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New Research & Analysis on Gluten-Free and Low-FODMAP Diets for Athletes—Part 2


In this series, I’ll be covering five studies relating to gluten-free (GF) and low-FODMAP diets. These studies came on my radar thanks to head researcher Dana Lis, who I am having on Endurance Planet soon. The research she’s doing on nutrition is groundbreaking for athletes and is giving us more insight on special diet considerations. What that means for you is that you can see what the science says to better decide your own dietary needs!

Read Part 1 here.

2. “No Effects of a Short-Term Gluten-Free Diet on Performance in Non-Celiac Athletes”

Overview

  • Up to 70% of endurance athletes commonly experience GI distress during intense exercise and many athletes believe gluten removal might reduce these symptoms (6).
  • This study investigated the effects of a gluten-free diet (GFD) on exercise performance, gastrointestinal (GI) symptoms, perceived wellbeing, intestinal injury, and inflammatory responses in non-celiac athletes.
  • 13 competitive endurance cyclists (8 males, 5 females) were allocated to a 7-day gluten-containing diet (GCD) or GFD separated by a 10-day washout in a controlled, randomized, double-blind, crossover study. Cyclists ate a GFD alongside either gluten-containing or gluten-free food bars (16 g wheat gluten per day) while habitual training and nutrition behaviors were controlled.
  • On day 7, cyclists completed a submaximal steady-state (SS) 45-min ride at 70% Wmax followed by a 15-min time trial (TT). Blood samples were taken pre-exercise, post-SS, and post-TT to determine intestinal fatty acid binding protein (IFABP) and inflammatory markers (cytokine responses: interleukin [IL] 1A, IL-6, IL-8, IL-10, IL-15, tumor necrosis factor a).
  • Throughout the study, three questionnaires were required to be completed each day: 1) postexercise GI questionnaire, 2) daily GI questionnaire, and 3) Daily Analysis of Life Demands (DALDA). The presence and severity of upper and lower abdominal and other symptoms were determined using a 10-point scale ranging from 0 ‘‘no problem at all’’ to 9 ‘‘the worst it has ever been.’’

Results 

  • No difference in GI symptoms, overall wellbeing, markers of GI injury, or systemic inflammation between the GCD and GFD.
  • TT performance was not significantly different between the GCD and GFD.
  • GI symptoms during exercise, daily, and questionnaire responses were similar for each diet.
  • There were no significant differences in IFABP or cytokine (inflammatory) responses.

Conclusions by Researchers (quoted from the study):

  • In this tightly controlled study, our data suggest that a 7-d GFD does not have a beneficial or a negative effect on cycling performance, GI health, systemic inflammation, or overall wellbeing in non-celiac athletes.
  • It is recommended that athletes seek evidence-based advice before adopting a GFD for nonclinical reasons to ensure that nutrition intake supports individualized and optimal fueling for sport performance.
  • Interestingly, aside from inflammatory mechanisms associated with strenuous exercise, Soares et al. found that an 8-week high-fat GFD attenuated inflammation associated with adiposity, reduced visceral fat, and improved glucose homeostasis in non-celiac rodents (7)… Future research with a longer duration of GFD adherence may help account for differential gut flora habituation, which could be influential on GI health, performance, and other parameters.

Tawnee’s Thoughts:

It’s totally important to point out that gluten is no all-evil for every single person. I know plenty of healthy people who don’t react to gluten. Don’t let “gluten-free” be a trendy bandwagon you jump on just, well, because…. But that said, I know more people who really need to avoid gluten even if they’re not celiac, and gluten is contributing to and/or causing their gut and health woes. Not to mention, many of the commercial foods with gluten have other ingredients that don’t help matters, from sugar to GMOs. (Of course, I’ll admit I’m biased in seeing more people with gluten issues due to my type of clientele.)

This Freakonomics podcast does a good job explaining that gluten really is dangerous for some, but for others not a problem. So if you go gluten free, understand WHY you are doing so.

