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New Research & Analysis on Gluten-Free and Low-FODMAP Diets for Athletes—Part 1


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!

Spoiler alert: A big theme in her research findings is that low-FODMAP diets appear to be a smart and more effective choice—rather than just gluten-free diets—for athletes who experience GI issues and/or want to prevent GI issues (i.e. knowing which foods to avoid before competition to prevent gut blowups, etc.). That said, in the first study I cover in this post, there’s a thorough look at the reported benefits of GF diets.

I’ve added my commentary at the end of each study summary. As an athlete who’s suffered from some serious gut issues (and who has successfully healed them), I’ve researched a ton on this stuff and have also tried a ton of things, so I feel comfortable saying I have the experience and base knowledge, as well as personal opinions based on anecdotal evidence not only in myself but my clients and colleagues. Thus, I’m happy to share constructive criticism as it relates to the studies mentioned. You’ll see that sometimes I agree and sometimes I disagree with these researchers’ interpretations.

Please note that I’ve pulled quotes directly from the studies so anything that’s not my commentary is directly from the article, with references at the end of the post.

1. Exploring the Popularity, Experiences, and Beliefs Surrounding Gluten-Free Diets (GFD) in Non-Celiac Athletes (NCA)

Overview:

  • Athletes (n = 910; female = 528, male = 377, no gender selected = 5).
  • Completed a 17-question online survey.
  • GI dysfunction is a common occurrence among endurance athletes and can be attributed to several mechanisms including exercise-induced gut dysfunction and high carbohydrate intake (6).
    • Exercise may increase intestinal permeability due to reduced splanchnic perfusion.
  • Hadjivassiliou et al. cites that only 5–10% of the population (overall) may benefit medically from a GFD (7).
  • This survey data indicated a high proportion of athletes adhere to a GFD without evidence-based necessity (i.e. they’re on self-diagnosed gluten-free diets). It is possible that athletes follow a GFD due to perceived physiological improvements that may coincide simultaneously with other dietary changes and/or the perception that gluten elimination will provide the same health benefits and even an ergogenic edge.

Results:

  • 59% follow a GFD less than 50% of the time (GFD < 50).
    • 10.7% purchased gluten-free products once in a while.
    • 9.3% followed a GFD sporadically (a few days per month).
    • 0.7% followed a GFD 1–2 weeks before competition.
    • 38.8% of this group did not follow this diet at all.
  • 41.2% follow a GFD 50–100% of the time (GFD > 50), including 18-world and/or Olympic medalists, and in this group:
    • Predominantly endurance sport athletes (70%) at the recreationally competitive level, between 31 and 40 years of age.
    • 57% self-diagnosed their non-celiac gluten sensitivity (NCGS) / gluten issues—in other words, not made based on clinical recommendations.
    • GFD > 50 athletes reported experiencing abdominal/gastrointestinal (GI) symptoms alone or in conjunction with two or three additional symptoms (e.g., fatigue) believed to be triggered by gluten.
    • 50% adhered to GFD 90–100% of the time.
    • 13% remained GFD for treatment of medical conditions.
    • 84% of the GFD > 50 group indicated symptom improvement with gluten removal.
      • Perceived reductions in GI distress, reduced inflammation, improved exercise performance and that the diet supports a favorable body composition for sport.
      • Other symptoms, including physiological, nutritional and skin-related symptoms, were perceived to be triggered by gluten and resolved with gluten-avoidance in the majority of GFD > 50 respondents.

More Data:

