A 2012 survey conducted by Vestcom titled, “Vitamins, Minerals, Supplements: The Retail Opportunity,” reported an even higher percentage, with 90% of U.S. consumers citing the strengthening of their immune system as the reason for taking vitamins, minerals or other nutritional supplements (1).
Therefore, retailers should take every opportunity to educate their clientele about the immune health support qualities of products they purchase regularly as well as recommend alternative or complementary products. Now is a particularly good time to do so, given the seasonal trends of consumers. For example, in a survey of the monthly sales of over-the-counter drugs, vitamins, herbal remedies and other health supplements at large retailers in Canada over three years (2014–2016), a clear trend emerges. Each year, sales peak in January after gradually increasing from the beginning of spring, then drop off drastically (2).
These are the months in which the threat of illness become very real and draws in customers wanting either protection or sweet relief. Dietary supplements can’t prevent, treat or cure diseases, but you can certainly listen to your customers, learn a bit about them and teach them how to support their immune health.
Best Medicine Is Not Needing MedicineIn addition to maintaining hygienic habits, supporting one’s immune health with dietary supplements can be an excellent way to reduce the chances of catching an illness. Modern medicine is an exceptional resource when we do fall ill, but we must not take it for granted and take independent measures to ensure our good health. This is particularly important in higher risk populations such as children and the elderly.
Modern day adults whether young or seasoned professionals, parents or both are also vulnerable to illness given the high level of stress they are subjected to. “Apparently over 75% of doctor visits are related to stress,” explains Marci Clow, MS, RDN, at Rainbow Light, Santa Cruz, CA. “When stress becomes chronic, the body can develop a resistance to cortisol and it ramps up production of cytokines, which are substances that promote inflammation and can lead to all sorts of health issues along with weakened immunity in those who are otherwise healthy.”
Eat Your VitaminsMany people find value in taking multivitamins daily to supplement their diets. Essential vitamins are needed for the body to function properly and must be acquired from food. However, our hectic lifestyles or personal neglect are not always conducive to getting our necessary daily value of vitamins and minerals, making multivitamins a helpful tool in supporting our health, particularly immune health.
Unfortunately, “several of the essential nutrients play critical fundamental roles in immune strength, yet a great majority of us are deficient,” says Michael Mooney, senior science advisor, SuperNutrition, Oakland, CA. For example, according to the U.S. Department of Agriculture (USDA), only 51% of the U.S. population has an adequate intake of vitamin C, perhaps the most well-known nutrient for supporting immune health (5).
Targeting these gaps is difficult to do with diet alone, making it necessary to supplement specific nutrients rather than take a blanket approach. Of course, it is wise to consult a physician first to determine your own personal gaps before pursuing supplementation. Vitamin C. Well established and often a go-to, who among us has not reached for a concentrated vitamin C supplement after feeling the onset of sniffles or sore throat? This, of course, is not necessarily the best course of action, as researchers have not amassed a solid library of data proving vitamin C stops illnesses in their tracks. Essential nutrients must be perpetually replenished through our diets so that the body can function optimally. Therefore, the best use of vitamin C supplements may be as a long-term regimen.
Neil E. Levin, CCN, DANLA, nutrition education manager of NOW Foods, Bloomingdale, IL, explains that vitamin C affects B- and T-cell function and histamine release as well as key immune cell production. “The effect of vitamin C supplements on the common cold is controversial; however, it is well known that vitamin C deficiency is associated with increased infections,” he adds.
So, long-term supplementation may make one less susceptible to infection. But, does the vitamin affect illness severity at all? Mooney cites a review of a 1975 meta-analysis of randomized, placebo-controlled trials that investigated the effect of vitamin C on the common cold. The analysis measured the difference between placebo and vitamin C based on the number of times subjects got sick in a year and the length of illnesses, finding that the vitamin C group had more favorable results (6). While the author of the original analysis found that the results were not significant enough to warrant consumption of vitamin C in large amounts, the review authors contest this conclusion (7).
