Minimising the impact of high fructose foods for patients with Irritable Bowel Syndrome: investigating the use of added glucose to assist with fructose absorption from food by the small intestine in healthy volunteers and in patients with IBS

INTERVENTION: This was a randomised, single‐blind crossover trial using whole foods as the source of fructose with and without added glucose. During a 36‐h low FODMAP (Fermentable, Oligosaccharides, Disacchardies, Monosaccharides and Polyols) run‐in period, followed by a 24‐h test day, all food was provided. Breath hydrogen samples were collected hourly for 14 h on two consecutive days, commencing before breakfast each day. For the test day, participants were randomised to either a diet high in fructose with no added glucose (high fructose diet), or high in fructose with glucose added to give a 1:1 ratio of free fructose to free glucose (fructose/glucose co‐administration diet). Following a one‐week washout period, participants crossed over to the alternative diet. For both test diets, foods included were naturally high in fructose in excess of glucose (including watermelon, apple/guava juice, pear and apple muffins). The remainder of the diet was low in total FODMAP content. For the fructose/glucose co‐administration diet, glucose was co‐ingested by participants in tablet form (Glucodin tablets; Reckitt Benckiser, NSW Australia) when whole pieces of fruit were eaten. Participants were asked to consume the glucose tablets at the time of meal consumption. Glucose powder (Glucodin Powder; Reckitt Benckiser, NSW Australia) was added during the baking process for apple muffins and pre‐mixed with apple/guava juice. For the high fructose diet, sucrose cubes and powder replaced the glucose to aid in blinding the participants. The high fructose foods provided 11 g of fructose in excess of glucose. The diets provided during the two run‐in periods were identical. The two high excess‐fructose diets were also identical apart from the addition of sucrose and/or glucose. There were no differences in macronutrient content between the two test diets including total carbohydrate, starch, dietary fibre and total sugar levels. The provided diet on the test day is listed below: † denotes high fructose foods Energy intake was not individualised, it was a standard amount, the same given to each participant. Total energy provided was 9.5MJ/day. Breakfast: Corn flakes (30 g), Milk (LF), Bread 2 slices (GF), Butter/margarine, Vegemite, † 1 slice fresh Watermelon (plus 1 *glucose tablet), †Apple‐guava Juice (200ml + 1.5 g *glucose powder) Morning tea: † 1 fresh Pear (plus 6 *glucose tablets), Sweet biscuit (GF) Lunch: Chicken pasta bake, † Apple‐guava Juice (200ml + 1.5 g glucose) Afternoon tea: † Apple muffin (GF + 0.1 g glucose) Dinner: Lasagne (GF) Supper: Drinking chocolate Note: Each glucose tablet contains 1.5g glucose. Participants completed food diaries to monitor compliance. Participants consume all meals at home at their own convenience. It was up to the participant as to what time of day each meal and snack was consumed. CONDITION: Irritable bowel syndrome PRIMARY OUTCOME: Breath hydrogen testing ; ; The breath hydrogen testing will measure the amount of carbohydrate which is not absorbed in the small intestine and hence travels to the large intestine and is fermented by the colonic bacteria. Therefore it will measure if the glucose is able to improve small intestinal absorption and subsequently reduce fermentation in the large bowel (measured via amount of breath hydrogen production). ; ; The outcome is therefore how much breath hydrogen is produced, which gives us a indirect measure of the amount of small intestinal fructose absorption. Overall symptom score. ; ; Participants are asked to score how their gastrointestinal symptoms were overall from 0‐100 (no symptoms at all to worst ever symptoms) on a 100mm visual analogue scale (VAS). ; ; They rate their symptoms at bedtime for how they felt for the day. ; ; This is for the 'overall symptom score' i.e. how they felt their IBS symptoms were overall that day. (Below in the secondary outcomes are the other questions for specific symptom types). SECONDARY OUTCOME: Abdominal pain ‐ measured on 100mm VAS ; Bloating ‐ measured on 100mm VAS Lethargy ‐ measured on 100mm VAS Nausea ‐ measured on 100mm VAS Wind ‐ measured on 100mm VAS INCLUSION CRITERIA: Inclusion criteria required participants to be aged 18‐70 years, and, within the past 3 months, to have fructose malabsorption identified by breath hydrogen rise of >15 ppm after 35 g fructose. Two groups of fructose malabsorbers were recruited: healthy subjects (without gastrointestinal symptoms) and patients with FBD, as determined by a gastroenterologist using the Rome III criteria. Those who expressed interest but had a positive fructose breath test more than 3 months prior were asked to repeat the fructose breath test prior to enrolment and only if fructose malabsorption was retained were they then invited to enrol.