And what that taught me about immune resilience
Last week, I was flat on my back.
Not “a bit under the weather, pushing through” flat. Properly horizontal. Bed rest, no work, the whole thing. And honestly? My first reaction wasn’t to reach for my clinical toolkit. It was something closer to disbelief — followed quickly by a very human dose of frustration. I’m a functional medicine practitioner. I eat well. I sleep. I manage my stress. I take my supplements. And yet, there I was, completely knocked over by a winter virus.
So what happened? And more importantly — what does this mean for you?
Your immune system isn’t failing. It’s doing its job.
Here’s what I had to remind myself from my bed: getting sick is not the same as having a broken immune system. In fact, for most people, an acute immune response — the fever, the fatigue, the aching, the craving to do absolutely nothing — is evidence that your immune system is mounting exactly the kind of response it’s designed to mount. The fever is intentional. It raises your core body temperature to create an environment that’s hostile to replicating viruses. The fatigue is intentional too. It’s your body redirecting every available resource — energy, nutrients, blood flow — toward the immune response and away from everything else. This is called sickness behaviour, and it’s a highly coordinated neurological and immunological process, not a malfunction. The malfunction would be if nothing happened at all.
So why do we keep getting sick in winter?
Several things converge this time of year, and understanding them helps.
First, there’s vitamin D. Most of us in Australia — yes, even in the sunshine — see our vitamin D levels drop across winter, particularly if we’re working indoors. Vitamin D isn’t just a bone nutrient. It’s a potent immune modulator that regulates the activity of T cells and natural killer cells, two of your primary viral defence forces. Low vitamin D means a less coordinated immune response.
Second, there’s light exposure. Reduced daylight in winter shifts our circadian rhythm, which directly affects cortisol production. Cortisol — your primary stress hormone — plays a surprising role in immune regulation. When the rhythm is off, immune signalling becomes less precise. We’re also spending more time indoors in close contact with other people, which simply increases viral exposure.
Third, and this one surprises people: cold air itself affects the mucosal lining of the respiratory tract. The cilia — tiny hair-like structures that physically sweep pathogens out of your airways — function less efficiently in cold, dry air. Your first line of defence is literally compromised before any virus has even reached your immune system.
What I actually did
I didn’t heroically dose myself with every immune supplement in my dispensary.Here’s what I actually did: I rested. Properly, without guilt. Sleep is when the immune system consolidates its response — cytokine production, T cell activation, and immune memory formation all peak during deep sleep. Fighting that with activity is counterproductive. I kept fluids up and dropped food intake right back. When your body is mounting an immune response, digestion takes a back seat. This isn’t the time for three meals a day. Broths, warm water with lemon, herbal teas — light, nourishing, easy to process. I supported rather than pushed. A small amount of zinc, vitamin C, and some additional vitamin D. Nothing aggressive. The goal was to give the immune system the micronutrient building blocks it needed, not to overwhelm a system already under load. And then I waited. Because sometimes, that’s the most evidence-based thing you can do.
What this doesn’t mean
Getting sick once in winter doesn’t mean your protocols aren’t working. It means you encountered a viral load your system needed to process. The more relevant question — one I’ll be exploring with my own data over the coming weeks — is how quickly you recover, how severe the illness is, and whether it leaves any lasting footprint. Chronic, recurrent infections, or illness that lingers for weeks and leaves you depleted long after the acute phase, are a different conversation entirely. That’s when we start looking at immune tolerance, gut-immune axis function, HPA axis dysregulation, and micronutrient insufficiencies that have accumulated over time. One winter virus, managed well? That’s just being human.
The takeaway
Even practitioners who understand this material deeply get sick. The difference — I hope — is that I didn’t panic, I didn’t push through, and I didn’t treat my immune system like an enemy that had let me down. I gave it what it needed and got out of the way.
If you’re finding yourself getting sick repeatedly this winter, or if you’re recovering slowly and never quite feeling back to yourself, that’s worth looking at more closely. Sometimes the body is asking for more than rest. If that sounds like you, I offer a 20-minute Discovery Call as a starting point — a chance to talk through what’s going on and whether a more thorough approach might help. You can book directly through my website at www.drshelleycavezza.com.au. In the meantime — if you’re sick right now? Rest. You have my permission.
— Shelley
📍 Sunshine Coast | 🌐 drshelleycavezza.com.au 📞 0419 821 666 | ✉️ info@drshelleycavezza.com.au
This post is for educational purposes only and is not a substitute for personalised medical advice. Please consult your healthcare professional before making significant changes to your health routine.
