5 supplements that may make IBS worse
MDlinx Apr 25, 2025
Industry Buzz
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“[The] problem of probiotics is [that] the[y] are not controlled by any agency.” — Ashkan Farhadi, MD
When it comes to irritable bowel syndrome (IBS), not all supplements are created equal. While some studies suggest that certain supplements may play a role in IBS management, other supplements may make symptoms worse.
Patel NV. “Let Food Be Thy Medicine”: Diet and Supplements in Irritable Bowel Syndrome. Clinical and Experimental Gastroenterology. 2021;14:377–384.
MDLinx took a deep dive into some supplements that may not benefit individuals with IBS—or that might just be a waste of money.
It's IBS Awareness Month. Read all our latest coverage:
Cheap probiotics
Research suggests that some probiotics might be beneficial for individuals with IBS, while others may not make a difference.
Niu HL, Xiao JY. The efficacy and safety of probiotics in patients with irritable bowel syndrome: Evidence based on 35 randomized controlled trials. International Journal of Surgery. 2020;75:116–127.
“[The] problem of probiotics is [that] the[y] are not controlled by any agency. Basically, whatever [manufacturers] like to claim, they would, because that is considered a food supplement, and when it's a food they cannot verify whatever they claim is accurate," says Ashkan Farhadi, MD, a board-certified gastroenterologist and director of the Digestive Disease Center at MemorialCare Medical Group in Orange County, CA, and the author of “The Rhymes of Happiness: Weaving Science, Art and Poetry in the Pursuit of Happiness.”
For example, if a manufacturer says there are 10 billion bacteria in a probiotic, who knows if one of those bacteria is alive, and if any of those even get to the gut, even if they are alive in that capsule—no one really knows, Dr. Farhadi explains.
“We only have a few of them [probiotics] that are proven to be effective, particularly in IBS, and those are the most expensive ones. People usually go for the cheaper one, and I don't blame them, because they’re really pricey,” Dr. Farhadi adds.
Some fibre supplements
While some fibre supplements might be beneficial for people with IBS, certain supplements may worsen IBS symptoms.
Muir J. An Overview of Fiber and Fiber Supplements for Irritable Bowel Syndrome. Gastroenterology & Hepatology. 2019;15(7):387–389.
Some fibre supplements are highly fermented and may cause pain, discomfort, bloating, diarrhoea, and excessive gas. This can occur in patients with and without IBS.
For patients with IBS, fibre supplements that have high FODMAP content may not be suitable. High-FODMAP fibre supplements include wheat bran, fructooligosaccharides, and inulin-based products.
Calcium
While calcium supplements can benefit bone health, they can cause gastrointestinal (GI) upset in some individuals.
NIH. Calcium. September 14, 2023.
Calcium supplements can cause constipation, gas, and bloating in some people.
Iron
People with iron deficiency may need to take iron supplements. When taken at high doses, especially on an empty stomach, these supplements can cause a variety of GI symptoms.
NIH. Iron. August 17, 2023.
These symptoms include constipation, nausea, abdominal pain, diarrhoea, and vomiting.
The daily upper limit for iron from all sources—food, supplements, and drinks—is 45 milligrams for adults.
Vitamin C
The majority of people in the United States get enough vitamin C through their diet. But vitamin C supplements are available, and they can cause GI symptoms if taken at high doses.
NIH. Vitamin C. March 22, 2021.
Too much vitamin C can cause stomach cramps, nausea, and diarrhoea.
The daily upper limits for vitamin C from all sources—supplements, food, and drinks—is 2,000 milligrams for adults.
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