The Low-FODMAP Diet for GI Symptoms

The Low-FODMAP Diet for GI Symptoms

Brigid Titgemeier

Brigid Titgemeier is the dream nutritionist. She’s a registered dietitian with a master’s degree in public health nutrition. She completed four years of advanced functional medicine training and was the founding dietitian at the Cleveland Clinic Center for Functional Medicine under Mark Hyman. She reads, cites, understands, and values research. She is not dogmatic. She helps people develop a healthy, joyful relationship to food. She listens to you and she comes up with plans and recipes that work for you, specifically you—that you can and want to follow through with. She’s nice.

Most people work with Titgemeier through her comprehensive and well-organized virtual nutrition program, My Food Is Health, which runs for ten weeks and includes lab testing. That is how one editor on our team met Titgemeier and finally managed to address some GI symptoms she’d been having for, oh, four or so years. In her case, this started with a low-FODMAP diet.

Titgemeier says that a low-FODMAP diet is one of the most well-studied interventions and, anecdotally, one of the most common recommendations made by GI doctors when someone comes in with a range of symptoms: gas, bloating, diarrhea, constipation, abdominal pain. It’s not a long-term lifestyle change. Titgemeier typically puts people on a six-week low-FODMAP protocol. Symptoms generally improve slowly over that period, maybe more slowly than you’d like, but the end result can be very satisfying.

A Q&A with Brigid Titgemeier, RDN

What is FODMAP?

It’s an acronym for a group of carbohydrates that are fermented by the gut bacteria that are in your intestine. In a healthy gut environment, this is a good thing. But for a person who has digestive distress or bacterial overgrowth, it can lead to accelerated fermentation, which can cause bloating and other GI symptoms.

The acronym stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols.

What are some foods that fall into these categories?

Oligosaccharides are fructans (chains of fructose sugars) and GOS (chains of galactose sugars). Foods high in this category include:

  1. Grains such as wheat, barley, and rye. (Some people who experience adverse symptoms from gluten may in fact have difficulty processing foods high in FODMAPs. Gluten-containing foods, such as wheat, are high in fructans. Some studies have shown that people who believe they have gluten sensitivities actually may have difficulty processing the fructans that are present in gluten-containing foods.)

  2. Some vegetables such as artichokes and alliums, like garlic, onions, and leeks.

  3. Some nuts and legumes, including lentils and chickpeas.

Disaccharides are lactose. This is all of your dairy—milk, ice cream, yogurt, sour cream.

For monosaccharides, you have foods with more fructose:

  1. Fruits like apples and mangos and dried fruits.

  2. Some vegetables such as asparagus.

  3. And sweeteners—agave syrup, honey, high-fructose corn syrup.

Polyols are sugar alcohols. This category includes things that are added to products and several foods that naturally have sugar alcohols in them:

  1. Fruits like apples, blackberries, peaches, and plums.

  2. Vegetables like cauliflower, mushrooms, and snow peas.

  3. Sorbitol, mannitol, malitol, and xylitol.

Why are FODMAPs an issue for some people and not all people?

If you have bacterial overgrowth, foods high in FODMAPS can lead to rapid fermentation by bacteria in the colon, which produces gases such as hydrogen, carbon dioxide, and methane. And that creates abdominal distention, abdominal pain, and uncomfortable flatulence.

These short-chain carbohydrates will tend to be poorly absorbed in your small intestine. If a person has small intestinal bacterial overgrowth (SIBO), which can contribute to irritable bowel (IBS) symptoms, the bacteria in the small intestine will ferment these carbohydrates and increase gas production. In those who do not have SIBO, these carbohydrates move on to and get absorbed in the colon, where they are fermented and can have an osmotic effect, creating an imbalance of water in your large intestine.

The most common symptoms that people have before they create a healthier gut microbiome are gas, bloating, diarrhea, constipation, and abdominal pain. Because the symptoms vary so much, I suggest working with a dietitian or a health care practitioner who is able to identify whether FODMAPs might be an issue. You may have general IBS symptoms, but often a root cause of IBS is SIBO, dysbiosis, food sensitivities, or a leaky gut. Temporarily moving to a low-FODMAP diet can be useful for some people who have IBS, SIBO (most accurately diagnosed with a breath test), general dysbiosis (bacterial overgrowth in the large intestine, which can be assessed with a stool test), and inflammatory bowel disease like Crohn’s disease. Consuming foods that are high in FODMAPs is not the cause of these conditions, but it can fuel more symptoms.

