What You Need to Know About a Low-FODMAP Diet for IBS

What You Need to Know About a Low-FODMAP Diet for IBS

What You Need to Know About a Low-FODMAP Diet for IBS

If you’ve ever had dinner and subsequently felt bloated, nauseous, had to run immediately to the bathroom, or otherwise felt uncomfortable, you’re familiar with how irritable bowel syndrome (IBS) feels.

Imagine “blocked up one minute and unable to go, then running to the toilet the next and feeling like the world might end,” (1) says Glenda Bishop, PhD. (2) “Having your belly so full and huge, although this time not from too much food, with so much pain that even loosening your belt doesn’t help. And over the top of all that… gas, so much of it that holding it in is next to impossible, and so terribly pungent that it could almost fell an ox. And then trying to keep everything hidden from the people around you so they don’t know what’s going on because it would be so terribly embarrassing if they did.” (3)

In a nutshell, that’s IBS. Researchers note symptoms of this chronic gastrointestinal (GI) disorder include abdominal pain, bloating, constipation, and diarrhea. (4)

IBS is more common than you might realize. Among general practitioners, this is the most common GI condition that accounts for up to 50 percent of patients seen in gastroenterology clinics. Based on diagnostic criteria and location, about 10 – 20 percent of the global population struggles with IBS. [The problem is more common with women than men and people under 50.] (4)

Specialists aren’t entirely sure what causes IBS, and they usually consider it a multifactorial problem. Symptoms include:

  • Heightened pain sensitivity or visceral hypersensitivity
  • Abnormal gut motility
  • Low-grade intestinal inflammation
  • Psychosocial factors
  • Dysregulated gut–brain axis
  • Small intestinal bacterial overgrowth (4)

Small intestinal bacterial overgrowth (SIBO) is the abnormal growth of bacteria in your small intestine normally found only in your colon. A healthy gut can prevent that excess bacteria from colonizing your small intestine, but certain conditions including hypothyroidism, diabetes, and potentially IBS can result in SIBO. (5)

But SIBO can also trigger or exacerbate IBS. (Like many conditions that are multifactorial, it has been considered both a sign and cause of the condition.) SIBO symptoms – including nausea, abdominal cramping, bloating, flatus, and diarrhea – overlap with those of IBS. (5)

“SIBO is a type of dysbiosis,” says Vincent Pedre, MD, in Happy Gut. “It is estimated that 50 to 75 percent of patients with IBS have SIBO (diagnosed by a hydrogen breath test) and benefit from treatments to reduce SIBO.” Among the problems with SIBO, says Pedre, include malnutrition (SIBO results from overpopulated bacteria consuming nutrients before they can be absorbed) and inflammation.

Inflammation can be another key driver in many gut problems. Among its havoc, inflammation can adversely impact your microbiome, which Pedre says is “hundred trillion microbes, which include a thousand different species of bacteria, a few dozen types of yeasts and fungi, an unknown number of viruses, and an occasional worm” that colonize your gut.

Researchers connect inflammation-triggered altered gut flora with various conditions including IBS. (6) Ultimately, gut inflammation with the resulting immune response and other problems trigger or exacerbate systemic inflammation, a contributing factor for nearly every disease including obesity. (7)

SIBO and other gut conditions usually require working with a healthcare specialist who can test, pinpoint underlying causes, and reduce the inflammation and other factors that contribute to problems like SIBO to restore gut health. That typically will involve providing nutrients and lifestyle factors but also eliminating triggers that create gut problems. Chief among them is your diet.


Some foods or ingredients are bad news, period. For example, high-fructose corn syrup in soda is undeniably unhealthy. But, other ingredients can be healthy for some people but create havoc for others.

Specific foods can become a major culprit for IBS. In one study among patients with IBS, researchers found about two-thirds had food-related symptoms.  Among those triggers included:

  • Fatty foods
  • Coffee
  • Alcohol
  • Spicy foods
  • Incompletely absorbed carbohydrates

That last one is crucial, yet many people overlook the incompletely absorbed carbohydrates that creates gut problems including IBS. Even foods that would be normally be perfectly healthy like legumes or fresh fruit can create or exacerbate these conditions. Researchers find when you remove the offending foods, you can often eliminate symptoms but more importantly, heal your gut condition.

These poorly absorbed carbohydrates are labeled Fermentable, Oligosaccharides, Disaccharides, Monosaccharides, And Polyols – mercifully shorted to the acronym FODMAPs.

