Fighting Colds and Flus in Athletes:
The Strategic Approach to Immune Defense
Part 1 of a series on immune system health for active people
When a scratchy throat appears, most athletes reach for vitamin C and push through training. This one-size-fits-all approach needs to be re-evaluated.
Your goal isn't always about boosting immune function—it's supporting a precise, targeted response that clears the virus efficiently. Over-stimulating an already-activated immune system triggers autoimmune flares, worsens allergies, and extends illness rather than shortening it.
Why Nasal Breathing Matters More Than You Think
This is your simplest immune defense tool. Nasal breathing during training directly supports upper airway immunity:
Increases nitric oxide production in your sinuses, which has direct antibacterial effects (1) Bonus you get more oxygen into your bloodstream.
Creates a chemical checkpoint that kills bacteria and viruses before they descend into deeper airways
Passive defense that costs nothing and works whether you're sick or trying not to get sick
If you're mouth-breathing during intense sessions, you've removed this defense entirely. The practice: Train nasal breathing during moderate-intensity work and easy sessions first. Start with 10-15 minutes per session and build from there.
Sounds easy? Trust me, it’s not. Personally, I’ve had to slow down my pace or start mouth breathing because I felt almost clausterphobic. But, I tried again my next session. Gradually I was able to build up some tolerance.
Protein and L-Glutamine: The Immune Cell Fuel
Your immune cells are protein-hungry. During viral infection, amino acid demand spikes hard, and inadequate protein intake actively impairs immune response.
L-glutamine specifically supports T cell proliferation—critical for clearing intracellular viruses. Research shows adequate protein and glutamine intake measurably improves immune response to infection (2).
Athlete Pro Tip – L-glutamine is needed by gut cells. Here’s why this is important to you.
Practical dosing during acute infection:
Maintain or increase protein intake: consider 1.6–2.2 g/kg body weight daily
Add L-glutamine if your baseline protein is low: studies suggest 5-10g per day during active infection only, not as preventive
For a 150-pound (68kg) athlete, that's roughly 110-150g protein daily during illness. Don’t feel hungry for protein? Even adding just a little more is helpful.
The Iron Mistake Athletes Make
This is where supplementation often backfires. Many of my active patients and athletes take iron supplements —yet viruses exploit iron for replication. Higher iron availability actually helps viral pathogens proliferate more efficiently within your cells and extends infection duration (3). Yikes!
What do to if you take iron supplements?
If fighting a cold or flu, pause iron supplementation immediately. Your body has adequate iron stores for this window. Resume supplementation only after you're fully recovered and symptom-free for 48 hours.
Training Rules That Actually Work
This is where athletes cause the most damage. Here's your framework:
Active infection (fever, body aches, respiratory symptoms): Stop structured training. Gentle movement only—no intense training while your immune system is maximized. Your body does not need the stress of training ON TOP of fighting an infection.
Post-acute phase (no fever, mild lingering symptoms): Easy aerobic work only. No intensity. Your immune system is still mobilized; hard efforts compromise recovery.
Before returning to intensity: Wait 48 hours after your last symptom. This isn't caution—it's the timeline your immune system actually needs to normalize.
Have a competition and Can’t wait? Then consider the increased cost of recovery if you push too soon. If you have a competition now, then plan for the additional recovery time. Remember that strenuous or prolonged exercise creates a 3-72 hour temporary immune suppression. (4)
Why Intense Training Suppresses Immunity
High-volume or high-intensity training itself temporarily suppresses immune function in the hours post-session. This is why overtraining while sick, or pushing back into hard training too early after illness, often triggers relapse or secondary infection.
The takeaway: The athlete who rests hard when sick and returns to training conservatively recovers faster and stronger than the athlete who tries to tough it out.
Next in this series: Your Menstrual Cycle and Immune Response: How Your Hormones Shape Your Infection-Fighting Power
References
Sophie Marion Schmidt. The role of iron in viral infections. Front. Biosci. (Landmark Ed) 2020, 25(5), 893-911. https://doi.org/10.2741/4839
Dr. Andrea Proulx, ND — helping female athletes crush fatigue, fix their hormones, and finally perform like the athlete they know they are. Read full bio