Targeted Natural Interventions
In addition to consuming a healthy, balanced diet and exercising regularly, the following natural interventions may help avoid influenza infection or ease flu symptoms (Siu 2012; Gardner 2011; Louria 2007).
Vitamin D – Vitamin D has a significant role in the regulation of the human immune system and may reduce the risk of certain viral and bacterial infections by modulating immune response to such pathogens (Beard 2011; Grant 2010). Vitamin D blood levels appear to be related to respiratory infections, in that a 4 ng/mL increase in vitamin D levels correspond to about a 7–10% decrease in infection risk (Berry 2011; Cannell 2011). Furthermore, vitamin D deficiency may be linked to an increased risk of influenza and respiratory tract infection (Beard 2011; Cannell 2008). In a comprehensive review, researchers analyzed data from 10,933 participants in 25 randomized controlled trials looking at the effect of vitamin D on risk of acute respiratory infections, such as colds and influenza. The analysis found that those receiving daily or weekly vitamin D supplements, in doses ranging from 300 IU to 4000 IU per day, had a 19% reduction in acute respiratory infection risk, and those with vitamin D deficiency (levels below 25 nmol/L or 10 ng/mL) at the beginning of the trial experienced a greater protective effect. A risk reduction was not seen in participants who received individual large doses of vitamin D (30,000 IU or more), either once or at intervals of one to three months, whether alone or in addition to daily or weekly doses (Martineau 2017). In one clinical trial, 1200 IU of vitamin D reduced influenza A incidence by 64% compared with placebo among schoolchildren who had not been taking any additional vitamin D supplements (Urashima 2010). Similarly, in a 3-year trial, postmenopausal African American women taking 2000 IU of vitamin D daily reported significantly fewer incidence of influenza compared to those taking a placebo (Aloia 2007).
Vitamin D is derived in the skin from its precursor 7-dehydrocholesterol following stimulation by ultraviolet B (UVB) light (eg, sunlight). It is then eventually converted to 1,25-dihydroxyvitamin D3, which combines with vitamin D receptors to trigger an immune response that may be effective against influenza infection (Shaman 2011). Studies suggest that vitamin D also helps prevent excessive expression of inflammatory cytokines (Cannell 2006, 2011). Because of this, it may help to prevent the occurrence of cytokine storm (Grant 2009).
Life Extension suggests an optimal 25-hydroxyvitamin D blood level of 50 – 80 ng/mL. If you do not already maintain a blood level of 25-hydroxyvitamin D over 50 ng/mL, then take 50, 000 IU of vitamin D the first day and continue for 3 more days. Slowly reduce the dose to around 5000 IU vitamin D daily. If you already take around 5000 IU of vitamin D daily, then you probably do not need to increase your intake.
Vitamin C – In order to protect against infections (particularly viral), the human immune system requires a sufficient daily intake of vitamin C. Vitamin C enhances the production and action of white blood cells; for example, it increases the ability of neutrophils (a type of white blood cell) to attack and engulf viruses (Heimer 2009; Jariwalla 1996; Anderson 1984). Daily 1-gram (g) doses of vitamin C have been shown to reduce the incidence and severity of a cold (Holt 2010). Additionally, very high doses of vitamin C administered before or after symptom onset have been shown to reduce reported cold and flu symptoms. Among asymptomatic young adults 18–30 years of age, three 1000 mg doses of vitamin C daily, or hourly doses of 1000 mg vitamin C for the first 6 hours after symptom onset followed by 1000 mg doses of vitamin C 3 times daily in symptomatic individuals, reduced reported flu and cold symptoms by 85% compared to placebo (Gorton 1999).
