Inflammatory bowel disease (IBD): what role does diet play?

Inflammatory bowel disease (IBD) is an umbrella term that describes chronic inflammatory disorders of the gastrointestinal tract. Crohn’s disease and ulcerative colitis are the two most common forms of IBD. In recent years, research into the role of diet in the cause and treatment of IBD has been gaining traction. In this podcast episode, I look at some of that evolving research into potential dietary triggers linked to causing IBD as well as possible treatments for managing IBD with diet.

Links referred to in the podcast

• Review of diet for IBD https://www.nature.com/articles/s41430-021-01051-9
• Faecal microbiota transplantation for the treatment of IBD https://www.frontiersin.org/articles/10.3389/fphar.2020.574533/full

Episode transcript
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Transcript

Inflammatory bowel disease (IBD) is an umbrella term that describes chronic inflammatory disorders of the gastrointestinal tract. Crohn’s disease and ulcerative colitis are the two most common forms of IBD. In recent years, research into the role of diet in the cause and treatment of IBD has been gaining traction. In this podcast episode, I’ll look at some of that evolving research into potential dietary triggers linked to causing IBD as well as possible treatments for managing IBD with diet.

Inflammatory bowel disease is a chronic inflammatory condition of the colon and rectum. Ulcerative colitis and Crohn’s disease are the two most common types of IBD. Ulcerative colitis affects the colon whereas Crohn’s disease can occur in any part of the intestines. Common symptoms of IBD include persistent diarrhoea, abdominal pain, rectal bleeding and bloody stools, weight loss and fatigue.

IBD should not be confused with irritable bowel syndrome or IBS. Although people with IBD may experience some symptoms that overlap with IBS, IBD and IBS are very different conditions.

The exact cause of IBD is not entirely known. It is believed to be caused by an interaction between genetic, microbial and environmental factors. These types of interactions can lead to an exaggerated inflammatory reaction in the digestive tract, causing a series of complications typical of intestinal inflammation.

The so-called typical Western dietary pattern (which is a diet loosely defined as one high in overly processed foods, red meats, added sugar and junk food, and low in fruits and vegetables, wholegrains, seafood and poultry) has been associated with a higher incidence of IBD in observational studies. Although the dietary factors responsible for the development of the disease are still to be determined, the cause may be related to the more pro-inflammatory nature of a typical Western diet. Some components of this dietary pattern with proinflammatory potential may cause changes in immunity as well as a change in the intestinal microbiota, leading to the inflammatory reaction that causes IBD. The opposite of a typical Western dietary pattern is one that is rich in fibre from a variety of plant foods and also has good sources of omega-3 fatty acids which together may offer some degree of protection from IBD.

Many people with IBD are likely to follow dietary advice from a variety of sources, including the Internet, and even though there is no shortage of dietary advice and a range of diets to try, there is not a lot of scientific evidence for most approaches.

And it is that last point on diet and IBD that I want to focus on for the remainder of this podcast. This comes about from a recent review on this topic about what we know so about diet in IBD. And I’ll link to this review in the show notes as it is a good summary document. https://www.nature.com/articles/s41430-021-01051-9

In a nutshell, and in no particular order, here are the key diets the review looked at: a low-FODMAP diet, gluten-free diet, lactose-free diet, a diet high in fibre, plant-based diets, the Mediterranean diet, a high-protein diet, Paleo diet, an anti-inflammatory diet, a specific carbohydrate diet that removes all carbohydrates except monosaccharides such as a glucose and fructose, an IgG4 exclusion diet which removes foods thought to trigger certain immunoglobulins, and finally a microparticle exclusion diet which removes very small non-biological items like titanium and silicates.

Now, it is beyond the scope of this podcast to go into detail about all of these diets, and some of them are a little way out there as far as the gap that exists in the theory of why they are promoted and having evidence to support it. Theories, just like dreams, are free. But the review paper goes into a bit more detail on them if you want to dig a bit deeper.

Instead, I’ll touch on a few of the diets that at least look promising for having some credible evidence behind them. The first is the low-FODMAP diet. FODMAP is an acronym for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols and includes carbohydrates such as lactose, fructose, fructans (which are long chains of fructose molecules like inulin) and sugar alcohols. FODMAPs are found in many foods including wheat, milk, pears, plums, onions, garlic and legumes.

