fiber Cause Diarrhea or Chronic Diarrhea?

Key takeaways:

• Although fiber in your diet is good for digestion, too much fiber can cause diarrhea.
• Most adults should consume 22 to 34 grams of fiber every day.
• Diarrhea may be more likely if fiber is introduced rapidly into your diet.

Adding dietary fiber, which is classified as soluble or insoluble fiber, can have many health benefits. Insoluble fiber is necessary to add bulk and solidify stool, but it also makes stool pass more rapidly through the digestive tract.

Soluble fiber is easier to digest. It absorbs water and forms a gel with food, letting you slow down digestion. Soluble fiber creates a sensation of fullness after eating, which can help with weight loss.

Most people add fiber to their diet to improve constipation. Dietary fiber is essential for digestion, but too much too soon can upset your digestive system and lead to diarrhea, constipation, bloating, flatulence (gas), and abdominal pain. This article will explain how to treat diarrhea caused by too much fiber and prevent it from happening again.

Is it normal to have diarrhea while on a high-fiber diet?

It is normal to have diarrhea when you begin a high-fiber diet or increase the amount of fiber in your diet too rapidly.

The optimal amount of dietary fiber depends on your age and sex. Older adults need less fiber than younger adults, and men need more fiber than women. The range for adult men and women extends from 22 to 34 grams.

How too much fiber can cause diarrhea

Insoluble fiber does not digest well, so it is more likely to cause diarrhea. It will not dissolve in water. Insoluble fiber speeds up the transportation of foods through the colon.

Soluble fiber, on the other hand, does absorb water. It forms a gel-like material that slows digestion. While soluble fiber is helpful for both diarrhea and constipation, insoluble fiber is only beneficial for constipation.

How to tell the difference between diarrhea from too much fiber and other causes of diarrhea

Fiber absorbs water and helps to produce formed stools. Diarrhea associated with increased fiber is not usually watery. If your diarrhea is runny, it may not be caused by fiber in your diet.

Other common causes of diarrhea

While you may have diarrhea caused by increased dietary fiber, your diarrhea may result from another condition. Some common causes of diarrhea include the following:

Infection

Parasites, harmful bacteria, and viruses can cause diarrhea. Some widespread causes are E. coli, Hepatitis A virus, and Giardia lamblia. Most cases of gastrointestinal infection resolve without treatment, but sometimes anti-infective medications are needed.

Medications

Some medications can alter the balance of bacteria in the GI tract, which can result in overgrowth of harmful bacteria. These medications include antibiotics, antacids with magnesium, and chemotherapy drugs.

Stress and anxiety

The intestine has more nerve cells (neurons) than any organ in the body except the brain. The neurons in the intestine and brain communicate by releasing chemicals called neurotransmitters. The nerves in the digestive system are part of the autonomic nervous system, which manages involuntary bodily functions like breathing and digestion.

Stress causes a fight-or-flight response that can increase the speed of peristalsis, the muscular contractions in the gut that move food through the system. Increased muscle contractions can shorten food’s transit time through the colon (large intestine).

Since most fluid is removed from the semi-digested food in the colon, a shortened transit time does not provide enough time for fluid resorption. That results in loose, watery stools.

Gastrointestinal disease

Disorders like chronic diarrhea, inflammatory bowel disease, and irritable bowel syndrome (diarrhea type) can cause dehydration and have been associated with kidney stones.

Caffeine and alcohol

Caffeine and alcohol speed up the movement of food through the colon, resulting in diarrhea. Diarrhea can lead to dehydration.

Endocrine conditions

Hyperthyroidism (an overactive thyroid gland) often speeds up digestion and causes diarrhea, leading to dehydration. Diarrhea is also associated with diabetes.

Food intolerance

People with intolerance to certain foods cannot digest properly, leading to increased food transit speed through the digestive tract. Some of these conditions include lactose intolerance and celiac disease, both of which are associated with diarrhea.