High-FODMAP foods are absorbed, rapidly fermented, short-chain carbohydrates that can lead to excessive fluid and gas accumulation, resulting in bloating, abdominal pain, and distention. Essentially, they become “fast food” for bacteria in your large intestine, drawing in what creates excessive gas, bloating, and abdominal pain. (4)

“What makes these compounds in food so problematic is that they attract water, are not easy to digest, are poorly absorbed (unless cleaved by enzymes), and are rapidly fermented by gut bacteria, which leads to increased water and gas in the gut,” says Pedre.

Let’s look more closely at these foods:

  • Lactose – overall, about 75 percent of the world is intolerant the main sugar in dairy products. (8) Researchers show symptoms of IBS and lactose intolerance overlap, hence removing foods with this sugar on a low-FODMAP diet. (9)
  • Fructose – as you might guess, fruit contains the highest amounts of fructose. But some are higher than others. The worst offenders include apples, cherries, mangoes, watermelon and pears. (10)
  • Fructans – these short-chain carbohydrates, sometimes referred to as fructooligosaccharides (FOS), are found in artichokes, leeks, garlic, and onions. But you might not suspect the biggest culprit. “The highest intake of fructans in people’s diets worldwide comes from wheat,” says Pedre. “Since we lack the enzyme to break down fructans, eating too much often leads to bloating, gas, and pain.”
  • Galactans – these come from the sugar galactose, the highest amounts occur in beans (including lentils), and they can create gas and other gut-related problems.
  • Polyols – if you’ve ever consumed too much no-sugar-added candy or other foods with excessive sugar alcohols and subsequently bolted for the bathroom, you’re familiar with the side effects of polyols including maltitol, sorbitol, and xylitol. While some people tolerate small amounts fine, for people with digestive issues including IBS even a little bit of polyols becomes a very big problem.


Doing a Low-FODMAP Diet

The low-FODMAP diet is an elimination diet that typically lasts two to six weeks (sometimes longer) where you avoid all high-FODMAP foods. You follow this elimination phase with a reintroduction phase, where high-FODMAP foods are re-introduced step by step. Along the way, you access tolerance to various high FODMAP foods. Based on how your body responds, you’ll need to restrict some but not all high-FODMAP foods.

Put more bluntly, on a low-FODMAP diet, you eliminate incompletely absorbed carbohydrates that beeline from your small intestine (where they should be absorbed) to your large intestine, where bacteria ferment them and create gas that triggers symptoms of IBS including bloating and flatulence.

Pedre says FODMAP intolerance symptoms resemble those of gut disorders like IBS. Eliminating these foods can relieve IBS symptoms and, in some cases, create better conditions for your gut to heal.

P. R. Gibson and S. J. Shepherd first proposed FODMAPs as a hypothesis for Crohn’s disease in 2005. (11) From their hypothesis, Monash University developed a Low FODMAP Diet based on patients with IBS to help determine which foods to eat and avoid. (12)

“A low-FODMAP diet has been clinically and scientifically proven to reduce abdominal symptoms in people suffering from irritable bowel syndrome, celiac disease (not responding to a gluten-free lifestyle), and inflammatory bowel disease (in remission, with low inflammation),” says Pedre.

Among gut conditions, research shows a low-FODMAP diet can benefit Crohn’s disease and ulcerative colitis. (13) Other studies show a low-FODMAP diet works very well for people with IBS. Studies show reducing high-FODMAP foods improve gas, bloating and other IBS symptoms. (5)

Overall, the results are impressive. One review found up to 86 percent of patients with IBS who used a low-FODMAP diet experienced improvements in overall GI symptoms along with other problems like abdominal pain, bloating, constipation, diarrhea, abdominal distention, and flatulence. (2)

Patients who respond to an elimination diet that removes high-FODMAP foods gradually reintroduce individual foods to determine whether symptoms recur. Resolution of symptoms suggests (but doesn’t confirm) a causal relationship between the food and IBS. (5)

Knowing what foods are low and high in FODMAPs can become confusing, and keeping a detailed chart handy as you eliminate trouble foods makes eliminating the right ones easier. You can print out this downloadable low FODMAP diet chart to help. You can also find apps for your smartphone if carrying a printable list doesn’t feel convenient.

The Downsides of FODMAPs

Not everyone is on board with a low-FODMAP diet, and criticisms include:

  • Unknown long-term health effects of a low-FODMAP diet,
  • Potentially inadequate nutrient intake, and
  • Potential adverse effects from altered gut microbiota. (4)

Just as important, a low-FODMAP diet can be hard to follow or feel overly restrictive, and you must be incredibly strict to avoid high-FODMAP foods.

