Treating patients with inflammatory bowel disease (IBD) remains challenging despite the multitude of medications available. This article explores the potential role of a low FODMAP diet (LFD) as an adjunct therapy for managing symptoms in IBD, particularly those resembling irritable bowel syndrome (IBS).
Understanding IBD and Associated Symptoms
Inflammatory bowel disease (IBD) encompasses Crohn’s disease and ulcerative colitis, both of which are auto-inflammatory conditions of the gastrointestinal tract. IBD is mostly managed with medications, which aim to treat the inflammation (i.e., heal the gut). Patients often receive numerous medications throughout their disease course, ranging from corticosteroids and immunomodulators to tumor necrosis factor alpha (TNF-α) and integrin inhibitors. However, symptoms commonly seen in people with IBD, including abdominal pain, diarrhea, bloating, and constipation, may not always indicate inflammation.
Even if patients attain some form of remission, approximately 50% can still experience functional-type symptoms consistent with irritable bowel syndrome (IBS). Frequently reported IBS symptoms include bloating, flatulence, abdominal pain, and diarrhea. Based on the nature of the reported symptoms, it can be challenging to classify a specific symptom as IBS or IBD-related. Evaluating the patient using laboratory and/or stool studies, imaging, and endoscopic procedures can assist in making this determination.
People with IBD are three times more likely than the general population to have irritable bowel syndrome (IBS), which refers to a condition affecting the ‘function’ of the bowel and involves an increase in bowel sensitivity rather than inflammation of the bowel. If you have IBD, it is important to ensure that the presence and degree of inflammation is not based only on symptoms. Your doctor will interpret various tests and guide you as to whether your symptoms are inflammatory (active IBD) or functional (IBS) or both.
Many patients with IBD may understandably become overwhelmed by the use of multiple medications. Thus, some will inquire about any potential adjunct “therapies”, such as certain diets.
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What is a Low-FODMAP Diet?
FODMAP is an acronym for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These are short-chain carbohydrates that are poorly absorbed in the small intestine. FODMAPs act as prebiotics in the gut, meaning they stimulate the growth of good bacteria, which is probably important if you have IBD, so always aim to minimize your FODMAP restriction.
Here's a breakdown of what each component means:
- Fermentable: These carbohydrates are fermented by gut bacteria, producing gas.
- Oligosaccharides: These include fructans (found in wheat, onions, and garlic) and galacto-oligosaccharides (GOS) found in beans and lentils.
- Disaccharides: Lactose, the sugar in dairy products, is the primary disaccharide of concern.
- Monosaccharides: Fructose, found in fruits and honey, is the main monosaccharide. However, it's only a concern when the amount of fructose is higher than the amount of glucose.
- Polyols: These include sugar alcohols like sorbitol and mannitol, found in some fruits, vegetables, and artificial sweeteners.
Because FODMAPs are difficult to digest, they draw water into the small intestine. When they reach the large intestine, bacteria ferment them, producing gas and potentially leading to bloating, pain, and altered bowel habits.
The Low-FODMAP Diet: A Three-Phased Approach
The low-FODMAP diet is a temporary dietary plan that limits the intake of certain types of fermentable carbohydrates, including oligosaccharides, disaccharides, monosaccharides, and polyols. It is used to treat symptoms of Irritable Bowel Syndrome (IBS). As some patients with IBD also have the coexistence of IBS, it may be helpful to treat persistent gastrointestinal (GI) symptoms in patients with IBD who have low levels of inflammation, where symptoms may be attributed to IBS rather than IBD.
The diet has three phases:
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- Elimination Phase: This involves strictly avoiding high-FODMAP foods for 2-4 weeks.
- Reintroduction Phase: Foods are systematically reintroduced to identify specific triggers.
- Maintenance Phase: A personalized diet is developed, limiting only the FODMAPs that trigger symptoms.
In following the Low-FODMAP Diet, specific carbohydrates (high-FODMAP foods) are excluded for a period of time and then slowly reintroduced in order to determine which ones in particular may activate symptoms. Small daily amounts of each carbohydrate type are generally well tolerated. The cumulative effect of consuming large daily amounts of higher FODMAP carbohydrate foods may be the cause of GI distress. Higher FODMAP fruits and vegetables that are excluded include onions, garlic, apples, etc; it is recommended to specifically include fruits and vegetables that are low in FODMAPs, such as berries, nuts, carrots, green leafy vegetables, etc.
