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FODMAPs

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 2007Shepherd et al. 2008Staudacher et al. 2011Staudacher at al. 2014).

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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).

References

Barrett & Gibson (2007) Practical Gastroenterology 53: 51-65

Böhn et al. (2015) Diet low in FODMAPs reduces symptoms of irritable bowel syndrome as well as traditional dietary advice: a randomized controlled trail. Gastoenterology 149(6):1399–1407.e1392

Halmos et al. (2014) A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology 146(1):67-75.e5.

Halmos et al. (2015) Diets that differ in their FODMAP content alter the colonic luminal microenvironment. Gut 64 :93-100

Hill et al. (2017) Controversies and Recent Developments of the Low-FODMAP Diet. Gastroenterology & Hepatology 13(1): 36-45

Nanayakkara et al. (2016) Efficacy of the low FODMAP diet for treating irritable bowel syndrome: the evidence to date. Clin Exp Gastroenterol 9:131-142

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]

Ong et al. (2010) Manipulation of dietary short chain carbohydrates alters the pattern of gas production and genesis of symptoms in irritable bowel syndrome. J Gastroenterol Hepatol 25(8):1366-73.

Pedersen et al. (2014) Low FODMAP diet vs Lactobacillus rhamnosus GG in irritable bowel syndrome. World J Gastroenterol 20(43):16215-26.

Shepherd et al. (2008) Dietary triggers of abdominal symptoms in patients with irritable bowel syndrome: randomized placebo-controlled evidence. Clin Gastroenterol Hepatol 6(7):765–771

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. (2012) Fermentable Carbohydrate Restriction Reduces Luminal Bifidobacteria and Gastrointestinal Symptoms in Patients with Irritable Bowel Syndrome. J Nutr 142(8):1510–1518.

Staudacher at al. (2014) Mechanisms and efficacy of dietary FODMAP restriction in IBS. Nat Rev Gastroenterol Hepatol 11(4): 256-66

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