Is a low FODMAP diet effective for IBS-M in adults?

Question

Hello doctor,

I am 33 and have had years of gut issues, alternating diarrhea and constipation, bloating, urgency, and incomplete bowel movements. I recently had a colonoscopy that came back normal. My GI now suspects IBS-M. I tried peppermint oil and fiber, but symptoms still bother me daily. My concerns are as follows:

Should I consider medications like Linaclotide or Rifaximin?
Also, my stool calprotectin was 37, and CRP was normal. How do we confidently rule out IBD?
Can food intolerance tests help, or are they a waste?
Is low FODMAP a long-term fix or just short-term relief?
What is the best management plan?

Kindly help.

Answer 1

Hello,

Welcome to icliniq.com.

I read your query and can understand your concern.

Given your normal colonoscopy, normal CRP (C-reactive protein), and calprotectin of 37, it does support your doctor’s suspicion of IBS-M (mixed-type irritable bowel syndrome) rather than inflammatory bowel disease (IBD), which typically shows higher inflammation markers and abnormal endoscopy findings. Here are my suggestions for your concerns-

Rifaximin (for bloating and diarrhea) and Linaclotide (for constipation-predominant or mixed IBS) are both evidence-based options that can be considered if fiber and peppermint oil have not provided sufficient relief. Depending on which symptoms dominate, these are typically used under the guidance of a gastroenterologist.
Food intolerance tests like IgG (immunoglobulin-G)-based panels are not scientifically reliable and often misleading. However, a structured elimination diet like low FODMAP (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols), which reduces fermentable sugars known to trigger IBS symptoms, has solid evidence.
It is meant to be followed short-term (typically four to six weeks), after which foods are gradually reintroduced with the help of a trained dietitian to identify your triggers. Long-term use without reintroduction is not recommended due to nutritional risks.
The best management plan usually involves a combination of dietary adjustments (like low FODMAP), stress and gut-brain axis support such as CBT (cognitive behavioral therapy) or gut-directed hypnotherapy, and medications tailored to your symptom pattern.
Keeping a symptom and food journal, ensuring regular physical activity, and avoiding over-restriction are also key to long-term success.

I hope I have answered your questions.

Let me know if I can assist you further.

Regards.