1. Vitamin D3
Vitamin D3 tops my list due to its ability to produce antiviral peptides (e.g. cathelicidin), which directly destroy invading organisms. Vitamin D prevents macrophages from releasing as many inflammatory cytokines and chemokines.[ii] One study[iii] found supplementing schoolchildren with 1,200 IUs per day of D3 cut their risk of influenza A by 42 percent.Traditionally, we received our vitamin D from the sun. In fact, it’s theorized the reason for influenza’s increased prevalence in the wintertime is our reduced sun exposure, with a resultant drop in our vitamin D levels. It’s best to get vitamin D3 from reasonable sun exposure, but if this is not practical, a D3 supplement can be used for just pennies a day.
2. Probiotics
The billions of microorganisms that reside in your digestive tract comprise 80 to 90 percent of your immune system. Practices such as antibiotic overuse, the standard American diet and today’s “germophobic” attitude have taken a heavy toll on the human microbiome. Therefore, probiotics can give a powerful boost to your immune function.3. Green Tea
If you feel a bug coming on, brew yourself a nice cup of green tea. Green tea is rich in catechins and is shown to enhance T cell function, as well as interfering with the replication of the influenza virus by inhibiting neuraminidase and hemagglutinin. A 2011 Japanese study found children who consume one to five cups of green tea per day have lower susceptibility to influenza. The EGCG (epigallocatechin-3-gallate) in green tea is a potent antioxidant offering numerous health benefits for your brain, heart, bones, eyes and other body parts. It is advisable to source your green tea from Japan instead of China in order to minimize levels of industrial pollutants, such as lead.4. Elderberry
The next celebrity in natural flu prevention is elderberry, or Sambucus nigra. (Black elderberry extract is also known as Sambucol.) A Norwegian study showed flu sufferers who took 15 ml of elderberry extract four times a day for five days recovered four days sooner and required less “rescue medication” than placebo. Elderberry extract has also been shown to inhibit several strains of influenza virus, in vitro. Besides antiviral properties, Sambucol activates your immune system by increasing cytokine production.[vi]5. Echinacea
Last but not least, echinacea purpurea has a long history of use with respiratory infections. Research supports its ability to reduce both the severity and duration of flu symptoms. The roots of echinacea have cytokine-modulating properties.References
[i] Medscape March 5, 2015 FDA Advisers Recommend Overhaul of 2015 Flu Vaccine [ii] Cannell JJ, Vieth R, Umhau JC, Holick MF, Grant WB, Madronich S, Garland CF, and Giovannucci E. Epidemic influenza and vitamin D. Epidemiol Infect 2006 Dec.;134(6):1129-1140.PMCID: PMC2870528 [iii] Urashima M, Segawa T, Okazaki M, Kurihara M, Wada Y, Ida H. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr. 2010 May; 91(5):1255-60 PMID: 20219962 [iv] Vitamin D Council Testing for Vitamin D [v] Ouwehand A, Leyer G and Carcano D. Probiotics Reduce Incidence and Duration of Respiratory Tract Infection Symptoms in 3- to 5-year-old Children. Supplement to Pediatrics January 1, 2008;121:S115. Doi: 10.1542/peds.2007-2022JJJ) [vi] Barak V, Halperin T, and Kalickman I. The effect of Sambucol, a black elderberry-based, natural product, on the production of human cytokines: I. Inflammatory cytokines. Eur Cytokine Netw. 2001 Apr-Jun;12(2):290-6. PMID: 11399518 [vii] Raus K, Pleschka S, Klein P, Schoop R, and Fisher P. Effect of an Echinacea-Based Hot Drink Versus Oseltamivir in Influenza Treatment: A Randomized, Double-Blind, Double-Dummy, Multicenter, Noninferiority Clinical Trial. Curr Ther Res Clin Exp. 2015 Dec; 77: 66–72. PMCID: PMC4528044 [viii] Karimi S, Mohammadi A and Dadras H. The effect of Echinacea purpurea and Sambucus nigra L on H9N2 avian influenza virus in infected chicken embryo. Veterinarski Arhiv 2014;84(2):153-165. ISSN 0372-5480