Artificial sweeteners

Sorbitol and mannitol, two common artificial sweeteners, can cause diarrhea because they pull fluid into the colon.

Read our guides on different types of diarrhea and common causes of diarrhea for more.

When to see a doctor about diarrhea from a high-fiber diet

If you have diarrhea from adding fiber to your diet, you should consider reducing your fiber intake. However, if your diarrhea lasts over a few days despite cutting back on fiber, you should see your doctor.

You should see a doctor for any of the following:

• Diarrhea lasting more than a few days
• Diarrhea that does not respond when you switch to a low-fiber diet

You should go to the emergency room if you have any of the following symptoms along with diarrhea:

• Severe abdominal pain
• Lightheadedness or feeling faint
• Significant amounts of blood in your stool
• Black tarry stool
• Fever
• Chills
• Vomiting
• No bowel movement

Questions to ask your doctor about diarrhea from a high-fiber diet

If you decide to seek medical care, there are a few questions you can ask your doctor to be sure you understand the causes and treatment of your diarrhea. Here are a few questions that may help you with this task:

• How much fiber should I take in every day?
• If I reduce fiber in my diet due to the diarrhea, when can I increase the fiber again?
• Is there a good way to advance fiber in my diet that can reduce the risk of diarrhea?
• How long does it take the body to adjust to dietary fiber?

How to treat or get relief from diarrhea from too much fiber

If you have diarrhea from too much fiber, there are a few steps you can take to minimize your symptoms and get relief. You might want to:

Adjust your fiber intake

If you have diarrhea due to too much dietary fiber, you should eliminate excess fiber and follow a low-fiber diet. A low-fiber diet has less than 10 grams of dietary fiber. Stop any fiber supplements you are taking, and avoid fiber-reinforced foods.

Hydrate

Drink water. Water is absorbed into soluble fibers to form a gel-like substance that slows digestion.

Get light exercise, including walking, as you are able

Exercise helps regulate the bowels and can be particularly useful for constipation. However, light exercise may also be helpful if you have diarrhea from too much fiber.

Reintroduce fiber gradually

Most American adults do not have enough fiber in their diet to reap the benefits. If you decide to introduce more fiber, it’s important to introduce it gradually to avoid diarrhea and GI upset. Try increasing your fiber by one or two grams per day.

Try an over-the-counter antidiarrheal medication

Imodium and Pepto-Bismol are two common over-the-counter medications that can treat diarrhea.

Read our full guide on treating diarrhea for more.

Frequently asked questions

Many other people have experienced diarrhea from too much fiber consumption, and they’ve asked questions like the ones below.

How long does diarrhea from too much fiber last?

Diarrhea from too much fiber can resolve the same day or within one or two days if you cut the fiber in your diet.

Can eating too much fiber with IBS cause diarrhea?

If you have irritable bowel syndrome (IBS), either diarrhea or constipation can result from fiber intake. It depends on the amount of fiber in your food and how your body reacts.

The take-home message about fiber and diarrhea

Dietary fiber is important for staying healthy. Consuming fiber lessens the risk of heart disease, stroke, diverticulitis, and colon cancer. Too much fiber, however, can cause diarrhea and may be an indication you should alter your diet.

General Medicine follows a strict editorial process, including using real experts to write our articles, vetted primary sources, fact-checking, a secondary medical review, and updates as necessary. This article was medically reviewed and fact checked by Dr. Adam Carewe, MD.

Sources

Dietary reference intakes (DRIs): Recommended dietary allowances and adequate intakes, total water and macronutrients. Institute of Medicine.

Gillman, M W, et al. “Protective effect of fruits and vegetables on development of stroke in men.” JAMA vol. 273,14 (1995): 1113-7. doi:10.1001l./jama.1995.03520380049034

Ioniță-Mîndrican, Corina-Bianca, et al. “Therapeutic Benefits and Dietary Restrictions of Fiber Intake: A State of the Art Review.” Nutrients vol. 14,13 2641. 26 Jun. 2022, doi:10.3390/nu14132641