Zinc – Zinc is required for numerous metabolic processes and serves as a cofactor for a large number of enzymes (Eide 2011; Classen 2011). Zinc plays an important role in maintaining healthy immune function (Roxas 2007). Zinc deficiency, which is common among the elderly, can impair cell-mediated immunity. This, in turn, can increase the risk of infection. Rectifying zinc deficiency through supplementation has been shown to be efficacious for a variety of infections. This is because zinc affects the expression of interleukin-2, which helps the immune system ward off viruses (Roxas 2007). In a comprehensive analysis of the effects of zinc lozenges on viral upper respiratory tract infections, doses greater than 75 mg daily were shown to reduce symptom duration by 20 to 42%. The authors of this study emphasized that doses lower than 75 mg daily did not shorten sickness duration (Hemila 2011). Life Extension Magazine® published a comprehensive overview of the evidence suggesting that zinc acetate lozenges dissolved in the mouth every two waking hours may be an ideal approach during the early stages of upper respiratory infections.
Selenium – Selenium serves as a powerful antioxidant in nearly all human tissues (Hoffmann 2008). In addition, selenium boosts the immune system and can provide protection against some pathogens (Hoffmann 2008; Goldson 2011). Data show that selenium deficiency promotes the spread of influenza by increasing its virulence, and increases susceptibility to viral infection by interfering with human influenza-induced host defense responses (Jaspers 2007; Stỳblo 2007; Beck 2003). An animal model showed a selenium-deficient diet was associated with significantly higher mortality from influenza than a selenium-supplemented diet (Yu 2011).
Vitamin E – Vitamin E is not only a potent antioxidant, but it is also involved in a variety of physiologic processes, ranging from cognitive performance to immune function (Dror 2011). For example, vitamin E supplementation has been shown to enhance certain functions of the human immune system and decrease influenza virus titers in preclinical models of influenza (Han 2000). Animal studies have shown that vitamin E deficiency may precipitate viral genome changes that increase virulence and may contribute to greater severity of influenza (Louria 2007).
Lactoferrin – Lactoferrin is an iron-binding component of whey protein (Roxas 2007; Orsi 2004). It is known to possess some immune-modulating effects as well as an ability to exert a broad spectrum of activity against bacteria, fungi, protozoa, and viruses (Roxas 2007; Orsi 2004). Laboratory studies reveal that lactoferrin inhibits viral infection by interfering with the ability of certain viruses to bind to cell receptor sites and prevents entry of viruses into host cells (Waarts 2005; Berlutti 2011). Lactoferrin may be beneficial for alleviating symptoms or complications of viral infections, like the flu, because it suppresses free radical-mediated damage and decreases availability of essential metals to microbial cells pathogens (Roxas 2007).
Elderberry – The purplish-black fruits of the elderberry plant are a rich source of antioxidants and have long been considered a folk remedy for the treatment of influenza (Ozgen 2010). Clinical studies have revealed that the extract of elderberry appears to be a safe, effective, and cost-efficient treatment option for those infected with influenza. Laboratory research indicates this clinical effect is achieved through elderberry’s ability to interfere with the influenza virus’ replication process (Zakay-Rones 2004). A 2009 study demonstrated that elderberry extract was capable of inhibiting influenza H1N1 infection by binding to the outside of the virus and keeping it from invading host cells (Roschek 2009).
Green tea – Green tea, which contains a powerful antioxidant called epigallocatechin gallate (EGCG), has been utilized as a medicinal product for the last 4700 years (Cooper 2012; Rowe 2007). EGCG has a variety of beneficial properties with regard to influenza. For example, it has been shown to directly kill the influenza virus and decrease the number of viruses found in blood during chronic viral infection. In addition, EGCG can decrease flu-like symptoms by reducing inflammation (Rowe 2007). The antiviral effects of green tea have been demonstrated for nearly all age groups (Park 2011; Rowe 2007; Guralnik 2007).
Beta-glucans - Beta-glucans are naturally-occurring glucose polymers that constitute the cell walls of certain plants and fungi (Akramiene 2007; Medeiros 2012; Cordeiro 2012). These polysaccharides have been shown to increase host immune defense and are associated with enhanced macrophage and natural killer cell function (Pence 2012; Akramiene 2007).
Korean researchers demonstrated anti-viral properties of beta-glucans against influenza in a swine model. In this experiment, one group of piglets received beta-glucans for 3 days before being infected with swine flu, while another group received only placebo. The lungs of piglets not given beta-glucans showed significantly more damage than those that received beta-glucans. Furthermore, piglets pre-treated with beta-glucan had significantly higher concentrations of natural immune-enhancing substances, including interferon-gamma, in fluid obtained from the lungs within a week of infection. Researchers concluded that beta-glucans reduced signs of lung disease and the viral replication rate in the piglets (Jung 2004).