Several randomized controlled trials have demonstrated that those who have IBS and follow a low-FODMAP diet are more likely to experience reductions in pain and bloating, compared to those following a traditional diet.

At what point do you recommend a low-FODMAP diet?

The low-FODMAP diet is one of the most well-studied interventions. There’s a lot of research behind it. Up to 86 percent of patients with IBS find improvements in their gastrointestinal symptoms, including abdominal pain, constipation, diarrhea, abdominal distention, and flatulence. If you were to go to a gastroenterologist with these symptoms, the low-FODMAP diet is a common nutrition recommendation that a GI doctor would make.

When I’m working with someone, my recommendations are based on the individual, their lab work, and their current diet. In conventional medicine, IBS is a blanket diagnosis for a lot of different symptoms. It doesn’t explain why the person is experiencing them. The goal in functional medicine is to go deeper for those with IBS, inflammatory bowel disease, and other gastrointestinal issues to understand the root cause and provide personalized recommendations. For some people, I might start with taking out all processed foods, adding in more whole foods, and decreasing their added sugar consumption, which we know can feed bacterial overgrowth. And then we see what kind of symptom resolution can happen. People can experience significant outcomes from those initial interventions—and from working on managing their stress.

For people who already have a healthy diet and are reporting ongoing bloating or distention that cannot be tied to any particular foods, I’ll explore whether FODMAPs seem to be a potential trigger. When someone comes in saying they eat a lot of vegetables, some fruits, fats like avocado and olive oil, seafood, some grains, and a little meat occasionally, for example, that’s a flag for me. This is common in people I see who are already eating healthily, eating more vegetables, and having symptoms: They’ll tell me that no matter what they eat, they feel bloated. But that certain foods seem to make it worse: raw vegetables and fruits, beans and lentils, and soups, which tend to include garlic and onion. They might also point to alcohol and overeating. Some will point out that they had courses of antibiotics before the symptoms began, which can be an indicator that their gut microbiome is out of balance.

Also keep in mind that although GI symptoms are most common in those who have gut imbalances, the health of your gut impacts many metabolic, inflammatory, autoimmune, mood, and cognitive processes. Gut disturbances could also manifest in autoimmune disease, brain fog, poor concentration, poor memory, depression, and anxiety.

How long does someone typically follow a low-FODMAP diet?

It’s usually recommended that you follow a low-FODMAP diet for only two to six weeks. I’ll generally recommend six weeks and then a reintroduction process. I see people have the greatest success when they pair the diet with the right supplements that help create a healthier microbiome.

Following a low-FODMAP diet is a short-term therapeutic intervention that can help reduce symptoms. It’s not a long-term solution. We need FODMAPs in our diet. FODMAPs are extremely helpful for the gut microbiome—they feed your bacteria. A low-FODMAP diet reduces the amount of prebiotics that a person has in their diet, which lowers short-chain fatty acids and has been associated with lower levels of Bifidobacterium species after just two to four weeks. If a person removes FODMAPs from their diet for a year because they’re experiencing improvements in their symptoms, it will simultaneously decrease the diversity of the microbiome, which may not be beneficial in the long term.

Can you recap the main foods to avoid? And what do you eat on a low-FODMAP diet?

It’s worth mentioning that high-FODMAP foods are often very nutritious foods. You may eat a very nutritious diet but still have GI symptoms. Sometimes it’s necessary to remove even nutritious foods from the diet short-term and replace them with alternative foods that do not cause as much fermentation.

The foods to avoid, which are generally going to be the highest in FODMAPs, would be the allium vegetable family. So your garlic, shallots, onions, and leeks. And then vegetables like cauliflower, mushrooms, asparagus, Brussels sprouts. Fruits like apples, pears, peaches, watermelon, and dried fruits. The dairy category includes cow and goat milk and yogurt. Legumes like lentils, chickpeas, and kidney beans. Grains like wheat, rye, and barley. And then sweeteners like high-fructose corn syrup.

