In recent days, amid the single-topic focus on COVID-19 (SARS–CoV-2) transmission, various “professionals” and people outside health sciences or nutrition have recommended an enormous number of supplements or nutritional guidelines claimed to prevent infection. Many make categorical statements such as “these substances will greatly improve the immune system”. But how much truth is there in this?
This article will not explicitly address every supplement or debate whether it can prevent infection, because there are not enough conclusive data to make such claims and doing so would amount to speculation. If a supplement in a given context helps “improve”—or more accurately, maintain—optimal immune function, that does not mean it will prevent infection by this new coronavirus. Likewise, helping alleviate acute stress or mitigate a deficiency does not mean the changes are clinically relevant over the long term. To preview this section's conclusion: the goal should be to educate athletes and give them the knowledge and agency to develop effective protocols, with tools that make food a firm foundation of their sporting careers. Even so, we will provide useful information on immune function in sport and elite athletes.
We know that an athlete who is ill or unwell is an athlete who does not compete or cannot train at their highest level or capacity.
Several studies show that international athletes with the lowest prevalence and shortest duration of infections are precisely those who win the most medals and achieve the best performance over the sporting season, because they can sustain greater training volume and intensity and obtain the desired exercise adaptations.
In three-year observational studies involving 322 Olympic athletes, approximately 70% of illnesses recorded by medical staff resulted in “time loss”—complete absence from training and competition—while the remaining illnesses resulted in “performance restriction”.
Other useful data show that infections account for approximately 1/3 of training time lost, with upper respiratory infections—URIs—among the most prevalent.
All of this is related to multiple variables, including excessive training load. Risk rises with load, particularly when other confounding factors coexist: poor or insufficient rest, a poor diet, and undernutrition, which in most cases involves chronic low energy availability caused by insufficient macronutrient and micronutrient intake. These nutrients are essential for the reactions, synthesis and proper functioning of the immune system and its cells.
Other factors include long-distance travel, environments and climates different from the training setting, time-zone changes, stress, anxiety, competition nerves, and inadequate hygiene.
Factors That Reduce or Impair Immune Function in Athletes (Neil P. Walsh 2018)
These processes do not occur acutely, but develop over time and through multiple factors. Sufficient post-exercise recovery is therefore important to prevent “overtraining syndrome”, which can be incompatible with appropriate immune function by adding yet another stressor to the body.
Adaptation / Performance Index Resulting From Appropriate / Inappropriate Recovery ( Nieman and Hazell 2017)
S-shaped curve in elite athletes and J-shaped curve in recreational or sub-elite athletes relating training load to illness (Schwellnus et al., 2016).
Understanding our defense barrier or protective system is essential. One important concept is the immune system's ability to eliminate viruses, bacteria and other pathogens, known as resistance. This depends intrinsically on an adequate supply of energy from its main fuel sources: glucose, amino acids and fatty acids.
Resistance to a pathogen is not the only important factor. Immunologists also describe the interesting concept of “tolerance”, the process that defines the degree of immune response to a pathogen. Using the metaphor of a castle, its inhabitants perform many daily tasks, including repairing the walls, working and distributing food. At the same time, they must decide whether a battle is worth fighting and which weapons are appropriate. The immune-system equivalent is to “choose battles wisely”. Effective tolerance requires an immune response proportional to the existing risk. An excessive response can cause unnecessary tissue damage and divert excessive energy resources from vital functions, while a weak response increases susceptibility to pathogen damage.
Homeostasis is achieved through an appropriate balance between resistance and tolerance. This allows us to fight infections when signals indicate that it is strictly necessary while maintaining a healthy relationship with mutualistic bacteria in the gut.
This model helps explain why some nutritional supplements have tolerogenic effects and could reduce infection burden in healthy athletes—for example, reducing severity and duration. It is no longer enough to ask whether a nutritional intervention will prevent illness. A more relevant question may be: will it reduce how long, and to what degree, the athlete becomes ill?
Relationship Between Resistance and Tolerance
The immunomodulatory role of nutrition and exercise is therefore extremely important in these processes. They directly influence cell proliferation and DNA and RNA synthesis and provide amino acids for producing proteins such as immunoglobulins, cytokines and plasma proteins.
Severe nutritional restriction—marasmus—and protein-calorie malnutrition—kwashiorkor—are also known to affect immunity and infection-related mortality in developing countries (Woodward, 1998).