  • Reasons for adopting a GFD:
    • Self-diagnosed NCGS based on symptoms or no symptoms (56.7%, n = 211).
    • Clinically diagnosed NCGS through gluten-challenge test (9.9%, n = 37).
    • Irritable bowel syndrome with symptoms thought to be triggered by gluten (8.9%, n = 33).
    • Recommended by coach, trainer, chiropractor, physiotherapist or paleo diet (8.9%, n = 33), naturopath bloodwork (7.0%, n = 26), family history of CD (3.2%, n = 12), other (4.8%, n = 18).
    • Recommended by nutritionist/registered dietitian (0.5%, n = 2).
  • Reported symptoms by respondents:
    • Physical symptoms including abdominal bloating, gas, diarrhea and fatigue thought to be triggered by gluten in 80.7% of the GFD > 50 athletes (n = 303).
    • Inflammation, physiological, nutritional and skin-related issues.
    • Only 1% did NOT benefit from gluten removal.
  • Gluten symptoms (confirmed in research):
    • NCGS has over 100 associated symptoms, including gluten ataxia, which due to reductions in neurological and muscular coordination would be detrimental to athletic performance (7).
    • Nutrient deficiencies, abdominal boating, GI symptoms, and fatigue.
    • GI disorders made worse by dietary triggers like gluten.
  • Negative issues surrounding adherence to a GFD according to the study:
    • The restrictive nature of the diet.
    • The risk of suboptimal nutrient intake (B vitamins, iron, fiber).
    • Increased difficulties with obtaining optimal food abroad for the traveling athlete.
    • The potential diminution of beneficial gut bacterial populations.
    • Increased food costs (on average of 242% for specialty items).
  • Conclusions by researchers:
    • GI distress reported in both the GFD < 50 and GFD > 50 groups was similar and this further demonstrates that the removal of gluten itself may not be the key modulating factor in a GFD and perceived symptom improvements. Given the complexity and importance of an athletes’ diet, diagnosis of CD or NCGS should be established before removing gluten from the diet.
    • Dietary changes with GFD such as an increase in conscientiousness of nutrition intake, increased fruit, vegetable and gluten-free whole grains and decreased processed food consumption.
    • Decreased energy and carbohydrate intake may result with a GFD, which may compromise energy and fuel availability for athletes (8).
    • It is unknown if reported performance improvements identified were simply perceived, a function of undiagnosed CD, NCGS, other dietary factors, or related to the GFD itself.
    • Belief may influence performance outcomes with this dietary intervention.
    • Self-selection may have biased a disproportional number of responses from athletes interested in or following a GFD. However, the proportionately high rate of athlete respondents that did not follow a GFD, or were unfamiliar with a GFD, support that our findings are most likely representative of an athletic population.

Tawnee’s Thoughts:

It’s great to see that nearly half of the 910 athletes surveyed follow a GF diet more than 50% of the time and of that group nearly all saw an improvement in reported symptoms. Is adopting this diet a result of people jumping on a bandwagon or people becoming more educated on nutrition and intuitive with their bodies? I hope it’s the latter.

Personally, I still think it’s incredibly valuable to test for gut dysbiosis to confirm the need for a GF diet or low-gluten diet, but I also believe in n=1 experimentation so if these athletes had no medical diagnosis and simply believed a GF diet would help based on their own research, trial and error, then so be it. If anything, the placebo effect is real.

Furthermore, I’d argue a GF diet is often even more nutrient dense and healthful when executed with care. With proper planning we can easily still get enough carbs through whole foods (including GF grains like buckwheat and rice, and starchy root vegetables like sweet potatoes) and with supplemental high-quality GF products (breads, pastas, sports nutrition bars). Meanwhile, most gluten-containing foods are not naturally occurring whole foods, thus usually not as nutrient dense, often have other “harmful” ingredients (added sugar, vegetable oils, etc.), may even have “anti-nutrient” that interfere with absorption, and are often highly refined with added synthetic vitamins, all of which present their own potential negative outcomes.

Lastly, I agree with the researchers in that I’d caution any athlete on making the switch to PLAN WELL. Initially, if you’re making changes to eliminate gluten-containing foods, you have to put in the effort to ensure you’re replacing old foods with high-quality GF foods and NOT “accidentally” going too low calorie or low carb.

 

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. Hadjivassiliou, M., Sanders, D.S., Grunewald, R.A., Wood- roofe, N., Boscolo, S., & Aeschlimann, D. (2010). Gluten sensitivity: from gut to brain. The Lancet. Neurology, 9, 318–330. PubMed doi:10.1016/S1474-4422(09)70290-X.
  8. Loucks, A.B. (2004). Energy balance and body composition in sports and exercise. Journal of Sports Sciences, 22, 1–14. PubMed doi:10.1080/0264041031000140518
  9. Despain, D. 2014. The surprising reason gluten-free diets actually work. [Online.] Available from outsideonline.com/1923951/surprising-reason-gluten-free-diets-actually-work.
  10. Golley, S., Corsini, N., Topping, D., Morell, M., and Mohr, P. 2015. Motivations for avoiding wheat consumption in Australia: results from a population survey. Public Health Nutr. 18: 490–499. doi:10.1017/S1368980014000652.