What you can eat:

  1. Fruits like blueberries, raspberries, strawberries, banana, rhubarb, lemons, limes, and oranges.

  2. Vegetables like arugula, Swiss chard, collard greens, bok choy, carrots, kale, lettuce, spinach, and squash.

  3. Black, brown, and wild rice (oats are technically low in FODMAPs, but I don’t include them because they can be a little unsettling for people who have more digestive distress).

  4. Milk substitutes would include your nut milks and coconut milk.

  5. Nuts and seeds like Brazil nuts, macadamia nuts, pecans, walnuts, chia seeds, and pumpkin seeds.

  6. Oils are a safe group overall, but I typically recommend sticking with avocado oil, extra virgin olive oil, and some coconut oil.

  7. Protein is a safe category—I typically recommend wild salmon, organic chicken, turkey, eggs, grass-fed beef, and organic tofu.

Why—or when—does serving size matter?

Certain foods are low in FODMAPs in smaller quantities but high in larger quantities. For this, the Monash University app is helpful. A group of PhD researchers at Monash University developed the low-FODMAP diet, and they’ve been conducting research on it for fifteen years. The first paper that described the FODMAP hypothesis was published by two of their researchers in 2005. In the last fifteen years, there have been studies published throughout the entire field of gastroenterology demonstrating significant improvements in various GI symptoms from the low-FODMAP diet.

The Monash University researchers have studied all these various foods and created an amazing guide with a list of foods that you can click on and the app will tell you how high the food is in FODMAPs at different serving sizes. The app has recipes and allows you to track what you’re eating. You can also search a group of dietitians who are trained through the university’s low-FODMAP protocol. (I’m not trained by Monash.)

Avocados are the best example of the importance of serving size. If you have an eighth of an avocado, that’s not going to trigger a response. But a quarter of an avocado would be considered high in FODMAPs—it has a moderate level of sugar alcohols.

Are there other helpful tools for navigating a new food protocol like a low-FODMAP diet?

I developed the Food Symptom Journal for My Food Is Health. I’ve found that most of the apps that I’ve looked into don’t allow you to correlate the foods you’re consuming with the symptoms you’re experiencing. They tend to be focused on numbers, including calories and macros. There are not many tools that help people correlate what they are eating with how they feel.

My journal is a great way to track the frequency of your bowel movements, in addition to symptoms such as bloating, abdominal pain, fatigue, joint pain, reflux, anxiety, headaches, and more. The goal is to help you identify a pattern in the relationship between your food and lifestyle choices and the symptoms you experience day-to-day. What I find is that people think to themselves, I’m eating pretty healthily so it’s probably not my diet. But I want to help people throw the “healthy” label out the window so that they can start paying attention to whether the foods they are eating are triggering them in some way. It’s not always about whether you eat healthy foods. It’s about whether you are eating the foods that make you feel optimal. And also paying attention to aspects like stress: Do your symptoms come up more frequently or intensely on days when you are under a lot of stress?

As people start feeling better, they often normalize how they feel, and it can become difficult to realize what kind of progress they’ve made. But if you’re tracking your symptoms in the food symptom journal, you’re able to clearly say, “Oh, this is how many symptoms I experienced when I started. I was writing three times per day that I was experiencing bloating. And then I see that in the next week, my symptoms decreased to two times. And then I see that two weeks later, they decreased to one time.” So it helps you see data at a micro level: how often you experienced the symptoms initially compared to how often you’re currently experiencing the symptoms. Sometimes making very small changes can lead to big shifts in your health.

It’s also important to track more than just your food. In addition to focusing on what you’re eating, the journal prompts you to track things like sleep, stress, movement, and hydration intake. Stress is a common cause of GI symptoms. Sometimes people want to restrict their food without looking at other lifestyle factors. I find that nutrition is usually the gateway for people to start caring about their health overall, but it is only one factor in the large picture of creating health. The feedback I hear from people who go through our program is that they’re surprised that we don’t focus on just nutrition. For example, most of my clients who start working with me know to limit processed foods, but at the same time, they let their stress run unchecked. However, increased stress levels can create symptoms similar to those that you would see in a person who eats a highly processed diet. I recommend treating stress like high-fructose corn syrup and actively filtering it out of your life!