Low-FODMAP Diet and IBD: What Does the Research Say?
There is increasing research interest in evaluating an LFD in patients with IBD. However, the amount of large, prospective, blinded studies is relatively limited.
Studies are underway to investigate whether diet can be used to treat gut inflammation in IBD, however there is currently not enough evidence to recommend any particular diet as effective. Studies show that a low FODMAP diet will help to treat up to three-quarters of people with IBS and there is evidence to show that a low FODMAP diet also helps control symptoms in the majority of people with both quiescent (inactive) IBD and IBS.
A group led by Bodini et al conducted a prospective study evaluating the LFD in 55 patients with IBD who were in remission or with mild disease activity (Mayo score <6). Patients were evaluated at baseline and after 6 weeks of LFD compared with standard diet (SD) using disease severity indices, fecal calprotectin (FCP), and quality of life assessments. There was a statistically significant decrease in median FCP at 6 weeks in the LFD group (76.6 vs 50.0 mg/kg; P =.004) but not in the SD group (91.0 vs 87.0 mg/kg; P =.175). There was no statistical difference in median C-reactive protein (CRP) value between the two groups at baseline and 6 weeks. The modified Harvey-Bradshaw index (HBi) was the only index to have a statistically significant difference in favor of the LFD. There was no significant difference between the two groups using the IBD-Q quality of life scale.
Cox et al conducted a 4 week prospective study evaluating LFD in 52 patients with quiescent IBD. Significantly more patients in the LFD group reported adequate relief of their GI symptoms compared with the control group (52% vs 16%; P =.007) and had higher health-related quality of life scores. LFD had the greatest impact on flatulence and bloating. There was no statistical difference in IBS severity scores between the groups. Patients in the LFD group also had lower numbers of certain bacteria, including several strains of Bidifobacterium, which play an important role within the immune system. While there were some differences in the gut microbiomes of both groups, the differences were relatively small.
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In a paper published today in Gastroenterology, a team of researchers carried out a trial of a diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) in patients with IBD, experiencing persistent gut symptoms despite gut inflammation being under control. Working with leading gastroenterologists from Bart’s Health NHS Trust and Guys and St Thomas’ NHS Foundation Trust, the researchers studied 52 patients who suffer from IBD, and who had persistent gut symptoms despite no on-going gut inflammation, and allocated them to two groups; one to a low FODMAP diet, restricting intakes of foods such as wheat, dairy, onions and garlic, and the other a controlled ‘normal’ FODMAP diet. Of the group that received the low FODMAP diet, 52% reported adequate relief of gut symptoms, had a greater reduction in gut symptom severity and had a higher health-related quality of life score.
The authors also found the low FODMAP diet reduces certain gut bacteria, such as Bifidobacteria, that may be beneficial to health and may reduce inflammation. “We carried out this randomised controlled trial to establish whether these common gut symptoms in patients with IBD in remission could be managed by the low FODMAP diet. When inflammation levels are low but GI symptoms persist, it may be related to irritable bowel syndrome (IBS) within IBD, or other Disorders of Gut-Brain Interaction (DGBI) which may be addressed with the Low-FODMAP Diet.
Potential Benefits of a Low-FODMAP Diet for IBD Patients
At this point, it appears that most research currently available indicates that short-term utilization of an LFD may help ameliorate some of the mild IBS symptoms associated with quiescent IBD.
- Symptom Relief: A low-FODMAP diet can effectively reduce symptoms like bloating, gas, abdominal pain, and diarrhea in IBD patients with co-existing IBS or functional gut symptoms.
- Improved Quality of Life: By alleviating these symptoms, the diet can lead to a higher health-related quality of life.
Considerations and Potential Drawbacks
- Nutritional Adequacy: As the low-FODMAP diet has not been shown to reduce inflammation, it is recommended for symptom relief only, rather than disease management. It is further recommended for use short term (4 weeks) rather than longer term because it may adversely affect the microbiome.
- Gut Microbiome Changes: The low FODMAP diet reduces fecal abundance of microbes believed to regulate the immune response, compared with the control diet, but had no significant effect on markers of inflammation. The authors also found the low FODMAP diet reduces certain gut bacteria, such as Bifidobacteria, that may be beneficial to health and may reduce inflammation.