Even though IBD and IBS are very different conditions, IBD does have some connection to IBS because IBS-like symptoms are over-represented in people with IBD. Considering the growing evidence of the beneficial role of a low-FODMAP diet to treat IBS, a low-FODMAP diet is at least being looked at for what role it could play in IBD.

We are now starting to see some clinical trials emerging in this area asking the question if a low-FODMAP diet could offer some therapeutic benefit in people with IBD. And the results are looking promising. People with IBD following a low-FODMAP diet are more likely to experience a decrease in disease severity and inflammation. But what is being seen so far is an improvement in symptoms, not so much the underlying medical condition. So, a low-FODMAP diet could be recommended to improve symptoms in some people with IBD in the remission phase. But as a low-FODMAP diet is meant to be used short-term because you want to eventually be eating again many of the beneficial foods it excludes, it is not a feasible option for the long-term management of IBD.

A diet high in fibre is another approach. Fibre itself is considered ‘anti-inflammatory’ and that is likely through its connection with the gut microbiota. Several observational studies have found an inverse relationship between fibre consumption and the risk of IBD so there may be something to the story. But we don’t just eat fibre; we eat a whole range of other nutrients in foods high in fibre so it is a complex relationship. Reducing fibre is a common characteristic seen in people with IBD during flare-ups, but it is unclear if this would be of benefit or not. So broad recommendations for people with IBD is to take a more middle-ground approach during periods of remission where the aim is more healthy eating goals, which by its nature, will mean a diet that contains plenty of dietary fibre.

Following from a diet high in fibre is another approach under the fairly meaningless term of ‘plant-based’ which people seem to define as a diet that is ‘mostly plants’ all the way to a vegan diet. But the common theme will mean a diet high in fibre if mostly minimally based plant foods are eaten.

Considering IBD is a condition of chronic inflammation, then a Mediterranean dietary pattern certainly has some merit. Taken as a whole, the dietary pattern ticks the box of an anti-inflammatory diet thanks to the presence of many of the foods and nutrients in it such as fibre, olive oil and omega-3s fatty acids. At least with observational evidence, there is a link between following a Mediterranean dietary pattern and having a lower risk of developing IBD. But there aren’t a lot of intervention studies looking at this diet in people with IBD, but the small number of studies that do exist point to a favourable change in the gut microbiota and markers of inflammation. Any advice on ‘healthy eating’ certainly can take cues from the theme of a Mediterranean diet for beneficial foods to include and foods to eat less of.

All of the other diets covered in the review didn’t have much evidence to support a benefit and were not to be recommended.

I thought I would finish up by mentioning a future direction. And it is to do with the highly experimental therapy of faecal microbial transplants or FMT for short. It is the literal transplant of an entire microbial ecosystem from the stool of a healthy donor to the recipient via a colonoscopy to help restore or restructure the gut microbiota.

In a study from 2015, it was found that a significantly greater percentage of people with active ulcerative colitis who were treated by FMT experienced remission, compared with those who were given a placebo. Compare that to a study from just last year that examined treating patients with Crohn’s disease who were in remission with FMT and also found a lower rate of flare-ups of the disease.

So, it is still early days for this sort of therapy before it moves from clinical trials to mainstream treatment, but it builds on what we know about our gut and the microbes in it for how they affect our immune system. If you want to read a recent update review on this field of FMT therapy in IBD, I’ll link to a paper in the show notes. https://www.frontiersin.org/articles/10.3389/fphar.2020.574533/full 

So, let’s wrap this up. Although none of the studies published to date suggests that dietary therapy should completely replace traditional therapy with medications or surgery for IBD, in certain people, diet could be tried as a first-line therapy with close follow-up and change of therapy if a complete response is not achieved. Based on the evidence, advice around ‘healthy eating’ is more suited to be applied as a dietary pattern that includes plenty of dietary fibre and which promotes a dietary pattern that aligns with anti-inflammatory effects of the beneficial foods and nutrients found in a Mediterranean-style diet that includes plenty of plant foods, fish and olive oil.

So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.

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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.