I should also note that the type of diet and nutrition I tend to advocate, i.e. more whole food-based paleo-style of eating, tends to be naturally low or free of gluten and gluten shouldn’t really be a staple anyways, whether or not you’re sensitive to it. Plus I also prefer gluten-free grains a lot of the time due to nutrient content.

Speaking to this study specifically: The athletes who were studied—just 13 total—were “normal” with no known health issues that could be made worse with gluten, which may be the reason that the results showed “no significant difference” between a GCD or GFD. Those with a gut of steel may indeed have no issues with gluten especially in a non-jarring sport like cycling. Call them the lucky 13!

Meanwhile, the exclusion criteria in this study was extensive and included those with diagnosed celiac disease, a known familial history of celiac disease, history of wheat allergy, clinically diagnosed non-celiac gluten sensitivity (NCGS), irritable bowel syndrome (IBS), those following a gluten-free or vegetarian diet, or those with any pre-existing medical condition that could be affected by this dietary intervention.

So if you read this study’s results and think, “Great, bring on the gluten because there’s no difference between a GFD and GCD and I’m not celiac,” … well, not so fast! Make sure you understand WHO was being tested and how you compare—again, there were only 13 subjects all of whom had no known GI or food sensitivity issues like many of us do. Thus, if you have any known GI or food sensitivity issues (or a history of such, clinical or otherwise), these results may not apply to your needs and you may indeed benefit from a GFD or a low-FODMAP diet. Plus there is new research from 2016 indicating that non-celiac wheat sensitivity (NCWS) is real (wheat contains gluten) and not just in peoples’ heads. (NCGS is essentially the same as NCWS; wheat contains gluten, but wheat also contains other potential disruptive proteins beyond gluten making NCWS a broader issue going beyond gluten.)

Positively speaking, I’m actually glad to see this study showed no difference between a GFD and GCD, and shows that gluten is not always all evil like some make it out to be. If gluten truly does not negatively affect an athlete, and the athlete has no known GI issue, including “leaky gut” which is often a non-clinical diagnosis, then there’s no reason to arbitrarily eliminate it. Yes, you may still want to consider gluten-free foods for health reasons, i.e. GF foods that are more nutrient dense and “clean” (i.e. a sweet potato vs. processed white bread) or to be preventative and protect your gut (a personal choice). But if you test and show no reaction to gluten and you have a squeaky clean gut then don’t fret over gluten, and also consider yourself lucky, too.

That said, I have beef with this study and others like it. Please don’t misunderstand, I’m so grateful it was conducted, but the sample population of just 13 leaves out a huge number of us with sensitive GI tracts, thus the findings may not accurately reflect the general population of athletes (and humans) this day in age. I understand why the experiment was conducted this way, but there are strong limitations in this study, so proceed with caution if intending to provide dietary advice to others based on this study alone.

Let me back up my statements a bit more:

