What are FODMAPs?
FODMAPs stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. They are a collection of simple and complex sugars that are rapidly fermented and have an osmotic effect. They are found in a wide range of foods including garlic, onions, artichoke, apples, pulses, wheat bread and honey.
For the majority of people, these FODMAPs are harmless and in fact beneficial for digestive health as they stimulate gut bacterial fermentation which leads to the production of short chain fatty acids (SCFAs) such as butyrate. However, for individuals suffering from irritable bowel syndrome (IBS) research has shown that the fermentation of FODMAPs, and the subsequent osmotic load and gas production in the distal small bowel and proximal colon, leads to the characteristic IBS gastrointestinal symptoms of abdominal pain, bloating, abdominal distention, flatulence, constipation and diarrhoea (Barrett & Gibson 2007, Shepherd et al. 2008, Staudacher et al. 2011, Staudacher at al. 2014).
The Low FODMAP Diet
This led to a team of dietitians and researchers at Monash University in Australia developing the Low FODMAP Diet – a two-phased intervention within an initial strict reduction of all dietary FODMAPs, followed by a gentle reintroduction phase to determine individual’s tolerance to FODMAPs contained in certain foods. Several randomised-controlled studies have shown significant reduction in symptom scores in IBS patients who have adopted a low FODMAP diet (Shepherd et al. 2008, Ong et al. 2010, Staudacher et al. 2011, Halmos et al. 2014, Pedersen et al. 2014, Böhn et al. 2015, Staudacher at al. 2017).
The use of the low FODMAP diet in the management of IBS is currently recommended as second line dietary advice, to be considered when symptoms persist while following general lifestyle and dietary advice considered first-line advice in IBS management (NICE 2019). It is important to emphasise that this diet is not meant to be adopted for the long-term and often people get confused with this. The low-FODMAP diet is specially formulated for IBS patients and subjects with other functional gastrointestinal symptoms, and must be carried out under the supervision of a qualified FODMAP trained registered dietitian due to its restrictive nature. This diet is not intended for the general public as cutting out food groups unnecessarily can be highly detrimental to health, due to compositional changes in the gut microbiota that it may lead to, and the long-term health effects of a low FODMAP diet are not known (Nanayakkara et al. 2016).
For more information on low or high FODMAP foods visit: www.monashfodmap.com/about-fodmap-and-ibs/high-and-low-fodmap-foods/
Effect on the gut microbiota
As the name suggests, FOMAPs are fermentable; they reach the lower gastrointestinal tract where they act as an energy source for bacteria and are fermented by them. Emerging evidence has shown that a reduced intake of FODMAP foods, such as those containing fructans and galacto-oligosaccharides (GOS), could lead to a natural reduction in beneficial bacteria, such as Bifidobacterium, due to the reduced amount of fermentable substrates within the gastrointestinal tract (Staudacher et al. 2012).
It has also been found that a low-FODMAP diet has been associated with a depletion in SCFA production with specific reductions in butyrate-producing bacteria and an increase in mucous degrading bacteria (Halmos et al. 2015).
However, the long-term health implications of these effects of a low-FODMAP diet on the gut microbiota are unknown as a low FODMAP diet is only recommended for 2-6 weeks under strict dietetic supervision, as mentioned above (Hill et al. 2017).
NICE (2019) NICE Pathways. Irritable bowel syndrome in adults. Available at: https://pathways.nice.org.uk/pathways/irritable-bowel-syndrome-in-adults [accessed 16 Aug 2019]
Staudacher et al. (2011) Comparison of symptom response following advice for a diet low in fermentable carbohydrates (FODMAPs) versus standard dietary advice in patients with irritable bowel syndrome. J Hum Nutr Diet 24(5): 487-95
Staudacher et al. (2017) A Diet Low in FODMAPs Reduces Symptoms in Patients With Irritable Bowel Syndrome and A Probiotic Restores Bifidobacterium Species: A Randomized Controlled Trial. Gastroenterology 153(4): 936-947