A pioneering study offers new hope to patients who have this challenging condition
Treating irritable bowel syndrome is notoriously difficult because the cause is elusive. This common digestive disorder affects up to one in 10 people and it is characterised by abdominal pain, bloating, diarrhoea or constipation but symptoms vary as do responses to diet and drugs.
Hope now comes in the form of a study showing how people with IBS respond to a low carbohydrate diet.
The research reveals that IBS patients with genetic defects in carbohydrate digestion have a better response to particular dietary interventions. This could lead to tailored treatments for IBS, using genetic markers to predict which patients benefit from which diets.
The study is led by Professor Mauro D’Amato of LUM University in Italy and an international consortium of scientists led by Dr Maura Corsetti of Nottingham University.
Patients often connect their symptoms to eating certain foods, especially carbohydrates, and elimination or reduction diets targeting them are often effective.
We know changes in DNA can affect the way we process food. A good example is lactose intolerance, where an ineffective lactase enzyme hinders the digestion of dairy products.
In exactly the same way, this pioneering study suggests genetic variations in carbohydrate enzymes (hCAZymes) may affect how IBS patients respond to a low-carbohydrate diet (low-FODMAP).
The team has now shown that people with defective variants in hCAZyme genes are more likely to benefit from such a diet.
This study of 250 IBS patients, compared two treatments: a diet low in fermentable carbohydrates (FODMAPs) and, secondly, medication otilonium bromide, which reduces spasms in the gastrointestinal tract.
Strikingly, of the 196 patients on the diet, those carrying defective hCAZyme genes showed marked improvement compared to non-carriers, and the effect was particularly pronounced in patients with diarrhoea-predominant IBS
(IBS-D), who were six times more likely to respond to the diet.
In contrast, this wasn’t seen in patients receiving medication, emphasising genes affect the effectiveness of diet treatment.
Dr D’Amato says: “These findings suggest that genetic variations in hCAZyme enzymes, which play a key role in digesting carbohydrates, could become critical markers for designing personalised dietary treatments for IBS.
“The ability to predict which patients respond best to a carbohydrate-reduced diet has the potential to strongly impact IBS management, leading to better adherence and improved outcomes.”
This knowledge could enable doctors to identify, in advance, which patients are most likely to see results from specific dietary interventions.
This would not only avoid unnecessary restrictive diets for those unlikely to benefit but also open the door to personalised medicine for IBS.