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Effective & Natural Immune Support for the Cold and Flu Season

Young Woman drinking Hot Tea in Snow - InterPlexus Blog Immune Support

“The only way to treat the common cold is with contempt.” ~ Sir William Osler

Fortunately, things have changed since 1888 when Sir William Osler, the first professor of medicine at Johns Hopkins University Medical School in Baltimore, made this statement.1,2 Modern research now confirms that supplemental vitamins, minerals, botanicals, and other natural remedies can decrease the severity and duration of the common cold.*

The common cold is the most frequent human illness. Adults typically experience 1–3 colds per year, whereas children have an average of five but could have up to 11 colds per year.1,3 Genetics, stress, smoking, nutrient deficiencies, and strenuous physical training can increase the risk of catching a cold.1,4

More than 200 viruses are reported to cause upper respiratory tract infections with common cold symptoms, and they include:1,3

    • Rhinoviruses (RVs)
    • Respiratory Syncytial Virus (RSV)
    • Influenza Viruses
    • Parainfluenza viruses
    • Coronaviruses
    • Adenoviruses
    • Enteroviruses, including Coxsackieviruses and Echoviruses
    • Bocavirus
    • Epstein Barr Virus (EBV)
    • Human Metapneumovirus (hMPV)1

Mutating Virus InterPlexus Blog Immune Support

Historically, rhinoviruses (RVs) are the most common underlying cause of common colds, responsible for up to 80 % of cases. RVs are also the viruses most commonly found in the respiratory tract throughout the year.1

Common colds are rare during the summer, but upper respiratory infections increase from the beginning of September until early spring each year. And the number of flu cases tends to increase in early November. So, we are in the midst of the cold and flu season right now!

Cold sick woman blowing nose - InterPlexus Immune Support Blog

Your immune system protects you from many infectious organisms, such as bacteria, viruses, fungi, and parasites. While your immune system is always active and carrying out surveillance to defend you against these potential threats, immune activity is significantly enhanced when an infection occurs. This heightened immune activity is accompanied by an increased rate of metabolism, which requires energy and compounds for the biosynthesis of immune molecules, all of which are ultimately derived from your diet.4

Decades of research on nutrient deficiencies confirm several vitamins and trace minerals play key roles in supporting a healthy immune response and reducing the risk of infections.

These nutrients include:

    • Vitamin A
    • Vitamin B6
    • Vitamin B12
    • Folate
    • Vitamin C
    • Vitamin D
    • Vitamin E
    • Zinc
    • Copper
    • Selenium4

Happy young black woman preparing vegetable salad

The use of herbal and nutritional remedies for supporting general health maintenance, enhancing the function of the immune system, and treating the common cold is becoming more popular as modern research continues to illuminate the benefits of supplementation. Consider the following evidence-based natural options to support your health during the cold and flu season!*

Organic Bioflavonoids

Bioflavonoids are present in all plants and offer an impressive range of physiologic effects, including antiviral, anti-inflammatory, antibacterial, and antioxidant benefits. Studies report bioflavonoids reduce the proliferation and replication of many viruses that cause cold symptoms, including the rhinovirus (RV), respiratory syncytial virus (RSV), and parainfluenza virus type 3.1,3 Bioflavonoids also reduce inflammation.3

Quercetin is a bioflavonoid found in citrus fruits, apples, and onions. Research shows quercetin blocks the entry of cold viruses into your cells. Quercetin also inhibits RV and poliovirus enzyme activity as well as RNA polymerase activity in some RNA viruses.1

Blackboard with the chemical formula of Quercetin - InterPlexus Blog Immune Support

In cell cultures and animal studies, treatment with quercetin during a rhinovirus infection induces a significant reduction in the viral load and the inflammatory response. Results of a clinical trial demonstrate quercetin supplementation over 12 weeks reduces the total number of sick days and cold symptom severity in adults.1

A thorough systematic review that examined the overall impact of bioflavonoids on upper respiratory infections (URIs) determined that an increased intake of bioflavonoids decreased the incidence of URIs by 33% with no adverse effects.3

