Why we catch seasonal colds, and how science can support us

When the temperature drops, many of us brace for the familiar sniffles and sore throat. But catching a cold isn’t just about cold weather or unlucky timing. Essentially, it’s how our body responds to stress and pathogens combined. And it is a conversation about our body’s interact with lifestyle, environment, and even the food we eat. Understanding these “hidden” factors can help us prevent illness and strengthen immunity naturally.

Have you ever wondered why we tend to catch more colds during seasonal transitions? It’s tempting to blame viruses, but viruses are everywhere, all year round. So why do they seem to strike more often in autumn or early spring?

The truth is, it’s not just about exposure to viruses; it’s about how our body’s resilience changes in response to multiple stressors happening at once.

Think about it: shorter days, less sunlight, more rain, colder temperatures. We sleep less, move less, and spend more time indoors breathing dry, heated air that dehydrates our nasal passages — one of our first lines of defense against pathogens. Meanwhile, outdoor humidity rises, creating conditions where many viruses thrive.

Each of these factors on its own might be of little harm. But together, they create a perfect storm — a subtle yet powerful stress load on the body. Our immune system, already working to adapt to changing light, temperature, and mood patterns, becomes overloaded, and even weakened.

In other words, seasonal colds are often the result of accumulated stress — biological, environmental, and lifestyle-related — rather than just bad luck or a single sneeze in your direction.

Let’s take a closer look at what’s really going on beneath the surface.

Sleep: the unsung hero of immunity

We ofter sacrifice it to something else: extra work, time with family and friends, going out, favourite series, or catching up with those ten thousand daily steps, for that matter.

However, sleep isn’t optional for your immune system — it’s essential. During deep sleep, your body produces infection-fighting proteins and antibodies. It also runs lots of other important processes, where your body detoxes and regenerates, including your immune system.

Chronic sleep deprivation reduces the activity of natural killer cells, making it easier for viruses to take hold.

The basic rule here is: aim for 7–9 hours per night and maintain a consistent schedule. Going to bed around 10-10.30pm (together with eating a proper dinner 3-4 hours before going to bed) ensures that your body produces somatotropin (the growth hormone that, among other functions, supports your cell clearance and regeneration) and delivers consistent REM sleep waves.

Stress: the silent saboteur

When stressed, your body produces cortisol, a hormone that suppresses immune function. Chronic stress leads to chronic low-grade inflammation, which diverts immune resources away from fighting infections.

Now, it’s important to understand that stress includes not only unpleasant conversations at work, but also lack of sleep, bad food, dehydration, minor shock events like oversleeping in the morning while being late for a meeting, alcohol and many similar things. Anxiety and overthinking are also types of stress.

Mindfulness, meditation, breathing exercises, and even short walks can help regulate stress hormones and support immunity.

Gut health: where immunity lives

About 70% of your immune system resides in the intestines. A diet high in processed foods and refined sugars can disrupt the gut microbiome, weakening immune signaling. Alcohol also disrupts gut integrity and alters microbial balance, as well as medication, poor eating, and, again, stress.

When people talk about “gut health,” they often think of probiotics or fiber. But the strength of your gut barrier — the microscopic layer of cells that decides what enters your bloodstream and what doesn’t — depends heavily on specific micronutrients. These nutrients support the tight junctions between intestinal cells, which act like the zipper that keeps your intestinal wall sealed. When these junctions loosen, the result is what’s commonly called leaky gut, a condition that can trigger inflammation and weaken immunity.

Zinc is one of the most important of these nutrients. It helps build and repair the proteins that form tight junctions, and its deficiency is directly linked to increased intestinal permeability. Foods rich in zinc include oysters, pumpkin seeds, lentils, and beef.

Vitamin D also plays a major role: receptors for it are found throughout the gut lining, and optimal levels help regulate immune balance while keeping the epithelial barrier intact. Low vitamin D status — common in colder, darker months — is associated with higher inflammation and weaker gut protection.

Vitamin A, meanwhile, helps maintain the mucous layer that coats the intestinal wall, acting as the gut’s first line of defense. It keeps epithelial cells healthy and supports their renewal. Carrots (especially cooked - cooking increases bioavailability of beta-carotene, the vitamin A precursor that is then converted by our body into vitamin A), sweet potatoes, eggs, and liver are excellent sources.

In addition to these, L-glutamine (an amino acid) is the preferred fuel for gut cells. It supports their growth, regeneration, and the production of tight-junction proteins. Even modest supplementation has been shown to help restore barrier integrity in people with gut irritation or chronic stress.

Other supportive nutrients include magnesium and selenium, which help neutralize oxidative stress that can damage the gut wall, and anti-inflammatory compounds like Omega-3 fatty acids and polyphenols from foods such as fatty fish, olive oil, berries, and green tea.

Together, these nutrients act like the maintenance crew for your intestinal wall — keeping it sealed, resilient, and capable of performing one of the most important immune functions in your body: deciding what gets in, and what stays out.

Environment: air, crowds, and temperature

Dry indoor air dehydrates mucous membranes, weakening the first barrier against pathogens. Crowded indoor spaces increase viral exposure. Cold air itself doesn’t cause colds, but it can stress the respiratory tract and allow viruses to spread more easily.

The best solution here (if you don’t live near a river, like me - in that case, good luck fighting with mosquitoes ;) ) is to use humidifiers in dry rooms, ventilate indoor spaces, and dress appropriately for cold weather.

Exercise: the Goldilocks zone

Moderate exercise boosts immune function, but excessive training without recovery can temporarily suppress immunity. In fact, we suppress immunity every time we exercise , but, done moderately, exercising also trains our immune system, our body adapts, whereas, when done excessively, it acts like a shock, a stressor.

The best advisor here will be your own body and your ability to hear its signals. A healthy exercising is whatever your body needs as long as you aren’t exhausted after and rather enjoy the feeling (which means, your body releases dopamine, it’s happy).

Lifestyle integration

Your immune system thrives when multiple factors align: sufficient sleep, stress management, balanced nutrition, moderate exercise, micronutrient adequacy, and mindful exposure to environmental factors. Small, consistent adjustments often have a bigger impact than drastic short-term interventions.

Start with one habit change per week — for example, adding an extra hour of sleep, a stress-reducing practice, or a fiber-rich food — and build from there.

Catching seasonal colds is rarely about a single cause. By understanding the hidden factors that influence immunity, we can take proactive steps to stay healthy — not just during cold season, but year-round.