The most common adverse effects of dietary fibre are minor gastrointestinal symptoms. There have been a few reports of allergic reactions to psyllium. In rare cases, obstruction of the large or small intestine has occurred in people consuming wheat bran or bran cereal.

Beans, a good source of soluble fibre, also contain special sugars that are often poorly digested, leading to wind. 

People with scleroderma (systemic sclerosis) should consult a doctor before taking fibre supplements or eating high-fibre diets. Although a gradual introduction of fibre in the diet may improve bowel symptoms in some cases, there have been a few reports of people with scleroderma developing severe constipation and even bowel obstruction requiring hospitalisation after fibre supplementation.⁴