Supporting Immune Function During the Cold and Flu Season: A practical guide

As seasons shift and viruses circulate more actively, the question of how to keep yourself and your family well becomes an important topic in most households. Emerging research suggests that some of the most powerful immune support happens at a level most people often overlook entirely or at least don't focus enough on, and the results can be significant. These key areas are: what you eat, how you sleep, and how you spend your days.

Diet: The Foundation

If you had to choose one thing to optimize for immune resilience, a lot of the research appears to point squarely in one direction: prioritize whole plant foods.

Recent studies comparing dietary patterns have found that people who eat predominantly unprocessed, balanced plant-based diets show stronger antiviral immune responses. Specifically, their bodies upregulate type I interferon pathways and antiviral defenses more robustly than normal and especially compared to people eating low-carbohydrate, high-protein diets. This matters a lot because interferon is your first-line defense against viruses. It's what stops replication in the first critical hours before antibodies even kick in.

In a study of healthcare workers across six countries during the pandemic, which seems to corroborate what the study above showed, those following plant-based diets had 73% lower odds of moderate-to-severe illness compared to those not following such diets. Pescatarian diets (plant-based with fish) showed similar benefits, though they were less pronounced pronounced than those eating 100% plant based. By contrast, low-carbohydrate, high-protein approaches were associated with higher risk of severe illness.

The mechanism isn't actually that complicated, and this makes the odds of it being a real effect high. Plant foods are micronutrient-dense: rich in vitamins A, C, E, folate, polyphenols, carotenoids, and minerals. These are substrates your immune system needs for lymphocyte proliferation, antibody synthesis, and managing oxidative stress. They also feed your microbiota diversity, which trains immune tolerance and responsiveness.

The practical takeaway: making vegetables, legumes, whole grains, and fruits the foundation of your diet, then take whatever simple steps are needed to assure nutritional adequacy of all essential nutrients (for most this can be a simple multivitamin, and daily intake of flax/chia/hemp seeds) can go a very long way for your immune function. If you choose to eat animal products, keep them secondary, and focus on wild, sustainably caught fish. The research is not totally clear that eating 100% plant based is necessary to obtain the best possible effects here but it does point in that direction, so if you are willing to try that might be best of all (and for your heart too). That said, it's also clear you don't need to be 100% rigid if that doesn't work for you, but the direction clearly seems to matter.

Sleep and Circadian Rhythm: The Underrated Pillar

You simply cannot have your best possible immune function with regularly poor sleep. During sleep, your body produces cytokines that coordinate immune responses. Studies show that even one night of inadequate sleep reduces antibody production and impairs T cell function. Chronic sleep deprivation increases susceptibility to infection and prolongs illness duration.

The target is straightforward: 7-8 hours nightly, with special focus on consistent sleep and wake times. This stabilizes your circadian rhythm, which also helps to regulate immune cell production and distribution. Your adaptive immunity works better when your clock is set.

One simple lever to pull that can help a lot here: get natural light exposure early in the day, ideally within an hour of waking. This anchors your circadian system and improves sleep quality. Research on circadian-disrupted populations shows elevated infection rates. Light synchronization reverses this.

Movement and Forest Time

Regular exercise enhances immune function through multiple pathways. Moderate activity increases circulation of immune cells, improves antibody responses, and reduces chronic inflammation. The evidence is clear: active people get sick less often.

That said, not all exercise is equal. Forest bathing (shinrin-yoku) and walking in natural settings may offer an additional layer. Exposure to phytoncides (antimicrobial compounds released by trees) has clearly been shown to increase natural killer cell activity, a key component of antiviral defense. Studies show that even a single walk in a forest can increase NK cell counts for days afterward. If you can build regular walks in nature, especially among trees, into your routine, you're recruiting the environment itself as immune support!

A practical recommendation: aim for multiple short walks throughout the day and ideally a longer one as well, interspersed with other types of exercise on some days. Then, as much of your walking that you can do outdoors or in nature, the better.

Cold Water and Respiratory Resilience

Research on cold water immersion activities shows it can activate the parasympathetic nervous system, increase production of certain immune cytokines, and improve resilience to stress. Over time, regular exposure to mild cold stress improves the body's ability to manage physiological challenge without dysregulation. To be clear this can just be a simple, small but consistent practice: finish your shower with a brief cold rinse. In other words, you don't have to do extreme ice-baths or anything, just end your showers with water that is cold enough to be noticeably uncomfortable for 30 seconds to a minute.

Micronutrient Sufficiency

Beyond eating well, it's worth checking that you're not running on empty in the micronutrients that matter most for immune health. Vitamin D (especially relevant in winter when sunlight exposure drops), zinc, selenium, and vitamin C are all involved in lymphocyte production and antiviral responses. Many people are subtly deficient without realizing it.

Again, a simple approach here that works for most is to just take a basic, high quality multivitamin, and eat a wide variety of plant foods.

Screen Time and Human Connection

Chronic stress suppresses immune function. Excessive screen time, especially before bed, dysregulates circadian rhythm and elevates cortisol, especially if what you are reading or listening to is stressful. Meanwhile, quality time with people you care about activates the parasympathetic nervous system and buffers stress.

The evidence on social connection and immunity is clear: isolated individuals get sick more often. Those embedded in meaningful relationships have stronger immune responses.

The practice is simple: spend less time on screens, and more time doing meaningful things with people who matter. Set a cutoff time for devices before bed, and prioritize in-person interactions.

Going Deeper: Ozone Therapy as a Complement

For those looking for an additional layer beyond diet and lifestyle, ozone therapy offers an interesting option. In the Portland area, I offer this treatment to my patients (see vital-human.com/ozone for more info and to schedule an appointment), who can get periodic ozone treatments (typically 1-2 times monthly) as a way to uniquely and powerfully support immune function during cold and flu season.

Ozone therapy, specifically what's called "major autohemotherapy", works by triggering the body's antioxidant defense systems and enhancing immune cell activation, an effect that actually has good science supporting it. The mechanism involves controlled ozone exposure that signals the body to upregulate its own protective responses. Regular seasonal ozone treatment appears to reduce the frequency and severity of colds and flus in people who use it.

It goes without saying, this isn't a replacement for the foundational work of diet and lifestyle, but it does have unique effects. Think of it as a powerful but complementary strategy for those who want to leave nothing on the table during the months when infections circulate most actively. Combined with a plant-rich diet, solid sleep, regular movement in nature, and stress management, it adds another dimension to immune support.

Putting It Together

Immune resilience isn't built on one lever. It's the compound effect of small choices made consistently: eating lots of plants, sleeping well, moving regularly in natural settings, stimulating your immune system, managing stress, and staying nutrient-sufficient. These aren't difficult or particularly exotic. They're accessible to most people and grounded in genuine science.

The public recommendations around preventing seasonal illness tends to stay narrow and focused mostly on vaccines, hand-washing, and antiviral drugs. But how you live your life can really help to shape whether you get sick in the first place, and how severely if you do. Your body, on its own, or gently stimulated, can be incredibly powerful.