This restrictive elimination diet isn't meant to be sustained long-term. Learn how to get started, what foods are allowed, what foods you should watch out for, and why it may be beneficial for you.

Christine Byrne

Pictured recipe: Low-Carb Blueberry Cobbler

Anyone with irritable bowel syndrome (IBS) or other digestive issues has likely read up on the low-FODMAP diet, be it at the recommendation of a doctor or dietitian, or just a Google search. If you're lucky enough not to fall into this camp, you may have seen the diet mentioned on Instagram, or heard about it from a friend. But there's a lot of confusion and misinformation about what the low-FODMAP diet is, why it exists and who can benefit from it. Here we dive into what FODMAPs are, what foods you can eat on a low-FODMAP diet and what foods you should limit or avoid during the elimination phase.

FODMAPs are a group of carbohydrates that are especially hard to digest.

Literally, FODMAPs are fermentable oligosaccharides, disaccharides, monosaccharides and polyols, "a group of commonly malabsorbed carbohydrates (sugars and fibers) that have been shown to trigger symptoms in individuals with irritable bowel syndrome (IBS)," says Kate Scarlata, R.D.N., L.D.N., author of The Low-FODMAP Diet Step by Step.

In layman's terms, FODMAPs are more difficult for the digestive system to break down and absorb, which isn't a problem for most people but can cause serious discomfort for people with IBS, and for people with certain forms of inflammatory bowel syndrome (IBD) like Crohn's disease and ulcerative colitis.

A low-FODMAP diet is only meant for people with IBS, so it's important to get a diagnosis.

"We know that the low-FODMAP diet helps the majority of IBS sufferers, but many individuals with IBD such as Crohn's and ulcerative colitis are prone to IBS symptoms as well, and the low-FODMAP diet has been shown to help manage symptoms in these individuals too," Scarlata says.

"Common symptoms of IBS include abdominal pain, gas, bloating, diarrhea and constipation, that occur at least one day a week for at least three months. If you suspect you have IBS, visit with your primary care doctor to discuss your symptoms and get a diagnosis," Scarlata says. A doctor can help design a treatment plan, and can diagnose or rule out conditions that may present with similar symptoms, such as celiac disease.

The diet is a nutrition therapy tool used to identify foods that trigger symptoms of IBS, such as stomach pain, constipation, diarrhea and severe bloating.

The diet consists of three phases, and should be done under the supervision of a dietitian. First is the elimination phase, during which high-FODMAP foods are completely eliminated. This phase typically lasts two to six weeks, depending on how a person responds to the elimination. If all IBS symptoms disappear within the first two weeks, the supervising dietitian may recommend moving onto the next phase; if symptoms are slower to disappear, the elimination phase may last longer.

The second phase is a reintroduction phase. "FODMAPs are systematically added back into the diet to identify which FODMAPs trigger symptoms," explains Scarlata. Typically, you'll reintroduce a single high-FODMAP food for three days to see how you react, then eliminate it again and move on to another high-FODMAP food. This is when it's especially crucial to work with a dietitian, who will guide you through reintroduction and help monitor your reaction to different foods.

After the reintroduction phase is the personalization phase. In this phase, you add back high-FODMAP foods that didn't trigger symptoms and monitor how you feel. This phase of the diet is meant to be sustained long-term, so it's important that you reintroduce as many foods as possible, both to make the diet sustainable and to protect against possible nutrient deficiencies that might result from being overly restrictive. Because this phase looks different for everyone-it's about personalization!-there's no official list of foods that you can and can't eat.

When people talk about a low-FODMAP diet, they're usually talking about the elimination phase. The personalization phase isn't necessarily a low-FODMAP diet, since you reintroduce all the high-FODMAP foods that don't cause problems.

During elimination, the list of common foods to cut out includes:

The elimination phase is incredibly restrictive. That's why it's only recommended for people with IBS or IBD and should be done under supervision and guidance from a registered dietitian. The foods listed below are high in FODMAPs and would be cut out during the initial, very strict elimination phase.

