Irritable bowel syndrome (IBS) is a common gastrointestinal (GI) tract disorder that affects about 10-15% of the population worldwide.
The condition is characterized by abdominal discomfort and changes in bowel movements. People with IBS may experience constipation, diarrhea, or a mixture of both.
It is commonly believed that adding more fiber to your diet can help you manage IBS symptoms. But this isn’t always true.
In this post, we will talk about the role fiber plays in your digestive health and why a low-fiber diet might be good for IBS. So, let’s get right into it!
How much fiber do you normally need?
The recommended daily intake of fiber by the U.S Department of Agriculture (USDA) is:
- Adult women: 28 grams
- Adult men: 35 grams
However, the problem is that everyone’s needs are different, especially if you're someone who suffers from a digestive disorder like IBS, where typical recommendations don’t always apply.
Some people need more fiber while others require less. This is especially true as we grow old and need lower amounts of fiber.
Is a low-fiber diet good for IBS?
Since constipation is a common symptom of IBS, increasing fiber intake seems like a logical dietary recommendation.
The International Foundation For Gastrointestinal Disorders (IFFGD) suggests that adding fiber may help increase bowel function, especially in individuals with IBS-C (the constipation-predominant form of the condition).
However, fiber tolerance in IBS can be variable. While the foods that trigger IBS may vary depending on the individual, fibrous foods are found to be one of the most common food triggers for the condition.
If you’ve tried a high-fiber diet and feel like it didn’t help your IBS or ended up making it worse, this may be why:
- The normal bacteria of your gut ferment fiber. Due to this fermentation, gases are released as a byproduct, leading to bloating, cramps, abdominal discomfort, and distension.
- You may also have a condition known as Small Intestinal Bacterial Overgrowth (SIBO), which occurs when you have an abnormal overgrowth of bacteria in your small intestines. The presence of an abnormally large number of bacteria in the small intestines can cause digestive distress when fermenting fiber.
Some studies have suggested that during a flare-up of IBS, a low-fiber diet (intake of ~10g of fiber/day) can help manage symptoms like diarrhea, especially in people with IBS-D (the diarrhea-predominant form) and IBS-M (mixed type IBS with alternating diarrhea and constipation).
This means eating more cooked foods, reducing intake of bran-based grains, bread, cereals, and eating less raw fruits and veggies is helpful for IBS.
Another publication showed that adding too much fiber to the diet for someone with IBS-C can cause significant abdominal distention, gas, and bloating.
In this study, when fiber intake was stopped for a short period of time and the candidates were reintroduced to a low-fiber diet, symptoms of IBS improved significantly.
This means a low-fiber diet can be potentially beneficial for IBS-C, IBS-D, and IBS-M. However, just like with every dietary change you make, make sure to discuss the low-fiber diet with your healthcare provider before trying it.
Which type of fiber is good for IBS?
Remember, a low-fiber diet has been shown to be beneficial for IBS, not a no-fiber diet, so you’ll need at least some of it in your diet.
There are various types of fiber out there. Some are soluble, while others are insoluble; some are fermentable while others aren’t. Understanding these key differences is vital to helping individuals with IBS find a diet that works the best for them.
- Soluble fiber, as the name suggests, is soluble in water. It creates a gel-like substance that helps make bowel movements smooth and soft, helping with diarrhea.
- On the other hand, insoluble fiber doesn’t dissolve in water, meaning it is mainly left intact and aids in adding bulk to stool. It makes your gut contract more, alleviating constipation.
- Plant-based foods often contain both insoluble and soluble fiber, but some foods can contain more of one type over the other.
- Foods rich in soluble fiber include barley, peas, oats, lentils, citrus fruits, apples, and Psyllium (a fiber supplement).
- Foods high in insoluble fiber include wheat bran, whole wheat flour, beans, nuts, root vegetables like potatoes, and veggies belonging to the cabbage family like cauliflower.
- The important thing to remember is that foods high in insoluble fiber are generally more likely to cause abdominal pain and bloating.
What are some of the best low-fiber diets for IBS?
The three most popular low-fiber diets for IBS include:
- Low-FODMAP diet
- Paleo diet
- SIBO diet
So which one is best? The low-FODMAP diet because we have plenty of evidence that it helps with IBS. If you’re going to try only one of these diets for IBS, make sure it’s the low-FODMAP one.
And as always, it’s recommended for people with IBS to keep a food diary to track how much fiber and which foods are well tolerated by your digestive system.
The Low-FODMAP Diet
FODMAP is an abbreviation for fermentable, oligo-, di-, monosaccharides, and polyols. A low-FODMAP diet has been commonly used for digestive conditions like Inflammatory Bowel Disease (IBD) and SIBO. And it is now being increasingly recommended as first-line therapy for controlling IBS as well.
This diet restricts the amount of fermentable carbohydrate intake, meaning less fermentation by your gut bacteria, less water in the digestive system, and reduced risk of stomach distension, diarrhea, gas, and constipation, resulting in a happy belly. Many studies have proven the efficacy of low-FODMAP diets for IBS.
This diet involves eating foods that were available to our ancestors during the Palaeolithic age.
It typically consists of lean meats, fish, veggies, fruits, and nuts while restricting legumes, dairy, sugar, grains, processed foods, and alcohol. By restricting legumes and grains, the Paleo diet is considered to be a natural, low-fiber diet.
SIBO-specific diet is a combination of the low-FODMAP and specific carbohydrate diet (SCD). This is more restrictive than other diets and is usually recommended only when alternative diets aren’t able to control your IBS.
Medically Reviewed by Onikepe Adegbola, MD PhD