Immune Boot Camp: Immune Support for Back to School and Beyond

In the course of one year, the U.S. population contracts approximately 1 billion colds.¹ Influenza accounts for 20-25 million doctor visits.¹ During the fall and winter, patients are at an increased risk. Going back to school can be a stressful time for many children, and the stress can lower their immune system’s defenses.

Kids bring home a medley of viruses that adults did not get exposed to over the summer. Even patients who don’t have kids or grandkids at home can get exposed at the grocery store, restaurants, and other proverbial human watering holes.

Why We’re At Greater Risk in Autumn and Winter

The seasonality of flu (influenza) is due to a combination of environmental, biological, and behavioral factors that make flu outbreaks more common in colder months in temperate regions (e.g., winter) and during the rainy season in tropical regions. Here’s a detailed explanation:

1. Environmental Factors
   • Temperature and Humidity
     • Influenza viruses survive and remain infectious for more extended periods in cold, dry air.
     • Low humidity in winter allows viral particles to remain airborne for more extended periods.
     • Cold temperatures may also impair the nasal mucosal defense mechanisms.

• • UV Radiation
    • During the summer, UV light from sunlight inactivates influenza viruses.
    • Reduced sunlight in winter decreases UV exposure, allowing the virus to persist longer in the environment.

2. Human Behavior

• • Indoor Crowding
    • People spend more time indoors during cold or rainy seasons, increasing close contact and facilitating transmission.
  • School Cycles
    • School terms (fall/winter) increase mixing among children, who are major spreaders of influenza.

3. Host Factors

• • Immune Function
    • Reduced vitamin D levels in winter (due to less sunlight) may impair immune responses.
    • Cold air can reduce mucociliary clearance in the respiratory tract, making it easier for infections to occur.

4. Viral Evolution

• • Antigenic Drift
    • Seasonal influenza strains undergo small mutations, allowing them to escape immunity from previous infections, contributing to recurring seasonal epidemics.

It’s Always Winter Somewhere

Even when it’s summer in the Northern Hemisphere (June – August), in the Southern Hemisphere it’s winter. Business travel, family holiday travel, and other reasons for traveling contribute to cross-exposure of two different hemispheres.

About a decade ago, I recall traveling to Hawaii for the summer from the U.S. I was surprised to see many people sneezing, coughing, and just looking not so well. They all seemed to share something in common: they were from New Zealand or Australia, two places in the Southern Hemisphere, which was in the middle of winter and its cold and flu season at that time. And yes, I walked across the hotel lobby through a mist of sneezes and coughing and caught a Southern Hemisphere flu. Since I am a stressed traveler, my immune system was more susceptible to getting sick.

In fact, whether a patient is exposed in the winter or summer, fall or spring, it all comes down to susceptibility.

Reducing Susceptibility

The key to keeping our patients’ immune systems healthy is to make them less susceptible to health threats. Ensuring a healthy diet rich in vegetables and fruits and low in refined sugar can help in this area. Exercise is also essential. To complement these other immune-boosting strategies, I routinely utilize a comprehensive array of immune-supporting nutrients and botanicals.

Astragalus

Research continues to support the use of this adaptogenic botanical for its immune-boosting actions. A systematic review and meta-analysis published in 2023 found that astragalus has immunomodulatory effects on humoral and cellular immune response.² Astragalus significantly reduced proinflammatory cytokines and enhanced cellular immune markers. According to a paper published in April 2025, astragalus may also delay cellular aging.³ As an adaptogen, astragalus protects against stress and may therefore make patients less susceptible to wintertime health challenges.

Zinc

Zinc is critical for immunity, yet its deficiency is common, impacting up to a quarter of the population in developing countries, and also affecting specific populations in the developed world as a result of lifestyle, age, and disease.⁴ Zinc-deficient populations are more susceptible to viral infections. An abundance of evidence has accumulated over the past 50 years to demonstrate the antiviral activity of zinc against a variety of viruses, and via numerous mechanisms.⁴

Vitamin C

Vitamin C is one of the best known and well-researched immune support vitamins. For example, a meta-analysis determined that vitamin C was effective at supporting the health of 11,077 people who had the common cold.⁵

EpiCor®

EpiCor® is a dried fermentate produced from Saccharomyces cerevisiae, an immune-modulating baker’s yeast. There are a number of good human studies showing EpiCor® acts as an antioxidant and supports a healthy immune response during exposure to colds and flus and during pollen season.^6-8 EpiCor® strengthens mucosal immunity and increases levels of salivary secretory immunoglobulin A, a substance coating mucosal surfaces that acts like a shield to stop unwanted substances from entering the body. EpiCor® increases natural killer cells and supports a healthy inflammatory response.

