The low-FODMAP diet (Low Fermentable, Oligo, Di, Monosaccharides, And Polyol), has been proven to be an effective tool to fight the symptoms of Irritable Bowel Syndrome (IBS).
These fermentable substances are simple or complex carbohydrates found in food.
Although not all carbohydrates or sugars are fermentable and are categorized within the FODMAP list.
The mechanisms by which the low FODMAP diet relieves symptoms are varied and are related to the pathophysiology of IBS.
Recent studies support the use of this diet as part of the treatment of this pathology.
The low FODMAP diet may generate changes in the intestinal flora
Although further research is required to determine the potential health implications and microbiota effects.
What is Irritable Bowel Syndrome (IBS)?
Irritable Bowel Syndrome (IBS) is a very common functional disorder, which is estimated to affect 15% of the population.
The diagnosis of Irritable Bowel Syndrome (IBS) is based on the presence of chronic gastrointestinal symptoms in the absence of underlying organic disease.
It is characterized by abdominal pain and discomfort.
IBS has an important effect on your quality of life, since affects your working life and determines a greater number of medical consultations.
What are the different factors involving IBS?
The pathogenesis of IBS is complex and involves multiple factors such as impaired gastrointestinal motility, increased fermentation, visceral hypersensitivity and deregulation of the neuro-enteric axis.
A dysbiosis of the intestinal flora has also been described with a reduced number of bifidobacteria and lactobacilli in the lumen when compared to healthy individuals.
What foods are rich in FODMAP?
Foods rich in FODMAP include those that contain fructans, galacto-oligosaccharides, galactans, lactose, fructose, and polyols.
Let’s go over some of these foods.
Inulin-type fructans are the main source of fermentable carbohydrates (CF).
Structurally, they are fructose molecules with a glucose molecule at one end.
A small part of them is digested in the small intestine so they arrive almost intact to the colon.
Some foods high in fructans are wheat and rye, onions, asparagus, broccoli, eggplant, shallots, beetroot, Brussels sprouts, cabbage, garlic, leek, persimmon, dandelion or inulin.
Fructans fall within the definition of prebiotic since they are non-digestible compounds that determine a selective stimulation of the growth or activity of one or several species of the intestinal microbiota, which gives a beneficial effect on the health of the host.
The human being lacks the enzyme α-galactosidase, which allows these compounds to reach the colon where they are fermented, also generating a prebiotic effect.
These molecules are mainly present in milk and derivatives, legumes, nuts, and seeds.
They can also be commercially originated through the reaction of lactose with β-galactosidase and are frequently adhered to infant milk formulas, dairy products, and beverages.
2. Disaccharides and monosaccharides
2.1. Fructose and Lactose
Fructose-glucose absorption occurs in a variable way and is dose-dependent.
It occurs through transportation facilitated by the co-transporters GLUT15 and GLUT2 conveyors.
Fructose is found primarily in fruit, its derivatives and in some types of sweeteners.
Some examples are apples, mango, nashi, pears, tinned fruit in natural juice, watermelon, corn syrup, dried fruit, and honey.
In regards to lactose, hypolactasia in adults is frequent, but variable according to the population.
Lactose is mainly found in yogurt, ice cream, custard, cheese or flavored kinds of milk.
It should be noted that lactose is widely used as an additive in bakery, pastry and some slimming products.
Polyols are polyhydric alcohols such as sorbitol and mannitol, which is found in certain fruits, vegetables, and sugar-free sweeteners.
Studies have shown that between 65-70% of controls and patients with IBS have incomplete absorption of sorbitol.
Some examples of fruits and vegetables are apples, pears, apricot, avocado, blackberry, cherry, nectarine, prunes, cauliflower, bell pepper, sweet corn, plums, and mushrooms are natural sources of polyols.
Chewing gum and sugar-free candies are some of the artificial products that have the highest polyol content, due to their high content of xylitol or sorbitol.
Some long-chain polysaccharides are not digested and therefore are fermented by the intestinal microbiota contributing to the symptoms of IBS.
In this group, cellulose, hemicellulose, and pectin, psyllium and resistant starches stand out.
All these compounds are part of what is called ‘dietary fiber.’
In patients with IBS and a predominance of constipation, the recommendation to increase the consumption of dietary fiber is common, which can lead to increase the symptoms of bloating, pain and meteorism.
This group includes whole grains, chestnuts, legumes, plums, pears, and apples.
Sugar can increase the osmosis
Sugars in polysaccharides cause an increase of water in the intestine by osmosis.
They may not be digested or absorbed correctly and supercharge bacteria in the intestinal microbiota that ferment them.
When this happens, discomfort such as diarrhea, constipation, gas, abdominal swelling and punctures in the abdomen may occur.
What foods can be eaten in the FODMAP diet?
Meat, fish, and eggs can be eaten without any problem.
Some nuts such as almonds, hazelnuts, and walnuts should be tested in each case to assess individual tolerance.
Small amounts of lactose-free or low-lactose dairy are also permitted.
When it comes to vegetables and fruits rich in FODMAP, it is advisable to limit them to a small garnish about the size of a tennis ball.
Eating this small size 2 times a day is better tolerated than taking a larger amount all together in the same intake.
In the case of constipation during the weeks that the diet is followed, you can introduce oatmeal, which is low in FODMAP but provides fiber.
In addition, you have to increase your water consumption.
What are the gastrointestinal benefits of FODMAP consumption?
The consumption of FODMAP rich foods determines multiple gastrointestinal effects.
Some of the effects can be beneficial, such as increased feces bolus volume, improved calcium absorption and increased short-chain fatty acid production.
A selective stimulation is also described on some components of the microbiota such as bifidobacterium and also a positive effect on the growth and function of the intestinal microbiota.
Halmos et al published a study in which the traditional Australian diet was compared with a low FODMAP diet.
For 21 days, 8 healthy individuals and 30 patients with IBS were randomized to receive a low FODMAP diet or a regular diet.
Then they spent 21 days on a free diet.
Then the groups crossed over to receive the alternative diet.
Symptoms were evaluated daily with a visual analog scale (VAS).
All stools were collected from day 17 to 21 of the study for weight control, water content and King’s Stool Chart classification.
The results showed that 70% of patients with IBS experienced an improvement in their symptoms.
Patients had a bigger improvement when following the low FODMAP diet
In a different study conducted by the Clinical and Experimental Gastroenterology, 82 patients with IBS who had received a standard diet had less improvement in general IBS symptoms (49%) than those who had received a low FODMAP diet (86%).
64% of the patients reported strict adherence to the diet during the 9 months of the study.
For how long should the low FODMAP diet be followed?
It is recommended to follow the low FODMAP diet for a period of 6 weeks.
When the symptoms of discomfort have disappeared, then its time to reintroduce food little by little and recording everything you eat and the symptoms you suffer.
In this way, it will be easier to identify if there is any food that is poorly tolerated by your organism and if so, therefore, should be excluded for longer or definitely from the diet.