What is Low FODMAP? Your Questions, Answered by Dr. Amy Myers

Last Update: May 15, 2023

For Dr. Amy Myers, food is medicine. As a medical doctor and a functional medicine physician, Dr. Myers has seen firsthand how nutritious foods like grass-fed meats and organic fruits and vegetables can support gut health. And because 80 percent of your immune system and 95 percent of your serotonin—the happy hormone—live in your gut, it’s the key to optimal health and wellbeing.

We polled our Thrive Market members and followers to see what questions they have about the Low FODMAP diet. Dr. Myers is answering them in today’s feature.

Let’s start from the beginning. Why is it important for us to know about Low FODMAP?

I’m always so happy when I find that people are educating themselves and taking back control of their health. I’m glad I can help by addressing the questions you sent in over the last few weeks about the low-FODMAP diet and how it can help with the symptoms of irritable bowel syndrome, or IBS.

You may not know that IBS affects an estimated 25 to 40 million people in the U.S. alone. Women make up roughly two-thirds of all IBS patients. IBS accounts for up to 12 percent of primary care visits — that’s up to 3.5 million visits every year! Yet, because IBS is a diagnosis of exclusion, if you’ve been diagnosed with IBS, there is a 50 percent chance that you actually have a gut infection called small intestinal bacterial overgrowth (SIBO). That’s a condition in which your gut flora becomes unbalanced. Bacteria in the large intestine overgrow into your small intestine where they don’t belong. This can happen for a variety of reasons, including diets high in sugar, alcohol, and carbs that feed the bacteria; hypothyroidism which slows your metabolism; low stomach acid; and certain medications, among other issues. Please take this free quiz I developed after working with thousands of patients to find out right now if SIBO might be the root cause of your health challenges.

What is a low-FODMAP diet?

A low-FODMAP diet temporarily restricts five categories of food that can irritate your digestive system. Each of the categories is a different type of short-chain carbohydrate. What these foods have in common is that they all pass undigested into your lower intestine where they can ferment, producing gasses including hydrogen and methane.

They can also draw additional water into the bowel. While avoiding FODMAPs may not treat the underlying cause, it has been very effective in eliminating painful and distressing symptoms.

What does it treat?

The diet was specifically developed to lessen the pain of IBS symptoms. These include abdominal cramping or pain, bloating, gas, and altered bowel habits including diarrhea, constipation, or alternating bouts of both. As I found in my clinic, if you have an underlying condition such as SIBO, you may need to take additional steps to get to the root of the problem. In the meantime, this diet may make you feel a whole lot better.

What do the letters stand for?

FODMAP is an acronym for the five groups to avoid. Each is a different short-chain carb. Those names are tough to remember (and pretty hard to say!) so the researchers who identified the food groups made an acronym for them. Here’s what each means:

Fermentable: The process in which gut bacteria ferment undigested carbs, producing gases.

Oligosaccharides: Sugars including fructans and galacto-oligosaccharides (GOS) found in wheat, barley, onions, garlic, and legumes.

Disaccharides: Lactose, found in dairy products such as milk, soft cheeses, and yogurt.

Monosaccharides: Fructose, a simple sugar found in honey, apples, high-fructose corn syrup, and agave.

Polyols: Includes sorbitol and mannitol, which are found in some fruit and vegetables and are used in artificial sweeteners.

What are the benefits?

This diet has many benefits for those dealing with painful symptoms. The five main ones are:

  1. It can relieve symptoms quickly. About three out of four people feel better in just a few days, and they felt the most relief after seven days or more on the plan.
  2. It’s completely natural. No pills, no powders, no chemicals, nothing special to buy. Just real, whole foods to enjoy!
  3. You’re in control. You can eat as much as you need of the low-FODMAP foods you select, whenever you want, prepared the way you like them. When it’s time to add foods back in, you select which ones and when.
  4. It’s not forever. The most restricted part of the diet is usually two weeks or less. After that, you start adding foods back in and expanding your diet.
  5. Knowledge is power. You will get to know the nuances of your body so you can balance what works for you in terms of the quantity and the combination. Maybe a teaspoon of honey is fine for you, yet a tablespoon causes symptoms. Or maybe avocado is fine and black beans are ok, just not together.

