Ultimate Guide to the Low FODMAP Diet

Posted 2 years ago

SaVanna Shoemaker, MS, RDN, LD

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If you’re considering a low FODMAP diet, you probably have many questions:

What exactly are FODMAPs?
Why are they problematic for some people?
What is the science behind the low FODMAP diet?
Can I stay on Keto while I do it?

We’ve got the answers to all of these questions and more in this ultimate guide to the low FODMAP diet. Let’s dive in.

What Are FODMAPs?

FODMAP is short for “fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.” It’s a mouthful, right? Here’s a quick explanation of what these terms mean:[*]

Fermentable: able to be fermented by the gut bacteria in the large intestine
Oligosaccharides: a type of multi-chain sugar found in foods like wheat, onions, garlic, and beans
Disaccharides: lactose, a two-molecule sugar found in dairy products
Monosaccharides: the single-molecule sugar fructose, which is found in a variety of fruits, honey, etc.
Polyols: sorbitol and mannitol, two types of zero-calorie sugar alcohols

FODMAPs are found in a wide range of foods, and the only way to know for sure the FODMAP content of a food is to analyze it in a lab. Unlike identifying Keto-friendly foods, you can’t glean any clues about the FODMAP content of a food from looking at the Nutrition Facts label or the ingredients list.

What’s a Low FODMAP Diet?

Put simply, a low FODMAP diet excludes foods that are high in FODMAPs. It’s typically used by people with chronic digestive issues to help them identify trigger foods.

The low FODMAP diet was developed by Monash University in Australia, and they now maintain a comprehensive database of low FODMAP and IBS resources at their Monash FODMAP website. They also have an app that is extremely helpful for anyone on a low FODMAP diet, providing an exhaustive list of FODMAP-approved foods and ‘safe’ serving sizes for each.

Who Might Consider a Low FODMAP Diet?

The Low FODMAP diet was designed for people with diagnosed irritable bowel syndrome (IBS).

Irritable bowel syndrome is a chronic digestive disease that’s characterized by a collection of digestive symptoms without any signs of disease in your digestive tract. This lack of apparent damage makes it difficult to determine the exact cause of IBS.[*]

Most people have either IBS with constipation (IBS-C) or IBS with diarrhea (IBS-D). Some people may have a combination. This is referred to as IBS-M. Other symptoms may include abdominal cramps, bloating, and gas.

People with IBS appear to be extra sensitive to high FODMAP foods. These foods move slowly through the digestive tract and pull water from the gut, before being fermented by bacteria in the large intestine — which causes excessive amounts of gas. This extra gas and water stretching the digestive tract may cause cramping.[*]

Monash FODMAP warns that there are many conditions with similar symptoms to IBS, but that people with these conditions may not respond well to the diet.[*]

Potential Benefits of a Low FODMAP Diet

There’s been a fairly decent amount of research done on the effectiveness of a low FODMAP diet in recent years.

One 2021 meta-analysis (that’s an analysis of multiple scientific trials on the same topic) of 12 studies on the low FODMAP diet for IBS found that the diet significantly reduced IBS symptoms and severity compared to a control diet. It also improved quality of life in participants with IBS.[*]

A similar meta-analysis, also from 2021, included 22 research studies and found that the diet induced a moderate improvement in IBS symptoms. They also found that in people with IBS-D, the diet helped decrease the frequency of bowel movements and improve their consistency.[*]

Potential Downsides of a Low FODMAP Diet

Unfortunately, the low FODMAP diet can be both restrictive and confusing.

The diet cuts out a lot of common foods, like apples, wheat, milk, yogurt, most legumes, sugar alcohols, cauliflower, garlic, mushrooms, and onions. This can make it fairly restrictive, so you’ll need to do a lot of planning and prep to be successful.

It’s also really difficult to decipher a food’s FODMAP content without the assistance of some specialized lab equipment, so the list of high FODMAP vs. low FODMAP foods can seem really random and arbitrary at times. Without the help of an app like Monash FODMAP or a health professional with experience working with low FODMAP diets, it may be really hard to keep track of what’s OK to eat and what should be avoided.

Getting Started on a Low FODMAP Diet

If you’re ready to get started on a low FODMAP diet, here’s a quick guide to help you.

