How to strengthen your defenses in cold weather immune system gut health and essential foods

How to strengthen your defenses in cold weather immune system gut health and essential foods

Autumn, in addition to shorter days, brings greater exposure to seasonal viruses, which is why it's essential to regulate the immune system so it has the capacity to fight them; the role of the gut and diet is key.
It's not a magic formula or a single supplement, but rather a balance between several fundamental pillars. What we do daily builds our defenses. Autumn brings us the opportunity to recalibrate our habits and attune our bodies to the changing season . In this sense, understanding that health is a daily construction allows us to move from reaction to prevention. Strengthening our biological shield requires consistency and a holistic view of how we inhabit our bodies.

“The immune system is, without a doubt, the most intelligent and perfect system in the human body , a manifestation of the natural intelligence and intrinsic wisdom that guides every cell and every process of our biology,” says Luisa Andreoli, an engineer and neuroscience researcher.
“Within this framework, the immune system plays a vital and unique role: it is the guardian of homeostasis, the mediator that restores natural balance when it is lost . It functions in a perfectly coordinated manner, without adverse side effects, restoring the body's internal harmony. Unlike drugs, which often generate secondary imbalances, the immune system repairs, regulates, and communicates recovery from the root of the problem,” Andreoli explains.

“Immunity doesn’t begin when a symptom appears. It begins when we sleep, when we eat enough, when we regulate stress , when we move intelligently, and when we take care of our gut. The immune system doesn’t respond to a single pill. It responds to daily consistency ,” says nutritionist Fiorella Vitelli, creator of a method that integrates nutrition, emotions, and simple habits.

Defending yourself is not a passive process: “Producing antibodies, activating immune cells, repairing tissues… all of that consumes energy. When the body enters a chronic deficit due to very restrictive diets or skipping meals, the priority changes. The body prioritizes survival instead of optimizing its defenses,” she warns. In addition to energy, the body needs small but essential building blocks: micronutrients. It's not about supplementation, but about avoiding deficiencies in iron, zinc, vitamins A, C, and D, as well as a conscious intake of protein, since without amino acids there are no antibodies.
Beyond prioritizing a varied, plant-based diet, Vitelli emphasizes that the immune system is further strengthened by three other pillars: frequent exercise, quality rest, and stress management . “This is no small detail: when stress becomes chronic, it directly impacts our defenses, leaving us much more vulnerable to any external threat,” she stresses. Therefore, it's not about reinforcing our defenses only when something goes wrong, but about building them every day through simple, sustainable habits.

According to Dr. Florencia Giecco, “immunity isn't a barrier: it's a communication system. It's not a wall that protects you or doesn't protect you. It's an intelligent network that's constantly communicating with your body, your gut, your emotions, and your sleep.” The specialist in Ayurveda and phytomedicine explains that the immune system doesn't need to be overactive; it needs to be regulated: “The concept isn't to stimulate immunity, it's to modulate it: to regulate it, to balance it... so that it responds when it needs to and doesn't overreact when there's no real threat.”
Giecco suggests considering the immune system under two possible imbalance scenarios: “On the one hand, a lack of response, which translates into recurring conditions such as infections or viruses that seem to never go away. The other extreme is equally complex: a hyperactive system. In this scenario, allergies or chronic low-grade inflammation arise, since the system is overly alert.”

Reishi, a great regulator
To modulate the immune system, in addition to addressing it from a holistic perspective, Giecco recommends that her patients take reishi . The doctor bases her recommendation on studies published in journals indexed in PubMed, the world's leading medical database. “Reishi ( Ganoderma lucidum ) is a medicinal mushroom used in traditional Chinese medicine for over 2,000 years. It is known as the mushroom of immortality or lingzhi . What it does in our bodies has a technical name: immunomodulation. This means that it doesn't simply raise or lower defenses randomly, but rather regulates them. It is important to note that its use is scientifically supported from the age of two.”
In a context where there is an increasing focus on boosting the immune system naturally and preventively, homeopathy also offers a holistic approach that integrates body and mind, promoting stronger and more balanced immunity. “Homeopathy is valued for its comprehensive approach to strengthening the immune system. Based on stimulating the body's own defense mechanisms, it offers personalized treatments that support the patient in their physical and emotional well-being,” explains Laura Celso, a physician specializing in internal medicine and classical homeopathy.

Patients undergoing homeopathic treatments often report a lower frequency of seasonal illnesses . According to Celso, “among the most commonly used remedies are Echinacea , recognized for its affinity with the immune system, and classic homeopathic medicines such as Sulphur, Silicea, Allium Cepa , and Phosphorus ; frequently prescribed to strengthen vitality, improve the response to recurrent infections, and promote a more harmonious recovery.”