Severe energy restriction may also affect immunity through the hypothalamic-pituitary-adrenal axis and increased stress hormones. Micronutrients play an important role in synthesizing nucleotides and nucleic acids—including iron, zinc and magnesium—and in antioxidants that limit tissue damage, such as vitamins C and E. This is probably particularly important during intense exertion or infection, when oxidative stress increases. Antioxidant supplementation remains controversial: as a general rule, its use is strongly discouraged when training adaptation is the objective, although illness, injury and/or competition may represent different contexts.
Some micronutrients may directly influence immune-cell function by regulating gene expression—vitamin D—reducing the risk of fractures and osteoporosis through calcium and bone metabolism, and lowering upper respiratory infection risk through a powerful anti-inflammatory effect. They may also improve innate immunity by inducing antimicrobial proteins and exert tolerogenic effects that prevent excessively strong immune responses after T-cell activation.
Supplementing with this vitamin may be useful when deficiency exists, commonly at high latitudes, in people with overweight or obesity, in people with dark skin, during winter, or when annual sun exposure is insufficient.
Other potentially useful substances include prebiotics and probiotics, which may influence immunity indirectly by modifying the gut microbiota, although much more research is needed.
One food that has received little attention in discussions of immune function is whey protein, because it contains many peptides with different bioactive properties.
- Two of its main proteins, α-lactalbumin and β-lactoglobulin, may improve innate immunity through neutrophil function.
- A glycine-leucine-phenylalanine tripeptide derived from α-lactalbumin may improve macrophage function.
- Its amino acids include glutamine, which also has some evidence for reducing post-race respiratory problems in marathon runners, although the study methodology was not ideal. Whey protein is nevertheless a food rich in this amino acid.
- Many proposed effects of whey protein in cancer relate to its high cysteine content and the resulting synthesis of glutathione, a powerful endogenous antioxidant, as well as the action of lactoferrin. In vitro studies report tumor-cell death and protective mechanisms in melanoma, breast cancer, stomach cancer, lymphoma, and different colorectal cancer cells and polyps.
This new perspective requires much more research to demonstrate whether candidate tolerogenic nutritional supplements reduce infection burden in athletes without attenuating training adaptations or causing side effects. When considering supplementation, athletes should verify that a product comes from a reliable source and has been tested under an established quality-assurance program, rather than following trends or inconclusive evidence. Many supplements work mechanistically but have limited practical applicability; when they are not prescribed or recommended by health professionals or dietitians-nutritionists, they may ultimately cause more harm than benefit. Nutrition is only one piece of the puzzle: rest, appropriate sun exposure, not smoking, limiting alcohol, managing stress, performing physical activity and high-intensity exercise, and maintaining optimal body composition all matter.
25% DISCOUNT AND FREE SHIPPING ON ALL PRODUCTS WITH CODE:
entrenoXcasa
Related Product:
Iso Whey Hydrolyzed
Pure hydrolyzed Optipep 90 whey isolate
Author:
Marcos Rueda Córdoba
Dietitian-nutritionist at Myosport Clinic and The Strength Society
Instagram: @marcosnutrition
Bibliography
- Williams NC, Killer SC, Svendsen IS, Jones AW. Immune nutrition and exercise: Narrative review and practical recommendations. Eur J Sport Sci [Internet]. 2019;19(1):49–61. Available from: https://doi.org/10.1080/17461391.2018.1490458;
- Sale C, Elliott-Sale KJ. Nutrition and Athlete Bone Health. Sport Med. 2019;49(198):139–51.
- Simpson RJ, Campbell JP, Gleeson M, Krüger K, Nieman DC, Pyne DB, et al. Can exercise affect immune function to increase susceptibility to infection? Exerc Immunol Rev. 2020;26(March):8–22.
- Nieman DC, Mitmesser SH. Potential impact of nutrition on immune system recovery from heavy exertion: A metabolomics perspective. Nutrients. 2017;9(5).
- Cadegiani FA, Kater CE. Novel insights of overtraining syndrome discovered from the EROS study. BMJ Open Sport Exerc Med. 2019;5(1):1–11.
- Palmowski J, Boßlau TK, Ryl L, Krüger K, Reichel T. Managing immune health in sports – A practical guide for athletes and coaches. Dtsch Z Sportmed. 2019;70(10):219–26.
- Schwellnus M, Soligard T, Alonso JM, Bahr R, Clarsen B, Dijkstra HP, et al. How much is too much? (Part 2) International Olympic Committee consensus statement on load in sport and risk of illness. Br J Sports Med. 2016;50(17):1043–52.
- Soligard T, Schwellnus M, Alonso JM, Bahr R, Clarsen B, Dijkstra HP, et al. How much is too much? (Part 1) International Olympic Committee consensus statement on load in sport and risk of injury. Br J Sports Med. 2016;50(17):1030–41.
https://examine.com/supplements/whey-protein/
