Does fiber help with bloating?

What trials of whole diets found

Two feeding trials gave people set diets and then asked about bloating:

• DASH-Sodium trial. 412 adults ate a high-fiber diet (32 g a day) or a low-fiber diet (11 g a day). The high-fiber diet raised the risk of bloating by 41% (risk ratio 1.41). The effect was greater in men.^[1]
• OmniHeart trial. 164 adults ate three high-fiber diets (about 30 g per 2,100 kcal) for 6 weeks each. Bloating was reported by 18% on their own diet, and by 24%, 33% and 30% on the three diets. The rise was not significant for the carbohydrate-rich diet.^[5]

These diets changed more than fiber, so the trials cannot show that fiber alone caused all of the rise.^[1][5] In both, the type of diet changed the result: less salt or more carbohydrate in place of protein meant less bloating.^[1][5]

What trials of fiber supplements found

In people with chronic constipation, a 2022 review of 16 trials found more gas with fiber than with control treatment.^[6]

In people with irritable bowel syndrome (IBS), a long-lasting bowel disorder, or similar disorders, results depend on the fiber:^[7][8]

• Prebiotics. A 2019 review of 11 trials with 729 people found no overall change in bloating and gas. Inulin-type fructans made gas worse, and doses of 6 g a day or less made it better.^[7]
• Other fibers. A 2026 review of 10 trials found that pectin improved bloating, a mix of sugarcane fiber and resistant starch improved gas, and agave fructans made gas worse. The trials were small and short, and most had some risk of bias.^[8]
• Soy fiber in food. In 52 young Japanese women with constipation, soup with 4.1 g of okara fiber per meal for 2 weeks was followed by less bloating, which was not seen with placebo soup.^[9]

A PubMed search for this page found no review of fiber for bloating alone in people without a bowel disorder. These reviews do not settle the question for healthy people.^[8][7]

Irritable bowel syndrome

Bloating is one of the symptoms that doctors look for in IBS.^[10] A 2014 review of 14 trials with 906 people found that soluble fiber improved overall symptoms: about 7 people had to be treated for one to benefit. Bran had no clear effect.^[2] In a trial of 275 people, 57% of those on 10 g of psyllium a day had adequate relief in the first month, against 35% on placebo.^[3]

These results measure overall symptoms, not bloating alone.^[2][3] In a 2020 analysis of older IBS treatments, peppermint oil ranked first for overall symptoms, with no significant differences between active treatments.^[11]

What guidelines say

• NICE (UK). Review fiber intake in IBS and usually reduce it. If more fiber is advised, it should be soluble, such as ispaghula or oats. People with wind and bloating may find oats and up to 1 tablespoon of linseeds a day helpful.^[10]
• NHS (UK). Foods high in soluble fiber, such as oats or linseed, are suggested for bloating when a person is constipated.^[4]
• American Gastroenterological Association. The 15 advice statements of this expert review do not name fiber. Medicines for constipation should be considered for bloating when constipation is present, and a dietitian should preferably monitor a low FODMAP diet.^[12]

What else was tested

A low FODMAP diet limits certain fermentable carbohydrates. In 23 trials in IBS, it improved bloating more than a usual diet.^[13] Inulin belongs to this group of carbohydrates.^[14] NICE says this advice should come only from a health professional with expertise in diet.^[10]

When to see a doctor

The NHS says to see a GP for regular bloating, bloating that stays after a change in diet, or bloating with weight loss or blood in the stool.^[4]