Beans and legumes:

Black beans

Borlotti beans

Fava beans

Kidney beans

Navy beans

Split peas

Soybeans (mature)

Dairy:

Cottage cheese

Cow's milk

Goat's milk

Ice cream

Sheep's milk

Ricotta cheese

Yogurt

Fruits:

Apples

Apricots

Bananas (ripe)

Blackberries

Cherries

Currants

Dates

Dried fruits and fruit juice concentrate

Grapefruit

Mangoes

Nectarines

Peaches

Pears

Plums

Prunes

Watermelon

Grains:

Barley

Rye

Wheat

Nuts:

Cashews

Pistachios

Sweeteners:

Agave nectar

High-fructose corn syrup

Isomalt

Maltitol

Mannitol

Sorbitol

Xylitol

Vegetables:

Artichokes

Asparagus

Cauliflower

Garlic

Leeks

Mushrooms

Onions

Scallions

Snow peas

As you can see, most of these are healthful, nutrient-dense foods that should not be limited long-term unless they cause IBS symptoms for you.

Foods you can eat on a low-FODMAP diet

During the elimination phase, you can eat certain grains, fruits, vegetables and legumes, plus meat, seafood and most nuts and seeds.

Because FODMAPs are carbohydrates, foods made up of mostly fat and protein are fine to eat on a low-FODMAP diet. Meat and seafood is fine, as are oils, most nuts (except cashews and pistachios) and seeds, lactose-free dairy products and most cheeses. Tofu and tempeh are also OK in small amounts, although other soy products are not.

Coffee, black tea, green tea, white tea and peppermint tea are allowed on a low-FODMAP diet, as are most sweeteners, including brown sugar, palm sugar, pure maple syrup, raw sugar, rice malt syrup and white sugar.

When it comes to fruits, vegetables, grains, beans and legumes, commonly allowed foods are:

Fruit:

Banana (unripe)

Blueberries

Cantaloupe

Grapes

Honeydew melon

Kiwi

Lemons

Limes

Oranges

Strawberries

Grains:

Corn flour

Oats

Oat bran

Quinoa

Rice

Rice bran

Spelt

Vegetables:

Bamboo shoots

Bean sprouts

Bell pepper

Bok choy

Carrot

Chives

Cucumber

Edamame

Eggplant

Ginger

Green beans

Lettuce

Olives

Parsnips

Potatoes

Turnips

Tomato

Zucchini

When eating these allowed carbohydrates, you'll likely need to watch portions-most have small amounts of different FODMAPs, so too large a serving can trigger symptoms.

The diet shouldn't be used for weight loss, or sustained long-term.

"This is a learning diet that helps people with IBS identify their triggers," says Scarlata. "It is not a fad diet for weight loss-it is prescribed as a form of medical nutrition therapy. If you don't have IBS symptoms, the low FODMAP diet is not for you."

Even people with IBS aren't meant to sustain the restrictive elimination phase of the diet long-term. "This is an elimination diet, not one you're meant to stay on forever-some people do not understand this," says Sharon Palmer, R.D.N, author of The Plant-Powered Diet and nutrition editor for Today's Dietitian. The end goal is to create a personalized diet that's as varied and inclusive as possible without causing discomfort, not to follow a super-restrictive (and potentially nutrient-deficient) diet forever.

Long story short: You shouldn't try the low-FODMAP diet without first talking to a doctor and a dietitian.

The diet is very restrictive, which can have a negative effect on both your physical and mental health if sustained long-term. If you're curious about FODMAPs, chances are it's because you're experiencing digestive issues and aren't sure what to do. Schedule an appointment with your doctor to talk through your symptoms and get a diagnosis, then work with a dietitian and use a low-FODMAPs diet to identify which foods might be causing these issues.

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