If you’ve ever trained hard for a race or pushed yourself through a brutal workout cycle, you’ve likely experienced that frustrating post-training slump—low energy, poor recovery, and worst of all, an annoying cold or sore throat just when you need to be at your best. Could an amino acid be the missing link? Science says yes.



Why Should You Care About Upper Respiratory Tract Infections (URTIs)?

• URTIs (colds, sore throats, sinus infections) can tank your training consistency and performance.

• Endurance athletes are at higher risk due to prolonged, intense exercise that temporarily suppresses immune function.

• Women, especially those with high training loads and lower caloric intake, may be even more vulnerable due to hormonal fluctuations impacting immune resilience.




Meet Glutamine: More Than Just a Protein Building Block

Glutamine is an amino acid that your body uses for a range of vital functions, particularly in muscle recovery, immune defense, and gut health. It’s also crucial for lung function—hello, better breathing during those tough intervals!

  • Muscle matters: About 80% of your body’s glutamine is stored in skeletal muscle.
  • Immune support: Glutamine acts as fuel for immune cells, helping them function optimally.
  • Gut defense: It strengthens gut barrier integrity, reducing the risk of immune dysfunction caused by increased gut permeability during intense training.




The Link Between Training, Glutamine & URTIs

Strenuous exercise temporarily depletes glutamine levels due to increased uptake by the liver and immune cells. This depletion is associated with immunodepression, increasing your vulnerability to infections.

  • Athletes with prolonged or high-intensity training see transient drops in plasma glutamine, correlating with increased susceptibility to URTIs.
  • Research suggests glutamine supplementation reduces lung inflammation, an essential factor in preventing respiratory infections.
  • Studies on elderly individuals (both sedentary and active) show glutamine improves immune response in the upper airways—suggesting benefits across different populations.




What About Female Athletes?

Women experience fluctuating immune function due to hormonal shifts throughout the menstrual cycle.

  • Follicular phase: Higher estrogen levels may enhance immune function against bacteria and viruses, potentially reducing the risk of an upper respiratory tract infection
  • Luteal phase: Increased progesterone may shift the immune response into a more pro-inflammatory state, aggravating asthma and increasing the need for recovery—especially when paired with high training loads. 
  • Low energy availability (LEA): Women with inadequate caloric intake may experience reduced glutamine synthesis, further weakening immune defenses.




Should You Supplement With L-Glutamine?

While not all research agrees on whether glutamine levels always drop in overtrained athletes, there’s enough evidence to suggest supplementation could be beneficial, particularly if you:

  •  Train intensely and experience frequent URTIs.
  •  Struggle with recovery or have gut issues.
  •  Engage in endurance sports where prolonged stress taxes immune function.



Glutamine is found in some sports supplements, but you can also increase intake through dietary sources like beef, eggs, dairy, and plant-based options like tofu and legumes. However, if you’re training hard, a supplement may provide an extra edge.




Bottom Line

If you’re an active adult pushing your limits, staying healthy is just as crucial as hitting PRs. Protecting yourself from URTIs with strategies like adequate nutrition, recovery, and possibly glutamine supplementation can keep you strong, consistent, and performing at your best. Because let’s face it—nothing ruins a great training block like a week in bed with a sore throat!


Talk to your healthcare provider such as your naturopathic doctor to know exactly the dose for you and the safety with other supplements or pharmaceuticals you may be taking.




References

https://pubmed.ncbi.nlm.nih.gov/30360490/

https://pmc.ncbi.nlm.nih.gov/articles/PMC5454963/

https://pubmed.ncbi.nlm.nih.gov/38193521/

https://pubmed.ncbi.nlm.nih.gov/11056250/

https://pubmed.ncbi.nlm.nih.gov/11056250/

https://journals.lww.com/co-clinicalnutrition/abstract/2010/01000/effect_of_physical_activity_on_glutamine.12.aspx

https://pubmed.ncbi.nlm.nih.gov/19841583/#:~:text=Recent%20findings%3A%20Strenuous%20physical%20exercise,depletion%20is%20associated%20with%20immunodepression