Oral Presentation Gastrodiet 2015

How to use the low FODMAP diet safely (#4)

Heidi M. Staudacher 1 2 , Peter M. Irving 3 , Kevin Whelan 1 , Miranda C.E. Lomer 1 2 3
  1. Diabetes and Nutritional Sciences Division, King's College London, London, United Kingdom
  2. Nutrition and Dietetics, Guy's and St Thomas' NHS Foundation Trust, London, United Kingdom
  3. Gastroenterology, Guy's and St Thomas' NHS Foundation Trust, London, United Kingdom

Dietary restriction of certain fermentable carbohydrates (low FODMAP diet, LFD) is effective for managing symptoms of irritable bowel syndrome (IBS). Exclusion diets carry a risk of nutritional inadequacy. Furthermore, reduction in prebiotic intake associated with the LFD impacts on the gastrointestinal (GI) microbiota. Hence, the safety of the low FODMAP diet in relation to its effect on nutritional and microbiological outcomes requires exploration.

Mean daily calcium intake is lower in patients with IBS following LFD advice compared with controls following their habitual diet1. Furthermore, we recently showed in a large RCT that nutrient intake was broadly maintained in 51 patients four weeks after LFD advice compared with baseline habitual diet. However, the proportion of patients meeting the United Kingdom calcium dietary reference value (DRV) was lower compared with baseline (49% vs 65%, p=0.039)2. Mean daily iron intake was reduced after LFD advice compared with baseline (10.3mg/d vs 11.3mg/d, p=0.009),although proportion of patients meeting the iron DRV did not change. Overall, nutrient intakes were similar to the general population.

Extensive dietary modification, particularly to carbohydrate intake, has a pronounced impact on the GI microbiota. Indeed, recent data suggests a 4-week LFD markedly reduces luminal Bifidobacteria concentration1 in the absence of changes to total bacteria abundance, whilst a 3-week LFD leads to reduced total bacteria abundance and reduced concentration of other bacterial groups e.g. Faecalibacterium prausnitzii3. Effects on markers of fermentation (e.g. faecal pH) has been demonstrated but results are conflicting1,3.

The LFD as a strategy for improving IBS symptoms presents a potential safety concern specifically in relation to nutrient intake and its impact on the GI microbiota.  Nutrient intake of patients following a LFD is broadly maintained, however inclusion of calcium sources should be emphasised. Whether LFD-induced microbiota alterations can be prevented with probiotic supplementation is being investigated.

Source of funding: National Institute for Health Research

  1. Staudacher HM, Lomer MC, Anderson JL et al. (2012) Fermentable carbohydrate restriction reduces luminal bifidobacteria and gastrointestinal symptoms in patients with irritable bowel syndrome. J Nutr 142, 1510-1518.
  2. Staudacher HM, Ross FS, Briscoe ZM et al. (2015) Advice from a dietitian regarding the low FODMAP diet broadly maintains nutrient intake and does not alter fibre intake Gut 64 (Suppl 1), A143-144.
  3. Halmos EP, Christophersen CT, Bird AR et al. (2015) Diets that differ in their FODMAP content alter the colonic luminal microenvironment. Gut 64, 93-100.