How to Boost Your Immune System Before Flu Season Hits

Nov 9

Estimated read time: 13 minutes

Every year, when the weather cools, the days shorten, and flu season creeps in, the best defense isn’t waiting until symptoms strike. The key to warding off the flu and other illnesses is strengthening your immune system before viruses start circulating.

According to the CDC, up to 20% of the U.S population gets the flu every year, usually between October and March, resulting in about 5 million serious illnesses and thousands of deaths among those who are most vulnerable.

A strong immune system depends on nourishment from the inside out: the right nutrients, herbs, gut balance, and lifestyle rhythms that keep your body resilient. Here’s a step-by-step look at how to prepare your defenses naturally, through both your diet and daily habits.

4+ Ways to Boost Your Immune System & Defend Against Flu Season

From nourishing foods to immune-activating herbs and lifestyle habits, these simple strategies help your body stay resilient all winter long, starting with the nutrients that form the foundation of immunity.

1. Build Your Foundation with Nutrient-Rich Foods

Your immune system relies on a steady supply of micronutrients to function well and fight off pathogens. Deficiencies in just one—such as vitamins A, C, and D, or zinc, for example—can weaken your response to flu-like viruses, as well as infections.

Vitamin D: The Sunshine Vitamin (and Winter Superpower):

Vitamin D acts like a hormone that regulates immune defenses. Low levels—which are very common, especially during the winter—are linked to higher respiratory infection risk. Because sunlight is the main source of vitamin D, most people (about 40% or more) fall short during colder months and have to be intentional about getting enough.

To bring your level up, get natural sunlight whenever possible, including through the winter, ideally aiming for 10–30 minutes daily on exposed skin without sunscreen.

While vitamin D isn't found in many foods, you can still eat foods that do provide some, like mackerel, herring, sardines, egg yolks, and liver from land and sea creatures (especially cod liver, which is one of the richest sources available).

Most adults and children can also benefit from supplementing wisely. Doubling your intake in winter (to about 2,000+ IU of vitamin D3 daily, or even more) is considered safe for most adults and can help maintain healthy blood levels. D3 is the type that most strongly mimics what our bodies naturally make and need, so this is the form to seek out.

Vitamin A: The “Anti-Infection” Nutrient:

Vitamin C might get all the immune-boosting credit, but vitamin A is also important, considering it supports mucous membranes, the body’s first line of defense in the nose, lungs, and gut. It also boosts antibody production, which helps to "train" your immune system to become stronger against threats.

The best sources of bioavailable vitamin A are animal-derived foods, including egg yolks, beef, chicken, and especially liver (like calf or beef chicken, which is nature’s richest source).

While beta carotene from carrots and leafy greens is beneficial, your body has to convert it to active vitamin A (retinol), which isn’t always efficient—especially if you have thyroid or gut issues.

Vitamin K2: The Unsung Partner:

Vitamin K2 works with vitamins A and D to direct calcium properly in the body and support immune cell development.

Why does this matter? Because without K2, calcium can end up in the wrong places—like arteries and soft tissues—instead of being directed into bones and teeth where it belongs. This not only supports skeletal strength but also prevents calcification that can impair circulation and immune function.

Research shows that vitamin K can act "as a therapeutic tool" for preventing or managing infections, inflammation, and autoimmune diseases. To boost your K2 intake, seek out sources like natto (fermented soy), aged cheeses, and grass-fed liver.

Vitamin C: The Classic Protector:

Vitamin C not only supports the body’s first line of immune defense by strengthening epithelial barriers, but it also helps white blood cells like neutrophils and lymphocytes respond more effectively to infections.

As a potent antioxidant, it helps protect immune cells from oxidative stress generated during illness, allowing them to function longer and more efficiently. Studies show that consistent vitamin C intake can help reduce the duration and severity of colds, especially in people under physical stress or with low baseline levels.

It’s best to take your C from food or a fat-coated (liposomal) supplement for better absorption. The best dietary sources include citrus fruits (I'm a big fan of lemons and limes, but oranges, grapefruit, and tangerines are great, too), berries, and cooked leafy greens.

Zinc and Copper: The Dynamic Duo:

Zinc is considered a "gatekeeper" of the immune system, since it assists in signaling and activates T-cells and natural killer cells that detect and destroy viruses. However, zinc and copper compete for absorption, so maintaining balance is key. Too much zinc without copper can impair immune and nervous system function. Aim for a 10:1 zinc-to-copper ratio.

Liver provides both minerals in ideal proportions, along with other immune-supportive nutrients like vitamin A, making it one of the best whole-food sources for maintaining this balance naturally. Other sources (aside from shellfish, which I don't recommend) include beef and lamb, dark meat chicken, pumpkin and hemp seeds, cashews, lentils, mushrooms, spirulina, and egg yolks.

