Low-FODMAP Diet – Foods to Avoid in IBS and Bloating

Short-Chain Carbohydrates May Cause Chronic Bloating and Diarrhea

It was found out that certain people complaining about abdominal bloating, excessive gas, chronic diarrhea or constipation, diagnosed with ‘dyspepsia’, irritable bowel syndrome (IBS) or functional bowel disease (FBD), actually cannot tolerate certain short-chained carbohydratescalled FODMAPs (1).

What Are FODMAPs?

FODMAPs (Fermentable Oligo-, Di-, and Mono-saccharides, And Polyols) are short-chain carbohydrates that are:

  • Osmotically active, so they, after ingesting, drag water from the intestinal vessels into the intestinal lumen, thus causing diarrhea
  • Fermentable (degradable by intestinal bacteria yielding large amount of gases, like hydrogen or carbon dioxide, thus causing abdominal bloating

FODMAPs include:

  • Oligosaccharides:
    • Fructans – chains of fructose with one glucose molecule on the end. Only minimal amounts of fructans may be absorbed in human intestine. They may interfere with absorption of fructose, thus aggravating symptoms in fructose malabsorption. Fructans-rich foods are: wheat (white bread, pasta, pastries, cookies), onions, and artichokes; other not commonly problematic foods with fructans are asparagus, leeks, garlic, chicory roots and chicory based coffee substitutes. Fructans with over 10 molecules of fructose in a chain are known as inulins and those with less than 10 fructoses are referred as fructo-oligosaccharide (FOS) or oligofructose. Fructans cause problems mainly in fructose malabsorption.
    • Galactans (like stacchyose and raffinose) are chains of galactose molecules with one fructose molecule on the end. They act much like fructans. Main galactans-rich foods are legumes (soy, beans, chickpeas, lentils), cabbage and brussel sprouts.
  • Disaccharides:
    • Lactose (milk sugar). Lactose is in dairy products, but it may be also found in chocolate and other sweets, beer, pre-prepared soups and sauces, and so on. Lactose is poorly absorbed in lactose intolerance, SIBO and in small intestinal inflammation (Crohn’s disease, celiac disease).
  • Monosaccharides:
    • Fructose (fruit sugar). Fructose-rich foods are honey, dried fruits like prunes, figs, dates, or raisins, apples, pears, sweet cherries, peaches, agave syrup, watermelon, papaya. Fructose is often added to commercial foods and drinks as high fructose corn syrup (HFCS). Fructose causes symptoms even in healthy people, if ingested in excess, especially in fructose malabsorption, but also in SIBO.
  • Polyols, also known as sugar alcohols (appearing as artificial sweeteners in commercial foods and drinks):
    • Sorbitol  may appear in “sugar-free chewing gum”, “low calorie foods”; naturally it appears in stone fruits: peaches, apricots, plums).
    • Xylitol naturally appears in some berries. A pack of chewing gum containing sorbitol or xylitol may cause bloating or diarrhea in a healthy child and especially in persons with fructose malabsorption or SIBO.
    • Other polyols, like mannitol, isomalt, erithrytol, arabitol, erythritol, glycol, glycerol, lactitol, ribitol, may be problematic in fructose malabsorption and SIBO.

Approach to a Low-FODMAPs Diet

In unexplained chronic diarrhea or bloating, FODMAPs should be considered as a possible cause, so their amount in the diet should be LIMITED (not necessary totally excluded).

General approach is to take off as much as possible FODMAPs from the diet for six to eight weeks. If FODMAPs are the cause of the symptoms, they should lessen considerably in the first week. Additional weeks of diet bring some rest to the small intestine and cause reduction of overgrown intestinal bacteria.

After six weeks, some foods that will least likely cause symptoms can be introduced back into the diet (diet challenge), one type of food every fourth day. For example, on the first day of the seventh week, a piece of food low in lactose, like yogurt, can be tried, and if in the next 72 hours no symptoms appear, other dairy products can be tried, and waited 72 hours again. If still no symptoms, it is not likely that dairy is problematic, or at least not problematic when taken in a limited amount. If symptoms appear, this speaks for lactose intolerance, so dairy should be avoided and next type of foods tried. This can be some low-fructose food like banana, then after 72 hours orange and then other foods with increasing amount of fructose. If you can eat 5 prunes in a row without having abdominal symptoms thereafter, it is not likely you have fructose malabsorption.

A registered dietitian may be needed to give instructions about introduction of the low-FODMAP diet and diet challenge.

Possible Symptoms of a FODMAP-Rich Diet

Excessive FODMAPs intake may cause:

  1. Diarrhea, since FODMAPs are osmotically active, so they drag water from the intestinal vessels into the intestine
  2. Bloating and flatulence, since FODMAPs are broken down (fermented) by intestinal bacteria to gases like hydrogen, carbon dioxide or methane
  3. Excessive belching (burping)
  4. Abdominal pain
  5. Unintentional weight loss
  6. Symptoms of vitamin and mineral deficiency, like paleness, tingling, tiredness, depression
  7. Headache

FODMAPS may also aggravate symptoms of:

How Long Should a Low-FOODMAP Diet Last?

When problematic FODMAPs are identified, some people will need to strictly avoid them for life, if they want to be symptoms free, others will be able to ingest them in a limited amount. General rule is: do not eat FODMAPs-rich foods in large amount in one sitting and do not eat them every day.

If Low-FODMAP diet does not lessen your abdominal symptoms, consider having tests for food allergies, dumping syndrome, celiac disease, and inflammatory bowel disease (Crohn’s disease).

Can a Low-FODMAP Diet Be Dangerous?

Low-FODMAP diet should not be introduced by any person with diabetes, hypoglycemia or other metabolic disorders, or in malnutrition, without prior consultation with a doctor. It may be necessary to interrupt Low-FODMAP diet in any severe acute disease, after injury or surgery and in other urgent situations.

None of FODMAPs (fructans, galactans, fructose, lactose, polyols) is essential nutrient for human, though, meaning they are not necessary for life.

Foods to Avoid in IBS

Foods that irritate individuals diagnosed with IBS, differ from person to person. It was found out that in many of them FODMAPs-rich foods are the culprit (1).

Related Articles:


  1. Low FODMAP diet (virginia.edu)
  2. Polyols – sugar alcohols (sugar.org)
About Jan Modric (209 Articles)
Health writer

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