For years, the low-FODMAP diet has been one of the best-studied dietary strategies for irritable bowel syndrome (IBS). By temporarily reducing certain carbohydrates that are poorly absorbed and rapidly fermented in the gut, the diet can help reduce symptoms such as bloating, abdominal pain, and altered bowel habits. The American College of Gastroenterology recommends a limited trial of low-FODMAP for improving overall IBS symptoms, while systematic reviews and meta-analyses, including a recent umbrella review also support its short-term effectiveness.

But going low-FODMAP has drawbacks, too. It can be restrictive and difficult to maintain, and it wasn’t designed to remain a strict elimination diet forever. Contemporary low-FODMAP care generally progresses from restriction to food reintroduction and, finally, a personalized long-term diet plan. A review in The Lancet Gastroenterology & Hepatology also noted that restrictive whole-diet approaches can pose challenges related to cost, food availability, nutritional adequacy, and food-related quality of life.

That has researchers asking a different question: rather than giving everyone with IBS the same broad list of foods to restrict, could an IBS diet be tailored to each individual's biology?

What Is A Personalized Microbiome Diet?

A 2024 randomized controlled trial tested exactly that idea. Researchers assigned 121 adults with IBS to either a standard low-FODMAP diet or an individualized 6-week diet.

The personalized diet was not simply a customized version of a low-FODMAP diet. Each participant provided a stool sample for gut microbiome analysis. A machine-learning system used the person's bacterial profile to calculate an ‘IBS index.’ It then modelled small shifts in the microbiome predicted to lower that score. Those desired microbial changes were translated into nutritional targets, and ultimately into customized food recommendations for the individual.

To achieve each personalized diet plan, the researchers used a database that links nutrients and foods to their potential effects on specific microorganisms. Around 300 foods were then scored for each participant from 0 to 10. Foods scoring 0-3 were avoided, those scoring 4-7 were used to diversify the diet, and foods scoring 8-10 were prioritized. Dietitians then built menus primarily from foods scoring 4-10.

Did The Personalized IBS Diet Work Better Than Low-FODMAP?

Initially… not really. After six weeks, IBS Symptom Severity Scale (IBS-SSS) scores fell by about 113 points with the personalized diet and 100 points with low-FODMAP. Both represented substantial improvements, and the difference between groups was not statistically significant.

The more interesting result appeared later: in a 2026 follow-up to the original study, researchers assessed the participants again at 6 and 12 months, without further dietary intervention. At one year, 62.5% of those remaining in the personalized-diet group were still IBS-SSS responders, compared with 34.5% in the low-FODMAP group- an absolute difference of 28 percentage points.

In other words, the personalized diet did not work better at first, but it did appear to work longer. Average symptom improvement was also better maintained with the personalized diet, and the group showed a persistent increase in microbial diversity over the year.

Does This Mean It's Time To Ditch Low-FODMAP?

Not just yet. Only 69 participants completed the 12-month clinical follow-up, and the original trial was powered for its 6-week outcome rather than the long-term comparison. The personalized technology was also developed by ENBIOSIS, which sponsored the follow-up study, and several authors had financial ties to the company.

There is another important caveat: the comparison group did not receive ongoing FODMAP reintroduction and customization. That's significant, because modern low-FODMAP treatment is itself supposed to become personalized over time. In a separate 12-month study of people who completed restriction, reintroduction, and personalization, 67% reported adequate IBS symptom relief after one year.

Meanwhile, personalized microbiome diets aren’t the only low-FODMAP alternatives under investigation. A 2025 randomized trial found that a Mediterranean diet improved IBS symptoms compared with traditional dietary advice, and a recent systematic review and network meta-analysis encompassing 28 randomized trials found benefits across several different dietary strategies, including the simple reduction of dietary starch and sucrose.

The Bottom Line

Low-FODMAP remains an evidence-based IBS diet, and these studies don't make it obsolete. What they do suggest is that the future of IBS nutrition may be increasingly personalized.

Choosing foods according to an individual's microbiome is certainly an intriguing possibility. In this case, its short-term results were no better than a standard low-FODMAP plan, but the benefits appeared more durable over one year.

Larger, independent trials are needed before microbiome-guided diets become routine IBS care- but the research raises an important prospect: the next advance may not be another list of foods everyone should avoid, but a better way of figuring out which foods work for whom.