Moderate, consistent exercise plays an important role in overall wellness; however, excessive training can potentially increase athletes’ vulnerability to feeling unwell. To support a well-planned training schedule, there are key nutrients that should be considered as part of an athlete’s diet. Keep reading to learn which amino acids, protein’s building blocks, play a role in immune health and how they can help athletes continue to push the limits.
Vital note: This article has been made available for informational and educational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice, or delay in seeking it, because of something you have read in this article. Your licensed healthcare professional can best provide you with the diagnosis and treatment of any medical condition and assist you as well in deciding whether a dietary supplement will be a helpful addition to your regimen.
What is the Immune System?
The immune system identifies pathogens like viruses, bacteria, parasites or any other microorganism that can contribute to symptoms of illness, infection or disease. Once identified, the immune system then responds by releasing specific cells to ‘kill’ or ‘destroy’ the threat:
- T helper cells
- Killer T cells
- Natural Killer cells
- Mast cell
- Dendritic cells
Although the immune system works as one fully-integrated system, it can be divided into two distinct arms.
- The innate immune system is what you are born with and refers to your natural immunity.
- It acts as your body’s first line of defense, responds in a non-specific way and typically generates a rapid response.
- Primary cell types of the innate immune system include macrophages, neutrophils and natural killer cells to name a few.
- The adaptive immune system, on the other hand, is known as acquired immunity and can’t respond rapidly instantly to infections. It actually needs time to ‘adapt’ to recognize them.
- The adaptive system learns from these experiences and creates ‘memory cells’ to be able to generate a response that is rapid, accurate, and effective should the pathogen try to invade the body again.
As long as our immune system is functioning and operating optimally, it performs the following tasks:
- Protects us against foreign invaders (viruses, bacteria, fungi and parasites) in order to preserve integrity of the body
- Recruitment of cells for removal of foreign substances
- Wound healing and repair of damaged cells
- Production of antibodies to bind antigens and facilitate removal from the body
The immune system works to protect your body from invading pathogens. The innate immune system is your natural immunity and rapidly responds in a non-specific way. The adaptive immune system is your acquired immunity and learns to identify pathogens over time.
How Does Exercise Affect the Immune System?
Well, it depends on the LEVEL of exercise. Research shows that physical activity level (low, moderate or high) can each have a different impact on the immune system. Although moderate levels of exercise has been shown to reduce susceptibility to illness compared to a sedentary lifestyle, long hard bouts of exercise and periods of intensified training may put athletes at increased risk of upper respiratory tract infections (URTI), including colds and the flu.
Studies have shown that chronic training paired with life stress has an influence on immune function through the activation of the hypothalamic-pituitary-adrenal (HPA) axis, which in turn impacts immunoregulatory hormones. Various measures of immune function such as natural killer cell activity, upper airway neutrophil function, and T- and B-cell function have been shown to be suppressed for at least several hours during recovery from prolonged, intense exercise. This suppression of both the innate and adaptive immune system function provides an ‘open window’ for opportunistic pathogens.
While the exact cause isn’t completely clear, researchers agree that those who are exercising intensely may be overtaxing their inflammatory and immune response, leading to increased susceptibility to upper respiratory tract infections (URTIs). Athletes face unique challenges like extended travel schedules, life stress, environmental extremes, nutritional deficits and intense training that challenge their immune systems. Fortunately, there are numerous evidence-based recommendations that athletes can implement to support immune function.
Amino Acids That Can Support an Athlete's Immune System
Immunonutrition, or “the potential to modulate the activity of the immune system by interventions with specific nutrients” is a concept that’s becoming more mainstream, especially among athletes. While immunonutrients can behave differently, they typically support the immune system by:
- Optimizing the inflammatory response by managing oxidative stress, and/or
- Optimizing the immune system response by reducing immunosuppression
The literature on immunonutrition for athletes is growing, and for good reason. Currently, there is no general consensus for a specific protocol, which is encouraging researchers to investigate more. A growing number of articles have examined how amino acids, protein’s building blocks, can help regulate key metabolic pathways in immune cells, and optimize the cellular oxidative stress response.
