All together, a familiar message is beginning to come through: a balanced diet that is rich in fruits, nuts, and vegetables, and not heavily based on certain types of meat (such as red, processed, or fried) might decrease an individual’s risk for developing IBD and might also help those who already have it to limit the occurrence of disease flares.
Inflammatory bowel disease (IBD) is a collective term for a number of intestinal conditions, primarily Crohn’s disease and ulcerative colitis. In the search for a fuller understanding of IBD, numerous recent studies have looked at the effects of specific foods on the development of the disease and management of its associated flares.1 Along the way, researchers have found that while some foods do appear to be associated with an increased risk of IBD and flares, others may actually have a protective effect.
What We Know
There has been a recent, dramatic increase in the incidence of IBD in certain countries, particularly those that have implemented a Western diet. Canada has the highest reported incidence of IBD in the world, so this trend is of particular concern right here at home.2 When families move to different geographical regions, the children take on the same degree of risk for IBD as is present in the new place of residence, whereas their parents maintain the same risk as is present in their previous location.1 As well, in pediatric Crohn’s disease patients, the introduction of exclusive enteral nutrition therapy (administering specially formulated nutrition to the GI tract via a feeding tube) has a high rate of controlling the disease, suggesting that diet does have an effect on gut inflammation. For these and other reasons, we know that environmental factors play a role in IBD, in addition to genetic predisposition. Research continues to point to the Western diet – typically rich in meat, fat, sugar, synthetic additives, and processed foods – as an important risk factor for IBD. There are two ways that certain foods might play a role in IBD: they could have a direct effect on the gut or they could disrupt the microbial balance, which in turn disrupts the gut mucosa, leading to inflammation.
All together, a familiar message is beginning to come through: a balanced diet that is rich in fruits, vegetables, and nuts, and not heavily based on certain types of meat (such as red, processed, or fried) might decrease an individual’s risk for developing IBD and might also help those who already have it to limit the occurrence of disease flares.
IBD patients, who are already vulnerable to nutritional deficiencies because their digestive tracts are compromised by disease, sometimes avoid certain types of food that they associate with disease activity, even if they are not certain that those foods actually elicit their symptoms. It can be very difficult to achieve a balanced diet when an individual lives in constant fear that particular foods will cause pain or trigger an IBD flare, but current research gives these individuals even more reason to try to include a variety of healthy foods in their diets whenever possible, as it might help decrease their risk of disease relapse. Here we present some highlights from the latest studies.
Studies examining the association between meat consumption and IBD have been conflicting, with some research showing a significant link but others showing none. A large study in France involving 67,581 middle-aged women showed an association between total meat and fish consumption (though not eggs or dairy) and an increased risk for developing IBD.3 Similarly, a recent survey of the Japanese population found that the high number of new Crohn’s patients had a strong correlation with increased protein consumption in the Japanese diet.1
In a small study that looked at 149 children newly diagnosed with Crohn’s and 251 control participants, researchers found that a high dietary intake of meat, fatty foods, and desserts correlated with a high risk of developing Crohn’s in girls, and a high intake of vegetables showed a low risk in girls.1 The researchers did not find these correlations in boys within this study.
One large study that included 20,686 men and women found no association between protein or any macronutrient and ulcerative colitis, but that study used very broad categorizations. For example, the researchers studied protein as a percentage of the total energy consumed, rather than considering the specific sources of protein, such as meat, fish, nuts, dairy, legumes, and so on.
In a study of 191 ulcerative colitis patients in remission, meat consumption, especially red and processed, as well as other forms of protein and alcohol, were associated with disease relapse.1
This doesn’t mean you should eliminate meat from your diet, but keep the portion of meat on your dinner plate in moderation and avoid fried and processed versions whenever possible.
Fish and Nuts
In a 2011 study,4 researchers analysed the potential protective effect of fish and nuts – both of which have known anti-inflammatory properties – on deaths related to several inflammatory diseases, including IBD. The study included 2,514 participants older than 49, who completed a detailed questionnaire on diet habits. The researchers followed up with the participants after 15 years and found that even moderate consumption of nuts had a significant protective effect against death from inflammatory disease-related conditions, particularly in women. Nuts have a number of properties the researchers say may play a role in the protective effect, including polyunsaturated fats, magnesium, and antioxidants.
The researchers were surprised to find no association between fish consumption and IBD-related deaths in either women or men, because numerous other studies have shown that eating fish has a protective effect. They note that they were studying mortality but not the incidence of these diseases or flare-ups, which means that fish could have a beneficial effect that simply wasn’t analysed in this study. They also hypothesize that if fish is fried, the harmful effects of frying may cancel out any protective effect.
