- The low-FODMAP diet is used to manage the symptoms of irritable bowel syndrome (IBS) and other gastrointestinal (GI) issues.
- FODMAP is an acronym that stands for “fermentable, oligosaccharides, disaccharides, monosaccharide, and polyols.”
- Wheat, onions, garlic, and apples are common high-FODMAP foods.
If you’ve heard about irritable bowel syndrome (IBS), a common disorder of the large intestine, chances are you’ve heard of something called the low-FODMAP diet. The low-FODMAP diet is not a weight-loss diet, but rather an elimination diet meant to treat the symptoms of IBS and other gastrointestinal (GI) issues.
FODMAPs are poorly absorbed, short-chain carbohydrates
According to Monash University, FODMAP is an acronym that stands for “fermentable, oligosaccharides, disaccharides, monosaccharide, and polyols.”
“The low-FODMAP diet focuses on five different sugar and fiber categories that tend to cause digestive upset for patients with functional gut disorders,” Nancee Jaffe, MS, a registered dietitian at the UCLA Vatche and Tamar Manoukian Division of Digestive Diseases, told INSIDER.
Foods on the diet are referred to as either low in FODMAPs or high in FODMAPs.
The low-FODMAP diet differs from regular diets in that it has three distinct phases
The low-FODMAP diet is generally approached in three parts: elimination, reintroduction, and personalization. In the elimination phase, you eat low-FODMAP foods exclusively for two to six weeks to see if your GI symptoms subside.
Next, you enter the reintroduction phase, which is where you try small amounts of higher-FODMAP foods to see what you can tolerate.
You are free to incorporate any high-FODMAP foods you are able to tolerate back into your diet while in the personalization phase.
If you’re in the elimination phase of the low-FODMAP diet, here’s a common list of high-FODMAP foods you should avoid.
High-lactose foods, like ice cream, are often high in FODMAPs
You’ll want to avoid some high-lactose foods during the elimination phase because too much lactose creates gas and pulls water into the gut.
“Some patients will experience this as bloating, others will experience it as distention, some may even experience it as pain or discomfort, and then, unfortunately, that water has to go somewhere. So, if it’s not reabsorbed, it will end up in the colon and that can then lead to diarrhea,” Jaffe said.
Milk, ice cream, yogurt, and cottage cheese are examples of high-lactose foods that should be avoided.
Foods with excess fructose, like apples, are considered high-FODMAP foods
According to Jaffe, “fructose actually means ‘fruit sugar’” and, if consumed in high amounts, it will also pull water into the gut.
“What’s happening is these sugars are very, very attractive to water,” Jaffe explained.
According to Jaffe, when a person has trouble absorbing fructose, the undigested fructose is then carried to the colon. This excess fructose then attracts water which accumulates in places like the small bowel. This excess water retention can distend the small and large intestine and lead to digestive symptoms such as bloating and gas.
Apples, boysenberries, figs, pears, watermelon, honey, and agave are examples of foods with high fructose.
Foods that are high in fructans and galactooligosaccharide (GOS), such as wheat, are high in FODMAPs
This category, namely oligosaccharides, includes two types of FODMAPs: fructans and GOS. Both fructans and GOS affect the gut similarly in that they both can produce gas.
Fructans are “chains of fructose sugars joined together” that are not absorbed by the gut and GOS are “chains of galactose sugars joined together” that evoke prebiotic activity in your gut. The chains of both sugars end with glucose.
Jaffe explained that our natural gut bacteria “eat away at the fructans and the GOS, and this can create gas, bloating, and cramping.”
According to Jaffe, it’s not that people needing to follow the low-FODMAP diet necessarily create more gas than a healthy control who doesn’t have digestive issues; Rather, it’s that they experience the gas as pain or a sensation of discomfort.
Dried fruits, nectarines, garlic, onions, wheat, barley, rye, black beans, kidney beans, pistachios, and cashews are examples of foods that are high in fructans or GOS.
Foods that are high in polyols, like cauliflower, are considered high-FODMAP foods
Similar to eating foods from the high-lactose and excess-fructose categories, eating foods from the polyol category can cause a person to retain excess water in their small bowel.
According to Jaffe, people, even those without GI issues, have trouble digesting polyols, which are “hydrogenated carbohydrates used as sugar replacers.” In fact, a 1987 study evaluating the intestinal absorption of lactitol and sorbitol, two types of polyols, in healthy people showed that it was not well absorbed by the small intestine.
Polyols cause more symptoms for those with sensitive GI systems than for someone who isn’t as sensitive.
Fruits like apples, pears, and peaches and vegetables like cauliflower, mushrooms, and sugar substitutes like lactitol, and sorbitol are examples of foods with high polyols.
Some low-FODMAP foods, like avocados, become high in FODMAPs when eaten in large quantities
Some foods that are low in FODMAPs actually become high in FODMAPs if eaten in large quantities.
For example, a half a cup of sweet potato is low fodmap, but anything more than a half a cup enters into high-FODMAP territory. One-eighth of an avocado is fine, but anything more is considered high in FODMAPs.
“The whole goal of the low-FODMAP diet is that in each sitting we want patients to get no more than 0.5 total grams of FODMAPs,” said Jaffe.
For a comprehensive list of high-FODMAP foods, check out University of Michigan’s Division of Gastroenterology & Hepatology’s high-FODMAP checklist. If you still aren’t sure if a food is high or low in FODMAPs, Monash University developed an app that frequently tests foods for their FODMAP levels.