In another experiment, young piglets were exposed to porcine reproductive and respiratory syndrome virus. White blood cells were then removed and exposed to varying concentrations of beta-glucans. Beta-glucans increased the production of interferon-gamma in a dose-dependent manner, leading scientists to conclude that soluble beta-glucans may enhance innate viral immunity (Xiao 2004).
Andrographis – Andrographis paniculata, an annual plant used as a medicinal herb among Asian cultures for centuries, has been reported to have anti-inflammatory, anti-hypertensive, anti-viral, and immune-modulating properties (Yang 2010; Akbar 2011). Chief among androgrpahis’ active constituents are andrographolides. Chinese researchers showed that an andrographolide called andrographanin enhances mobility of white blood cells in response to cytokine stimulation (Ji 2005), which may allow for more efficient immune response against pathogens. A 2009 study found that an extract of andrographis enhanced immune function, as well as reversed drug-induced immunosuppression (Naik 2009). In a clinical trial conducted on 540 people diagnosed with influenza, andrographis was shown to speed flu recovery and reduce the risk of complications (Kulichenko 2003).
Probiotics – Probiotics are “friendly” microorganisms that confer health benefits to the host (Gilliland 2001; MacDonald 2010; Leyer 2009). Clinical studies suggest that certain probiotics may help prevent viral respiratory tract infections by modulating the immune system. Probiotics may also be useful for treating influenza, given their association with a reduction in severity and duration of symptoms caused by common upper respiratory tract infections (de Vrese 2008; MacDonald 2010; Wolvers 2010; Vouloumanou 2009; Baron 2009).
Probiotics may be useful for managing infectious diseases because of their potential for stabilizing the micro-flora of the gut, enhancing resistance against pathogenic colonization, and modulating immune function (Wolvers 2010). For example, a probiotic strain of Bacillus coagulans has been shown to significantly increase T-cell production upon experimental exposure of blood samples from healthy people to an influenza A virus (Kimmel 2010; Baron 2009). Probiotics, such as Lactobacillus plantarum, have also demonstrated immune-stimulating effects that may help improve influenza vaccination responses among the elderly (Bosch 2012).
Reishi - Reishi mushrooms attack and reverse immunosenescence – age-related decline in immune system function – through the combined effects of three compounds: first, a group of long-chain carbohydrates called polysaccharides, second, a unique protein named LZ-8 and third, a small group of steroid-like molecules called triterpenes (Bao 2001; Xu 2011; Yeh 2010). Reishi mushrooms’ immune-stimulating effects play directly into their ability to fight off both bacterial and viral infections (Karaman 2010). Both polysaccharide and triterpene components of the mushrooms contribute to this activity (Iwatsuki 2003; Z. Li 2005). Reishi extracts have been shown to inhibit growth of a number of bacterial germs, especially infections of the urinary and digestive tracts. They also enhance the activity of standard antibiotics in treating bacterial infections. Scientists evaluated combinations of Reishi with four different antibiotics, and found an additive effect in most cases. And true synergy (the effect of both exceeds the combined effects of either alone) was demonstrated with the combination of Reishi and cefazolin, a common antibiotic for surgical infections (Yoon 1994).
But it’s in the realm of viral disease that Reishi mushrooms truly flex their muscles (Eo 1999a,b). In laboratory cell cultures, Reishi mushrooms stop or slow growth of influenza, HIV, hepatitis B, and many other viruses (Eo 1999a,b; Y. Q. Li 2006; el-Mekkawy 1998). Additional laboratory studies have shown that extracts from Reishi are especially effective against viruses in the herpes virus family, which include not only the well-known oral and genital herpes infections, but also the viruses that cause chickenpox and shingles, and the Epstein- Barr virus, a viral cause of certain lymphomas (Iwatsuki 2003; Eo 1999a,b; Eo 2000; Oh 2000). In human studies, supplementation with Reishi dramatically shortens the time until symptomatic relief by more than 50% in people with oral or genital herpes, and in people with shingles, the excruciating adult sequel to childhood chickenpox infection (Hijikata 2005; Hijikata 2007).