- Long-Term Effects: Long term studies are needed to further evaluate the impact of an LFD on a patient’s gut microbiome and their overall nutritional status.
- Adherence: Although compliance is reported as relatively high in many studies, “real-life” adherence rates will need to be closely monitored, as an LFD may not be practical for many patients.
Key Things to Know About Diet in IBD
- Studies are underway to investigate whether diet can be used to treat gut inflammation in IBD, however there is currently not enough evidence to recommend any particular diet as effective.
- Studies show that a low FODMAP diet will help to treat up to three-quarters of people with IBS and there is evidence to show that a low FODMAP diet also helps control symptoms in the majority of people with both quiescent (inactive) IBD and IBS.
- FODMAPs act as prebiotics in the gut, meaning they stimulate the growth of good bacteria, which is probably important if you have IBD, so always aim to minimise your FODMAP restriction. A dietitian can guide you on how to find the level of FODMAP restriction suitable for you.
- A gluten free diet will only heal the gut in people with coeliac disease, not IBD. However, many people with IBD feel better on a low gluten or gluten free diets to treat their IBS. Gluten and FODMAPs are found in the same grains, so people may feel better because FODMAPs are incidentally reduced on a gluten free diet.
- Low fibre and low residue diets are only recommended in special circumstances, e.g., if you are at risk of bowel obstruction (blockage). Your doctor and dietitian will tell you if this type of diet is indicated.
- People with IBD may have increased requirements of certain nutrients, so it is important that you do not restrict your diet without advice from a dietitian.
Implementing a Low-FODMAP Diet
Patients with IBD seeking to implement a Low-FODMAP Diet should consult with a dietary professional. Low-FODMAP Diet may not be a good choice for everyone, particularly for those at risk of developing eating disorders. It is also difficult to implement properly, so it is best undertaken with an experienced dietitian. Excessive fiber intake from fruits and vegetables can cause GI pain and an increased risk of a bowel obstruction, particularly in patients with strictures. Fiber-containing foods should be added in small quantities at a time to allow the body to adapt to processing more fiber and build the proper muscles and bacteria to handle fiber. Patients with strictures should take extra care to first peel fruits and vegetables and cook them well and may need to consider pureeing them initially.
For patients who are not currently consuming many fiber-containing foods, slowly adding in high-FODMAP foods could cause gastrointestinal symptoms due to the fiber rather than the carbohydrates. High-FODMAP foods draw water into the intestines, which can perpetuate diarrhea. The fermentation of high-FODMAP foods by bacteria in the colon can cause bloating, gas, and cramping pain.
Other options for treating persistent symptoms are a Gluten-free, Dairy-Free and/or Lactose-Free Diets or avoiding Trigger Foods.
Low- and High-FODMAP Foods
| Low-FODMAP Foods | High-FODMAP Foods |
|---|---|
| Eggplant, green beans, bok choy, bell pepper, carrot, cucumber, lettuce, potato, tomato, zucchini | Apples, pears, mangoes, cherries, figs, nashi pears, pears, watermelon, dried fruit (high in fructose) |
| Cantaloupe, grapes, kiwi, orange, pineapple, strawberries | Artichoke, garlic, leek, onion, spring onions (high in fructans) |
| Almond milk, brie and camembert cheese, feta cheese, hard cheeses, lactose-free milk, soy milk (made from soy protein) | Mushrooms, cauliflower, snow peas (high in mannitol) |
| Eggs, firm tofu, plain cooked meats/poultry/seafood, tempeh | Wholemeal bread, rye bread, muesli containing wheat, wheat pasta, rye crispbread (Fructans and GOS) |
| Corn flakes, oats, quinoa flakes, quinoa/rice/corn pasta, rice cakes (plain), sourdough spelt bread, wheat-/rye-/barley-free breads | Red kidney beans, split peas, falafels, baked beans (high in GOS) |
| Dark chocolate, maple syrup, rice malt syrup, table sugar | Soft cheeses, milk, yogurt (high in lactose) |
| Macadamias, peanuts, pumpkin seeds, walnuts | Cashews and pistachios (high in GOS and fructans) |
| Honey, HFCS, artificial sweeteners (high in polyols) |