What is a FODMAP you ask? FODMAP is an acronym that stands for “fermentable oligo-, di-, monosaccharides, and polyols”. Fermentable oligo-, di-, monosaccharides, and polyols are short-chain carbohydrates that aren’t digested in the same way as most other carbs, and so are classified as “dietary fiber”. When you eat most carbohydrates, specialized chemicals in your saliva and stomach start their breakdown immediately, so that the energy from the carbohydrates can be absorbed quickly into your bloodstream for use by cells throughout the body. FODMAPS however, are resistant to these chemicals, so these carbs are likely to make it all the way from your mouth to your gut without much change. It is in the gut that they start to cause trouble for some individuals.
“Prebiotics” resist digestion in a similar way; the differences between beneficial, prebiotic fiber and FODMAPs are the types of intestinal bacteria that feed on them and the types of waste those bacteria produce after they feed. Generally, fiber is important in the diet because it feeds the probiotic bacteria that contribute to healthy digestion, immune function, and general well-being. FODMAPs, on the other hand, are more likely to feed bacterial species that do not benefit the health of the host. In addition, these bacteria occupy valuable space that could be used by more beneficial bacterial species and release hydrogen gas as a waste product which can lead to bloating, painful gas, cramping, and constipation [1]. FODMAPs are also known to draw water into the intestine, which can cause diarrhea [1]. Examples of FODMAP carbohydrates that are most commonly found in the average American diet are fructose (a sugar found in fruits and vegetables, table sugar, and most added sugars), lactose (a sugar found naturally in milk and dairy products), fructans (found in grains like wheat, spelt, rye, and barley), galactans (abundant in legumes), and polyols (sugar alcohols like xylitol, sorbitol, maltitol, and mannitol, which are found in some fruits and vegetables and often isolated and used as sweeteners in processed foods).
Why might I choose a low-FODMAP diet?
If a person experiences symptoms such as painful gas, bloating, stomach cramps, diarrhea, and/or constipation that cannot be attributed to a specific food intolerance or disease, they are often diagnosed with irritable bowel syndrome (IBS) [2]. It was recently estimated that although many go undiagnosed and untreated, at least 11% of the population suffers from IBS [2]. Although the causes of IBS have yet to be defined, studies have shown that severely limiting FODMAP-containing foods from the diet can help to reduce symptomatic discomfort in most people with IBS [3]. Patients with IBS may be experiencing dysbiosis (an imbalance of good vs. bad bacteria in the gut, or even small intestinal bacterial overgrowth (SIBO), another diagnosis in which a low-FODMAP diet may be recommended to heal the gut bacterial population imbalance [4]. SIBO is a condition in which bacteria are growing where they shouldn’t, rather than just in the wrong proportions.
For a long time, elimination diets were commonly suggested when food seemed to be the trigger for IBS. Patients cut out many groups of likely trigger foods for a period of time, and add one at a time back until the symptoms return, implicating a specific food or food group as the culprit causing digestive intolerance. According to new research related to FODMAPs however, an elimination diet may be less effective than a low-FODMAP diet, as all FODMAPS may need to be cut out of the diet simultaneously and more permanently than prescribed by a traditional elimination diet. For example, if your gut is FODMAP-sensitive, cutting out only dairy (lactose) or only grains (fructans) will not be as effective as cutting out (or severely reducing) all FODMAPS.
If you have been suffering from digestive discomfort and have either been diagnosed with IBS or have been struggling with elimination diets to pinpoint a specific food sensitivity as the cause of your gastrointestinal symptoms (to no avail), a low-FODMAP diet may be right for you.
On top of physical discomfort, IBS is very commonly linked to anxiety and depression [5]. The body of scientific research related to the gut-brain connection is relatively new and slowly growing, but early evidence shows that intestinal health and mental health are likely tightly linked. If you are suffering from symptoms of these mental disorders in combination with gastrointestinal discomfort, eliminating FODMAPs from your diet may help both issues by getting to the root of the problem.
What foods can I eat on a low-FODMAP diet?
When reading the list of common FODMAPs above, you may feel overwhelmed by how many food groups they seem to be associated with, but fear not! Within a food group (such as fruit or grains, for example) there will be some foods that are significantly higher in FODMAPs than others. You don’t need to cut out the whole food group, just learn which specific foods within the group you should avoid. Once you learn the specific low-FODMAP foods, you’ll find the diet to be much less restrictive than an elimination diet. For example, you can still eat eggs, sugar, hard cheeses, most soy products, and corn, which would all be off-limits on an elimination diet.
Also in your favor is the fact that there are a lot of great resources available online for low-FODMAP recipes and grocery shopping lists with “eat this, not that”-type options. Below is one example: a table listing some foods to avoid and safe, low-FODMAP options from a paper by Gibson and Shepherd titled, “Evidence‐based dietary management of functional gastrointestinal symptoms: The FODMAP approach”, and published in The Journal of Gastroenterology and Hepatology in 2010 [6]. This is a great educational resource because not only does it show high-FODMAP foods to avoid and safe alternatives, it also specifies which type of FODMAP the avoidable foods contain in high quantities.
Once I go low-FODMAP, do I have to stay on the diet forever?
Not necessarily. Some patients have a greater sensitivity to a specific category of FODMAPS. If a low-FODMAP diet seems to be helping to relieve gastrointestinal discomfort, you may try re-introducing categories of FODMAPs after 1-2 months to see if your sensitivity is specific to one or more groups (much like you would after an elimination diet). Alternatively, If your IBS was caused by SIBO, once the gut population has been balanced, you may no longer feel sensitivity to FODMAPS and may be able to return to a diet including all FODMAPS. Talk to your doctor about having your SIBO tested before reintroducing FODMAP groups.
References
- Ong, Derrick K., et al. “Manipulation of dietary short chain carbohydrates alters the pattern of gas production and genesis of symptoms in irritable bowel syndrome.” Journal of gastroenterology and hepatology 25.8 (2010): 1366-1373.
- Makharia, Archita, Carlo Catassi, and Govind Makharia. “The overlap between irritable bowel syndrome and non-celiac gluten sensitivity: a clinical dilemma.” Nutrients 7.12 (2015): 10417-10426.
- Halmos, Emma P., et al. “A diet low in FODMAPs reduces symptoms of irritable bowel syndrome.” Gastroenterology 146.1 (2014): 67-75.
- Pimentel, Mark, Evelyn J. Chow, and Henry C. Lin. “Normalization of lactulose breath testing correlates with symptom improvement in irritable bowel syndrome: a double-blind, randomized, placebo-controlled study.” The American journal of gastroenterology 98.2 (2003): 412-419.
- Lydiard, R. Bruce. “Irritable bowel syndrome, anxiety, and depression: what are the links?.” The Journal of clinical psychiatry (2001).
- Gibson, Peter R., and Susan J. Shepherd. “Evidence‐based dietary management of functional gastrointestinal symptoms: the FODMAP approach.” Journal of gastroenterology and hepatology 25.2 (2010): 252-258.