Got gut issues? The low FODMAP diet may help

Laine Bergeson Becco
Medically Reviewed
January 10, 2020

For many years, people with functional gastrointestinal issues, issues like irritable bowel syndrome (IBS) and small intestinal bacterial overgrowth (SIBO) , faced limited options for managing their symptoms. Typically patients were given fiber supplements or counseled to abandon specific foods, like fatty or spicy foods, regardless of their predominant symptoms . Others were told that there simply wasn’t much that could be done.

Luckily, the arsenal of treatment options for functional GI conditions today has greatly improved, and it includes a therapeutic eating protocol called the low-FODMAP diet. If you struggle with IBS or SIBO , or if you regularly experience gas , bloating , diarrhea, constipation, or abdominal pain or distention and other approaches haven’t worked for you, a low-FODMAP diet, used in combination with other interventions, may help with symptom management and improve your quality of life.

What are FODMAPs, anyway?

FODMAP is an acronym. It stands for fermentable oligo-saccharides, di-saccharides, mono-saccharides, and polyols, which are types of fermentable carbohydrates found in certain foods. Some people, including those with IBS and SIBO, have a hard time digesting FODMAPs, either because of a bacterial imbalance in their intestine, a sluggish digestive system that increases the transit time of food through the gut, or both.

“When the body is not digesting food properly, some of these foods can sit in the gut and produce gasses,” says Tracy Scott , a health coach at Parsley Health in New York City. These gases contribute to gas, bloating, diarrhea, gut pain, and even acid reflux.

For those with intestinal bacterial imbalance, the fermentable fibers in FODMAPS can overfeed the colonies of certain gut bacteria. As the bacteria digest the fibers, they produce an excess of hydrogen, methane, and carbon dioxide gases which lead to symptoms.

A similar process happens for those with slow movement through the digestive tract: high fiber foods, which are healthy but indigestible, start to ferment in the intestine because of the slow transit time, leading to digestive symptoms.

What is the low-FODMAP diet?

A low-FODMAP diet restricts foods that are high in these difficult-to-digest, quick-to-ferment carbs. Studies suggest that a low-FODMAP diet can improve GI symptoms and quality of life for people with IBS. At the same time, it’s important to remember that the low-FODMAP diet is best used as a short-term therapeutic intervention, during which a person strictly avoids FODMAPs for the first four to six weeks and then slowly introduces them one by one. (If a food is reintroduced during the re-introduction period and it causes symptoms, it is taken back out again, but that doesn’t necessarily mean it is out of your diet forever. Your gut may just need more time to heal and build resilience before trying it again.)

Another key fact about the low-FODMAP diet? “It is not curative,” says Scott. “The low-FODMAP diet is more about symptom management.” If you try the low-FODMAP diet and it reduces or alleviates your symptoms, that’s a clue that something isn’t working optimally in your GI system. In other words, having a sensitivity to a high-FODMAP food isn’t the root cause of your digestive distress. It’s a symptom that something else is wrong, like SIBO or IBS. Hence, doing a low-FODMAP protocol is only half the battle in reversing symptoms. The other half of the battle is to identify the root cause of your discomfort, which is something best done with a practitioner who is familiar with functional GI issues.

What’s the research on the low-FODMAP diet?

The low-FODMAP diet was established by a group of scientists at Monash University in Australia about 15 years ago. At that time, it was well known that eating certain carbohydrates could trigger symptoms similar to those experienced by people with IBS. So the Monash team set out a hypothesis: by reducing and eliminating these foods—in other words, by eating a low-FODMAP diet—people with IBS and SIBO might find symptom relief.

The team was on to something. Today, the low-FODMAP diet for IBS and SIBO has been intensively studied and shown to be an effective short-term intervention. As Peter Gibson notes in a paper published in the Journal of Gastroenterology and Hepatology , “In many parts of the world, the low-FODMAP diet is now considered a front-line therapy for IBS.”

A meta-analysis published in the journal Nutrients in 2017 found “a significant reduction in abdominal pain and bloating” in IBS patients on a low-FODMAP diet. The authors of the meta-analysis conclude that “there is evidence that a low-FODMAP diet could have a favorable impact on IBS symptoms .”

Who can benefit from a low-FODMAP diet?

To date, most of the research has looked at the low-FODMAP diet for IBS patients . Symptoms of IBS include abdominal pain, bloating, gas, and change in bowel habits, and the condition can significantly impair quality of life. In prospective trials, 75 percent of participants with IBS experienced an improvement in symptoms on the diet . The low-FODMAP diet appears to be especially effective in reducing symptoms of gas and bloating.