A bottle of elderberry syrup - InterPlexus Blog Immune Support

Black Elderberry

Black elderberry (Sambucus nigra) has historically been used as both a food and a remedy for health concerns, including colds and flu. A recent systematic review confirmed elderberry extract shortens the duration of colds and the flu and is beneficial for those with upper respiratory symptoms.5

Specifically, elderberry extracts have demonstrated inhibitory effects on human coronaviruses, influenza A, influenza B, and H1N1 viruses in well-designed research studies.5,6,7

Black elderberry contains anthocyanins, a subset of bioflavonoids that appear to have immune-modulating and anti-inflammatory benefits. The anthocyanins in elderberry attach to the viruses to prevent them from entering your cells, thereby offering an inhibitory effect on the virus.5 If the virus cannot enter your cells, it cannot replicate or multiply.

So, if elderberry extract is taken immediately after exposure to a virus or at the onset of viral symptoms, your immune system might only need to fight and clear a hundred or a thousand viruses rather than a million or a billion viruses.

A recent review of clinical studies concluded that elderberry extracts reduce the symptoms of an upper respiratory infection when taken within the first 48 hours of symptom onset by an average of 50% after 2-4 days of supplementation. The symptoms relieved by elderberry extract in adults include fever, headache, nasal congestion, and runny nose. The review also confirmed no serious side effects were experienced by the participants supplementing with the elderberry extracts.8

Girl drinks a drink from a mug - InterPlexus Blog Immune Support

Since research shows that elderberry supplements, including elderberry tea, could be most effective when taken immediately after cold or flu symptoms begin, consider keeping a healthy supply of elderberry on hand throughout the cold and flu season.9

And since elderberries are easy to grow in many climates, you might choose to grow elderberries at home. If you cultivate and harvest elderberries, always cook the elderberries sufficiently before consuming them because raw elderberries can be toxic. More information and delicious elderberry recipes are available here.

Zinc Ascorbate

Zinc is the second-most abundant trace metal in the human body after iron. Zinc is essential to the structure and function of proteins, including approximately 2000 enzymes that are necessary for critical cellular processes.10

The global prevalence of zinc deficiency is estimated to be approximately 17% to 20% and occurs most frequently in the elderly, vegans, vegetarians, and individuals with chronic diseases such as liver cirrhosis or inflammatory bowel disease. Zinc deficiency could result in a suboptimal immune response, particularly during the cold and flu season.10

Zinc contributes to numerous immune signaling pathways and plays an essential role in an effective antiviral response. Supplementation with zinc has the potential to drastically improve the clearance of viral infections, as well as the awful symptoms associated with viral infections.10

Foods High in Zinc - InterPlexus Blog Immune Support

Research confirms zinc inhibits viral replication.10 Specifically, zinc inhibits the replication of coronaviruses, rhinoviruses (RV), influenza viruses, RSV, and coxsackieviruses.1,11,12 Zinc also blocks RV’s ability to bind to cells, alters the configuration of viral proteins, and modulates aspects of the inflammatory response.1

In clinical trials, zinc reduces the average duration of the common cold in healthy people when taken within 24 hours of the onset of symptoms.1,4 Clinical trials of oral and topical zinc preparations demonstrate they are effective for clearing viral warts. Year-long supplementation with zinc by elderly subjects dramatically reduces the number of infections.10

When different forms of zinc are studied, research shows chelation influences the efficiency of zinc transport across cell membranes. Zinc is most effective as an antiviral when shuttled inside cells, so increasing transport across cell membranes enhances the antiviral effects.13

According to research, zinc ascorbate increases the intracellular level of zinc more significantly than other chelated forms, including zinc citrate, zinc sulfate, and zinc chloride. Zinc ascorbate is a chelated compound produced by binding vitamin C (ascorbic acid) to zinc. Thus, when vitamin C is attached to zinc, it enhances zinc absorption into cells and antiviral activity.13

