Preface: this post is aimed towards nonceliac athletes. Those suffering with celiac disease should continue their treatment via a gluten-free diet, allowing for the disappearance of the signs/symptoms of disease.

“It’s gluten-free, it must be healthy.”

The popularity of gluten-free foods and adherence to a gluten-free diet (GFD) among the general public has grown rapidly in recent years. Sales of gluten-free foods and beverages have risen, celebrity endorsements have contributed to an increased awareness of perceived benefits of gluten avoidance (including weight loss) and gluten-free has become the new must-have “healthier” choice.

Adherence to a GFD has notably increased in prevalence in nonceliac athletic populations, with one study finding that 41.2% of athletes (a mixture of professional and recreational) adhered to a GFD over 50% of the time (Lis et al. 2015) – especially interesting when the prevalence of celiac disease has been approximated as 0.5%-1% in different parts of the world. Obviously, nutrition is important to the athlete with such concerns as consuming adequate energy, macronutrient distribution and hydration. But, does a gluten-free diet benefit or hinder performance?

As a former student-athlete – even though my diet largely consisted of tacos, pizza and beer – I possess firsthand experience of the importance of nutrition with regards to athletic performance: dealing with deficiencies of both iron and vitamin D which facilitated a state of general fatigue was certainly disadvantageous to my performance. Coincidentally, a potential negative of adhering to a GFD for nonceliac athletes, due to its restrictive nature, is the risk of suboptimal nutrient intake.

Regardless of perceived reductions in GI distress, reduced inflammation, improved exercise performance and that the diet supports a favourable body composition for sport, there’s no data to suggest that gluten avoidance benefits health or performance. In fact, gluten may improve blood lipid levels and play a role in blood pressure control (Gaesser & Angadi 2012).

In addition to the hit your wallet takes, the avoidance of gluten has the potential of causing numerous nutrient deficiencies and compromising gut health by reducing beneficial gut bacteria. Athletes, especially those involved in winter sports, are prone to an increased risk of illness – placing additional emphasis on meeting energy and macronutrient needs. Alterations in gut microbiota associated with a GFD appear to exert lower immune stimulatory effects on peripheral blood mononuclear cells (e.g., lymphocytes and macrophages), with an apparent increase in “unhealthy” bacteria weakening host defences against infection and chronic inflammation (Sanz 2010). On top of this, persons who consume gluten suggest an increase in natural killer cell activity which could enhance immune monitoring against viral infections (Gaesser & Angadi 2012) – thus, the first unnecessary consequence of following a GFD for a nonceliac (consider: malnutrition increases risk of infection).

According to some studies many gluten-free foods contain significantly less thiamin, riboflavin, niacin, iron and folate in comparison to their fortified gluten-containing comparative products (Shepherd & Gibson 2013). One of the main key points of nutrition and athletic performance is that athletes consume diets that provide at least the recommended dietary allowance for all micronutrients. Thus, hypothetically, restricting the intake of one of more of these nutrients may detrimentally impact performance…

  • Thiamin (found in cereals, nuts, legumes and orange/grapefruit juice) plays a key role in carbohydrate and protein metabolism. Although no significant effects of graded dietary thiamin intakes on physiological function have been found, brief thiamin insufficiency may result in increased circulating lactate during work, promoting fatigue, impairing training, and ultimately reducing performance (Lukaski 2004).
  • Riboflavin (found in milk and dairy, fortified cereals, offal and dark green vegetables) is required for oxidative energy production. Dieting and exercise increase the intake of riboflavin needed to maintain adequate status however, impaired riboflavin status appears not to have adverse effects on physical performance (Lukaski 2004).
  • Niacin (found in liver, beef, fish, cereals and peanuts) influences the use of fatty acids. It was previously hypothesised that a beverage containing a mixture of nicotinic acid and glucose would reduce free fatty acid concentrations and increase dependence on glycogen stores and glucose from the beverage, hypothetically attenuating the use of muscle glycogen and increasing performance. However, time trial performance was again unaffected (Lukaski 2004).
  • Folate (found in cereals, bread, potatoes, liver and dark green vegetables) is required for the synthesis of purines and pyrimidines that are needed for DNA production and erythropoiesis. Even though folate deficiency results in abnormally large red blood cells that cannot effectively transport oxygen or remove carbon dioxide the response to folate supplementation is similar to the prior mentioned micronutrients with no improvement of physical performance (Manore et al. 2011, Lukaski 2004).
  • Here’s where things get interesting: iron (found in fortified cereals, meat and dark green vegetables) is required for the delivery of oxygen to tissues and plays a critical role in energy use during work. It serves as a functional component of iron-containing proteins including haemoglobin, myoglobin, cytochromes and specific iron-containing enzymes. The effects of iron supplementation, particularly in iron-deficient, non-anaemic athletes, are rather inexplicit. Some studies show no effect on physiological performance markers such as peak oxygen uptake or blood lactate concentrations, whereas others have found an improvement in endurance time, significant decreases in blood lactate concentrations and significantly enhanced muscle function. Indeed, a definitive conclusion remains elusive, but considering iron’s functional roles and some of the current literature, the assumption that insufficient iron stores may lead to feelings of lethargy and decrements in athletic performance may not be too farfetched (Goodman et al. 2011, Lukaski 2004) – a personal experience I’m willing to attest.

So, is there really a conclusion to this post?

Well, one thing’s for certain: gluten won’t make your dick fly off (South Park clip here).

Will it harm your athletic performance? That remains an ambiguous topic however, there exists reason for concern in adopting a GFD with the potential for deleterious effects on immunity and physiological function. Perceived performance benefits associated with the adherence of a GFD among nonceliac athletic populations may be the result of a placebo-like effect, however, to maintain long-term success it would be advisable that such athletes sustain concerns regarding the consumption of adequate energy, macronutrients and micronutrients due to the diet’s restrictive nature.