When cold, darkness, and cold season arrive outside, our body faces special demands. But what does it actually mean to be winter-proof, and what role does our gut play?
Winter doesn't have a particularly good reputation health-wise. As soon as days get shorter and temperatures drop, the season of colds, flu-like infections, and other respiratory illnesses begins. At the same time, we spend more time indoors, move less, and get significantly less daylight.
Especially during the cold season, our immune system comes into sharper focus. This is about far more than individual vitamins or supposed "immune boosters". Our immune system functions through a highly complex interplay of different organs, tissues, cells, nutrients, and messenger substances—and our gut plays a crucial role. Let's take a closer look at everyday habits that can support this interplay.
Our immune system doesn't function like a battery that we can charge to 100 percent with the right product. It has to recognize pathogens, react appropriately, and then downregulate the immune response again. What we eat, how we sleep, how much we move, and how we structure our daily life can all influence these processes.
Our Immune System Is Constantly Active
Our body is in permanent contact with its environment. Countless microorganisms and foreign substances enter through our skin, respiratory tract, and digestive tract daily. Therefore, immune defense doesn't start only when we notice the first symptoms of a cold.
Skin and mucous membranes form important physical and biological barriers. In the respiratory tract, mucus and the movement of cilia help transport inhaled particles back out. If pathogens do come into contact, various mechanisms of innate and adaptive immunity work together.
By the way, it's not about making the immune system as "strong" as possible. A good immune system must primarily react appropriately and regulate well. It should recognize and fight a pathogen without maintaining unnecessary or permanent inflammatory processes.
Therefore, immune function cannot be reduced to a single nutrient or vitamin. It arises from the interplay of many systems. And one of them sits right in our gut.
The Gut: An Important Partner of the Immune System
When we talk about our defenses, many people think of vitamin C or zinc first. The gut is far less often in the spotlight.
Yet large parts of the lymphatic tissue, which forms the main component of the immune system, are located in the gut area. At the same time, our digestive tract harbors a complex ecosystem of bacteria, fungi, and other microorganisms: our gut microbiome.
This microbiome is by no means only relevant for digestion. Its microorganisms are in constant communication with cells of our immune system and influence, among other things, the development and activity of various immune cells, the gut barrier, and inflammation-regulating processes.
The connection goes beyond the gut: the immune system and the respiratory tract are also in close exchange with the gut microbiome.
The Gut-Lung Axis
Gut and lungs are connected via various immunological and metabolic pathways. Microorganisms in the gut produce metabolic products like short-chain fatty acids, which can act outside the gut via the bloodstream.
This so-called gut-lung axis is the subject of intense research. Scientific studies describe various mechanisms through which the gut microbiome can influence the immune response in the respiratory tract. Conversely, respiratory infections and shifts in the immune system can also impact the gut microbiome.
This makes the gut particularly interesting during cold season. And this is where nutrition comes in. A varied diet with vegetables, fruit, legumes, whole grains, nuts, and seeds delivers a variety of different fibers and other plant compounds that our gut microorganisms can use.
Do Probiotics Help the Immune System?
Here, too, a closer look pays off. Probiotics are live microorganisms that can offer health benefits when taken in adequate amounts. Synbiotics additionally combine probiotics with substrates that can be utilized by microorganisms.
Research on probiotics and respiratory infections offers interesting insights. A meta-analysis of randomized controlled trials with more than 9,000 adults found potential small benefits regarding the frequency, duration, and severity of respiratory infections. At the same time, the studies varied widely, and the authors pointed out limitations in evidence.
This is an important point: not all probiotics are the same. Effects and study results can depend on the specific microorganisms used, combinations, dosages, and target groups.
Those who want to support their gut in addition to diet can consider a scientifically developed synbiotic like BioME+ as a supplement. It combines probiotic bacteria with prebiotic components. Not as a replacement for a varied diet, and certainly not as a guarantee against the next cold, but as one possible building block in a system much larger than any single product.
Movement Keeps Our Immunity Active
We initially associate movement with muscles, cardiovascular health, and metabolism. But the immune system also responds to physical activity.
During and after moderate exercise, the number and distribution of various immune cells in the blood change. Regular physical activity is associated with better immune regulation and a lower risk for various respiratory infections.
