NUTRITION: Food Intolerance Part 2 | Great Health Guide
NUTRITION: Food Intolerance Part 2

NUTRITION: Food Intolerance Part 2

‘Food Intolerance Part 2’ by Dr Helen Dodd published in Great Health Guide (Nov 2016). In the previous issue of GHG magazine, Food Intolerance Part 1 described the difference between Food Allergy and Food Intolerance. Many people suffer from food intolerance after eating certain foods. However, it is harder to diagnose food intolerances. This concluding article by Dr Dodd discusses the diagnosis of food intolerances as well as IBS (irritable bowel syndrome). Read the rest of this article to find out more.
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NUTRITION: Food Intolerance Part 2

written by Dr Helen Dodd

In the previous issue of Great Health GuideTM, Food Intolerance Part 1 described the difference between Food Allergy and Food Intolerance. Many people suffer from food intolerance after eating certain foods. These symptoms can be similar but are more moderate than with a food allergy. Food intolerance is harder to diagnose as there is no specific test for this condition.

Food intolerance is the most common cause of undiagnosed Gastrointestinal (GI) tract problems. Many factors cause intolerance to foods that were previously well absorbed. Cells along the lining of the bowels are altered, damaged and destroyed by various infections and medications. Alteration in the gut flora, from infections, use of antibiotics, stress and age are some other factors in food intolerance. Lactose intolerance is the only food intolerance that can be diagnosed with the Hydrogen Breath Test. 

Food Intolerance is a hypersensitivity to certain foods and there are no specific tests for this condition. Symptoms include diarrhoea, constipation, flatulence, bloating of stomach and bowels, nausea, vomiting, reflux (GERD), fatigue, dizziness, rashes, brain fog to list a few. Thus the simplest way to deal with food intolerance is to use an Elimination Diet. If food intolerance is left undiagnosed and untreated, it can become chronic Irritable Bowel Syndrome (IBS).

Food Intolerance is diagnosed using an Elimination Diet, with Two Phases:

During the initial Exclusion Phase, many known intolerant foods are excluded from the diet. It is necessary to keep an accurate and detailed diary of all foods consumed, when they were eaten and the time if symptoms occur. It is then possible to determine a pattern of which foods may be causing the problem. A pattern is sometimes difficult to see as symptoms may not appear for 24 hours. The GI tract should become less sensitive after 2-3 weeks of the exclusion phase.

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The Reintroduction Phase is where a single food is introduced into the diet for 3-4 days and symptoms are noted in the diary. Since the symptoms may take up to 48 hours to appear after the problem food is ingested, 3-4 days testing of a single food is necessary. If upon reintroducing the suspected food, the symptoms return, then this is a reliable diagnosis of intolerance to that food. If asymptomatic, a second food is reintroduced and checked in the same manner. This is repeated with other excluded foods being slowly added and presence or absence of symptoms noted. A very simple description of an Elimination Diet with a suggested choice of foods to eliminate is found here.


This is a common disorder of the GI tract. The underlying cause is not known but certain factors are related to the condition. This hypersensitive bowel may be triggered after a severe bout of gastroenteritis or the prolonged use of strong antibiotics. Symptoms do vary but in general IBS has symptoms of abdominal pain, excessive wind, bloating, diarrhoea, constipation, heartburn, nausea and sometimes vomiting. With IBS, microflora that normally inhabit the bowel are altered with an overgrowth of bacteria or a new bacterial species becoming dominant. Foods that are not tolerated with IBS include chocolate, alcohol, fatty foods, dairy products & sugars.

SUGARS are major problems in IBS. A detailed Elimination Diet for IBS, was pioneered by Dr Sue Shepherd, an Australian dietician. This diet is called The Low-FODMAP diet, and lists in detail, foods containing sugars and related compounds that will cause IBS.

Sugar such as lactose: ‘milk sugar’ is one of the main triggers for IBS. It comprises two simple sugars, glucose & galactose. Intolerance to lactose is due to the lack of the enzyme lactase, which breaks down lactose into the two simple sugars. Lactose intolerance can be readily diagnosed by replacing regular milk with lactose free milk. Thus milk, yoghurt, cream, ice cream and deserts made with regular milk, will cause IBS. Butter and older, matured cheese do not contain lactose, so can be included in a lactose-free diet.

Other sugars, with the acronym FODMAP: Fermentable, Oligosaccharides, Disaccharides, Monosaccharaides And Polyols, are not absorbed in the small intestine. They pass into the large intestine where bacteria use them as a food source, causing IBS symptoms. These natural sugars are present in freshly grown fruits & vegetables, nuts, grains and natural sweeteners such as honey and maple syrup. These foods with high quantities of FODMAP sugars are listed in FODMAPs. Many other sweeteners added to processed foods trigger IBS, including High Fructose Corn Syrup (HFCS), sorbitol and mannitol.

The Low-FODMAP Diet, using Elimination and Reintroduction Phases, will identify the problem foods and their related sugars. The diet plan is followed over these two phases and any problem foods are totally removed from diet. 

Avoid FODMAP’s:

  • Prepare you own food, then you know exactly what is in it.

  • Do not purchase processed or pre-packaged food as all the ingredients may not be listed or if listed, under a different name or a coded number. 

  • The ingredients in the processed food may not specify the word ‘sugar’ and there are many ways to hide the fact that certain sugars are present. 

Always seek advice from your GP rather than attempting to diagnose or treat these problems yourself. It is very important that your doctor take numerous tests initially to exclude other possible conditions. It is important that a GP or dietician manage an elimination diet to balance nutritional requirements. 

Food intolerance is treatable. Many people have symptoms for years and only when symptoms become a chronic digestive disorder, are food intolerance and IBS recognised. By eliminating the offending foods, life becomes so much more pleasant.

Author of this article:
Helen Dodd BSc. BPharm. PhD, is a retired pharmacist, continuing to provide information and education on nutrition and diseases that affect modern society. Contact Helen by email

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