According to them, the meta-analysis had some major shortcomings. Among these shortcomings was neglecting to take the dosage into account. “While 250 to 500 mg per day of supplemental vitamin C had no significant effect, 1,000 mg to 6,000 mg per day reduced the duration of cold symptoms by 21%,” explains Mooney (7). It should be noted that large amounts of vitamin C can cause digestive discomfort in some people, however.
In addition to dose response, something to consider when supplementing with vitamin C is the form. “Vitamin C is a water-soluble vitamin, meaning it washes out of your system,” explains Dorie Greenblatt, director of marketing, American Health, Ronkonkoma, NY. “To maintain the levels that our bodies require, we need to ensure that what we may lose throughout the day is continually replenished.”
That is why is she recommends a patented form of vitamin C (Ester-C) that offers better absorption and sustained presence in one’s system. The patented form, says Greenblatt, is clinically studied and developed to be retained by white blood cells for 24 hours, allowing users to take a single 1,000-mg dose daily for optimal health and wellness. It is also pH-neutral and non-acidic, making it gentle on the stomach.
Vitamin A.Despite the recognition that vitamin C is an important immune support ingredient, Mooney states that vitamin A is an under-recognized and critically important immune health nutrient. Levin concurs, explaining that “Vitamin A deficiency increases the severity and mortality risk of infections in general; in particular, measles and infections that lead to severe diarrhea.” Interest in vitamin A as an “anti-infective” therapy began as early as the 1920s on through the 1940s before the positive outcomes of antibiotic treatments overshadowed the results of vitamin A trials, reducing the amount of further research (8). However, more recent research is confirming vitamin A’s important immune support qualities.
“Today, it is recognized that vitamin A, through its metabolite retinoic acid, is able to induce gut homing receptors on T and B cells, allowing the trafficking of these cells to the intestine (and probably also to the inflamed tissues) to perform their effector functions and maintain an appropriate gastrointestinal balance between immunity and tolerance,” explains a 2016 review on the topic (9). Vitamin A’s role in people’s immune health is particularly important considering that 54% of the U.S. population is deficient in vitamin A, leaving more than half of our population susceptible to disease (5).
Its importance even extends prior to birth. That same 2016 review explains, “exposure to vitamin A in the womb is an important determinant for the development of secondary lymphoid organs during embryogenesis and after birth through induction of lymphoid tissue-inducer cells” (9). This basically means that vitamin A is also crucial to the development of an optimal immune system. For this, Mooney recommends that pregnant women receive their 5,000 IU daily value of vitamin A, though he suggests that 10,000 IU per day would be better and considered safe for pregnant women by the World Health Organization.Over 75% of doctor visits are related to stress.
— Marci Clow, MS, RDN, Rainbow Light
Vitamin D.Another very popular vitamin associated with immune health is vitamin D, which Mooney says 77% of the U.S. population is deficient in (10). “Vitamin D influences the regulation of immune function through its effect on the synthesis of cathelicidin, which protects against pathogenic agents, including Mycobacterium tuberculosis,” says Stachowicz et al. in a review (11). By maintaining the optimum levels of vitamin D, it will reinforce the immune system potentially reducing the amount of bacterial infections of the upper respiratory tract, which is particularly relevant for athletes (11).
In addition to being an important component of immune health, as is true with many nutrients, it cannot work on its own. “Vitamin D, without enough vitamin A, actually increased the number of fatal infections,” says Mooney. “Too much vitamin D without adequate vitamin A has actually been shown to cause toxicity by inducing a relative deficiency of vitamin A.” This means that vitamin A should be supplemented alongside vitamin D.
Mind Your Gut“People don’t realize that most of your immune cells reside in the gut, in the lining of the intestine,” says Mike Bush, president of Mayfield Heights, OH-based Ganeden and the International Probiotics Association. Josée Fortin, a naturopath and biochemist representing Bioforce USA, Ghent, NY, adds that this majority makes up about 70–80% of immune tissue.