Research also suggests that supplementation with zinc and vitamin C as individual nutrients does not increase the intracellular zinc level as efficiently as the zinc ascorbate chelate. Therefore, supplementation with zinc ascorbate is more effective for antiviral support than taking zinc and vitamin C as separate supplements.13

Bare feet barefoot on ground with green leaves. grounding and earthing technique - InterPlexus Blog Immune Support


What is earthing? Earthing is a free but powerful treatment option to support the health of the immune system and other systems in your body. Earthing offers natural anti-inflammatory benefits and is a source of antioxidants for the human body. To participate in earthing, simply walk on the earth with bare feet.14

Walking on the earth with bare feet allows you to ground and physically connect your body to the healing energy of the earth.14

A severe inflammatory response to a viral infection can include a potentially destructive phenomenon known as a “respiratory burst” or an “oxidative burst.” An oxidative burst is the increased production of charged oxidizing agents, which are also known as free radicals.14,15

The highly reactive free radicals accumulate at the site of the infection and can harm healthy tissues. Recent research emphasizes the importance of charge transfer to neutralize free radicals during and after the oxidative burst.14

When living systems, including your body, are connected to the healing energy of the earth, it can mitigate the consequences of inflammation by neutralizing and clearing free radicals. Research on earthing also demonstrates other improvements in the immune response.14

vitamin-gold-shining-pill-capsule-icon-ascorbic-acid-shining-golden-substance-drop - InterPlexus Immune Support Blog

Vitamin C (Ascorbic acid)

According to a thorough review that analyzed the results of 31 randomized controlled trials, vitamin C supplementation does not change the number of common colds in the average person but does shorten the duration of common colds and decreases the severity of the infections. The results of the review also reveal vitamin C supplementation reduces the number of colds experienced by those under heavy short-term physical stress, including athletic training.4

The results of a clinical study confirm taking 100 mg of vitamin C with 10 mg of zinc together may stop a runny nose, which is an uncomfortable and frequent symptom of the common cold.1 Therefore, combining several nutrients that support the immune system might offer synergistic effects. And as noted above, when zinc is bound to ascorbic acid as zinc ascorbate, the antiviral benefits increase.13

Stay tuned to learn more about the beneficial effects of Vitamin C and other nutrients on your adrenal glands in our next blog!

A girl in a winter park looks at the screen of a tablet, smartphone - InterPlexus Blog Immune Support

Doctors tend to recommend lots of rest and extra fluids when you have a cold, but they might not offer additional treatment options. Fortunately, research shows supplemental nutrients, botanicals, and other immune-supportive natural compounds could help you recover more quickly from a cold. Research also suggests natural immune support might prevent severe upper respiratory infections when taken immediately after exposure to a virus or at the onset of symptoms.9*

In rare cases, the common cold and the flu can trigger life-threatening diseases in individuals with preexisting conditions, such as asthma.1 So, if symptoms are severe or continue to worsen, promptly consult with a healthcare provider for assessment and treatment.

Zinc ascorbate and an Organic Citrus Bioflavonoid Complex are available as a potent synergistic blend in Zinc PlusTM from Interplexus.*

Vitamin C and several bioflavonoids are also available in the popular Flavo PlexCTM formulation from Interplexus.*

* This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.



Summer is an opportune time to focus on health – the weather tends to be pleasant, which makes many people naturally feel like being more active and vigorous. Since June is also Men’s Health Month, let’s discuss a few nutrients that could be beneficial for men during a fun and healthy summer. According to the research, supplementing with zinc, vitamin C, and citrus bioflavonoids together could support optimal testosterone levels, recovery from injuries, and athletic performance.*


It’s that time of year! Are you suffering from a runny nose, itchy eyes, sneezing, nasal congestion, or other symptoms of seasonal allergies? If so, you are not alone! Over 40% of the US population has allergies. According to the National Health and Nutrition Examination Survey (NHANES), 44.6% of the US population has detectable Immunoglobulin E (IgE) antibodies in their blood, and we know IgE antibodies play a central role in instigating the symptoms associated with allergies...


