Beating IBS with the low-fodmap diet

If you are plagued by Irritable Bowel Syndrome (IBS), you will be happy to learn that a diet low in fodmap foods can improve your symptoms dramatically.

Fodmaps (Fermentable Oligosaccharides Disaccharides Monosaccharides And Polyols) are carbohydrates (sugars) found in many common foods. When poorly absorbed, these carbs cause symptoms of IBS. In an Australian study, 75% of IBS patients showed improvements in their symptoms on the low-fodmap diet.

Chemistry of fodmaps

DietDoc recently attended a symposium organised by Nutritional Solutions in Johannesburg, which featured a presentation on "Beyond Belly Aches: The implementation of fodmaps in clinical practice" by Prof Joanne L Slavin, a professor in the Department of Food Science and Nutrition at the University of Minnesota, in the USA.

Prof Slavin firstly explained the chemical properties that characterise these carbohydrates. Probably the most relevant characteristic is that all of them get fermented in the large intestine or bowel (colon) because they are incompletely digested and absorbed in the small intestine.

These partially digested carbohydrates such as mono-, oligo- and disaccharides, as well as polyols, travel from the small intestine into the bowel where they are fermented by the resident bacteria. Various positive and negative compounds are formed during this bacterial fermentation process.

On the one hand, fermentation produces short chain fatty acids with have in recent years been identified as beneficial to health with potentially protective properties relating to prevention of gastrointestinal disorders, cancer and cardiovascular disease (Hijova & Chmelarova, 2007).

On the other, possibly more negative side, the fermentation produces considerable quantities of various gases such as hydrogen, carbon dioxide and methane. This is thus, the reason why patients with IBS tend to suffer bloating which increases over the course of the day until some patients complain that they look as if they are nine months pregnant by suppertime. These gases, particularly methane and hydrogen sulfide are also particularly noxious, which is another aspect of IBS that causes great distress.

Examples of fodmaps

Prof Slavin went on to describe the various compounds that make up the fodmaps family and listed foods that have a high fodmap content:

1) Oligosaccharides

a) FOS or Fructans

Inulin as found in chicory root and Jerusalem artichokes (the root-version of artichokes)
FOS/Inulin are also found in peach, watermelon, Brussels sprouts, fennel, garlic, leek, onion, wheat, rye, barley, legumes, lentils and chickpeas

b) GOS or Galacto-oligosaccharides

GOS occur in human milk, and nowadays they are also added to infant formulas.
The trio of stachyose, raffinose and verbascose are found in legumes (dry cooked or canned beans, peas, lentils or soy products) and are linked to pronounced gas production. Prof Slavin mentioned that research is underway to remove these galacto-oligosaccharides from legumes to make these otherwise healthy and excellent foods more accessible to persons who suffer from IBS and other complaints that are exacerbated by high gas production.

2) Disaccharides

a) Lactose

Prof Slavin pointed out that lactose (which consists of a glucose and a galactose molecule) is only classified as a fodmap and only causes fermentation if the individual in question suffers from lactose intolerance because he or she does not produce sufficient lactase enzyme in the intestine. This is important to remember, because I am sure that most IBS patients will try eliminating milk and dairy products from their diet the moment they read about fodmaps, just because this class of food is such a favourite for elimination by the lay public.

"I suffer from IBS/mucous/bronchitis/blocked nose/overweight/eczema/etc and have eliminated milk and dairy from my diet!" is a refrain that I hear practically on a daily basis.

So before you banish milk and dairy products and all that valuable calcium from your diet because you "think" it may be triggering your IBS, please ask your doctor to have you tested for lactase deficiency. Don’t throw the calcium out with the bathwater and then develop brittle bones within months or osteoporosis a few years down the line.

If you do have a lactase deficiency then avoiding milk and all products that contain milk (i.e. many processed foods - so check your food labels), will probably help a great deal to relieve your symptoms of IBS. Just remember to take a calcium supplement such as Calcium Sandoz, MenaCal.7 or Caltrate every day to make up for the lack of calcium in your diet. Also be aware that eliminating one source of fermentation such as lactose, does not mean that all your IBS symptoms will be cured. You may still be sensitive to one or more of the other fodmaps and need to identify them, preferably with the assistance of your registered dietitian.
3) Monosaccharides

a) Free Fructose

Because fructose has a low glycaemic index (GI), it may be added to foods and drinks that make claims about "Low-GI" or "Sugar-free" (which is not allowed according to the SA Labelling Regulations seeing that the product still contains a sugar called fructose, even if it does not contain a sugar called sucrose!). Sports drinks and most sweetened cold drinks in countries such as the USA also contain high-fructose corn syrup (HFCS).

According to Prof Slavin the following foods are also naturally high in fructose: apples, pears, mangoes, cherries, watermelon, asparagus, Jerusalem artichokes, sugarsnap peas and honey.
4) Polyols

a) Erythritol, xylitol, sorbitol, lactitol, isomalt, maltitol, polyglycitol syrup

In general only one third of these carbohydrates is absorbed in the intestine and they therefore pass into the bowel where they are fermented by the colonic bacteria.
These polyols are naturally found in apples, pears, cherries, prunes, avocado and mushrooms.
Because they are so difficult to absorb, polyols have been used as sweeteners in diabetic and slimming products for many years. In addition, they are added to most sugar-free chewing gums. If you chew sugar-free gum that contains polyols as a sweetener you may well be causing a massive buildup of abdominal gas - from the fermentation of the polyols in your chewing gum and from swallowing air when you chew. Try cutting out chewing gum for a week or so to see if this does not relieve the flatulence.

The pros and cons

Prof Slavin was careful to point out the following:
  • The various compounds that are classified as fodmaps have different physiological effects and should not be lumped together
  • If you suffer from IBS, do not try cutting out all the fodmaps from your diet because you may only be sensitive to one of the categories
  • If possible, get the help of a registered dietitian to help you figure out which one of the fodmap categories you are sensitive to and what steps you need to take to prevent deficiencies if you do need to cut out a whole food group such as milk and dairy
  • Keep in mind that even if you are sensitive to one category of fodmaps that the other categories may have very beneficial effects and should not be cut out (see below).
Benefits of fodmaps

Fodmaps have many beneficial properties which Prof Slavin listed for us:
  • Reduced energy values (4.2 to 14.7 kJ/gram) compared to sucrose (17 kJ/gram)
  • Low GI
  • Don't cause tooth decay
  • Prebiotic effects (i.e. prebiotics such as inulin are used by the beneficial microorganisms in the colon as a food source)

The most serious negative effect of a blanket ban on all fodmaps in the diet is that this could result in reduced intake of the above mentioned prebiotics and therefore also affect the beneficial microorganisms in the gut (Slavin, 2013).
It is, therefore, important to get professional help from a registered dietitian when you start trying to identify which fodmaps you need to avoid and also not to cut them all out of your diet indiscriminately.

Fodmaps may well be the answer to IBS, but the concept must be carefully and circumspectly applied if the patient is not going to do more harm than good.
(References: Hijova E, Chmelarova A. 2007. Short chain fatty acids and colonic health. Topical Review. Bratisl Lek Listy; 108 (8): 354 – 358; Slavin JL, 2013. Beyond Belly Aches: The implementation of fodmaps in clinical practice. Paper presented at: Nutritional Solutions CNE, Johannesburg 11 April 2013.)

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