Irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) are two distinct gastrointestinal disorders, though the differences between the two can be confusing for many people.
Irritable bowel syndrome (IBS) is classified as a functional gastrointestinal disorder which involves disturbance in bowel function, due to the intestinal muscles that do not allow a correct passage of the food along the digestive tract. It is the most common gastrointestinal condition that affects up to 21% of the general population; with women are more affected than men.
Inflammatory bowel disease (IBD) is a group of inflammatory conditions in which the body’s own immune system attacks parts of the digestive system. This is a more severe condition that can cause destructive inflammation and permanent harm to the intestine. It can also lead to colon cancer if not treated.
The major differentiator between the two, is patients suffering from IBS have no structural or biochemical abnormalities as well as no inflammation, whereas IBD patients do.
The confusion with these two conditions often occurs because they are characterised by similar symptoms which include abdominal pain, cramps, bloating and diarrhoea.
It is very common that IBD patients have IBS symptoms. However, your doctor will be able to recognise the difference by performing a blood and stool test or a colonoscopy. Two important indicators of IBD are the presence of markers that indicate the immune system is causing inflammation and a deficiency in red blood cells. IBD patients are very likely to suffer from anaemia because the inflammation of their bowel causes internal bleeding.
On the other hand, it is very rare to have internal bleeding in IBS patients. Moreover, the consistency of the stool is different: it is more watery and loose with blood in IBD patients than IBS patients, because IBD is characterised by constant diarrhea, whereas IBS involves diarrhoea alternating with constipation.
The pathogenesis of IBS seems to imply alterations in motility, visceral sensation, brain-gut interactions and microbiome. One of the most common causes of IBS is an imbalance (dysbiosis) between the gut and the microorganisms in our microbiome. This imbalanced is caused by excessive stress or a weakened immune system. Changes in the microbiome activate mucosal innate immune responses resulting in increased epithelial permeability and bile acid malabsorption which triggers the IBS symptoms.
On the other hand, IBD involves inflammatory reactions which are characterised into Chron’s disease and ulcerative colitis. The aetiology of the disease is very complex, and it involves a combination of genetic, environmental, immunological and gut microbial factors.
Recurring and bloody diarrhoea is the most prevalent and debilitating symptom in IBD. The reason why IBD patients have a constant diarrhoea is attributed to the persistent inflammation of the bowel which results in dysregulated intestinal ion transport and an increased accessibility of the pathogens to the intestinal mucosa. As a result, these patients experience an altered expression of ion transporters that do not allow the excretion of water. Water is therefore accumulated in the intestinal lumen leading to diarrhoea.
The best dietary treatment that we recommend for patients suffering from IBS is a low FODMAP diet. This diet consists of restricting foods with highly fermentable oligo-di and monosaccharides as well as polyols which trigger the symptoms. Oligosaccharides include the brassica family as well as wheat, barley, rye, onion, garlic, cabbage and pulses.
Particularly, gas producing foods such as beans, chickpeas, cabbage and onion need to be avoided. Disaccharides mainly involve dairy products such as processed cheese and milk. Monosaccharides include honey, mango, sugar snaps and fructose sweeteners. Finally, polyol include mannitol, sorbitol and xylitol.
The main mechanism of action of low-FODMAP diet is believed to be a reduction in small intestinal absorption of osmotically active short-chain carbohydrates (SCCs). These carbohydrates force the entrance of water inside the GI tract. Moreover, after entering the colon, they represent a food that is easy to use by the intestinal microbiota, which ferment them and thus increase gas production. As a consequence, a reduction of SCCs results in diminished intestinal water content and gas production. Along with a low FODMAP diet, we also advise a reduction of fibre intake when diarrhoea is prevalent over constipation.
The best dietary approach for treating IBD is more complex, as there are five possible diets that are recommended based on the course of the disease, surgical procedures and type of pharmacotherapy:
- The specific carbohydrate diet (SCD): is a diet that excludes complex carbohydrates such as oats, buckwheat, rye, barley and pulses. It excludes milk, grains, soft cheeses and non-honey sweetener, and it is low in fibre.
- The low FODMAP diet: this diet can also be suitable for IBD patients (see above)
- The gluten-free diet: this diet involves the elimination of gliadin from food. It allows gluten-free grains from corn and cereal, poultry, meat, fruits, vegetables and dairy. Current evidence shows that 60% of IBD patients are sensitive to gluten and they benefit from a gluten-free diet. This is recommended along with the low FODMAP.
- The anti-inflammatory diet: this diet aims at reducing inflammation by the intake of anti-inflammatory phytonutrients, herbs and spices, and omega-3 fatty acids from fish, nuts and seeds. The diet allows a small consumption of grains, gluten and probiotic foods.
- The Mediterranean diet: it involves the replacement of saturated fats with unsaturated fats. For example, olive oil, oily fish, avocado, nuts are encouraged. It is a high fibre whole-grain diet and low in red meat and processed meat.