On the left, an assortment of high-Fodmap foods that can cause gas — and in people with IBS bloating, pain and diarrhoea. On the right, low-Fodmap foods that are easier to digest and less likely to cause stomach issues. Photo / Liz Clayman, The New York Times
On the left, an assortment of high-Fodmap foods that can cause gas — and in people with IBS bloating, pain and diarrhoea. On the right, low-Fodmap foods that are easier to digest and less likely to cause stomach issues. Photo / Liz Clayman, The New York Times
This sweeping diet can relieve symptoms of IBS, but it isn’t right for everyone, experts warn.
When Tamara Duker Freuman learned about the low-Fodmap diet just over a decade ago, she started using it with her patients who were suffering from irritable bowel syndrome. It was “a game changer,” theregistered dietitian said.
In one review of studies published in 2020, for instance, researchers estimated that between 52 per cent and 86 per cent of patients with IBS who followed the diet had significant improvements in symptoms such as bloating, pain and diarrhoea.
But the diet — which temporarily eliminates foods that are high in certain types of carbohydrates known to cause IBS symptoms — isn’t appropriate for everyone, experts say. Here’s how it works, and how to tell if it’s right for you.
Fodmaps are certain types of carbohydrates — called fermentable oligosaccharides, disaccharides, monosaccharides and polyols, as the acronym suggests — that often can’t be fully digested or absorbed in the small intestine and are instead fermented by microbes in the colon. This can cause gastrointestinal distress.
The list of foods containing high levels of Fodmaps is long: It includes dairy products such as milk, yoghurt and ice cream; fruits such as apples, mangoes and watermelon; vegetables including onions, garlic and asparagus; wheat-based pastas and breads; legumes including beans and lentils; nuts such as cashews and pistachios; and sweeteners such as honey, high-fructose corn syrup and low-calorie sweeteners.
If you don’t have digestive issues, Fodmaps typically don’t “cause anything except a bit more flatulence,” said Dr William Chey, a professor of gastroenterology and nutritional sciences at Michigan Medicine.
But if you have IBS or certain other gastrointestinal conditions, they can cause symptoms including pain, bloating and diarrhoea.
On the low-Fodmap diet, you’ll need to avoid these kinds of foods - but only temporarily. Photo / Liz Clayman, The New York Times
Who might - and might not - benefit from the diet?
Because Fodmaps are found in so many foods, the low-Fodmap diet is very restrictive, which is one reason experts advise caution and suggest careful planning before embarking on it.
Good candidates include IBS patients who regularly consume high-Fodmap foods and who notice that their symptoms worsen after meals, said Dr Lin Chang, a gastroenterologist and professor of medicine at the David Geffen School of Medicine at the University of California, Los Angeles. They should also be people who are open to trying a complex, new diet, she said.
The low-Fodmap diet may also help soothe the symptoms for those with other gastrointestinal conditions such as inflammatory bowel disease and functional dyspepsia (chronic stomach discomfort and pain), and those with an overgrowth of bacteria in the small intestine, Chey said.
The diet is not a good fit, however, for people who have symptoms of disordered eating, which can be common among those with GI conditions, Chang said.
Because the low-Fodmap diet is so restrictive, it can worsen an existing eating disorder, which may be life threatening in some cases, said Beth Rosen, a registered dietitian in New York.
How does the diet work?
The low-Fodmap diet includes three phases, and it’s best to navigate them with the help of a trained dietitian, Rosen said.
In the first phase, called the elimination phase, you’ll replace all high-Fodmap foods with low-Fodmap foods for two to six weeks (two weeks is usually long enough to see if the diet is helpful), she said. Popular foods you can eat in this phase include rice, quinoa, eggs, hard cheeses, most types of meat and fish, and many fruits and vegetables such as citrus fruits, strawberries, carrots and broccoli.
If your symptoms don’t noticeably improve during this phase, you should stop the diet; Fodmaps are probably not a problem for you, Chang said.
If you do start to feel better, it’s time for the reintroduction phase, during which you add back foods high in Fodmaps one at a time, in increasing amounts over several days, Freuman said. The goal is to identify which Fodmaps, and in what amounts, lead to symptoms.
The final phase is the personalisation phase, during which you add back any high-Fodmap foods in amounts you can tolerate and create a balanced diet sustainable for the long term.
“It’s a learning diet,” Freuman said. It’s “about empowering you with the knowledge to really understand your triggers.”
After identifying the most bothersome foods, you can also consider taking an over-the-counter enzyme supplement — such as Lactaid, Beano or Fodzyme, depending on which types of Fodmaps are giving you trouble — to help you tolerate them, Freuman said.
If the classic low-Fodmap diet is not appropriate or realistic for you, a “gentle” Fodmap diet may be a better fit, Rosen said, especially if you’re malnourished, pregnant, have other dietary restrictions or a history of disordered eating, or if you are under 18 or an older adult.
For this version of the diet, the first phase involves eliminating a smaller group of foods that are most often problematic, such as wheat, onions, garlic, beans, milk and certain fruits; then you move on to the reintroduction and personalisation phases as usual.
Plan your meals around foods like these while you’re on the low-Fodmap diet. Photo / Liz Clayman, The New York Times
What are some other downsides of the diet?
A common pitfall of the diet is that people become stuck in the first phase, Freuman said. “They become so attached to the strictest form of the diet, and they’re terrified to eat anything off of the diet.”
This can affect quality of life — people are unable to enjoy eating out, for instance — or lead to malnutrition and disordered eating, she said.
A registered dietitian can help you follow the diet correctly and safely, particularly during the tricky reintroduction phase, Chey said. But there are also many evidence-based resources available to help you navigate the diet on your own, including a smartphone app from Monash University in Australia and books written by registered dietitians, he added.
Keep in mind that the low-Fodmap diet is just one approach to managing IBS, Freuman said. Other people may find relief by adjusting fibre intake, for example, or eating smaller meals and avoiding fatty or spicy foods.