Where is the immune system regulated? In the gut . Ayurveda, the traditional Indian medicine, has been telling us for over five thousand years that the key to health lies in our gut, and the latest scientific studies are reaching the same conclusions. There is growing evidence of the interaction between the gut, brain, mind, emotions, and immunity.
Digestive fire
“In Ayurveda, our health and vitality depend on agni , our digestive fire. Agni is our digestive power: the fire that digests food and allows the cascade of nourishment to begin in all the body's tissues. The end product of this nourishment is ojas , the vital essence of physical resistance: vigor, fertility, and immunity. If digestion is insufficient, not only are we not nourished or does this essence not generate in adequate quantities, but toxins, or what Ayurveda calls ama , are also generated . From this perspective, the accumulation of ama is the origin of the disease process,” explains Liliana Gastal, a pediatrician trained in Ayurveda.

It's crucial to understand that, for this ancient medicine, nourishment encompasses everything that enters through the senses . Gastal explains: “Our immunity depends not only on the proper digestion and absorption of the food we eat, but also on the proper digestion of what we hear, see, smell, what we put on our skin, who touches us, the environments we inhabit, and everything that happens to us. We can then ask ourselves: What am I allowing to enter through my senses? Can I digest it? Physical indigestion can last a few hours, perhaps days, but mental or emotional indigestion from something we saw or heard and couldn't process can last for years or even a lifetime,” the specialist observes.

Ayurveda also tells us that we not only have a physical body, but also an energetic, mental, emotional, and spiritual body . According to Dr. Gastal, "at these more subtle levels, the one responsible for digesting what enters our mind through the senses, our emotions, and thoughts is the buddhi , or intellect." She explains that she is not referring to our ability to process information or what we would know as intelligence, but rather to our capacity for discernment. "Discerning both between what is real and what is false, and between what is right and what is wrong. Based on this discernment, making decisions aligned with our inner wisdom. Its proper functioning produces mental clarity, well-being, inner peace, and, of course, ojas , or immunity," she affirms.

“Ayurveda understands immunity as the result of a well-nourished body and a peaceful mind. In autumn, the air element within us increases, making the body more vulnerable and the mind more unstable. That's why it's key to maintain simple routines: warm, easily digestible foods, spices like ginger and turmeric , good rest, and moments of pause. More than fighting disease, it's about creating habits that align us, choosing our companions wisely, and returning to the essentials , to that inner place where body and mind find calm,” suggests María Alejandra Avcharian, an Ayurvedic specialist trained in India, who shares this health system on her social media, bringing this wisdom closer to everyday life.
The microbial ecosystem
The gut microbiota is the collection of microbes that reside in the gastrointestinal tract, where 70% to 80% of our immune cells also live. It comprises more than a thousand different species that contribute 3.3 million unique microbial genes to the human gastrointestinal tract. This complex microbial ecosystem includes bacteria, viruses, fungi, and parasites that live in a symbiotic relationship with the host. There is a strong link between the gut microbiota, chronic non-communicable diseases, mental health, and the immune system.
How to promote a healthy gut microbiota through diet?

Reduce consumption of ultra-processed industrial products, sweeteners, simple sugar, refined flours, and medications.
Increase your intake of plant-based foods, such as vegetables, fruits, whole grains, legumes, nuts, and seeds. Beneficial bacteria regulate inflammation, train the immune system, and help block pathogens. These can be obtained through supplements, or by making homemade fermented foods, which provide live and active microorganisms.
Martin Lui, a chef specializing in raw vegan food, shares the recipe for a fermented seed dressing, known as wild fermentation, considered a superfood for our microbiota. "You can make it with sunflower seeds, cashews, walnuts, or almonds, and it's very simple. The first step is to wash and activate the seeds (overnight). Once activated, blend them with a little water until you get a smooth cream. Then, add lemon juice, salt, and spices to taste, such as garlic powder or smoked paprika. You can also add a carrot to soften and balance the flavor. The next step is to transfer the mixture to a jar, seal it, and leave it at room temperature until small bubbles appear, which means the mixture has risen. Then, put it in the refrigerator. Ideally, it should be consumed fresh, as it will become more acidic over time (that's part of the magic). If you don't like the acidity, balance it with sweet and/or aromatic spices. It can be used as a spreadable cheese, jam, in sauces, or as a dip."

Chronic stress: the silent saboteur
Robert Sapolsky, a neurobiologist at Stanford, is the leading authority on the study of stress. Sapolsky distinguishes between two types of stress: adaptive and chronic . Adaptive stress is a short-term response to an acute physical crisis. This is what happens when a zebra runs to escape a lion. It's a brilliant survival response, and once the danger passes, the system quickly returns to equilibrium—homeostasis. The human problem, according to Sapolsky, is that we are the only species capable of activating the stress response in a sustained manner for purely psychological reasons , such as worrying about traffic, bills, or social status.