The newest study (published 2024) on EpiCor® found that EpiCor® supplementation in children led to significantly lower cold/flu symptom severity and less cold/flu medication compared with placebo. The EpiCor® group experienced fewer sore throat and muscle aches or pains symptoms compared to placebo.⁹

Olive Leaf Extract

Research suggests that olive leaf interacts with the protein of virus particles, weakening viral actions.¹⁰ It also promotes a healthy immune response by encouraging phagocytosis, the ability of immune cells to engulf invaders,¹ and it stimulates the production of natural killer cells.¹¹ A randomized, placebo-controlled study of 32 high school athletes found olive leaf extract supported upper respiratory tract health.¹² Tru Immune Support contains olive leaf extract with a generous 16% oleuropein for optimal potency.

Berberine

Berberine supports host immune response. It modulates different steps in the viral life cycle.¹³ It reduces viral replication and targets specific interactions between the virus and host and can reduce viral replication.¹³

N-Acetyl L-Cysteine

 N-Acetyl-L-Cysteine (NAC) is an antioxidant used to provide powerful support to the lungs and respiratory tract due to its ability to break up mucus and clear the respiratory passages.¹ Human studies have shown NAC can significantly support immune system health and lung function during cold and flu season.^14,15 A study published in 2025 found that NAC has synergistic effects on immunity when combined with vitamin D in older adults.¹⁶

Garlic

This botanical may promote immune system health. One double-blind, placebo-controlled study of 146 participants found that a garlic supplement was able to support immunity from November to February.¹⁷ A study of obese humans found that supplementation with garlic for six weeks influenced immune cell distribution, prevented the increase of serum TNF-α and IL-6 concentrations, and reduced blood low-density lipoprotein (LDL) concentration.¹⁸

Citrus Bioflavonoid Complex

Citrus bioflavonoids are beneficial compounds derived from such fruits as oranges and lemons. Citrus bioflavonoids like hesperidin are able to maintain immunity.^19,20 They work synergistically with vitamin C to promote optimal health.

 

Category	Recommendation	Examples
Nutrition	Eat a balanced diet	Include fruits, vegetables, whole grains, lean proteins, and healthy fats (nuts, seeds, fish).
Hydration	Drink enough water	Supports lymph flow and mucosal barriers; aim for ~2–3 liters/day (varies by person).
Exercise	Regular exercise	30 minutes of moderate activity (e.g., walking, cycling) most days; avoid overtraining.
Sleep	7-9 hours of sleep nightly	Consistent bedtime improves immune cell activity and recovery
Stress management	Reduce ongoing stress	Meditation, deep breathing, yoga, journaling, or hobbies.
Sunlight	Get regular sunlight or supplement with vitamin D if deficient	15–20 min daily sun exposure; consider vitamin D supplements in winter.
Avoid harmful habits	Limit alcohol and quit smoking	Smoking weakens respiratory immunity; alcohol suppresses immune response.
Immune supplements	Supplement with botanicals and nutrients designed to reduce stress and support immunity	Consider supplementing with astragalus, EpiCor®, zinc, vitamin C, olive leaf extract, berberine, N-acetyl L-cysteine (NAC), garlic, berberine, and citrus bioflavonoids (TruGen3’s Tru Immune Support)
Gut Health	Support microbiome	Eat probiotic foods (yogurt, kefir) and fiber-rich foods (whole grains, vegetables), supplement with probiotics.

 

 

The Key to Comprehensive Immune Support

Astragalus, EpiCor®, zinc, vitamin C, olive leaf extract, berberine, N-acetyl L-cysteine (NAC), garlic, berberine, and citrus bioflavonoids are all researched for their ability to support immunity. Furthermore, astragalus can soothe away the effects of stress, and by doing so defend against reduced susceptibility to viral challenges. Ingredients like these bundled together will help ensure that patients stay healthy every season of the year.