What is NOT low FODMAP?

This can be a little confusing, so let me explain. Anything that is a short-chain carb is a high-FODMAP food and everything else is a low FODMAP. So all foods that are not short-chain carbohydrates work on this plan.

That means proteins including meat, fish, and poultry. Most nuts and seeds are also permitted, as are many fats. Some fruits like blueberries are low FODMAPs. Many vegetables such as carrots, eggplant, zucchini, peppers, green beans, lettuce, cucumbers, potatoes, and tomatoes are low FODMAPS as well. Finally, some grains and pseudograins such as oats, quinoa, and rice are also low FODMAP. You can find a complete list on the low-FODMAP app, created at Monash University.

How do I know if I should follow a low FODMAP diet?

If you have been diagnosed with IBS, or have symptoms of abdominal cramping or pain, bloating, gas, and altered bowel habits including diarrhea, constipation, or alternating bouts of both, and have ruled out SIBO, then a low-FODMAP diet may be just what you need. Check with your healthcare professional before beginning any new dietary regimen. Working with a nutritionist may be especially helpful if you are a vegetarian, have food intolerances, or dietary restrictions due to another condition such as diabetes.

What are the rules of low FODMAP?

I don’t like to lay down rules, so let’s call these steps. They’re pretty straightforward and easy to follow.

  1. Restrict your intake of high-FODMAP foods to reduce painful symptoms. You’ll do this until your symptoms resolve, usually in less than two weeks.
  2. Over a period of eight to 12 weeks, you’ll reintroduce foods one at a time, a small amount at a time, and assess how you feel after each reintroduction. If something doesn’t feel right, eliminate that food and don’t add anything new for a few days. If you feel fine, try increasing the amount of the introduced food or increasing the frequency you eat it. Keep notes and focus on how each new food makes you feel.
  3. This is where you learn to find a balance among foods that don’t bother you at all, foods that you can eat sparingly, and foods that you should avoid completely. For example, you may find you can eat only half an apple if you are eating other high-FODMAP foods, but you can enjoy a whole one if you are eating only low-FODMAP foods otherwise. This will be completely unique to you.

What’s the best way to follow the diet?

Here are a few tips that I’ve found really helpful in successfully following the diet.

  1. Plan. As with any change, the best way to succeed is to plan. Set a start date for yourself and clear out any foods you won’t be eating during the first step. If they’re perishable, give them away or toss them out. Set shelf-stable items aside in a section of your pantry or a cupboard because you’ll soon be reintroducing them one by one.
  2. Download. Download the FODMAP app, developed by Monash University. Seeking the guidance of a nutritionist can also be helpful.
  3. Shop. Stock up on the low-FODMAP foods you will be enjoying.
  4. Journal. When you begin the reintroduction phase, keep a journal noting the amount of each new food and how you feel. Going forward, jot down any occasions where your symptoms flare up and note any special circumstances, including the food you ate, your stress level, and any illness you might be experiencing.
  5. Congratulate. This one is really important: Congratulate yourself for taking back control of your health! This process is so empowering!

How long should I try low FODMAP?

One of the best parts about the low-FODMAP diet is that you’ll feel the effects pretty quickly if it’s working for you. Many people feel their symptoms ease right away after starting a low-FODMAP diet.

The elimination part of the diet should not take more than two to three weeks. It is not a long-term eating plan because it is too restrictive in terms of nutritional intake. The reintroduction phase depends on how many foods you are reintroducing and how well you tolerate each one. The ultimate solution, of course, is to get to the root cause of your symptoms.

What products does Thrive Market have for Low FODMAP?

You can find many products at Thrive Market for a low-FODMAP diet. One of the best parts about this eating plan is that it’s rich in all types of protein, including the fish, poultry, beef, and pork that Thrive is known for. Healthy fats such as olive oil and avocado oil are also important on this diet. You can find great options at Thrive for all steps of the low-FODMAP diet.

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Lily Comba

Lily Comba has never met a baked good she didn't like. When she's not baking, you'll find her writing, taking a Pilates class, or collaborating with the editorial and social team as a Senior Content Writer at Thrive Market.

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