What Is the Low-FODMAP Diet, and What Can You Eat on It?

There are so many eating practices today that focus on lowering carbs, so if you’ve heard the “low-FODMAP” diet included as part of that conversation you may have justifiably lumped it in as another form of paleo, keto, or low-carb eating. But it’s not the same at all. In fact, it is far from these weight-loss-focused diets, and it’s centered around something called FODMAPs. So what are FODMAPs? And what is a low-FODMAP diet?

Here is what the low-FODMAP diet is, why some people try it, and what you can eat while on it.

FODMAPs are specific kinds of carbs — so a low-FODMAP diet is low in some kinds of carbs. FODMAP is an acronym that stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols. It’s a mouthful, but all you need to know is that these are carbohydrates that can’t be broken down by digestive enzymes. Instead, they get fermented by good bacteria in the gut. This fermentation process draws water into the large intestine and produces gas.

Most people have no problem eating foods with FODMAPs, other than possibly getting a little gassy if they eat a large amount. However, for individuals who are sensitive to FODMAPs, the fermentation process can wreak havoc on the digestive system, triggering symptoms like abdominal pain, bloating, excessive or painful gas, diarrhea or even constipation. 

If you suffer from any of the above symptoms or have been diagnosed with irritable bowel syndrome, your doctor may recommend you try a low-FODMAP diet. The diet is designed to keep the fermentable carbs that are triggering digestive issues at low levels. Initially, it’s more of an elimination protocol, where all FODMAPs are cut out. Then, foods are slowly added back individually in an attempt to determine which ones (if any) are triggering the GI distress.

Once this is determined, you must avoid those foods, but can usually resume eating the others. Note that having trouble with FODMAPs is not like having a food allergy, where all traces of the allergen have to be avoided. In fact, it’s impossible to completely avoid all FODMAPs. Instead, the long-term goal is to keep the particular FODMAPs that have been identified as irritants at low levels.

One woman’s story of a low-FODMAP diet: Why Going on a Low-FODMAP Diet Has Given Me the Ultimate Food Freedom

FODMAPs aren’t an issue for most people, but they do tend to be an issue for those with Irritable Bowel Syndrome (IBS).  Identifying which FODMAPs are problematic for those with IBS can drastically improve symptoms and quality of life for about 75% of those individuals. However, not everyone with IBS always sees improvements. And it’s important to note that you don’t necessarily have to have IBS to potentially have a FODMAP sensitivity that’s triggering digestive issues.

The hard part about FODMAPs is that it’s not obvious which foods are high or low in them. FODMAP types and amounts vary among foods, even those in the same food group.  Here’s a breakdown of common foods where they are found in high levels.  

• Oligosaccharides: Foods that are high in these include wheat and rye; most all beans and legumes (such as chickpeas, kidney beans, lentils, and soy); cashews and pistachios; and some vegetables such as onions, garlic, asparagus, and many in the cruciferous family (like broccoli, Brussels, cabbage, and cauliflower). 
• Disaccharides: Foods that are high in these are those that contain lactose, the natural sugar found in dairy. This includes milk, yogurt, soft cheeses, sour cream, and ice cream. 
• Monosaccharides: Foods that are high in these are those that contain fructose. So this means avoiding some (but not all) fruits, such as apples, pears, peaches, cherries, and watermelon. High levels of fructose are also found in sweeteners like honey, agave nectar, and foods with high-fructose corn syrup (as you might expect). 
• Polyols: Foods high in these are certain fruits and vegetables such as blackberries and mushrooms, as well sorbitol which is a low-calorie sweetener used frequently in gum and candy. 

The good news is that there are also a lot of foods that contain very low amounts of FODMAPs. Here’s a list of foods that are considered to be low in FODMAPs. 

• Grains: Rice, oats, quinoa, corn and polenta, millet, buckwheat, arrowroot, spelt 
• Vegetables: Spinach, tomato, zucchini, bell peppers, carrots, green beans, potatoes, lettuce, turnips, celery, squash
• Fruits: Bananas, blueberries, strawberries, oranges and most citrus fruits, pineapple, cantaloupe, honeydew, grapes, kiwifruit 
• Nuts & Seeds: Walnuts, almonds, pine nuts, pecans, peanuts, pepitas, sesame seeds
• Dairy:  Hard cheeses, lactose-free milk and other lactose-free dairy products, plant-based milks and yogurts

There appears to be little to no benefit to following the diet if you don’t have FODMAP sensitivities, and fermentable carbohydrates can play a beneficial role in gut health. But those who have been diagnosed with IBS may want to talk to their doctor and consider a low FODMAP diet, as well as those who have digestive issues that they haven’t been able to find a cause for.

The process of identifying problematic FODMAPs takes six to eight weeks, so it’s recommended one work with a registered dietitian during the initial elimination and testing to accurately identify sensitivities and then to get help creating a long-term eating approach. 

More information on FODMAPs or a low FODMAP diet can be found at Monash University or the American College of Gastroenterology. 

Have you ever tried a low FODMAP diet? What was your experience? Tell us in the comments, below!

Carolyn Williams, PhD, RD. Carolyn Williams is a 2017 James Beard award-winning dietitian who has contributed to sites such as Cooking Light, EatingWell, Real Simple, Parents, Health, AllRecipes and Prevention. She has written three cookbooks, including Meals That Heal: 100+ Everyday Anti-Inflammatory Recipes in 30 Minutes or Less. You can find more about her on her own site as well as follow on her Instagram and Facebook.