While there are 20 amino acids in the human body, glutamine, arginine and Branched-Chain Amino Acids (BCAAs) have received much of the attention. For decades, researchers have been studying the impact of these amino acids, and evaluating their role in immune system support.
Glutamine is an abundant amino acid that plays an important role in the function and homeostasis of the immune system.
How it works
Glutamine supports the immune system in a variety of different ways, including:
- As a major source of glutamate, glutamine regulates the synthesis of glutathione, which is crucial for defending cells from oxidative stress
- Glutamine is required for proliferation of lymphocytes
- Glutamine is required for nitric oxide (NO) synthesis in macrophages and monocytes
The significance of glutamine supplementation has been well-supported in the literature, especially for athletes. Evidence has suggested that glutamine supplementation (0.1g/kg body wt) can have a beneficial effect by minimizing the decrease in plasma L-glutamine, lymphocytes and the risk of URTIs.
Arginine is a “conditionally essential” amino acid that has been researched for its role in immune protection.
How it works
- Being a precursor of NO, which plays an important role in many functions in the body regulating vasodilatation, blood flow, and immune system activation
- Boosting the activity of a particular type of immune cells, called T cells
Thirty-nine male jiu-jitsu practitioners engaged in an acute bout of high-intensity exercise using placebo or L-arginine (100 mg · kg-1 of body mass · day-1). Those who consumed the arginine supplementation experienced a reduction in lymphocytes and ammonia when compared to the placebo group, potentially suggesting the intervention may have contributed to a modulated inflammatory and immune system response.
BCAAs include three amino acids, valine, leucine and isoleucine, and are typically associated with muscle protein synthesis and repair. However, some evidence suggests these three amino acids may play a role in the immune system as well. Although the literature is inconclusive at this point, athletes are curious about the potential additional benefits of BCAAs.
How they work
It’s believed that BCAAs can promote the immune system in many different ways, but primarily by:
- Modulating inflammation through the L-glutamine pathway
- Attenuating a higher inflammatory responses by helping to increase the expression of genes involved in the antioxidant defense
Researchers evaluated the impact of BCAA supplementation on endurance runners. While one group received a placebo, the other acutely and chronically received 6g/day of BCAAs. Upon the end of the study, investigators found the intervention group had better maintained their plasma glutamine concentration and supported their immune compared to the control.
Collagen & the Immune System
Currently, there is not a significant amount of research investigating the direct relationship between collagen, a source of amino acids, and the immune system. However, when you dive deeper into the literature, there are promising findings that may prompt more.
First of all, many of the amino acids found in collagen have been shown to play a role in the immune system. Collagen, along with being a source of glutamic acid*, arginine and BCAAs, also contains high concentrations of glycine, which has been shown to help regulate the inflammatory process and support the immune system.
Glycine has long been considered an amino acid that exhibits anti-inflammatory properties, and growing evidence has mounted in favor of its immunomodulatory and cytoprotective effects as well. It’s been suggested that glycine helps boost the functionality of macrophages, which in turn, suppress the formation of free radicals and inflammatory cytokines.
A study involving 74 subjects with Type II diabetes mellitus found that those who received glycine supplementation as an intervention experienced a decrease in proinflammatory cytokines and an increase in interferon-γ, a cytokine that is critical for innate and adaptive immunity against viral and some bacterial infections.
Secondly, some interesting research suggests that collagen protein itself may play a role in fighting infection. In a recent study, investigators sought to evaluate if collagen impacts the immune system by activating NK cells and macrophages in the lymphatic system. Their findings:
- Support the notion that the subcapsular sinus represents an important site for the initiation of immune response
- Provide evidence that macrophages in this region can promote NK cell activity, and
- Suggest collagen may help position activated NK cells close to relevant target cells, which can help productive delivery of cytokines and other effector responses
*Glutamic acid is found in food sources, and in the presence of ammonia, converts to glutamine in the body.