If your bowel has ever been irritable, you were well aware of its complaints. Pain, bloating, and altered states in the bathroom may indicate irritable bowel syndrome or IBS.
Frustratingly, IBS cannot be explained by a test or evidence of tissue damage, such as in lactose intolerance, celiac disease or colitis. Diagnosis follows elimination of these abnormalities.

The prime suspect appears to be a disturbed gut-brain interaction with local contributors of immune activation, intestinal permeability, altered microbiome and food sensitivities. Poorly understood, IBS appears to be an exaggerated response to certain foods. Diet modification—though difficult—has become central to control.

Fortunately, a new publication sorts out the evidence. The Dietary Management of Patients with Irritable Bowel Syndrome: A Narrative Review of the Existing and Emerging Evidence was published online in Nutrients September 2019.

For such a recalcitrant problem, the remedies have been many over the years, write the authors. Take a look at the brief summaries I have condensed from the article:

Wheat bran

In the 1970s, wheat bran was all the rage. But addition of wheat fiber yielded mixed results with many reporting exacerbation of symptoms.

Specific food intolerances

Wheat, corn, dairy products, coffee, tea, and citrus fruits were found to be relevant for food intolerance in a few IBS patients. Patients were assessed for presence of immunoglobulin (Ig) G antibodies towards food items. Use is limited today.

Soluble fibers

Opinion then swung towards use of soluble fibers (psyllium) to relieve gas production over the previous support for the unfounded insoluble fiber additions (wheat bran).

NICE guidelines

The National Institute for Health and Care Excellence (NICE) guidelines from the United Kingdom offer an initial approach to IBS.

The guidelines include: healthy foods, exercise, regular mealtime, ample fluids as well as restricting caffeine, alcohol, spicy foods and fatty food. Resistant starch, gas-producing foods (onions, cabbage, beans, carbonated beverages and artificial sweeteners) and certain fiber foods are also restricted

Low FODMAP diet

FODMAP is a mouthful. It is an acronym which stands for: Fermentable Oligo-, Di-, and Monosaccharides And Polyols.
The diet can be nutritionally restrictive. Carbohydrates such as these are found in many fruits, milk, cheese, beans, and vegetables. FODMAP is a collective term for short-chain carbohydrates that are incompletely absorbed in the small intestine leading to abdominal pain, diarrhea, flatulence and bloating.

A FODMAP restricted diet may improve symptoms for some with IBS. But a recent meta-analysis found the evidence for it is low-quality.

Thus the current recommendation is to initially restrict the diet for a short period and then to gradually reintroduce food items rich in FODMAPs in order to identify FODMAPs that should be restricted long-term.

Lactose

Many IBS patients avoid lactose, the main carbohydrate in milk. If the enzyme lactase is deficient (prevalence of deficit ranges from minimal in Northern Europe up to 90% in Asia), undigested lactose enters the intestines where it causes gas, bloating, cramps and diarrhea.

Note that IBS and lactose intolerance are different conditions with similar symptoms. Lactose intolerance via a hydrogen breath test should be ruled out before an IBS diagnosis is made. Though restricted in a FODMAP diet, avoiding lactose may only give minor benefits in most patients with IBS.

Low-Fructose/Fructan Diet

With fructose consumption dramatically increased in the past few decades, GI problems may be exacerbated. A small percentage may benefit from restriction. Because it is difficult to follow, recommendations to restrict fructose and fructans (polymer of fructose molecules) are rare.

Low-Carbohydrate Diet

Apart from a small study (pain and stool consistency and frequency improved) not much is known about the impact of a low-carbohydrate diet in IBS patients. More studies may reinforce the evidence.

Gluten

Unlike that in animal muscle, the proteins in wheat, barley, rye and oats are not popular these days. Up to 20% of the population of Western countries follows a strict gluten-free diet. The evidence is conflicting; excluding so many foods may also restrict other triggers such as fructans. In any case, a healthy microbiota may lessen the need to restrict gluten.

Gut Microbiota Alterations

Microbes, given their proximity, are clearly involved. A 2018 study revealed that responsiveness to a low FODMAP diet may be predicted by the bacterial profile in IBS patients before starting the treatment. Additionally, Lactobacilli and Bifidobacteria are heavily compromised in IBS patients.

Could probiotics help in the resulting dysbiosis? Absolutely!

  • In some studies strains of Bifidobacterium and Lactobacillus noticeably improved symptoms in IBS.
  • Several meta-analyses found probiotics to be superior in trials comparing probiotics against placebo in reducing IBS symptoms.

Takeaway

IBS is a mystery. But no one would dispute our workhorse intestines are assaulted with more new foods, chemicals and toxins than ever before in history. Who wouldn’t rebel? Diet management, with low FODMAPs and gluten-free leading the charge, are the current recommendations. The microbiota may be the light at the end of the tunnel as we learn more about its role in IBS. Stay tuned for more specifics on this in a future blog.