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Exploring the practises and effects of gluten-free and low FODMAP diets in noncoeliac athletes

Lis, DM 2017 , 'Exploring the practises and effects of gluten-free and low FODMAP diets in noncoeliac athletes', PhD thesis, University of Tasmania.

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Abstract

Background and Aims
Exercise-associated gastrointestinal (GI) symptoms are widespread and estimated to occur in
30-50% of endurance athletes. GI symptoms are multi-factorial but primarily caused by
physiological, mechanical and/or nutritional triggers. Symptoms generally occur during
exercise or within the few hours following exercise. Gluten is touted by many to be detrimental
to GI health in athletes particularly with a compromised gut barrier caused by reduced
splanchnic blood flow, which most commonly occurs during higher exercise intensities. It is
suggested that exercise-induced injury to the gut barrier could in turn increase susceptibility to
dietary triggers, such as gluten. Gluten is further perceived to elicit undesirable proinflammatory
responses in healthy athletes, partially through compromised gut epithelial
barrier function, allowing the passage of gluten peptides or the interaction of these peptides
with tight junction proteins. However, these theories alongside the overall idea that a glutenfree
diet (GFD) provides an ergogenic benefit have yet to be substantiated.
Athletes persistently explore dietary strategies perceived to offer ergogenic benefits or
beneficial impacts on parameters influencing performance, such as reducing GI symptoms.
There has been an explosion in the prevalence and use of gluten-free products in recent years,
which is exacerbated by unsubstantiated commercial health and sport performance claims.
This has led to numerous athletes touting a gluten-free lifestyle as the secret to their success. It
is well known that a GFD is necessary for the treatment of clinical conditions such as coeliac
disease or noncoeliac gluten (wheat) sensitivity (NCGS). However, anecdotal reports suggest
that many athletes believe a GFD directly improves exercise performance and parameters
influencing performance, particularly GI symptoms as well as inflammation and immune health.
Dietary changes may occur alongside the avoidance of gluten-containing foods that could
influence health parameters or GI symptoms. A predominant dietary change that occurs
subsequent to eating a GFD also includes a reduction in the intake of short-chain carbohydrates,
otherwise known as fermentable, oligo-, di-, monosaccharides and polyols (FODMAPs).
Significant FODMAP reduction may actually modulate GI symptoms, and not necessarily the
gluten itself. Given the absence of peer-reviewed data on the effects of either gluten or
FODMAPs on athlete performance, the studies that comprise this thesis were first aimed to
understand and quantify the prevalence of GFD adherence, and relatedly, high FODMAP food
avoidance among noncoeliac athletes (NCA). A second step was to undertake intervention
studies to investigate the efficacy of these diets on GI symptoms, performance and related
parameters in an athletic population.
Methods and Results
An electronic-based questionnaire (n=910) was distributed internationally to athletes to
determine athlete-specific GFD and high FODMAP avoidance food behaviours and beliefs.
Specifically, this questionnaire was designed to evaluate GFD practises, demographics,
experiences, and sources of dietary recommendation and information. Our initial findings
established that 41% of NCAs followed a GFD at least 50% of the time. Negative GI symptoms
(e.g. diarrhoea, bloating) were the most highly reported indicators believed to be triggered by
gluten with 84% of respondents indicating symptom improvement with gluten-removal.
Athletes adhering to a GFD also perceived a GFD to improve body composition for sport
(74.4%), reduce inflammation (73.3%), decrease GI distress (61.1%), and improve exercise
performance (56.3%). Self-diagnosed gluten-related conditions were the primary reason for adopting a GFD with non-medical dietary prescription and advice from coaches/other athletes
reported as the most common source of GFD information.
Given the high uptake of a GFD in athletes and the belief that a GFD improved exercise
performance, GI health and wellbeing, the next study within this thesis aimed to investigate
the effects of a GFD on performance in endurance-based NCA. Thirteen competitive NCA
(endurance cyclists) were allocated to a 7-day gluten-containing diet (GCD) or GFD (16 g
gluten.day-1) using a controlled, double-blind, crossover intervention design. During each diet,
cyclists completed GI questionnaires (daily and during exercise), the Daily Analysis of Life
Demand for Athletes (DALDA) and an exercise test on day seven of each dietary period. Blood
