Inflammatory Bowel Disease (IBD) is the umbrella term for a group of complex and multifactorial disorders afflicting the intestinal tract. As the name implies, acute and chronic inflammation of the intestine is a major symptom in IBD. Crohn's disease and ulcerative colitis are the two main disorders in IBD, in which this relapsing inflammation of the intestinal tract is seen.
IBD onset typically happens between 20 and 40 years of age and usually persists for life.
Although the highest disease incidence is currently in Canada and Europe, incidence rates are increasing worldwide.
Ulcerative Colitis (UC) and Crohn's Disease (CD)
Though Crohn's disease and UC both fall under the IBD banner, and present with similar symptoms, both the location of the disease in the intestine and the histologic, i.e. tissue changes are different in each subtype.
Disease symptoms are unpredictably exacerbated and occur intermittently, followed by variable-length periods of remission.
A Perfect Storm
A few factors: genetic predisposition, environmental factors, and alterations in the intestinal microbiome combine in a perfect storm to bring about the inflammation that is characteristic of IBD.
In addition, consumption of a western diet may act in combination with these to speed up the onset of IBD. This is because genetics, microbes, and what we eat are all factors in maintaining the balance of gut health, a.k.a "homeostasis."
When all these factors are in synergy, gut health is at its best, but when the synergy is broken or altered for various reasons, it adversely impacts gut health.
Alteration of any one component might upset the system, but it is not enough, by itself, to cause IBD.
Of all these factors, we know the most about the genetics of IBD.
The genetics of IBD
Over 160 loci have been linked to increased IBD susceptibility. These loci implicate a wide and diverse lineup of genes that code for a whole range of physiological processes, mainly:
- Microbe recognition
- Lymphocyte activation, and
- Intestinal epithelial defense.
Environmental factors contributing to IBD
One of the main theories being floated is the "hygiene hypothesis." It is thought that given the highly sanitary conditions in developed countries, crucial early childhood exposure to a variety of enteric germs simply does not happen. As a result, there are crucial gaps in the "training" of the immune response.
The other prominent theory is the "cold chain hypothesis." This suggests that prolonged refrigeration of foodstuff promotes the growth of psychotropic bacteria such as Yersinia and Listeria.
In other words, any tip in the balance of the intestinal gut population has the potential to flag off the kind of immune responses that are linked to the IBD pathway.
In addition, certain drugs and activities have the capacity to damage the intestinal epithelial barrier properties. These include non-steroidal anti-inflammatory drugs, alcohol, smoking, or bacterial toxins.
The connection between IBD and diet
A standard Western diet rich in animal fat and protein, and low in fiber has been strongly linked to the development of IBD. A high intake of digestible carbohydrates, starch, and refined sugar has also been shown to upset the gut microbial balance.
Omega-6 polyunsaturated fatty acids and long-chain fatty acids, in addition to the above, act in concert to alter the bacterial components of the microbiome, increase intestinal permeability, and promoting inflammation.
The mechanisms of protein-induced inflammation are not yet fully understood, but the consumption of red meat is thought to be a factor in IBD relapse.
Obesity is another fallout of a high-fat diet that, like IBD, is characterized by inflammation and elevated levels of proinflammatory cytokines and adipokines.
On the other hand, high vegetable intake can lower the risk of UC, whereas greater intake of fiber and fruit can lower the risk of CD. Omega-3 fatty acids, medium-chain triglycerides (MCTs) and nondigestible carbohydrates improve these parameters and thus overall intestinal well-being.
Exclusionary diets, where one food category is left out, has shown some efficacy in relieving the symptoms of IBD. Further research will reveal how diet can be leveraged to improve the quality of life of patients with IBD.