The Low-FODMAP Diet, Explained
When Tamara Duker Freuman learned about the low-FODMAP diet a little over a decade ago, she began using it with her patients suffering from irritable bowel syndrome. It was “a game changer,” said the registered dietitian.
In an overview of studies published in 2020, researchers estimate that around 52 to 86 percent of the patients with IBS who followed the diet had significant improvements in symptoms such as bloating, pain and diarrhea.
But the diet — which temporarily eliminates foods rich in certain types of carbohydrates known to trigger IBS symptoms — isn’t for everyone, experts say. Here’s how it works and how to see if it’s right for you.
What are FODMAPs?
FODMAPs are certain types of carbohydrates — called fermentable oligosaccharides, disaccharides, monosaccharides and polyols, as the acronym suggests — that often cannot be fully digested or absorbed in the small intestine and are instead fermented by microbes in the colon. This can cause gastrointestinal upset.
The list of foods that are high in FODMAPs is long: it contains dairy products such as milk, yogurt and ice cream; fruits such as apples, mangoes, and watermelon; vegetables such as onions, garlic and asparagus; wheat-based pasta and bread; legumes such as 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 problems, FODMAPs typically cause nothing but a little more flatulence, says 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 such as pain, bloating, and diarrhea.
Who can – and who might not – benefit from the diet?
Because FODMAPs are found in so many foods, the low-FODMAP diet is very restrictive, which is one of the reasons experts advise caution and careful planning before embarking on the diet.
Good candidates include IBS patients who regularly consume high-FODMAP foods and find 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 also have to be people who are open to trying a complex, new diet, she said.
The low-FODMAP diet may also help ease symptoms for people with other gastrointestinal conditions, such as inflammatory bowel disease And functional dyspepsia (chronic stomach upset and pain), and people with a overgrowth of bacteria in the small intestinesaid Dr. Chey.
However, the diet is not suitable for people with symptoms of disordered eating, which is common in people with gastrointestinal conditions, said Dr. Chang.
Because the low-FODMAP diet is so restrictive, it is may exacerbate an existing eating disorderwhich can be life-threatening in some cases, said Beth Rosen, a registered dietitian in New York.
How does the diet work?
The low-FODMAP diet involves three phases, and it’s best to work through them with the help of a trained dietitian, Ms. Rosen said.
In the first phase, called the elimination phase, you will 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 beneficial), she said. Popular foods to eat during this phase include rice, quinoa, eggs, hard cheeses, most meats and fish, and many fruits and vegetables such as citrus fruits, strawberries, carrots, and broccoli.
If your symptoms do not noticeably improve during this phase, you should discontinue the diet; FODMAPs probably aren’t a problem for you, Dr. Chang said.
When you start to feel better, it’s time for the reintroduction phase, in which you add high-FODMAP foods one at a time, in increasing amounts over several days, Ms. Freuman said. The goal is to identify which FODMAPs, and in what amounts, lead to symptoms.
The final phase is the personalization phase, where you add all FODMAP-rich foods in amounts you can tolerate and create a balanced diet that is sustainable for the long haul.
“It’s a learning diet,” Ms. Freuman said. It’s about “giving you the knowledge to really understand your triggers.”
After identifying the most bothersome foods, you might also consider taking an over-the-counter enzyme supplement — such as Lactaid, Beano or Fodzyme, depending on which types of FODMAPs give you problems — to help you tolerate them, Ms Freuman said . .
If the classic low-FODMAP diet isn’t right or realistic for you, a “soft” FODMAP diet may be a better fit, Ms Rosen said, especially if you’re malnourished, pregnant, have other dietary restrictions or a history of disordered eating, or if you’re 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; after that you will continue with the reintroduction and personalization phases as usual.
What are some other disadvantages of the diet?
A common pitfall of the diet is that people get stuck in the first phase, says Ms. Freuman. “They get so attached to the strictest form of the diet and they’re terrified to eat anything on the diet.”
This can affect quality of life — people can’t enjoy dining out, for example — or lead to malnutrition and disordered eating, she said.
A registered dietitian can help you follow the diet correctly and safely, especially during the tricky reintroduction phase, said Dr. Chey. 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 dietitianshe added.
Keep in mind that the low-FODMAP diet is just one approach to managing IBS, Ms. Freuman said. Other people may find relief by, for example, adjusting their fiber intake or eating smaller meals and avoiding fatty or spicy foods.