The FODMAP diet is a fairly new diet, so it’s important to understand exactly what it is and who it’s intended for. Due to the complex nature of the diet it’s important to work with your FODMAP trained Registered Dietitian whilst following the low FODMAP diet.



Fermentable, Oligo-saccharides, Di-saccharides, Mono-saccharides And Polyols (FODMAPs) are a group of short-chain carbohydrates. Why are they relevant? Well, research shows that symptoms of irritable bowel syndrome (IBS), a gastrointestinal disorder that affects around 10-20% of the global population, can be worsened by eating a diet high in these FODMAPs. FODMAPs are osmotically active which means they can pull water into the intestine and can cause diarrhoea and/or bloating. In addition, a build up of FODMAPs in the small intestine can lead to bacterial fermentation, releasing gas and other by products which contributes to the symptoms associated with IBS. Research indicates that following a low FODMAP diet can be effective in reducing IBS symptoms for around 70% of sufferers.

Studies from 2006 onwards started to investigate the effects of fermentable carbohydrates (fructose, fructans and polys) on gut symptoms. In 2011, Staudacher et al published a study suggesting that a low FODMAP diet could be effective in those with IBS. Following on from this, researchers at Monash University Australia have published guidelines on the low FODMAP diet. This diet protocol consists of a strict exclusion of high FODMAP containing foods for 4-6 weeks, as well as medium FODMAP containing foods depending on sensitivity, followed by a reintroduction phase to determine tolerance levels of particular FODMAP containing foods. This process should be undertaken under the close supervision of a FODMAP trained Registered Dietitian once a diagnosis of IBS has been confirmed and other medical conditions excluded.

The FODMAP diet is a medical diet and should only be undertaken if advised by a Registered Dietitian, under close supervision.

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What are FODMAPs?

So let’s take a closer look. Sources of FODMAPs include:

  • Fructans – chains of fructose. Sources include wheat and rye, various fruits and vegetables, added ingredients such as fructose-oligosaccardies (FOS), oligofructose and inulin.
  • Galacto-oligosaccarides (GOS) – chains of galactose. Sources include pulses and legumes.
  • Polyols – sugar alcohols. Sources include various fruit and vegetables, sugar-free chewing gum and mints.
  • Fructose – a single unit of sugar. Sources include various fruit, honey and agave nectar.
  • Lactose – a double unit of sugar found in milk.

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What does high, medium and low FODMAP mean?

Research is constantly taking place to determine the FODMAP content of new foods. Testing is done at Monash University, Australia. Once a food is tested, it will be grouped into one of three categories:

High FODMAP – The level of FODMAPs in the particular food is considered not suitable for those on the low FODMAP diet and eating these foods may aggravate symptoms of IBS.

Medium FODMAP – These foods are ok but only in small quantities. For example, less than 10 almonds are considered ok but any more could aggravate symptoms. Speak with your Dietitian for more support on specific portion sizes of medium level FODMAP foods.

Low FODMAP – These foods are considered ok for someone following the low FODMAP diet and can we eaten freely.

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Who is the FODMAP diet intended for?

Irritable bowel syndrome (IBS) is a common, long term condition of the digestive system. It’s characterised by lower abdominal pain, bloating, wind, and altered bowel habits such as constipation and diarrhoea. It is thought 10-20% of the global population suffer from IBS, and it’s most common amongst women and people under the age of 50. Diagnosis of IBS is carried out by medical practitioners and therefore if you suspect you have IBS you should discuss this with your GP.

The low FODMAP diet should not be followed long term

Following the Low FODMAP diet long term could potentially lead to some health risks.

Because the diet is complex and requires the exclusion of large groups of foods, some health professionals have voiced concerns around the nutritional adequacy of the diet. The main concern here is that due to the restrictive nature of the diet, those on a Low FODMAP diet may not get all the nutrients needed in a balanced diet. It is therefore vital that the diet be followed with the help of a Registered Dietitian that can ensure suitable substitutes are made.

Researchers have also speculated that following a low FODMAP diet could alter gut microbiota which play a critical role in health and disease however this does require further research.

If you are on a Low FODMAP diet, it’s important that it is followed with these potential risks in mind.

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  • Halmos EP, Power VA, Shepherd SJ, Gibson PR, Muir JG. (2014) A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology; 146:67–75.e5.

  • Khanbhai, K., Sura, D.S. (2013) “Irritable bowel syndrome for primary care physicians”. British Journal of Medical Practitioners. 6(1): a608.

  • Marsh, A., Eslick, E.M. & Eslick, G.D. (2016) “Does a diet low in FODMAPs reduce symptoms associated with functional gastrointestinal disorders? A comprehensive systematic review and meta-analysis”. European Journal of Nutrition. 55: 897. doi:10.1007/s00394-015-0922-1

  • Nanayakkara, W,S., Skidmore, P.ML., O’Brien, L., Wilkinson, T.J., Gearry, R.B. (2016) “Efficacy of the low FODMAP diet for treating irritable bowel syndrome: the evidence to date”. Clinical and experimental gastroenterology. 9, pp131-142. Doi:10.2147/CEG.S86798.

  • Low FODMAP Diet for Irritable Bowel Syndrome. Monash University; [Accessed January 9, 2017]. Available at:

  • Staudacher, HM., et al. Fermentable carbohydrate restriction reduces luminal bifidobacteria and gastrointestinal symptoms in patients with irritable bowel syndrome. The Journal of Nutrition (2012);142(8):1510-8. doi: 10.3945/jn.112.159285. Epub 2012 Jun 27.

  • Staudacher, HM., Whelan,. Altered gastrointestinal microbiota in irritable bowel syndrome and its modification by diet: probiotics, prebiotics and the low FODMAP diet. Proceedings of the Nutrition Society (2016);75(3):306-18. doi: 10.1017/S0029665116000021. Epub 2016 Feb 24.

  • Staudacher, HM., Whelan, K., Irving, PM., Lomer, MC. Comparison of symptom response following advice for a  diet low in fermentable carbohydrates (FODMAPs) versus standard dietary advice in patients with irritable bowel syndrome. The Journal of Human Nutrition and Dietetics (2011); 24(5): 487-95. doi: 10.1111/j.1365-277X.2011.01162.x.

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