“Bundles of lymphoid tissues known as ‘Payer’s Patches’ can be found all over our small intestine, and help protect it against infection by secreting lymphocytes,” explains Fortin. “Our intestinal flora also has a very important role to play in our immunity by enhancing the ‘natural killer’ effectiveness of the lymphatic system.” That is why a proper diet is conducive to optimal immune health and various dietary supplements influence the microbiome to support immunity.
Vitamin A.In a more focused analysis, one in vitro and in vivo study explored what effect vitamin A had on norovirus, which “causes approximately 90% of all epidemic nonbacterial outbreaks of gastroenteritis around the world, and is responsible for approximately 50% of all food borne outbreaks of gastroenteritis in the United States and many other countries” (12).
Results showed that vitamin A had an inhibitory effect against norovirus both in vitro and in vivo, directly or indirectly through microbiome changes, particularly Lactobacillus strains (12). This relationship with vitamin A and the microbiome underlines the significance of a properly balanced gastrointestinal flora to our wellbeing, extending beyond products specifically designed for supporting gut health.
Probiotics.This has become an incredibly popular category for both dietary supplements and functional foods, which can make for a saturated and confusing marketplace for many consumers. “Everything is strain specific,” advises Bush. This means not all probiotics are created equal and we should look out for ingredients that are studied extensively and have demonstrated effectiveness in areas we wish to address, in this case, immune health. Speaking of his firm’s patented ingredient GanedenBC30, Bush says “when faced with bacterial or viral challenges, the immune system will express higher levels of pro-immune cytokines.”
Shaheen Majeed, marketing director at Sabinsa Corporation, East Windsor, NJ, echoes this, saying, “When normal gut microflora is destroyed due to poor immunity, infection or antibiotic use, the harmful bacteria tend to colonize the intestinal lining and further reduce immunity. Studies also indicate that certain strains of Bacillus coagulans have significant effects on phagocytosis which plays an important role in preventing infections.” This is supported by an in vivo study of Sabinsa’s patented LactoSpore probiotic, a shelf-stable L(+)Lactic acid producing strain of B. coagulans in combination with Cinnulin, an aqueous extract of cinnamon (13).
To further support the intestinal flora, Fortin recommends a concentrated whey rich in L(+) Lactic acid (Molkosan by A. Vogel). Probiotic bacteria need an optimal pH to grow, but factors such as poor diet and stress can alter our gastrointestinal pH. As a prebiotic, this concentrated whey can “naturally promote the growth of a variety of good bacteria in our gut while it also helps the elimination of harmful bacteria and Candida by correcting the intestinal pH,” says Fortin.
Another product that complements probiotics is a proprietary avian immunoglobulin (IgY as IgY Max) whose antibodies, says Sue Hewlings, chief science officer, IgY Nutrition, Oklahoma City, OK, help to eliminate the non-beneficial bacteria in the gut while also reducing inflammation. This allows the good microbes to prosper and do their job.
Yeast.A more specialized ingredient targeting immune health is a proprietary yeast fermentate (EpiCor), which has eight human clinical trials making the ingredient eligible to bear the claim in Canada, “Helps reduce the incidence of cold and flu symptoms.” You will not, however, see this on product labels in the United States as dietary supplements are prohibited from making claims and must stick to structure function claims.
Despite this, research supports the ingredient’s use for modulating immune health, even in the event of illness. Two separate randomized, double-blind, placebo-controlled trials studied the effects of the fermentate on cold and flu-like symptoms. In the first, published in 2008, 112 subjects who had recently been vaccinated for seasonal influenza took either 500 mg of EpiCor or placebo for 12 weeks. Results showed that it significantly reduced the incidence and duration of cold and flu compared to placebo (14).