However, "harder training equals stronger defense" does not apply. Very high training loads combined with insufficient sleep, energy intake, or recovery can place additional demands on the body. The relationship between exercise volume, recovery, and infection risk is complex. For winter months, movement should be regular, varied, and reasonably dosed.
Cycling, hiking, running, swimming, or targeted strength, mobility, and coordination training belong just as much as a brisk walk or a movement break between meetings.
The winter resilience of our immune system is supported and promoted by a variety of movement, both indoors and outdoors.
Sleep Gives the Immune System Time to Regulate
When we are sick, we feel clearly that our body needs rest. We become tired, withdraw, and often sleep more. However, the connection between sleep and the immune system also exists independently of acute illness.
During sleep, various immune processes shift. Sleep influences communication between immune cells and messenger substances and plays a role in regulating innate and adaptive immune responses. At the same time, immune reactions themselves can affect our sleep.
Therefore, it's not just about how many hours we sleep. The regularity of our sleep-wake rhythm also plays a role.
Chronically insufficient sleep is different from a single short night. Nevertheless, research shows that even short-term sleep deprivation can cause measurable changes in certain immune parameters. Winter might be a good time to view sleep as what it biologically is: not wasted time, but active regeneration.
Daylight Influences More Than Mood
Less daylight is one of the most obvious changes in winter. But light is not only relevant for our mood and alertness.
It is the primary timekeeper for our internal clock. Through special light-sensitive cells in the eye, the brain receives signals about day and night. This circadian rhythm coordinates numerous biological processes. Various immune functions also follow a circadian rhythm.
Research shows time-of-day changes in the activity and distribution of certain immune cells as well as inflammatory mediators.
This doesn't mean a walk in daylight instantly boosts your defenses, but regular light-dark signals help keep the internal clock stable. And a well-synchronized circadian rhythm is part of functioning physiological regulation. One more reason not to spend the whole day indoors during winter. A walk after lunch, for instance, benefits blood sugar while bringing movement and daylight into your day: two simple factors that help your body stay in rhythm.
Hydration: Not an Immune Booster, But a Foundation
Flids are rarely discussed in the context of immunity, which makes them worth a quick look.
Our body requires water for numerous physiological processes. Mucous membranes also depend on adequate hydration. Cold temperatures can cause mucous membranes to dry out faster, partially losing their protective barrier function and making us more susceptible to infections.
Individual needs depend on body size, diet, activity level, and ambient temperature. In winter, we often feel less thirsty and forget to drink.
Water, unsweetened tea, and water-rich foods like fruit, vegetables, or soups are simple ways to ensure adequate fluid intake. There's no need to make it more complicated.
Together Through Winter
Cold and early darkness make staying cozy at home tempting. And retreating has its place, especially when daily life is full. Over time, however, social isolation can become a burden.
Our immune system doesn't work isolated from the rest of the body. The nervous system, stress regulation, and immune function are closely interconnected. Chronic psychological stress can affect immune regulation, and social isolation and loneliness are linked in research to changes in immunological and inflammatory processes as well as various health risks.
This doesn't mean an evening with friends prevents the next cold. But it shows that health encompasses more than diet, exercise, and sleep. Sharing a meal, taking a walk, or having a phone or video call can be valuable resources during the dark season.
Winter Resilience Needs No Perfect Plan
Our immune system cannot be brought to peak performance with a single food, supplement, or morning routine. It functions through the interplay of various lifestyle factors.
We don't need to do everything perfectly in winter, but it's important to offer our body good baseline conditions during the cold season. A varied diet providing different fibers to the gut, regular movement, sufficient sleep, daylight, hydration, and time with loved ones all contribute.
Winter resilience happens right there: in the small, simple habits we maintain even on a cold, dark winter day.
Author:
Mag. Carmen CREPAZ, MSc.
Nutritionist and Functional Health Coach
Master's in Nutrition and Sports
www.carmencrepaz.com/blog
Co-Author:
Mag. DDr. Manfred LAMPRECHT
Privatdozent for Physiology
Chief Science & Product Officer, Braingood Swiss AG
www.braingood.com, www.greenbeat.at