While many of us know that daily supplementation with probiotics supports health, research is now beginning to teach us about the fascinating world of POSTbiotics!


Think you don’t need supplements? Think again! You may want to reconsider your thoughts about supplements to improve your health and well-being since your body requires a certain amount of each of the essential nutrients daily to function optimally!


  1. Passioti M, Maggina P, Megremis S, et al. The common cold: potential for future prevention or cure. Curr Allergy Asthma Rep. 2014;14(2):413. doi:10.1007/s11882-013-0413-5
  2. Pickering G. Sir William Osler, Baronet. Encyclopædia Britannica. Published July 18, 2022. Accessed August 30, 2022.
  3. Somerville VS, Braakhuis AJ, Hopkins WG. Effect of Flavonoids on Upper Respiratory Tract Infections and Immune Function: A Systematic Review and Meta-Analysis. Adv Nutr. 2016;7(3):488-497. Published 2016 May 16. doi:10.3945/an.115.010538
  4. Calder PC. Nutrition, immunity and COVID-19. BMJ Nutr Prev Health. 2020;3(1):74-92. doi:10.1136/bmjnph-2020-000085
  5. Wieland LS, Piechotta V, Feinberg T, et al. Elderberry for prevention and treatment of viral respiratory illnesses: a systematic review. BMC Complement Med Ther. 2021;21(1):112. doi:10.1186/s12906-021-03283-5
  6. Weng JR, Lin CS, Lai HC, et al. Antiviral activity of Sambucus FormosanaNakai ethanol extract and related phenolic acid constituents against human coronavirus NL63. Virus Res. 2019;273:197767. doi:10.1016/j.virusres.2019.197767
  7. Mocanu ML, Amariei S. Elderberries-A Source of Bioactive Compounds with Antiviral Action. Plants (Basel). 2022;11(6):740. doi:10.3390/plants11060740
  8. Harnett J, Oakes K, Carè J, et al. The effects of Sambucus nigra berry on acute respiratory viral infections: A rapid review of clinical studies. Adv Integr Med. 2020;7(4):240-246. doi:10.1016/j.aimed.2020.08.001
  9. Chen C, Zuckerman DM, Brantley S, et al. Sambucus nigra extracts inhibit infectious bronchitis virus at an early point during replication. BMC Vet Res. 2014;10:24. doi:10.1186/1746-6148-10-24
  10. Read SA, Obeid S, Ahlenstiel C, et al. The Role of Zinc in Antiviral Immunity. Adv Nutr. 2019;10(4):696-710. doi:10.1093/advances/nmz013
  11. te Velthuis AJ, van den Worm SH, Sims AC, et al. Zn(2+) inhibits coronavirus and arterivirus RNA polymerase activity in vitro and zinc ionophores block the replication of these viruses in cell culture. PLoS Pathog. 2010;6(11):e1001176. doi:10.1371/journal.ppat.1001176
  12. Govers C, Calder PC, Savelkoul HFJ, et al. Ingestion, Immunity, and Infection: Nutrition and Viral Respiratory Tract Infections. Front Immunol. 2022;13:841532. doi:10.3389/fimmu.2022.841532
  13. Cingolani V. Hypothesis of zinc ascorbate as best zinc ionophore for raising antiviral resistance against Covid-19. J Med Virol. 2021;93(9):5205-5208. doi:10.1002/jmv.26989
  14. Mousa HA. Prevention and Treatment of Influenza, Influenza-Like Illness, and Common Cold by Herbal, Complementary, and Natural Therapies. J Evid Based Complementary Altern Med. 2017;22(1):166-174. doi:10.1177/2156587216641831
  15. Ma Y, Zhang Y, Zhu L. Role of neutrophils in acute viral infection. Immun Inflamm Dis. 2021;9(4):1186-1196. doi:10.1002/iid3.500

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