You mentioned taking supplements in tandem with the low-FODMAP diet—which ones?

For people who appear to have bacterial or yeast overgrowth, based on symptoms and labs, I’ll often recommend antimicrobial herbs combined with a low-FODMAP food plan. This helps to address the root cause. For yeast, I often recommend an antifungal product for a six-week period, such as Candibactin-AR. For bacterial overgrowth, I’ll recommend different types of antimicrobial supplements, such as Candibactin-BR, a blend that includes Oregon grape extract and skullcap, which is an herb used in traditional Chinese medicine. This helps with the weeding and seeding process—you want to weed out bacterial overgrowth before you seed with healthier bacteria to reduce symptoms.

After two weeks of the weeding protocol, I’ll add a probiotic to help feed and seed healthy bacteria.

Are other supplements typically helpful for creating a healthier microbiome and digestion?

The functional medicine model approaches gut healing with five steps, called the 5R Process: remove, replace, reinoculate, repair, and rebalance.

  1. The remove step is when I would use an antimicrobial or antifungal herb and a low-FODMAP diet to remove bacterial overgrowth.

  2. Replace could include adding digestive enzymes, hydrochloric acid (if a person has low stomach acid), Swedish bitters, or other components that aid in digestion.

  3. Reinoculate involves the feeding and seeding stage of incorporating a probiotic and fermented foods.

  4. Repair speaks to repairing the lining of the gut. If a person has bacterial overgrowth, it increases the chance of having a leaky gut. Bone broth, collagen, L-glutamine, and aloe vera can help improve the lining of the gut. Glutagenics combines L-glutamine, licorice root, and aloe vera. It also includes zinc, omega-3 fatty acids, and antioxidants.

  5. Rebalance involves stress reduction and lifestyle changes that help to create a healthy shift.

Always talk to your own personal doctor or dietitian before starting any supplements.

Do you recommend taking probiotics long-term?

The way that I see it is that probiotics are a great option for people to create balance in their system. If they’ve gone on antibiotics and their microbiome has been wiped out, probiotics can help reset their system and help repopulate some of those microbes that were impacted. Your microbiome environment is in constant competition—the least beneficial microbes are essentially competing with the more beneficial microbes. And if you have fewer beneficial microbes, that creates more opportunity for opportunistic bacteria that could be pathogenic or lead to unwanted bacterial overgrowth. So probiotics can be very important in the short term.

The research is still unclear on whether and how much people benefit from taking probiotics in the long term . For people who are more predisposed to autoimmune disease or who have a history of a lot of food sensitivities and more leaky gut, I might recommend a probiotic for a longer period of time. But you want to rotate your probiotics so that you’re not taking the same one again and again and again. Because you want different strains to feed different microbes.

I don’t think that most people need a probiotic long-term if they’re eating enough dietary fiber (or prebiotics that fuel probiotics) and fermented foods that contain live cultures, such as sauerkraut, yogurt, dairy-free yogurt, kimchi, and apple cider vinegar. The other important factor is to incorporate a variety of colors in the diet with each meal. If a person gets to the point that they’re able to create a healthy microbiome and they’re not having any symptoms, then they can use fermented foods to help regulate a healthy gut environment.

How do people typically feel over the course of a six-week low-FODMAP diet?

Typically, they’ll notice improvements in their GI symptoms—their bloating becomes less intense and less frequent. And that usually happens slowly and gradually. So it’s easy for people to miss some of the improvements that they experience. A lot of times, people will think that nutritional interventions are this overnight thing, that they’re going to go from feeling horrible to amazing overnight. That’s part of the difficulty with being able to demonstrate improvement: It happens gradually over a six-week period of time or however long a person needs to heal their gut.

What if someone doesn’t feel better afterward?

It’s rare for people not to experience improvements in their symptoms. But it does happen. I would recommend working with a functional practitioner and asking for further testing. For some people who have mild imbalances in their gut microbiome, they can feel much better very quickly. For others who may have more potentially pathogenic bacteria, SIBO, a leaky gut, hormonal imbalances that stem from issues in their gut, etc., it will require patience and continuing to look at different areas under the hood.