samples were taken pre-exercise, after a 45-minute steady state exercise bout at 70% Wmax and
following a 15-minute time trial (TT) to measure acute intestinal injury and inflammatory
markers. Exercise and dietary intake was tightly controlled and replicated during each dietary
period. A GFD had no beneficial or negative effect on 15-minute cycling TT performance
(GCD 245±53 and GFD 245±55 kJ). GI symptoms, DALDA evaluation and biomarkers of
acute epithelial injury and systemic inflammation were also similar in the GCD and GFD
periods.
The GFD intervention did not show a GFD to be ergogenic; however, when a GFD is adopted,
FODMAPs may be reduced. The low rates of GI symptoms reported in our initial study may
have been confounded by a reduction in fructans on both trials, which are part of the FODMAPs
family. Initial findings led to subsequent studies investigating FODMAP avoidance or
reduction in NCA. First, athletes’ dietary behaviours regarding FODMAPs were established
via FODMAP-specific questions in the preliminary questionnaire-based study. Offending
foods that happened to be part of the FODMAP family were quantified as a popular strategy
employed by 51% of NCA to reduce GI symptoms with 83% of this group reporting symptom improvement. To examine the effects of short-chain carbohydrate restriction on GI symptoms,
a short-term low FODMAP dietary intervention was conducted utilizing a case-study
methodology in a multisport athlete with persistent exercise-associated GI distress. A 6-day
low FODMAP compared to a habitual high FODMAP diet was implemented and the athlete
was evaluated for GI symptoms and DALDA scores indicating ‘worse than normal.’ On each
day of the intervention a measurable reduction, from symptom severity scores of 0-9 to 0, in
exercise and daily GI symptoms was observed. DALDA scores remained stable across the
habitual and intervention periods. The GI symptom improvement in this athlete suggested the
necessity for a larger crossover intervention to further explore the use of a FODMAP restricted
diet as a tool to reduce GI distress in healthy symptomatic endurance athletes.
To further explore the potential of a low FODMAPs intervention to reduce GI symptoms, a
larger preliminary trial was conducted. GI symptoms and perceptual wellbeing were assessed
during a high FODMAP vs. low FODMAP diet in runners (n=11) with persistent exerciseassociated
GI symptoms, but no diagnosed functional gastrointestinal disorder or food
intolerance. Runners were randomized to low (<9 g FODMAP.day-1) and high FODMAP (>20
g FODMAP.day-1) dietary periods of 6-days each with prescribed strenuous running sessions
completed on day-4 and day-5 and a single day washout before crossing over to the other diet.
Exercise and diet were replicated with study meals and snacks provided alongside suitable low
or high FODMAP food choices. During each dietary trial runners recorded dietary intake and
exercise and completed electronic GI symptom and DALDA questionnaires. Large variability
in GI symptoms was apparent with no statistical difference in exercise GI symptom frequency
or severity and DALDA score. While exercise GI symptoms were not different, daily GI
symptoms were lower each day of the low FODMAP dietary period. Short-term FODMAP
reduction may be a novel tool in improve daily GI symptoms in healthy runners with exerciseassociated
GI distress. Future work in this area should incorporate exercise protocols with higher intensity and longer duration to better assess the impact of this diet on GI symptoms
occurring during exercise.
Conclusions
This progressive work has quantified widespread adherence to a GFD amongst NCA.
Although, many NCA adhere to a GFD due to beliefs underpinned by unsubstantiated health,
GI and performance benefits, a short-term GFD was not found to have a beneficial (or negative)
effect on performance, GI health, systemic inflammation or overall wellbeing. FODMAP
intake may be consequently reduced with a GFD and is proposed to modulate GI symptoms,
rather than gluten itself. Relatedly, elimination of high FODMAP foods were found to be a
common dietary strategy employed by athletes aimed at attenuating GI symptoms with high
rates of self-reported success. Results from our successive intervention studies showed
improvement in GI symptoms with elimination of high FODMAP foods. Based on these
findings, FODMAP manipulation, rather than gluten-elimination, may be a more successful
and novel intervention to consider for the sport nutrition practitioner’s toolbox for management
of GI distress in athletes. A practitioner supported systematic and individualized approach will
be essential for the potentially successful implementation of these dietary approaches.

Item Type: Thesis - PhD
Authors/Creators:Lis, DM
Keywords: gluten-free, athletes, FODMAPs, gastrointestinal, performance, inflammation
Copyright Information:

Copyright 2017

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