References

1. Roxas M, Jurenka J. Colds and influenza: a review of diagnosis and conventional, botanical, and nutritional considerations. Altern Med Rev. 2007;12(1):25-48.
2. Zhang X, Qu X, Zou Y. The Effect of Astragalus on Humoral and Cellular Immune Response: A Systematic Review and Meta-Analysis of Human Studies. Complement Med Res. 2023;30(6):535-543.
3. Borowicz KK, Jach ME. Astragalus Membranaceus-Can It Delay Cellular Aging? Nutrients. 2025;17(8).
4. Read SA, Obeid S, Ahlenstiel C, Ahlenstiel G. The Role of Zinc in Antiviral Immunity. Adv Nutr. 2019;10(4):696-710.
5. Douglas RM, Hemila H, D’Souza R, Chalker EB, Treacy B. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2004(4):Cd000980.
6. Jensen GS, Redman KA, Benson KF, et al. Antioxidant bioavailability and rapid immune-modulating effects after consumption of a single acute dose of a high-metabolite yeast immunogen: results of a placebo-controlled double-blinded crossover pilot study. J Med Food. 2011;14(9):1002-1010.
7. Moyad MA, Robinson LE, Zawada ET, Jr., et al. Effects of a modified yeast supplement on cold/flu symptoms. Urol Nurs. 2008;28(1):50-55.
8. Moyad MA, Robinson LE, Kittelsrud JM, et al. Immunogenic yeast-based fermentation product reduces allergic rhinitis-induced nasal congestion: a randomized, double-blind, placebo-controlled trial. Adv Ther. 2009;26(8):795-804.
9. Singh RG, Garcia-Campayo V, Green JB, et al. Efficacy of a yeast postbiotic on cold/flu symptoms in healthy children: A randomized-controlled trial. Pediatr Res. 2024;96(7):1739-1748.
10. Lee-Huang S, Zhang L, Huang PL, Chang YT, Huang PL. Anti-HIV activity of olive leaf extract (OLE) and modulation of host cell gene expression by HIV-1 infection and OLE treatment. Biochem Biophys Res Commun. 2003;307(4):1029-1037.
11. Magrone T, Spagnoletta A, Salvatore R, et al. Olive Leaf Extracts Act as Modulators of the Human Immune Response. Endocr Metab Immune Disord Drug Targets. 2018;18(1):85-93.
12. Somerville V, Moore R, Braakhuis A. The Effect of Olive Leaf Extract on Upper Respiratory Illness in High School Athletes: A Randomised Control Trial. Nutrients. 2019;11(2).
13. Warowicka A, Nawrot R, Goździcka-Józefiak A. Antiviral activity of berberine. Arch Virol. 2020;165(9):1935-1945.
14. Rasmussen JB, Glennow C. Reduction in days of illness after long-term treatment with N-acetylcysteine controlled-release tablets in patients with chronic bronchitis. Eur Respir J. 1988;1(4):351-355.
15. De Flora S, Grassi C, Carati L. Attenuation of influenza-like symptomatology and improvement of cell-mediated immunity with long-term N-acetylcysteine treatment. Eur Respir J. 1997;10(7):1535-1541.
16. Rastgoo S, Pourvali K, Raeissadat SA, Eslamian G, Zand H. Co-administration of vitamin D and N-acetylcysteine to modulate immunosenescence in older adults with vitamin D deficiency: a randomized clinical trial. Front Immunol. 2025;16:1570441.
17. Josling P. Preventing the common cold with a garlic supplement: a double-blind, placebo-controlled survey. Adv Ther. 2001;18(4):189-193.
18. Xu C, Mathews AE, Rodrigues C, et al. Aged garlic extract supplementation modifies inflammation and immunity of adults with obesity: A randomized, double-blind, placebo-controlled clinical trial. Clin Nutr ESPEN. 2018;24:148-155.
19. Saha RK, Takahashi T, Suzuki T. Glucosyl hesperidin prevents influenza a virus replication in vitro by inhibition of viral sialidase. Biol Pharm Bull. 2009;32(7):1188-1192.
20. Kim HK, Jeon WK, Ko BS. Flavanone glycosides from Citrus junos and their anti-influenza virus activity. Planta Med. 2001;67(6):548-549.