Honours project

Investigating the role of fodmap carbohydrates in the genesis of gastrointestinal symptoms

Supervisor: Peter Gibson, Jane Muir, Sue Shepherd and Jaci Barrett.
Sites: Department of Medicine Monash Medical Centre Clayton, Box Hill Hospital

Project 1 Outline

One in seven Australians suffer from Irritable Bowel Syndrome (IBS), a condition that is characterized by abdominal bloating, pain, and irregular bowel habit. Standard medical therapy is generally inadequate at controlling these symptoms. Our research team has identified dietary triggers that might be responsible for the induction of symptoms in the majority of patients with IBS. These triggers involve a group of small carbohydrates that are commonly found in a wide variety of foods and can be poorly absorbed in the small intestine and include; fructose (in apples, pears and fruit juice, high fructose corn syrups), lactose (milk), fructans (onions, garlic, wheat), galacto-oligosaccharides (legumes) and sugar alcohols [sorbitol (pears & apple) and mannitol (mushroom, celery, cauliflower)]. We have named this group of compounds FODMAPs - Fermentable Oligo-. Di- and Mono-saccharides And Polyols. The major dietary strategy currently used in our department to treat patients with IBS is to minimizing the total level of FODMAPs in the diet.

We plan to assess vitamin C status by food intake, and biochemistry, and assess levels of clinical depression by questionnaire before and after supplementation, in a double-blind manner, to see whether or not treatment of inpatient depression should be accompanied by treatment with vitamin C.

Project 1: Investigating the use of glucose to assist with fructose absorption from drinks and juices in healthy volunteers and patients with Irritable bowel syndrome.

One of the major FODMAPs to cause problems for patients with IBS is fructose. Four out of 10 healthy people will mal-absorb a 25gram dose of free fructose. This malabsorption of fructose is even higher for people with IBS. Minimizing fructose malabsorption has therefore become a major goal of dietary management for patients. The major dietary strategy we use to achieve this goal is to reduce the dietary intake of high fructose-containing foods. Another possible strategy that requires more research involves improving the absorption of fructose in foods via glucose. There is good evidence that the absorption of fructose is greatly enhanced in the presence of glucose. While the mechanism of this effect has not been fully understood it is believed that the GLUT-2 transporter is involved. This glucose-effect has been shown to operate in healthy individuals with drinks and juices to greatly reduce the impact of mal-absorbed fructose. We have recently completed a study in which this approach was trialed in volunteers who were known ‘fructose malabsorbers’ and included 9 patients with IBS and 9 healthy individuals. Whole foods and fruit juices and realistic levels of excess fructose (about 12 grams per day) were used. The results found that while this ‘glucose-assisted absorption of fructose worked well in healthy individuals who malabsorb fructose- it did not work well in patients with IBS. The aim of this proposed project is to investigate this area further. We plan to recruit both healthy volunteers and patients with IBS who are know fructose malabsorbers. These volunteers will be given a series of drink challenges with pure sugars (ie. 25grams fructose± 25 grams of glucose and fruit juices (naturally high in fructose and glucose). Improvement in the absorption of fructose will be monitoring via changes in breath hydrogen. We will also monitor changes in gastrointestinal symptoms.

Project 2 Outline

One in seven Australians suffer from Irritable Bowel Syndrome (IBS), a condition that is characterized by abdominal bloating, pain, and irregular bowel habit. Standard medical therapy is generally inadequate at controlling these symptoms. Our research team has identified dietary triggers that might be responsible for the induction of symptoms in the majority of patients with IBS. These triggers involve a group of small carbohydrates that are commonly found in a wide variety of foods and can be poorly absorbed in the small intestine and include; fructose (in apples, pears and fruit juice, high fructose corn syrups), lactose (milk), fructans (onions, garlic, wheat), galacto-oligosaccharides (legumes) and sugar alcohols [sorbitol (pears & apple) and mannitol (mushroom, celery, cauliflower)]. We have named this group of compounds FODMAPs - Fermentable Oligo-. Di- and Mono-saccharides And Polyols. The major dietary strategy currently used in our department to treat patients with IBS is to minimizing the total level of FODMAPs in the diet.

Project 2: Reducing dietary levels of FODMAP carbohydrates (particularly sugar polyols) by breastfeeding mothers to improve colic-like symptoms in young breast-fed babies.

Infantile colic affects up to one third of infants in their first month of life. While the etiology of this condition is still not fully understood, it generally resolves by 4 months of age. A number of dietary factors have been attributed to colic including intolerance to cow’s milk protein. One study has reported that colic associated with carbohydrate malabsorption from apple juice (ie. high in excess fructose and sorbitol) was eased by switching to white grape juice (fructose and glucose in a 1:1 ration, low sorbitol). In general, however, there has been little research into the potential role of short chain carbohydrates (FODMAPs) that may be present in the milk of breast-feeding mothers that may exacerbate this condition.

We have recently detected sugar polyols- sorbitol and mannitol in breast milk. Sugar polyols include sorbitol (found commonly in pears, apples and stone fruits and often used as artificial sweeteners-for example ‘Extra’ chewing gum) and mannitol (found mushrooms, cauliflower and celery). In adults the malabsorption of polyols varies widely and may be as high as 74% for some individuals. Sugar polyols can cause gastrointestinal problems for adult patients with IBS

The aim of this proposed project is to investigate if manipulating levels of sugar polyols (sorbitol and mannitol) in the diet of breastfeeding mothers has any effect on the polyol composition of breast milk. Also, if a diet that is low in FODMAP carbohydrates (and in particular sugar polyols) provides any relief from colic-like symptoms in young infants.