Repeated cycles of a low-calorie, plant-based diet have shown promise as a treatment for inflammatory bowel disease (IBD).

A low-calorie diet rich in vegetables may reduce inflammation in IBD.

IBD and gut inflammation

The term IBD mainly covers two conditions, Crohn’s disease and ulcerative colitis, whose principal feature is long-term inflammation of the intestines. This constant inflammation eventually damages the tissue of the gut.  The main difference between these conditions is that Crohn’s disease can occur anywhere in the gut between the mouth and the anus, while ulcerative colitis affects the colon and rectum.

According to 2015 survey data in a Centers for Disease Control and Prevention (CDC) study, about 3 million adults in the United States have reported ever having had a diagnosis of IBD.  This figure suggests that at least 1.3 percent of the U.S. adult population has IBD, which often occurs with other illnesses and results in poor quality of life and complications requiring hospitalizations and surgical procedures.

The main symptoms of IBD are abdominal pain and diarrhea. People with ulcerative colitis can also experience rectal bleeding.  Risk factors for IBD include genetic predisposition and factors that alter gut bacteria, such as antibiotics.

For a while, experts thought that IBD was a “classic autoimmune” disease, where the immune system attacks the tissue of the gut as if it were a threat similar to that of disease-causing viruses and bacteria.  More recently, however, other explanations about the origins of IBD have emerged, and there is a growing view that Crohn’s disease and ulcerative colitis are a complex combination of diet, gut bacteria and genetics where diet may be the driving factor for all others.

IBD and Diet

Diets that alter gut bacteria in ways that promote inflammation have consistently been associated with the development of IBD.  To understand the relationship between diet and IBD better the researchers tested a “fast-mimicking” diet on a mice.  The study compared a water-only fasting diet with periodic 4-day cycles of a fast-mimicking diet.  That is, one group of mice was put on a low-calorie, low-protein, fast-mimicking diet and another on a water-only fast.  Both groups of mice had long-term features of IBD.  The mice on the fasting-mimicking diet consumed 50 percent of their normal intake of calories for 1 day, and then only 10 percent of their normal calories for a further 3 days. The mice on the water-only fast consumed no food at all; they only had water for 48 hours.

The results revealed reductions, and even reversals, in some IBD features in the fast-mimicking diet mice that had two cycles of the 4-day diet and then resumed their normal food intake.  In comparison, the mice on the water-only fasting diet showed fewer improvements.  This would suggest that the fast-mimicking diet contains certain nutrients that increase the effect of fasting on gut bacteria to reduce inflammation.  The researchers concluded that it’s not just about the cells of the human body but it’s also about the gut bacteria that are affected by both the fasting and the diet.

The researchers also saw tissue repair and an increase in stem cell activity in the colon and small intestine of the mice on the fast-mimicking diet. Also, the animals’ small intestines grew longer after several cycles on the diet.  The research team indicated that this confirms that while fasting readies the tissue for improvement, replenishing cells and repairing tissue only occurs when “refeeding” takes place.

This study, and also in previous work, the research team tested the effect of a fast-mimicking diet on humans. This aspect of the research showed that people with high levels of C-reactive protein (CRP) – a marker of inflammation – experienced a drop in the inflammation marker.  The fast-mimicking diet also reversed the increase in white blood cells that accompanies a rise in CRP and inflamation.

Conclusions and Next Steps

Taking these results together, the researchers conclude that a low-calorie, plant-based, fast-mimicking diet has potential as an effective treatment for IBD.  This study brings together two worlds of research.  The first, is about what you should eat every day, and many studies point to a diet rich in vegetables, nuts, and olive oil. The second is fasting and its effects on inflammation, regeneration, and aging.

The researchers reasoned that water-based fasting does not seem to be as effective as the fast-mimicking diet could be because while fasting produces many of the desired effects, the body still needs essential nutrients to do the rest.

The investigators are already planning a randomized clinical trial to evaluate the safety and effectiveness of fast-mimicking diet cycles in humans with IBD.