FODMAPs are short-chain carbohydrates that are poorly absorbed in the small intestine and rapidly fermented in the large intestine, or colon. Not everyone experiences discomfort when they consume FODMAPs, but FODMAPs are implicated in symptoms of irritable bowel syndrome (IBS) such as diarrhea, bloating, and cramping.
The low FODMAP diet, which eliminates high FODMAP foods for a limited time and then gradually reintroduces them, provides relief from IBS symptoms for many people. In this article, we’ll talk about what the low FODMAP diet is, what kinds of foods are high and low in FODMAPs, and whether the low FODMAP diet is something you should try.
What Are FODMAPs?
FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. The components of FODMAPs are:
Fermentable. Rapid fermentation by bacteria in the gut can result in increased gas production, bloating, and ultimately intestinal pain.
Oligosaccharides. Carbohydrates formed from a small number of monosaccharides, or simple sugars, such as raffinose and stachyose.
Disaccharides. Carbohydrates formed from two monosaccharides, such as sucrose, lactose, and maltose.
Monosaccharides. The simplest, most basic carbohydrates, such as glucose, fructose, and galactose.
Polyols. Low-calorie sweeteners also known as sugar alcohols, such as sorbitol, xylitol, and mannitol.
Why Are FODMAPs a Problem?
The carbohydrates included under the FODMAP umbrella are very diverse, but they have certain problematic characteristics in common:
- They are poorly absorbed. Nutrients in our food are broken down by enzymes in the small intestine and pass into circulation through the intestinal wall. FODMAPs resist this enzymatic action and leave the small intestine intact.
- They have a laxative effect. FODMAP molecules are small, and their buildup in the small intestine causes water to be drawn in to dilute them, which can lead to diarrhea.
- They are rapidly fermented. FODMAPs leaving the small intestine enter the large intestine, or colon, where they are fermented by the bacteria that live there. Rapid FODMAP fermentation produces large amounts of gas as a by-product, which can cause bloating, pain, and a slowing of gut motility.
- They can increase mucosal inflammation and gut permeability. FODMAPs create alterations in the gut microbial community by increasing the number of gram-negative bacteria present. The outer membrane of these bacteria contain lipopolysaccharides (LPS), which are molecules that play a role in inflammation when they are released during breakdown. Consequently, the higher LPS levels can evoke impaired intestinal permeability. This compromised physical barrier may allow toxic substances to cross the intestinal wall.
Who Is the Low FODMAP Diet For?
The low FODMAP diet, specifically designed for those with IBS, is not recommended for everyone. For some it can be helpful, but for others it may restrict necessary nutrients without offering any real benefit. Get coached by a Nutritional Therapy Practitioner to discover your current health baseline and nutritional status to get a nutritional protocol that is right for your particular autoimmune symptoms.
Low FODMAP Diet Risks
Because this diet involves cutting out a large group of foods (healthy ones, too!), it can risk nutritional inadequacy if not done properly. Potentially reduced nutrients include carbohydrates, iron, fiber, B vitamins, and calcium.
Moreover, most FODMAPs are prebiotics that support the growth of good bacteria and so are beneficial to your gut. Some studies have shown that the low FODMAP diet alters the gut microbiome by reducing populations of beneficial gut bacteria (Actinobacteria, Bifidobacterium, and Faecalibacterium prausnitzii) and promoting dysbiosis.
The low FODMAP diet can also lead to a decrease in fecal butyrate, which is a short chain fatty acid that serves as an important nutrient for many bacteria in the large intestine, as well as supporting the colon’s epithelial lining. Additionally, the diet may reduce populations of bacteria that have immune-regulatory effects, although this hasn’t been shown to have a negative impact on immune function. (Source, Source, Source, Source)
Low FODMAP Diet Benefits
For those who experience symptoms after eating high FODMAP foods, the low FODMAP diet can be beneficial. An array of clinical studies show that up to 86% of people with IBS see symptom relief when following the low FODMAP diet, with success most likely for those who consult with a specialized dietician and adhere closely to the diet. Even so, it is key to note the diet may not work for everyone. (Source, Source)
Predicting Response to the Low FODMAP Diet
Evolving research shows we may be able to predict whether someone is likely to respond to the low FODMAP diet. Predictions may be based on symptom history and by analyzing the gut microbiome composition and function. (Source)
- symptom history: Most people with IBS can identify the foods that make their symptoms worse, and this suggests which FODMAPs they might benefit from avoiding. For example, wheat contains fructans, which are chains of fructose molecules. If you know you have IBS symptoms after consuming wheat, the problem may be the fructans, and you may be able to reduce your symptoms by avoiding foods that contain them. (Source)
- microbiome composition: Symptoms of FODMAP sensitivity are largely due to fermentation by bacteria in the colon, so some studies have focused on identifying which bacteria are involved. Testing stool samples for the presence of known culprits may help determine whether limiting FODMAPs will reduce IBS symptoms. (Source)
- microbiome function: As bacteria metabolize FODMAPs in the colon, gases known as volatile organic compounds (VOCs) are released. The presence of those gases in feces may be an indicator of bacterial activity. A study done at King’s College London found patterns in the baseline levels of fecal VOCs differed between those who responded to the diet and those who didn’t, suggesting another possible method of predicting success with a low FODMAP diet. (Source)
Symptoms of a FODMAP Intolerance
After consuming high FODMAP foods, you may experience IBS symptoms such as:
- uncomfortable bloating
- abdominal pain
- gas (belching, flatulence)
What Is the Low FODMAP Diet?
The original low FODMAP diet is a protocol designed by researchers at Monash University in Australia. The university recommends the diet only for those who have been diagnosed with IBS by a health care provider, as it has not been found to be helpful for people without the condition.
The Monash protocol calls for an elimination phase in which food choices are highly restricted, followed by a reintroduction phase in which preferred foods are brought back into the diet. The university recommends following the diet under the supervision of a registered dietician or other health care provider. (Source)
FODMAP Sensitivity Varies
When eliminating high FODMAP foods, it’s important to note that an individual may not be sensitive to the entire group of FODMAPs. While some people may react after eating all types of carbohydrates, others may only show symptoms following intake of just one or a few types.
For example, someone may be able to eat apples, which contain monosaccharides, but have symptoms after eating dairy products, which contain disaccharides. Identifying which group of foods are causing symptoms may help pinpoint FODMAP sensitivity. This is complicated, however, by the fact that some foods contain multiple types of FODMAPs. (Source, Source, Source)