The Three Steps to a Low FODMAP Diet

Because the low FODMAP diet is extremely restrictive, you’re not meant to stay on the strictest version of the diet forever — never reintroducing any high-FODMAP foods. Using the three steps, you can safely use the low FODMAP diet to help you identify exactly which foods trigger your IBS symptoms so that you can avoid those — while reintroducing other high FODMAP foods into your diet.[*]

Step 1: Strict Low FODMAP Diet

Follow a strict low FODMAP diet for 2-6 weeks. Use the Monash FODMAP app and stick mostly to “green” foods (indicating that they are low in FODMAPs).

Step 2: FODMAP Reintroduction

Next, if the low FODMAP diet has improved your symptoms, continue your strict low FODMAP diet, but choose one high FODMAP food (“red” in the Monash app) to reintroduce daily for three days. Note how you respond and if the food triggers any symptoms.

It may take up to 12 weeks to work through this reintroduction phase and identify which high FODMAP foods you’re able to tolerate.

Step 3: FODMAP Personalization

The final phase is the long-term version of the low FODMAP diet. In this phase, you’ll be able to confidently reintroduce any high FODMAP foods that don’t exacerbate your IBS.

What To Eat

Here’s a list of some “green light” foods from Monash FODMAP that are low in FODMAPs:[*]

Vegetables: eggplant, green beans, bell peppers, carrots, lettuce, zucchini, bok choy
Fruits: cantaloupe, pineapple, green kiwi fruit, oranges
Dairy (and alternatives): almond milk, brie, feta, hard cheeses (like parmesan), lactose-free milk
Protein: eggs, plain meats, tofu and tempeh
Grains: oats, quinoa, gluten-free breads
Sugars: maple syrup, stevia
Nuts and seeds: macadamia nuts, walnuts, peanuts, pumpkin seeds

What To Avoid

Here are some high-FODMAP foods that should be avoided while on the low FODMAP diet and slowly reintroduced during the second phase:[*]

Vegetables: asparagus, cauliflower, garlic, mushrooms, onion
Fruits: apples, cherries, mango, peaches, nectarines, plums, pears, watermelon
Dairy: milk, ice cream, yogurt
Protein: beans and legumes
Grains: wheat, rye and barley
Sugars: honey, sugar-free candy
Nuts and seeds: cashews, pistachios

Personalizing a Low FODMAP Diet

What about customizing this diet? Can you, for instance, eat Keto and low FODMAP?

The answer is yes! The low FODMAP diet is fairly easy to combine with other types of diets that you may want to pursue for their added health benefits. For example:

Paleo: Paleo and low FODMAP go hand-in-hand, especially since the low FODMAP diet eliminates wheat, legumes, dairy, and many types of added sugar. On a paleo low FODMAP diet, you’ll also need to avoid any packaged, highly processed foods — even if they’re low FODMAP.
Keto: Keto is also a natural choice for people pursuing a low FODMAP diet, especially if you’re also interested in weight loss or improving your blood sugar control. With a low FODMAP Keto diet, you’ll simply avoid low FODMAP foods that are high in carbs in addition to avoiding high FODMAP foods.
Vegan: While a vegan low FODMAP diet may be a bit more challenging, it can be done. The most important consideration is protein, since legumes -a significant source of protein for many vegans — are high in FODMAPs. However, tofu and tempeh (fermented soy) are low in FODMAPs.

Keys to Success on a Low FODMAP Diet

Here’s how Carb Manager can help you to be successful on your low FODMAP diet.

Plan ahead. Search the Carb Manager recipe database for a delicious range of FODMAP-friendly recipes. You can easily plan out your meals and snacks using these recipes and our Premium meal planning tools, alongside the Monash FODMAP app to help you identify specific low FODMAP foods.
Prep in advance. Premium members can generate a shopping list on the Carb Manager app that will make grocery shopping a breeze so that you can prep your meals and snacks in advance. This is key, especially for the stricter first phase of the diet, where you need to avoid all high FODMAP foods.
Track your symptoms. Another important part of the low FODMAP diet is tracking your symptoms, especially when you begin reintroducing foods. The food log makes it easy to keep track of dates you reintroduce, and you can use the notes section of the food log to keep track of your symptoms.

Low FODMAP Recipes

Don't know where to start? Try these Monash-approved recipes from the Carb Manager kitchen.

If you have IBS, a low FODMAP diet may be the right answer for you. It may seem tough at first, but the Monash app can help. And if you need more help, it’s definitely worth working with a dietitian who has experience with low FODMAP diets. (Here’s a directory of them from Monash University.) Additionally, Carb Manager has all the tools you need to make meal planning, reintroduction, and symptom logging a snap.

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