You might find less complicated alternative more compliant and sustainable. “Often, doing a gut healing protocol works wonders for many patients and they do not have to go on a FODMAP diet or take other radical measures,” says Mark Hyman, MD. (Hyman wrote the forward to my book Align Your Health.) (14)

Your practitioner might also recommend a modified version of a low-FODMAP diet. Researchers in one older study asked 25 patients with IBS to limit their diets to one meat, one fruit, and distilled or spring water for one week. Fourteen (or two-thirds) of those who completed the diet were symptom free. (15)

That type of diet works for other people to eliminate guesswork about what foods to avoid; for others, it would feel incredibly restrictive. After all, if a diet doesn’t work for you, maintaining it will feel like a herculean challenge.

5 Ways to Optimize a Low-FODMAP Diet

For many people with IBS and other gut conditions, low-FODMAP diets get great results. But they can also become a challenge to comply with when you’re, say, visiting your family over the holidays and insist you have a few bites of your aunt’s pound cake.

Even when you do comply – and once you know which foods to eat and avoid, following a low-FODMAP diet can become easier – maintaining that diet can feel like a challenge.

The important thing to remember is that this diet isn’t forever; you’re just eliminating possible culprits that could trigger IBS symptoms so you can find relief.

With that in mind, these five strategies can make doing a low-FODMAP diet and simplify reintroducing foods:

1. Don’t do it alone.

Ideally, you’ll do a low-FODMAP diet working with a chiropractor or other trained professional who can understand your symptoms, address any glitches that come up along the way, and customize diet that considers individual preferences. Researchers recommend restricting total FODMAP load for six to eight weeks, after which the diet might be modified to be less restrictive based on symptom improvement. (5) Your practitioner might determine a different length of time or modify the diet according to your needs.

2. Remember you’re treating the underlying cause.

Conventional practitioners oftentimes prescribe drugs to treat IBS, but they simply treat the symptoms. The low-FODMAP diet addresses the underlying cause (or causes) of IBS, allowing you to heal for life. Doing this diet allows you to discover your food triggers and how much of each high-FODMAP food you can occasionally tolerate.

3. Read labels when shopping.

Especially with processed foods, seemingly innocuous ingredients such as inulin (a probiotic fiber found in some protein shakes and bars) can actually be high-FODMAP. The easiest solution is to eat whole, unprocessed, low-FODMAP foods, but if keep that list handy if you’re shopping for most foods in the center aisles.

4. Keep a food journal.

Tracking what foods you eat and any underlying symptoms can help pinpoint particular culprits. Your practitioner can identify problematic foods you might not realize contribute to your gut condition. A food journal increases compliance and accountability, but it also tracks your journey to better health.

5. Focus on overall gut health.

Once you heal your gut on a low-FODMAP or other food elimination diet, you’ll need to be especially scrupulous to optimize gut health. That requires eating gut-healing foods and supplementing with sufficient probiotics, prebiotics, and dietary fiber; ingredients and supplements your practitioner can help incorporate into your diet. One systematic review and meta-analysis of 14 randomized control trials found a modest improvement among IBS patients after they used probiotics four to 26 weeks. (16) (Researchers noted these results could vary depending on the quantity and quality of your probiotic, so always buy professional-quality.)

Combined with other modifications – including optimal sleep, managing stress levels, getting the right nutrients, and exercising regularly – a low-FODMAP diet can provide relief for IBS and other gut conditions. These changes don’t happen overnight and oftentimes require patience.

Your practitioner may not feel you need to do the low-FODMAP diet if you find it overly restrictive or challenging, although if you’re willing to comply you might find it surprisingly effective. What these and other elimination diets reveal is the power of food to heal or harm, and how specific foods that can be healthy for most people can become problematic for others.

What You Need to Know About a Low-FODMAP Diet for IBS

Dr. B.J. Hardick

About Dr. B.J. Hardick

Dr. B.J. Hardick is a Doctor of Chiropractic and internationally-recognized natural health author and speaker. His health journey began as a child — alternative medicine is the only medicine he has ever known. In 2009, he authored his first book, Maximized Living Nutrition Plans. In 2018, he authored his second book, Align Your Health. An energizing and passionate speaker, Dr. Hardick shares his lifestyle methods to numerous professional and public audiences every year in the United States and Canada. His teachings encompass the principles of ancestral nutrition, detoxification, functional fitness, mindfulness, and green living. Learn More