FODMAP is a diet gaining increased interest in the management of some people with irritable bowel syndrome (IBS). FODMAP stands for "fermentable oligosaccharide, disaccharide, monosaccharide, and polyglycans." It has been suggested that a diet that is low or excludes these elements may have a benefical effects on people with IBS. The original research was conducted  by a research group in Australia and has been attracting increasing attention in the UK, and slowly people are beginning to understand the potential importance in some individuals. The intake of certain dietary sugars seems to play a role not only in fermentation and osmotic effects in the bowel but also in the nervous system in the Gut. It seems the influence of these foods in some individuals with IBS can be profound. With FODMAP, we are referring to dietary sugars or “carbohydrates” Carbohydrates are one of the three major food groups in our diet and consist of a variety of sugars;

Lactose is a disaccharide (double sugar) that is very common in milk & dairy  products. Up to 90% of people have some degree of lactose intolerance, a rate that increases on the basis of racial background. Lactose intolerance is more common in blacks, Indians, and Hispanics. There may be a relative tolerance to lactose in Europeans, but this tolerance tends to be lost with age. Certain things will change a person's tolerance to lactose, because it requires lactase, a small bowel enzyme located on the brush border of the small intestine (each epithelial cell has microvilli that protrude into the lumen of the intestine and is termed “brush border”). If a person develops food poisoning  or if someone with Crohn’s disease experiences a small bowel flare, this may lead to transient lactose intolerance. Lactose intolerance is the inability to tolerate lactose in foods. One food that you need to be aware of that is relatively free of lactose is hard cheese, because the whey is typically taken off as these hard cheeses develop. They [hard cheeses] have a very low lactose component, along with sour cream and butter. These foods are allowed on a FODMAP diet. The enzyme lactase, such as in Lactaid, is added to certain food products to make people more tolerant to lactose. Yogurt, because of the lactobacillus, may also be tolerated. However, frozen yogurt is not on the list. Patients may need to test the water with yogurt. Often people think they are  not milk intolerant. However there is often a lot of variability in symptoms day to day. If people consider the relative proportion of milk intake on a particular day and combine it with other  FODMAP-type foods, they might consider that milk is contributing to the symptoms. So, with the  FODMAP exclusion diet, there may be foods that people discover that they don't have to exclude entirely; however, they may choose to minimize these foods or add products such as Lactaid to their diets.

Fructose is a monosaccharide ("single sugar)". The monosaccharides are glucose, fructose, and galactose. Fructose and glucose combine to form sucrose, which is standard table sugar. Fructose is a sugar that we see in honey and in a lot of fruits, such as pears, apples, grapes, raisins, prunes, peaches, and pineapples. These fruits are very high in fructose. The fructose balance of food is what drives the absorption of fructose. When the fructose component exceeds the sucrose component in foods containing both, there is an intolerance of fructose. These fructose-rich foods may warrant elimination from the diet. Fructans are oligosaccharides, polymers of fructose molecules, found in wheat and many types of vegetables (eg, asparagus, artichokes, onions). Longer-chain fructans are called inulins. Inulins are sometimes added as soluble fibre to yogurt. However, some yogurts can actually work against you. If someone who eats a lot of yogurt is having a lot of bloating or diarrhoea, the yogurt could actually be exacerbating their symptoms. Fructans may also be found in a variety of sugar-laden fruits, such as pears, pineapples, bananas, prunes, and apples. I always tell people to avoid apples when they have diarrhoea because of the amount of fructans present. Wheat is the most common source of fructans, accounting for about 70% of fructan intake in the UK. If your doctor tests you for coeliac disease and it comes back as coeliac negative and TTG negative, it may well still be worth trying wheat or gluten exclusion because of the fructan content. This goes back to the idea of good days and bad days with IBS. A patient may consume more of the fructan-containing wheat and have a bad day. This may be related to the relative balance of the other FODMAP components that they ingested during this time.

Galactans are polymers (long chain) of galactose. Humans lack a digestive enzyme necessary to break down and absorb galactans. Galactans are found in certain vegetables, such as legumes, soybeans, peas, wax beans, and baked beans. The inability to digest galactans has given beans the nickname "musical fruit" because they contain stachyose and raffinose. Without enzymes to digest these oligosaccharides, galactans are poorly digested. They create not only an osmotic effect leading to diarrhoea, but as a fermentable sugar (bacterial effect) in the colon, they also can lead to bloating, and there may be an effect on the gut's nervous system as well.

Polyols are the sugar alcohols. Where these polyols really make a difference is in sorbitol, which is a natural component of certain fruits, such as apples, prunes, and particularly watermelon. If you are going to try the FODMAP diet, then you will need to  become a good label reader and start to look at these hydrogenated polyols that may be components of sweeteners. Corn syrup is a fructose-rich component frequently added to foods as well. Polyols (mannitol, sorbitol, and xylitol) are used in many dietetic foods, confectionary, and gum as sweeteners. Polyols can make a big difference when you start to do a component analysis of the FODMAP diet.

Improving Care for patients with IBS

We have a lot to learn about IBS. The answer is not just "eat more fibre." It is to understand the individual components of the diet and how they can potentially interact. Individuals are just that - individuals. There may be certain foods that people are particularly sensitive to. If you are interested in the FODMAP diet, there are books available. Unfortunately, education about exclusion diets is not a service dieticians have traditionally provided due to their heavy workload. However this may change. It is alway important to exclude conditions such as Coeliac disease or Crohn's disease, as often the symptoms are similar to IBS. However, once we are happy, the symptoms are due to IBS, then it is important to consider the role of diet. I think the FODMAP diet is definitely worth a considering for people with diarrhoea predominant Irritable bowel syndrome.




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