How does your food reintroduction process work?

The reintroduction process is incredibly important. And people sometimes realize that foods they thought they needed to avoid don’t bother them.

I use a four-day food-reintroduction process that I have been using for years and with thousands of patients. Every four days, you reintroduce one new food. On day one and day three, you eat that “challenge” food two times during that day, at a specific serving size. And you try to have the food as close to alone as possible. Meaning that if you’re going have broccoli or Brussels sprouts, have half a cup cooked, by itself, instead of with a meal.

You record any symptoms that happen right after or within twenty-four hours of eating it. Some people observe symptoms within one hour or two hours of eating the food, but food-sensitivity responses could also be more delayed. Continue to record how you feel for the four-day process.

If you go through the four days and you don’t notice symptoms, then that food just becomes a part of your diet and you move on to testing the next food.

If you do notice symptoms, you might decide, Okay, I’m not going to add the food into my regular diet. If you’re not sure, you could test again.

Monash University has its own reintroduction process that is three days long.

Do you recommend that people follow a certain order of foods when they’re reintroducing?

I try to start with the foods least likely to give you issues and then gradually work up to gluten and dairy, which are more common for people to have sensitivities to. For someone who has just done a low-FODMAP diet, I’d push onion and garlic toward the end.

Monash University bases its reintroduction on the level of FODMAPs the food contains and does not base it on potential food sensitivities to gluten or dairy.

What else helps long-term?

Overall, raw fruits and vegetables can be hard on the digestive system. So even though this isn’t a low-FODMAP suggestion, I do typically recommend cooking more of your vegetables or mechanically breaking them down in a blender or food processor, because it’s one less step of digestion.

How you are eating and how quickly you’re eating influences digestion. Typically, if people are sitting and eating more slowly and chewing their food, that will decrease the air they’re swallowing and help with digestion. If a person is eating quickly and swallowing a lot of air, it can create a lot of gas bubbles, which can lead to more symptoms. Also, people who are eating in a relaxed, present state will activate their parasympathetic response (rest and digest), which naturally increases the body’s production of digestive enzymes and supports the digestion and absorption of food.

Some people don’t tolerate grains well. This is more common for those who were on a lot of antibiotics as a kid, who were bottle-fed versus breastfed, and who were delivered via C-section versus vaginal birth. All of these factors can create a less resilient microbiome long-term and make it more difficult to feel good eating foods like grains. For this group, I recommend eating grain-free or trying sprouted foods like sprouted rice or quinoa, which can be easier to digest.

Limiting coffee and alcohol can be helpful for improving digestion long-term.

Try to add variety. Once you get to the point when your gut health has improved, microbiome diversity is critical, and you can foster it by eating an abundant diversity of foods and colors.

It’s also important to work on managing stress, which might mean trying breathwork, doing yoga, spending more time in nature, listening to calming music. You cannot supplement your way out of poorly managed stress. The relationship between stress and the microbiome is self-perpetuating: A healthy microbiome can improve stress resilience. And stress influences the intestinal microbiota. Researchers have found that different types of stress—maternal separation, chronic social defeat, heat stress, and so on—can alter the composition of those microbiota. And the more stress you endure, the more imbalance can occur among various microbial populations. The gut and brain are so closely connected through your gut-brain axis, a bidirectional highway that is always sending messages back and forth.

Brigid Titgemeier is a functional medicine registered dietitian and a health advocate. She has a master’s in public health nutrition and is board-certified in integrative and functional nutrition. Titgemeier was a founding dietitian at the Cleveland Clinic Center for Functional Medicine under Dr. Mark Hyman. Throughout her career, Titgemeier has worked with more than 4,000 clients. In 2018, she founded the functional nutrition and health consulting business, BeingBrigid Nutrition, which incorporates a data-driven personalized nutrition approach, advanced lab testing, education, and coaching.

This article is for informational purposes only. It is not, nor is it intended to be, a substitute for professional medical advice, diagnosis, or treatment and should never be relied upon for specific medical advice. To the extent that this article features the advice of physicians or medical practitioners, the views expressed are the views of the cited expert and do not necessarily represent the views of goop.