If you prefer not to eat liver, you can take desiccated capsules for convenience.

2. Support Immunity Through Nourishing Foods

Bone Broth for Gut and Immune Strength:

Bone broth provides amino acids like glycine, collagen, and proline that help repair the gut lining and support liver detox—two key immune hubs. It can also help stimulate neutrophils, your immune system’s first responders.

Enjoy a warm cup daily during cold months, or use it as a base for soups and stews.

Fermented and Sour Foods for Probiotic Power:

About 70% of your immune system resides in your gut, so supporting healthy gut flora can make a big difference in resilience.

Eat probiotic-rich foods like kimchi, sauerkraut, kefir, and fermented pickles, which provide natural probiotics. Fermented and sour foods like kimchi, green tea, and oat tree leaves provide polyphenols and quercetin that help reduce inflammation and strengthen the gut barrier. These compounds act as natural antioxidants, supporting the growth of beneficial bacteria and helping regulate immune activity in the gut.

Regularly consuming fermented and quercetin-rich foods can also help improve nutrient absorption and overall digestive health.

3. Herbs, Spices, and Botanicals That Defend

Nature offers a pharmacy of immune-supportive plants. For example, many herbs and spices are warming, bitter, or aromatic, all qualities that promote circulation and microbial balance.

Echinacea: Can stimulate white blood cell production and potentially help reduce the duration of colds or respiratory infections when taken early.

Elderberry: Rich in anthocyanins and other antioxidants that can help block viral replication and support recovery.

Goldenseal: Contains berberine, a potent antimicrobial compound that helps fight bacteria and supports the gut.

Andrographis: A warming Ayurvedic herb shown to help reduce cold symptoms and boost antiviral defenses.

Warming spices like ginger, turmeric, cinnamon, clove, and cayenne can also help increase circulation, reduce inflammation, and provide powerful antioxidant effects. You can use these by brewing herbal teas, adding spices to meals, or taking standardized extracts for targeted immune support.

4. Lifestyle Habits That Strengthen Your Defenses

Move Daily—But Don’t Overtrain

Moderate exercise like walking, yoga, or strength training boosts immune cell circulation. Overtraining, however, can deplete energy and weaken defenses. Aim for 30–45 minutes of targeted exercise each day, along with plenty of "non-exercise movement" (like walking) most days.

Sleep: Your Overnight Immune Reset

Because your immune system performs much of its repair and regulation while you sleep. Studies show that sleep-deprived adults can even produce fewer antibodies after vaccination and have lower cytokine levels, weakening their defense against viruses.

Even a single night of poor sleep can reduce natural killer cell activity, leaving you more susceptible to infections. Prioritize consistent sleep, get daytime sunlight, and minimize blue light exposure at night, which can help your body mount a strong immune response.

Manage Stress and Stay Connected

Chronic stress suppresses immune activity through elevated cortisol. Practices like prayer, deep breathing, time outdoors, and fellowship can all help lower stress hormones and increase resilience.

Key Takeaways for Building Your Flu-Season Defense

Get your vitamin D levels up before winter—double your intake if necessary.
Include nutrient-dense animal foods in your diet regularly: liver, egg yolks, and fatty fish.
Balance zinc and copper through real food like organ meats.
Support your gut with probiotics and sour foods like kimchi and kefir.
Drink bone broth to nourish your gut and immune system.
Use immune herbs and spices daily for warmth, circulation, and protection.
Rest, move, and manage stress to keep your immune system adaptable.

Final Thoughts

God designed your immune system to be strong, but it thrives on nourishment, rest, and stewardship. By aligning your habits with creation’s design, you can meet flu season with resilience instead of fear.

As Scripture reminds us: “A joyful heart is good medicine, but a crushed spirit dries up the bones.” (Proverbs 17:22). Fuel your temple with warmth, color, and connection this season, and watch your body respond in kind.

References:

https://www.cdc.gov/flu-burden/php/about/index.htm

https://my.clevelandclinic.org/health/diseases/15050-vitamin-d-vitamin-d-deficiency

https://nutritionsource.hsph.harvard.edu/nutrition-and-immunity/

https://pmc.ncbi.nlm.nih.gov/articles/PMC10053989/

https://pmc.ncbi.nlm.nih.gov/articles/PMC6162863/

https://pmc.ncbi.nlm.nih.gov/articles/PMC10893789/

https://pubmed.ncbi.nlm.nih.gov/31487891/

https://pmc.ncbi.nlm.nih.gov/articles/PMC8078152/

https://pubmed.ncbi.nlm.nih.gov/40180691/

https://pmc.ncbi.nlm.nih.gov/articles/PMC5748737/

https://pmc.ncbi.nlm.nih.gov/articles/PMC8001875/