On Nutrition

For many people suffering from irritable bowel syndrome (IBS), the low-FODMAP diet can feel like a miracle. If you were plagued with abdominal pain, cramping and bloating, along with diarrhea or constipation (or both) — and frequently afraid to leave the house because you might not be near a toilet when you urgently need one — you would know what I mean.

What is a FODMAP, you ask? FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These are types of carbohydrates that are highly fermentable by bacteria and other microbes in your large intestine, or colon. This is fine — even good — for most people, but if you have IBS, FODMAPs can trigger symptoms once they reach the colon. FODMAPs include fructose and lactose, the natural sugars found in fruit and dairy, respectively, as well as types of fiber found in wheat, rye, onions, garlic beans, some nuts and many vegetables. Polyols include the common artificial sweeteners sorbitol and xylitol.

Unfortunately, much like the gluten-free diet — which serves a genuine purpose for the small percentage of people diagnosed with celiac disease or non-celiac gluten/wheat sensitivity — the low-FODMAP diet is being co-opted for purposes it wasn’t designed for. And that’s no miracle.

IBS is a functional gastrointestinal disorder, which means it doesn’t damage the intestines (the good news), although its symptoms can significantly harm quality of life (the bad news). It affects about 12% of people in the U.S., and women are twice as likely as men to suffer from it. New cases usually happen before age 50, and having a family member with IBS or a history of stressful and traumatic events can increase risk.

The low-FODMAP diet can be attractive to individuals trying to self-diagnose their gastrointestinal symptoms — something that is never a good idea.

Many IBS symptoms overlap with symptoms of far more serious gastrointestinal conditions, including celiac disease, inflammatory bowel disease — which includes Crohn’s disease and ulcerative colitis — and less commonly, colon cancer. While there’s no test for IBS, getting a real diagnosis usually requires ruling out more serious problems that can be detected with testing and screening.


Because it restricts so many foods, some people have also been turning to the low-FODMAP diet for weight loss. Odd, because there’s only scant research showing that some people with IBS who follow the diet also lose a small amount of weight.

The low-FODMAP diet may also be appealing to individuals struggling with an eating disorder, either as a cover for their disorder — “I’m only avoiding these foods because I have IBS … really” — or because they truly think they have IBS. However, eating disorders often cause gastrointestinal distress all by themselves. Chronic food restriction, bingeing, purging, laxative abuse and excessive intake of carbonated beverages and artificially sweetened beverages, gum and foods can all disrupt normal digestion and cause gastrointestinal symptoms, such as the bloating and constipation commonly associated with IBS.

I talked with fellow dietitian Diana Reid, owner of The Global Dietitian, an international nutrition consultancy, about this issue. She agreed that this diet, which is so good for some, is definitely not good for all.

“The low-FODMAP diet has been shown to highly effective in relieving symptoms of IBS, both in published research and in my own clinical practice, however it is definitely not for everyone,” she said. “Individuals who are already following a restricted diet due to preexisting medical conditions, diagnosed nutritional deficiencies, and/or a long history of dieting or disordered eating, should not attempt this diet without thoughtful consideration and the close supervision of their medical team, including their doctor, gastroenterologist and dietitian.”

For someone who is at high risk of an eating disorder due to genetics and environment, undertaking an elimination diet — even when otherwise warranted — can be the tipping point.

I have one client who began working with me on recovery from orthorexia (an unhealthy obsession with eating “healthy”). She told me she had a possible diagnosis of IBS and had tried a low-FODMAP diet on her own, but stopped because she realized she liked the restrictiveness of it too much and feared it would lead her to a dark place. The good news is that as her diet has become less rigid — she had been a strict “clean eater” — her constipation and bloating have improved.


Here are three major reasons why you don’t want to follow the low-FODMAP diet if you don’t actually have IBS:

It’s restrictive. While the elimination phase of this diet is less restrictive than some elimination diets, it requires cutting out many healthy, nutritious foods. If it’s not planned well, it can be low in key nutrients and in fiber, specifically prebiotic fiber, the fiber that our beneficial gut bacteria like to eat.

It’s meant to be very temporary. When followed as intended for the treatment of IBS, the diet protocol begins with eliminating all high-FODMAP foods for a few weeks. If this successfully reduces symptoms, then these foods are reintroduced in a very structured, methodical way, while watching for any returning symptoms. The goal is to pinpoint which FODMAPs, in what amounts, trigger symptoms, so that the person with IBS can enjoy as varied a diet as possible while still managing their symptoms. I’ve had clients who felt so much better on the elimination phase that they just wanted to stay on it, which isn’t good for long-term health.

It’s hard to follow without help. I’ve had clients who thought they were following the elimination diet to the letter, and were mystified when they had a symptom flare up, only to find that they forgot that asparagus is high in FODMAPs, or because they didn’t realize that there was a lot of garlic in the salad dressing they had at a restaurant. Also, it’s easy to become too relaxed during the reintroduction phase, making it difficult to be sure which FODMAPs are responsible for any symptom flare-ups.