People with small intestinal bacterial overgrowth (SIBO) may also benefit from the diet—especially because research has shown one third of IBS patients test positive for SIBO . SIBO is a condition in which bacteria from the large intestine gets trapped higher up in the GI tract (where they aren’t supposed to be) and triggers bloating, gas, diarrhea and/or constipation, burping, and abdominal pain.

If you regularly experience one or more of these symptoms, but you haven’t been diagnosed with SIBO, you might want to try the low-FODMAP diet as an easy preliminary test. If the diet helps reduce your symptoms, there is a good chance you may have SIBO, says Scott, and you should consult a doctor to address the root causes of the condition.

The diet may also help reduce symptoms in people with inflammatory bowel disease (IBD), says Scott, and emerging research supports this theory. But as with SIBO and IBS, IBD can’t be cured by the low-FODMAP diet. It’s value is in helping with symptom management in the short-term.

Getting started with the low-FODMAP diet

The low-FODMAP diet isn’t necessarily about “good” and “bad” foods. A lot of foods contain FODMAPS, including healthy ones like garlic, onions, beets, and Brussels sprouts. To add to the confusion, some healthy foods are low-FODMAP in small amounts, but high-FODMAP in larger amounts. Take blueberries, for example. “A quarter cup of blueberries are low-FODMAP,” says Scott. “More than that is high-FODMAP.”

So the goal isn’t to avoid FODMAPS forever—that would diminish the diversity of essential phytonutrients in your diet and ultimately work against your health goals—but to identify which specific foods activate your symptoms and limit them while working to manage symptoms. Many people who are sensitive to FODMAPS will find that they tolerate some high-FODMAP foods just fine, but that they are sensitive to others.

To find out which foods trigger your symptoms, follow the diet strictly for four weeks, says Scott. “You want to give the body a break,” she says. “You want to calm down the gas and bloating and you really need those few weeks to clear out your system.” After that, you will introduce high-FODMAP foods one by one over the course of several weeks.

High-FODMAP vs. Low-FODMAP foods

What food can you eat in the strict four-week “elimination phase,” and what foods should you avoid?

An acceptable FODMAP diet list of foods is long and labyrinthine—broccoli heads are low-FODMAP, for example, but broccoli stalks are high-FODMAP. Or consider artichokes: canned artichoke hearts are low-FODMAP. A fresh, whole artichoke is high FODMAP. This makes the dos and don’ts of eating low-FODMAP hard to commit to memory, and a printed list of acceptable and unacceptable foods impractical and unwieldy.

“The best resource for choosing the right foods is the Monash University FODMAP app ,” says Scott. The app uses a stoplight system, assigning the color green to low-FODMAP foods, yellow for medium-FODMAP foods, and red for high-FODMAP foods. “We instruct a lot of patients to use the app,” says Scott. With its extensive, searchable database (which is being updated all the time), it is an invaluable resource for grocery shopping, meal planning, and eating out.

How to follow a Low-FODMAP diet

When you’re in the first four weeks of the diet (the elimination phase), you remove all the red light (high FODMAP) foods, says Scott. You want to be strict during this period so you can reset your system and improve your chances of identifying trigger foods when you start to reintroduce them.

When it is time to reintroduce FODMAP foods, take it slow. Start with one of the six FODMAP carbohydrate groups—for example, foods in the polyol group, like avocados and peaches—and eat increasing quantities of those foods on the first three days of the week. Pay attention to any symptoms that crop up. If it helps, you can track symptoms in a journal or on your phone. On days four through seven, avoid all polyols again to clear them from your system. “The last half of the week is a washout period,” says Scott. This will help clean the slate so you can test the next group of foods the following week and assess any late onset digestive symptoms that might be experienced from that week’s reintroduced FODMAP group.

If you don’t experience any symptoms with the reintroduction of the polyols, great. You can keep them in. If, however, your symptoms return when you reintroduce polyols, remove them from your diet for a few more months. With more time to heal, your system may be able to tolerate this food group. Retest that food group in a couple months.

Follow the same method each week with each new FODMAP carbohydrate group you reintroduce.

Once you have a good idea of which foods trigger your symptoms and which don’t, you can avoid trigger foods while incorporating as many diverse, whole foods as possible. Ultimately, “you want to eat a wide variety of foods so your microbiome is more diverse,” says Scott. “The strict low-FODMAP diet is not meant to be a forever thing.”

Perhaps most critically, consider working with someone while you do a low-FODMAP protocol. “It can get a little complicated,” says Scott. “So it is great to work with a functional medicine practitioner.”

Laine Bergeson Becco

Laine Bergeson Becco is a freelance journalist, ghostwriter, and functional-medicine certified health coach. She recently won a Folio award for Best Range of Work by Single Author for her writing in Experience Life magazine. In her spare time, she is an avid jigsaw puzzler and a mediocre piano student.

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