Two types of fibre come from plant materials, which the human body cannot digest without bacterial help. Soluble fibre can absorb water and transform into a gel-like consistency in the gut, whereas insoluble fibre does not absorb water and works as a bulking agent to aid digestion. Most fibre-containing foods include varying amounts of both types. Although our gastrointestinal secretions and enzymes cannot break down fibre, given the right colonic microflora (bacteria and yeasts), our body can still derive a nutritive benefit from it. Some bacteria, for example, are able to break down soluble fibres to produce short chain fatty acids, including one called butyrate, which reduces mucosal inflammation.1,5
Studies have shown that a combination of probiotics and a high-fibre diet, which includes prebiotics, can improve the balance of beneficial over detrimental microbial species in the gut, preventing inflammation that can result from imbalances in the gut microbiota. Prebiotics are specific carbohydrates that nourish the probiotics.
Fibre-rich foods also contain many beneficial substances, including flavonoids that assist in intestinal barrier function and antioxidants that may protect against some types of inflammation. Although these reasons lead scientists to suspect that foods high in dietary fibre would have a protective effect against IBD, further research is required to confirm this. Some studies have found that a diet high in fibre-rich vegetables and fruits has a protective effect against IBD.1 Surprisingly, however, the same large study with 260,686 participants that found no correlation between protein and risk for ulcerative colitis, also found no protective effect between fibre and ulcerative colitis.6
Until more research is available, it would be wise to keep those whole grains, fruits, and vegetables on the menu. Studies are consistently finding a link between a high intake of dietary fibre and protection from other GI-related conditions, such as diverticular disease, constipation, and even colorectal cancer. Health Canada considers a food product to be a ‘high source of fibre’ if it contains 4-6g of fibre per serving, and a ‘very high source of fibre’ if it contains more than 6g of fibre per serving. It is important to consume plenty of liquid with high-fibre foods, to ensure well-formed stool.
A recent study showed that nutrients from leafy greens, which include numerous vegetables such as broccoli, kale, bok choy – and yes, Brussels sprouts too – help to strengthen the immune system and provide a positive influence on bacterial composition and healthy quantity in the gut.7
How does it work? Intraepithelial lymphocytes (IELs) are cells located just under the inner lining of the intestine. IELs help to regulate the bacteria and yeasts within the intestine and stimulate the growth of the protective epithelial lining. Loss of IELs leads to an imbalance of the microbiota (an increase in pathogenic organisms and loss of beneficial organisms), hindering the immune system, and making the intestinal lining more vulnerable to inflammation. There is evidence that alterations in the intestinal microbial composition have a causal role in the mucosal inflammatory response experienced by individuals with IBD.
Researchers have discovered that the consumption of foods such as leafy greens, which are high in AhR (a protein carbon that forms part of IELs), increased the number of IELs in the gut. Conversely, when they fed study mice a diet lacking in leafy greens, they found that the mice experienced a dramatic loss of IELs. The study shows that leafy greens are not only an important source of AhR, but that AhR deficiency caused by a diet low in leafy greens results in damage to colonic epithelial cells. The researchers recommend further studies into the role of AhR and the onset or relapse of IBD.
Even if you don’t especially love them on their own, there are plenty of leafy greens to choose from and lots of ways to incorporate them into your meals. Leafy vegetables are tasty when blended with fruit into a refreshing smoothie, and in this form are easily included in the diet.
There is limited evidence that a diet high in sugar, such as the refined sugar or glucose-fructose (derived from corn-syrup) that is found in most desserts, soft drinks and other sweet and processed foods, may increase an individual’s risk of developing Crohn’s disease,8 but a large cohort study found no risk association between sugar and ulcerative colitis.6 Future research may shed more light on any connection between sugar and IBD. However, some researchers theorize that artificial sweeteners may be a risk factor, even if sugar itself is not. Diets that are high in sweets are more likely to have increased amounts of artificial sweetener consumption as well as real sugar.9 As with other potentially risky food, enjoy sweets in moderation.
In their review of studies on IBD and diet, researchers in Denmark found many important methodological problems in most studies, particularly in retrospective studies, in which participants’ accuracy in recalling and recording dietary consumption, sometimes long after the fact, might not be reliable.1 They conclude that ongoing and future studies should provide data that is more definitive. In the meantime, the research seems to corroborate what our physicians and dietitians have been telling us for decades – it is a good idea to implement a balanced diet, such as that recommended in Canada’s Food Guide. This is often a challenge for patients with IBD, especially during episodes of intense disease activity, but since there is evidence that diet also affects the risk of relapse, these individuals – and family members who may be at an increased risk for the disease – should include a diversity of healthy foods on their dinner plates whenever possible.