  • First, cycling is a relatively gentle non-jarring sport so it may not induce GI issues as much as other sports like running (where gut issues are more prevalent) or even triathlons especially long-course triathlons (how many stories have you heard where participants were fine on the bike but “blew up” on the run).
  • Second, the duration of this study was very short and like with research evaluating the different between low-carb and high-carb diets in athletes, GFD vs. GCD may require a longer intervention to see observable differences. The researchers point this out too, so we agree that there’s a need to do a longer-term study with athletes on these diets. But to the researchers’ point, it’s hard to conduct such long-term studies, especially those involving dietary interventions and also complications in accounting for training adaptations.
  • Third, if we could repeat this study on NCWS and/or NCGS athletes, I predict we’d see a different outcome and that GFD may prove to be superior. Keep in mind that NCWS/NCGS is largely self-diagnosed based on individual symptoms so a lot of people don’t “buy” that it’s a real thing since it’s not at a clinical level, but thankfully a study done in 2016 says otherwise (8); so for all you who suffer with your guts and feel better on a GFD, you’re validated to stick with that approach.
    • Eighty individuals with self-diagnosed NCWS were recruited to Columbia University Medical Center for research to see if their condition could be verified as a legit issue (8). There were 160 subjects total: 80 with NCWS, 40 with celiac disease and 40 healthy individuals. The researchers found those with a NCWS did indeed show problems when they ingested wheat/gluten including increased intestinal permeability (i.e. leaky gut), gut epithelial cell damage and increased systemic immune activation and that “there was a significant change towards normalisation of the levels of [fatty acid-binding protein 2] and immune activation markers in a subgroup of individuals with wheat sensitivity who observed a diet excluding wheat and related cereals (8).”
  • Fourth, from what I’ve seen and heard, anecdotally, it appears that some athletes may start out in their athletic careers handling gluten just fine, but over time and with repeated stress on the GI tract via training and racing their guts weaken leading to leaky gut and/or other GI issues, and gluten may become problematic (as do other trigger foods like FODMAPs, alcohol, etc.). It’s true that the subjects in this study were well trained to begin with and none appeared to have leaky gut from what we’re told, which would dispel that theory, but we’re only looking at 13 athletes here.
  • Fifth, the placebo effect aka the “belief effect” is real, folks. In other words, in athletes who go on a GFD but don’t really need it, the “belief effect” could be at play for the beneficial outcomes. This study states, “A recent review by Halson and Martin summarized the ‘belief effect,’ which suggests that the belief in an intervention can contribute a 1% to 3% improvement in performance regardless if it actually has ergogenic mechanisms (9).” So if you feel better with it, even if it truly is just in your head in this case, that may be enough to get the boost. Just make sure you’re meeting carb and calorie needs as discussed in Part 1.

 

Full References

References #1-5 are all articles in (upcoming) series with the article covered in this post bold, plus more resources cited above and worth browsing:

  1. Lis D, Stellingwerff T, Shing CM, Ahuja KD, Fell J. Exploring the popularity, experiences and beliefs surrounding gluten-free diets in non-celiac athletes. Int J Sport Nutr Exerc Metab. 2014; 25:37–45.
  2. Lis D, Stellingwerff T, Kitic CM, et al. No effects of a short-term gluten-free diet on performance in non-celiac athletes. Med. Sci. Sports Exerc. 2015b; 47:2563-70.
  3. Lis D; Fell J, Ahuja K, Kitic CM, Stellingwerff T. Nutrition and Ergogenic Aids. Volume 15 & Number 4 & July/August 2016
.
  4. Lis D, Ahuja KDK, Stellingwerff T, Kitic CM, Fell J. Case Study: Utilizing a Low FODMAP Diet to Combat Exercise-Induced Gastrointestinal Symptoms. International Journal of Sport Nutrition and Exercise Metabolism. 2016; http://dx.doi.org/10.1123/ijsnem.2015-0293.
  5. Lis D, Ahuja KDK, Stellingwerff T, Kitic CM, Fell J. Food Avoidance in Athletes: FODMAP Foods on the list. Appl. Physiol. Nutr. Metab. 41: 1002–1004 (2016); dx.doi.org/10.1139/apnm-2015-0428.
  6. Pfeiffer B, Stellingwerff T, Hodgson AB, et al. Nutritional intake and gastrointestinal problems during competitive endurance events 
(Med Sci Sports Exerc. 2012;44(2):344–51.
  7. Soares FL, de Oliveira Matoso R, Teixeira LG, et al. Gluten-free diet reduces adiposity, inflammation and insulin resistance associated with the induction of PPAR-alpha and PPAR-gamma expression. J Nutr Biochem. 2013;24(6):1105–11.
  8. Uhde M, Ajamian M, Caio G, et al. Intestinal cell damage and systemic immune activation in individuals reporting sensitivity to wheat in the absence of coeliac disease. Gut 2016;65:1930-1937.
  9. Halson SL, Martin DT. Lying to win—Placebos in sport science. Int J Sports Physiol Perform. 2013;9:597–9.