Understanding the low FODMAP Diet
What are FODMAPs?
FODMAPs are a group of small carbohydrate (sugar) molecules found in everyday foods. Carbohydrates are made up of carbon, hydrogen and oxygen and provide an important source of energy for the body. FODMAPs are carbohydrates that may be poorly absorbed in the small intestine of some people. FODMAPs move through the digestive tract to the large intestine (colon), where they can draw water into the colon and are rapidly fermented (digested) by naturally-occurring gut bacteria. The fermentation of FODMAPs produces gas and other by-products.
It is estimated that 50% of people with IBS may benefit from a low FODMAPs diet, however the quality of scientific evidence is very low. Of these people, there is a possible benefit for overall symptoms such as abdominal pain, cramping, bloating, excess gas, constipation, and/or diarrhea. 1
What does FODMAP mean?
FODMAP is an acronym for Fermentable – Oligosaccharides – Disaccharides – Monosaccharides – And – Polyols. Each of these is explained below:
- Fermentable carbohydrates are sugars that are broken down and digested by bacteria in our intestines, producing gas and other by-products.
- Oligosaccharides are short chains of carbohydrate molecules linked together.
- Fructans (a chain of fructose molecules) and galacto-oligosaccharides (a chain of galactose molecules) are oligosaccharides that humans cannot break down and properly absorb in the small intestine.
- Disaccharides are two carbohydrate molecules linked together.
Lactose, the sugar found in milk and dairy products, is a disaccharide composed of glucose and galactose.
- Lactose must be broken down by the digestive enzyme lactase before it can be absorbed in the small intestine. In people with lactose intolerance, the level of lactase enzyme is insufficient to properly digest lactose and lactose travels to the colon where fermentation occurs
- Monosaccharides are single carbohydrate molecules.
- Fructose, the sugar found in many fruits and some vegetables, is a monosaccharide and does not require any digestion before it is absorbed.
- When foods containing equal amounts of fructose and glucose are eaten, glucose helps fructose to be completely absorbed.However, when fructose is present in greater quantities than glucose, fructose absorption depends upon the activity of sugar transporters located in the intestinal wall.
- The ability to absorb excess fructose varies from person to person. In people with fructose malabsorption, the capacity of sugar transporters is limited and excess fructose travels to the colon where fermentation occurs.
- Polyols, or sugar alcohols, are a type of carbohydrate that humans can only partially digest and absorb in the small intestine.
- Polyols, such as sorbitol, mannitol, xylitol, maltitol and isomalt, mimic the sweetness of sucrose (table sugar), however, because their absorption is much slower, only a small amount of what is eaten is actually absorbed.
- Polyols are often used as low-calorie sweeteners in sugar-free and diet products.
How do FODMAPs affect people with digestive disorders?
Although FODMAPs are not the cause of digestive disorders such as IBS, they can trigger gastrointestinal symptoms. When FODMAPs reach the colon, they draw fluid into the bowel and bacteria ferment the FODMAP molecules to produce hydrogen and methane gases. The liquid and gas distend (stretch) the intestine and signal nerves surrounding the digestive organs.
For many people with IBS, the nerves of the gut are unusually sensitive and even a small change in the intestinal volume can cause the nerve network to overreact and trigger IBS symptoms.
What foods contain FODMAPs?
FODMAPs are found in a wide variety of everyday foods including fruits, vegetables, legumes, milk products and sweetening agents. Each person has an individual threshold for tolerating FODMAPs and some foods may pose more of a problem than others. A diet that reduces the intake of high FODMAP foods (shown in Table 1) and manages the total FODMAP load at each meal, may help to improve gastrointestinal symptoms for some people.
Table 1: High FODMAPs Foods
High FODMAP foods can be replaced with choices from the low FODMAP foods list (as seen in table 2) to help maintain a nutritious and well-balanced diet.
- dandelion leaves
- onion and garlic salt or powders,
- radicchio lettuce
- spring onions (white part)
- wheat (in large amounts)
- baked beans
- bortolotti beans
- kidney beans
- some soy milk
- milk (cow, goat or sheep)
- condensed and evaporated milk, dairy
- ice cream
- powdered milk
- soft and unripened
- cheese (ricotta, cottage, cream, mascarpone)
- syrup solids
- corn syrup
- green pepper
- snow peas
- sorbitol (420)
- mannitol (421)
- isomalt (953)
- maltitol (965)
- xylitol (967)
Table 2: Low FODMAP foods
Examine ingredients on gluten-free breads and cereals to ensure other FODMAPs such as honey and agave are not present
- bok choy
- bean sprouts
- bell peppers
- garlic or onion-infused oil
- gluten-free bread
- gluten-free pasta
- rice noodles
- corn bread
- oat spelt bread
- rice cakes
- potato chips
- tortilla chips
- firm tofu
- lactose-free milk
- lactose-free milk products including cottage cheese, ice cream and sorbet
- Certain cheeses such as cheddar, parmesan, swiss, and mozzarella
- ripe bananas
- passion fruit
- table sugar
- maple syrup
- passion fruit
- table sugar
Who should follow a low FODMAP diet?
If you experience any of the symptoms commonly associated with IBS, consult your physician. In addition to other treatments, your doctor may recommend, following a low FODMAP diet may be an effective strategy to ease the pain, gas, and altered bowel patterns commonly experienced in IBS.
When reducing FODMAPs in the diet, it is important to replace restricted foods with nutritious alternatives and ensure that your diet is healthy and well-balanced. A re-introduction of FODMAP foods should be done gradually to help identify which FODMAPs can be tolerated over the long term.
The low FODMAP Diet is best implemented under the supervision of a qualified health care professional, such as a registered dietitian. This diet is a new and evolving area of nutritional science. Additional research into the role of FODMAPs in IBS and the FODMAP content of specific foods is continually emerging. We encourage you to seek additional sources that are supported by recent scientific evidence.
Is the FODMAP diet permanent?
No. You should be working collaboratively with your healthcare professional to eliminate high FODMAP foods and reintroduce them slowly over a six month period to eliminate which foods are negatively affecting you.
When you report your health status completely, concisely and accurately, your physician can provide you with the best care and treatment plan. Be sure to stay informed on ways to maintain your health and well-being, track and record your symptoms, and write down questions and concerns to discuss at your next appointment.
This guide is meant to explain the basics only, and CDHF encourages any IBS patients who are thinking about attempting this elimination diet for themselves to do so under the guidance of a registered dietitian.
- Ford AC et al, American College of Gastroenterology Monograph on Management of Irritable Bowel Syndrome. Am J Gastro 2018; 113:1-18)