Enzymatically modified rice bran - Enzymatically modified rice bran is made by fermenting rice bran with enzymes extracted from the shiitake mushroom (Lentinus edodes). Through the fermentation process, immunologically active polysaccharides, including one called arabinoxylan, become more bioavailable (Choi 2014).
Animal research provides support for the immune-stimulating ability of enzymatically modified rice bran. In an experimental model of immune senescence using aged mice, treatment with enzymatically modified rice bran led to increased NK cell activity (Ghoneum, Abedi 2004). And, in a study in rats, immune cells from those fed enzymatically modified rice bran for two weeks exhibited a stronger response to an immune challenge (Giese 2008).
A number of laboratory studies performed on immune cells further demonstrate the immune-enhancing effects of enzymatically modified rice bran. Human natural killer (NK) cells treated with fermented rice bran extract increased their production of the immune-stimulating cytokines interferon-gamma and tumor necrosis factor-alpha (Ghoneum 2000). Human monocytes, macrophages, and neutrophils have been shown to increase their phagocytic activity (ie, engulfing and digestion of foreign substances) upon treatment with enzymatically modified rice bran (Ghoneum, Matsuura 2004; Ghoneum 2008). Enzymatically modified rice bran was also found to stimulate maturation and increase activity in human immature dendritic cells, which are immune cells that help activate other immune cells (Cholujova 2009; Ghoneum 2011; Ghoneum 2014).
Enzymatically modified rice bran and its arabinoxylan fraction may protect against viral infections. In healthy individuals, arabinoxylan increased levels of interferon-gamma (Choi 2014), a cytokine essential to the body’s antiviral defenses (Chesler 2002). Arabinoxylan was found in one study to protect against upper respiratory viral infections (common colds) in older people. In a double-blind, placebo-controlled, crossover trial, 36 subjects between 70 and 95 years of age received both 500 mg arabinoxylan and placebo, each for six weeks. Scores measuring total common cold symptoms were three times higher and duration of symptoms twice as long in participants during the placebo phase compared with the arabinoxylan phase. In those with low NK cell activity, the increase in NK cell activity was more than double in the arabinoxylan group compared with placebo (Maeda 2004).
- Dehydroepiandrosterone (DHEA), a multifunctional steroid hormone derived from cholesterol, has antiviral activity and enhances host resistance to infections (Romanutti 2010; El Kihel 2012; Torres 2012; Kuehn 2011; Padgett 2000b; Prom-Wormley 2011). The enhanced immune response conferred by DHEA allows it to have activity against a wide range of viral, bacterial, and parasitic infections (Caetano 2009; Powell 2006). Low levels of DHEA have been shown to suppress the host’s antibody response by altering cytokine production (eg, TNF-α and IL-10) (Powell 2006). Higher baseline DHEA levels appear to result in better immunization against influenza (Corsini 2006; Degelau 1997). In a 20-week clinical trial, 50 mg of DHEA daily bolstered white blood cell populations among aging men. Immune cell activity was enhanced as well (Khorram 1997).
- Melatonin is a hormone produced in the brain by the pineal gland. In addition to regulating the sleep-wake cycle and acting as an antioxidant, melatonin is also capable of influencing the state of the immune system both directly and indirectly. Melatonin has been shown to combat many types of viral infections (Srinivasan 2012; Arushanian 2002; Boga 2012). While the mechanism behind melatonin’s involvement with immune function is still being studied, research has shown that its binding to immune-governing cells called T-helper cells can trigger a cascade of events leading to an enhanced immune responsiveness. In addition, melatonin administration can increase the production of antibodies (Bonilla 2004). In some instances, melatonin also acts as an anti-inflammatory mediator (da Silveira Cruz-Machado 2012); thus, may be preventive or supportive for cytokine storm. Because age-related impairment of the immune system usually begins to occur around age 60 and coincides with decreased melatonin concentrations, melatonin supplementation may be beneficial among seniors (Srinivasan 2005).