Food sensitivities may contribute to irritable bowel syndrome symptoms

Last Updated: 2015-07-03

By Will Boggs MD

NEW YORK (Reuters Health) - Sensitivities to various foods may contribute to symptoms in individuals with irritable bowel syndrome (IBS), researchers say.

Multiple factors have been proposed to cause symptoms in the 10% to 25% of the general population who have IBS. But only a few studies have linked food consumption to functional symptoms in these individuals, Dr. Peter R. Gibson from Alfred Hospital in Melbourne, Australia, and colleagues note in Gut, online June 15.

In their report, the researchers address the ongoing controversy about wheat, gluten, and fermentable oligo-di-monosaccharides and polyols (FODMAPs) in IBS. They provide some evidence that foods could trigger IBS symptoms via immune and mast cell activation, mechanoreceptor activation through luminal distension associated with visceral hypersensitivity and altered motility, and chemosensory activation by bioactive chemicals in food.

The team also points to the controversy that muddies the distinction between non-celiac gluten sensitivity (NCGS), non-celiac wheat protein sensitivity (NCWPS), and IBS itself.

About 5% of IBS patients test positive for celiac disease, and celiac disease itself may present with typical IBS-like symptoms, they note. Most patients with NCGS report IBS-like symptoms, and about a third of IBS patients may have NCWPS.

As for FODMAPs, seven published studies have shown efficacy of a low-FODMAP diet in reducing symptoms of about 70% of IBS patients. Problems with these studies include the choice of placebo, their short duration (three days to six weeks), and the lack of blinding.

Moreover, it is not even clear that a low-FODMAP diet is nutritionally adequate.

"One missing aspect is whether the intestinal responses to the dietary proteins are actually translated into altered gut physiology such as visceral hypersensitivity or abnormal motility responses," the researchers say. "If that can be proven, then it places even greater importance of defining methods of detecting such sensitivities accurately so that the underlying condition can potentially be cured rather than just symptomatically treated."

"The place of diet, whether it be low FODMAP diet, gluten-free diet (GFD), or other fancy diets, is now established in the therapeutic strategies that clinicians can offer their patients," they conclude. "While the truth remains clouded, facts are emerging from the fiction."

Dr. Magdy El-Salhy from the National Centre for Functional Gastrointestinal Disorders at Haukeland University Hospital, Bergen, Norway, recently reviewed the impact of diet in IBS patients.

"Our long experience with IBS patients showed there is a large individual difference regarding the tolerance to wheat and wheat-products," Dr. El-Salhy, who was not involved in the new study, told Reuters Health by email. "This difference is caused probably by the individual difference in intestinal microbiota. This assumption gets support from the clinical observation that IBS patients with regular intake of probiotics tolerate wheat products better than before consuming probiotics. In other words it is not only diet, but also intestinal microbiota that play an important role for the tolerance of wheat."

"In a recent paper published from our group, we concluded that there is no convincing evidence that IBS patients suffer from food allergy/intolerance," Dr. El-Salhy added.

"As a healthcare provider, I find it unfortunate with the huge media drive supported by celebrity endorsement that gluten-containing diet is harmful for health," Dr. El-Salhy said. "Wheat and wheat-based products make substantial contributions to the dietary intake of protein, dietary fiber, minerals (especially iron, zinc, and selenium), vitamins, phytochemicals, and energy, and several billion people rely on wheat for a substantial part of their diet. Furthermore, initiation of gluten-free diet (GFD) without dietetic supervision or education can cause inadequacies of nutrient intake including fiber, thiamin, folate, vitamin A, magnesium, iron, and calcium."

In a recent report, Dr. Antonio Carroccio from the University Hospital of Palermo in Italy, who also was not involved in the new work, focused on the role of non-celiac wheat sensitivity in IBS. He told Reuters Health by email, "A great percentage of IBS could be linked to a food allergy/intolerance, and the elimination diet could be a useful (the first, probably) therapeutic approach to the IBS. Much must be still understood about the mechanisms."

Studies of NCGS/NCWS are highlighting potential relationships between food antigens and autoimmunity, Dr. Carroccio said. "Wheat, in particular, could contain proteins which could play a role in the activation of the innate immunity, and we have very recently demonstrated a possible link between NCWS and autoimmune diseases."

Dr. Gibson was not available for comments.

SOURCE: http://bit.ly/1R6SXCJ

Gut 2015.