If the 'emergency' switch is left on, the body self-destructs. Allostatic load, that is, the accumulated wear and tear on the body and brain, is the price the body pays for being forced to adapt continuously. This constant state of alert keeps cortisol, the stress hormone, elevated; in turn, it decreases the activity and proliferation of lymphocytes (key cells of adaptive immunity); increases inflammation; and raises susceptibility to infections , among other effects. The body prioritizes survival and relegates defense and cellular repair functions to a secondary role.

Regarding this, pediatrician Ximena Lorca explains: “Children need to grow up in a nurturing environment where their routines are maintained. In a world that constantly demands things of them, both at home and at school, with endless schedules and activities, this leads to an internal imbalance that has consequences. Elevated cortisol levels will impact both their learning capacity and cognitive development, as well as their health. The immune system weakens, metabolic disturbances occur, and in the long term, the risk of obesity, high blood pressure, and diabetes increases.”

“Chronic stress can last for weeks, months, or even years. This chronic, sustained, silent stress has signs such as fatigue, gastrointestinal symptoms, headaches, and lower back pain, among others,” explains Patricia Faur, psychologist and professor at Favaloro University. How does this burden impact the immune system? “Chronic stress, with elevated cortisol levels, alters the immune system's response capacity. It especially affects T lymphocytes, decreasing the lymphoproliferation of these lymphocytes, which are like patrol cells responsible for detecting and eliminating both viruses and cancer cells,” elaborates Faur, who holds a master's degree in Psychoneuroimmunology.

Furthermore, she explains that it reduces the cytotoxicity of natural killer cells , which are cells involved in innate immunity and must have cytotoxic capacity to fight off foreign bodies. “They have less fighting capacity. On the other hand, a state of chronic inflammation develops, which is usually the most serious consequence. A sustained chronic inflammatory state begins to have repercussions on diseases such as type II diabetes, cardiovascular diseases, and even on mental health, as it leads to depressive states,” summarizes the specialist, who also teaches neuroscience training for therapists.

She also describes how there are psychosocial situations in which stress can become chronic , with some consequences for the immune system. “Some examples are marital stress , when a relationship is experienced as threatening; or caregiver stress when someone has to take care of a family member with dementia; it can also be work-related stress with situations like mobbing or workplace harassment, or in children and adolescents, with bullying ,” Faur warns.

Ultimately, strengthening our immune system in anticipation of colder weather isn't a race against time, but rather a pact of trust with our own biology: an invitation to pause and observe ourselves, in an exercise of listening and coherence. As experts point out, our defenses aren't a static wall, but an intelligent network, a dynamic process nourished by what we eat, as well as by what we think, what we feel, and how we rest.

In a world that pushes us to be constantly on alert, choosing to pause, prioritizing sleep, exercising, and eating well becomes the most revolutionary act of prevention. Autumn invites us, precisely, to tune into a change of pace. To let go of what exhausts us and cultivate, habit by habit, a natural shield by inhabiting our bodies consciously.
IRON: Energy for immune cells. Iron not only transports oxygen, but also allows immune cells to multiply and function properly. When iron is deficient, cellular immunity decreases and the risk of infections increases.

Sources : beef, chicken, fish, lentils, chickpeas, beans, spinach, oats, pumpkin seeds.
VITAMIN C: More than just a remedy for colds, vitamin C plays a role in immune cell function (antioxidant protection against inflammatory stress); it also contributes to the integrity of epithelial barriers (it doesn't magically boost your defenses, but it helps them function better and improves the absorption of plant-based iron). Combining lentils with bell peppers or lemons isn't just a detail; it's a biological strategy.

Sources : citrus fruits, kiwi, strawberries, bell peppers, broccoli, parsley.
Zinc: The silent regulator. Zinc is essential for the development of T cells (a type of white blood cell, part of the adaptive immune system); it regulates inflammation; maintains the integrity of mucous membranes (nose, lungs, intestines); and participates in wound healing and repair. Even a mild deficiency can impair immunity.

Sources : beef, seafood, chicken, legumes, pumpkin seeds, nuts, oats.
Vitamin D: This is an immunomodulatory hormone. It helps prevent T cells from overreacting; it modulates inflammation (neither too high nor too low) and plays a role in defending against respiratory viruses. While vitamin D alone does not prevent infections, correcting a deficiency improves immune regulation. Low levels are common in winter due to fewer hours of sunlight.

Sources : responsible sun, egg yolk, fatty fish.
VITAMIN A: The Barrier. Vitamin A keeps the respiratory and intestinal mucous membranes healthy. They are the first line of defense. What are mucous membranes? They are the tissues that line the nose, throat, lungs, and intestines. They function as a first physical barrier against viruses and bacteria. If this barrier is strong, many microorganisms cannot even enter.

Sources : liver, egg yolk, whole dairy products, carrot, pumpkin, spinach.
PROTEINS: Without amino acids there are no antibodies. Without proteins there are no new immune cells. The body cannot defend itself if it doesn't have the building blocks to do so.