From elite athletes to the weekend warrior, having the right balance of the appropriate training intensity, rest and recovery, as well of the correct nutritional support, is key to maximising an individuals’ physical gains and optimising their performance potential. In terms of general health and wellbeing, it is vital to understand that the body is an integration of numerous interconnected systems, which work synergistically to enable the body to function properly. As all systems within the human body have an influence upon one another in some way, any major disruptions occurring within one of these systems can knock the body out of homeostasis. This may ultimately have a detrimental effect upon other organs and systems within the body and thus impede optimal functioning of the body as a whole.
With this in mind, from a physical performance perspective, it is important for an athlete to consider the many variables that can affect the way in which the systems of their body function. This would generally include conducting a full analysis of their nutrition, exercise programme, stress, sleep and other lifestyle factors and making the appropriate adjustments where necessary, in order to attain optimal physical performance. However, there can sometimes be a tendency for athletes to focus solely upon the physical training element as the key component to sporting success, with the need to focus on the appropriate nutrition, rest, recovery and stress management often overlooked. This increases susceptibility to overtraining, injury and ultimately the exact problem every athlete wants to avoid, a reduction in physical performance.
Intense exercise and the stress response
Factors that are often found to affect physical performance, including fatigue, gastrointestinal distress, food intolerance and mood disturbance are inherently linked and notably common amongst athletes, particularly at the elite level. The psychosocial and physical demands which go hand in hand with intense exercise are additional stressors. Anything that initiates a stress response activates the sympathetic-adrenomedullary and hypothalamus-pituitary-adrenal (HPA) axes. This means the release of stress and catabolic hormones, as well as inflammatory cytokines and microbial molecules, all of which can negatively influence gut health and can therefore affect performance (Clark and Mach, 2016).
Intense exercise and digestive function
Strenuous and exhaustive exercise stimulates the production of heat shock proteins that directly affect gut barrier integrity by opening up tight junctions, causing increased intestinal permeability (known as a “leaky gut”) and negatively impacting gut health (Ballantyne, 2017). The stress hormone cortisol has also been suggested to affect intestinal integrity, making the gut more permeable to potential toxins (Kelly et al, 2015). Stimulation of the HPA axis has been shown to reduce gut motility, with chronic stress also being associated with a decrease in mucus production in the gut and inhibition of gallbladder function (Chang et al 2014, Rodiño-Janeiro et al 2015, Earley et al 2003). Furthermore, adrenal steroid hormones including cortisol have been shown to impede digestion by reducing pancreatic enzyme secretion (Beaudoin et al, 1986) and research has indicated that high stress may even directly alter the gut microbiome (Knowles et al, 2008).
In order to prioritise blood flow to the heart and skeletal muscles during intense exercise, blood is diverted away from the gastrointestinal tract and other visceral organs (Brouns and Beckers, 1993). This lack of sufficient blood flow to the gut can further disrupt the intestinal barrier and also increases intestinal permeability (Lambert, 2008).
Intestinal permeability, IgG food intolerance and sport performance
Intestinal barrier dysfunction increases the risk of uncontrolled immunological reactions to food-derived antigens, as well as environmental toxins and microbial antigens, by enabling these particles that would normally remain within the gut, to penetrate the intestinal lumen and interact with the mucosal-associated immune system (Rodiño-Janeiro et al, 2015). This stimulates the production of IgG antibodies to those specific food antigens. If food-specific antibody levels continue to rise, it may eventually result in an IgG mediated food intolerance to that particular food with subsequent symptoms experienced as a result (Cai et al, 2014)
The results of a recent longitudinal study, showed that elimination diets based on IgG mediated food intolerance, led to a significant improvement in gastrointestinal discomfort symptoms and sport performance (Kostic-Vucicevic et al, 2017).
This is the first study of its kind to investigate the potential performance benefits to athletes, in identifying food intolerances through the measurement of food-specific IgG antibodies and then using this information to adjust their diets accordingly. While more studies are required, this study shows the potential benefit of using IgG food intolerance testing as an additional diagnostic tool to further enhance an individual’s physical performance, which for an athlete of course, is the ultimate goal.