In the second, published in 2010, 116 unvaccinated subjects were also given either 500 mg of EpiCor or placebo for 12 weeks. Results showed that the ingredient significantly reduced the incidence of cold and flu, though in this case, not duration (15). “For acute use, EpiCor has shown some immune benefits such as activating the white blood cells called Natural Killer Cells and increasing serum antioxidant capacity in as little as 2 hours,” explains Robinson, “For the full benefits of EpiCor, including increased sIgA antibodies and gut support, 500 mg of EpiCor should be taken every day.”
The yeast fermentate’s function in the gut is as a prebiotic. According to an in vitro study, “Gradual changes, indicative of an adaptation of the microbiota over time, were observed in both colonic microbial community activity (e.g., butyrate production) and composition in the gut lumen (decrease of potential pathogens and increased lactobacilli concentrations) and mucus layer (e.g., increased adhesion of lactobacilli)” (16).
Rice bran.Hank Cheatham, vice president of marketing and sales at Daiwa Health Development, Gardena, CA, recommends a proprietary Rice Bran Arabinoxylan Compound (RBAC) (PeakImmune4), a polysaccharide dietary fiber derived from rice bran, modified by an enzyme from Shiitake mushrooms. Clinical studies and research, says Cheatham, have shown the ingredient to enhance the immune response by increasing the count and activity of the body’s white blood cells, enhance natural killer (NK) cell function and increase the count of T and B lymphocytes.
One study, testing the effects of Arabinoxylan rice bran on neuroblastoma, a cancer typically found in the adrenal glands, showed that the ingredient “upregulates NK cell activation markers, stimulates NK cell cytotoxic activity against neuroblastoma in vitro and in vivo and selectively augments the expansion of NK cells” (17).
Immune Support for AthletesImmune health can be compromised in multiple ways, so it’s also important to consider how you utilize dietary supplements to achieve proper support. Probiotics, for example, are an important supplement for athletes to consider. “It is through sports and heavy training that you’ll see lots of immune suppression,” explains Bush. This is due to the increase in stress hormones such as cortisol as well as inflammatory markers, says Hewlings. She does add, however, that if you have a sedentary lifestyle, small to moderate exercise enhances immune function.
That is why the sports nutrition category is a relevant space for probiotics and an important factor for athletes to consider when purchasing sports supplements, even if immune support may not be the first priority. A recent study in which athletes were either given protein on its own or in combination with GanedenBC30, it was observed that the probiotic supported protein utilization resulting in decreased soreness after damaging exercise and faster recovery (18).
IgY has also shown promise in sports nutrition in addition to immune health. Citing a small study conducted by the College of Charleston, Hewlings explains that 24 active individuals supplementing their diet with IgY for 10 days experienced 16% better recovery as measured by bench press and endurance, as well as decreased muscle soreness (19).
Another functional immune support ingredient is a natural beta 1,3/1,6 glucan derived from the cell wall of a highly purified, proprietary strain of baker’s yeast (Wellmune) that has been incorporated into products including food, beverages, and sports supplements in over 60 countries, says Donald Cox, Ph.D., R&D director of Wellmune, Eagan, MN. Safe for everyday use, the ingredient is able to boost immune function without overstimulation, he explains.
In its overall support of immune health, one randomized, double-blind, placebo-controlled trial, published in Nature, observed a 22% reduction in the duration of upper respiratory tract infection symptoms in fourth-year medical school students who took the 250 mg of the beta glucan for 90 days (20). For athletes looking to minimize the amount of supplements or pills they take, like probiotics, it’s a good complement to sports supplements by providing an added layer of support on the immune front.
“Athletes benefit from the ingredient’s ability to help athletes stay healthy, enabling them to train harder and longer by preventing immune suppression during intense exercise training,” explains Cox, citing a clinical study published in the Journal of Sports Science and Medicine. In the study of 182 marathon runners, those who took 250 mg of Wellmune for four weeks experienced a 22% reduction of upper respiratory tract infection symptoms (21).
By allowing athletes to more effectively train, the proven immune support of these ingredients will make them less vulnerable to illnesses that would further hamper their progress.
MineralsZinc.“Zinc is a major ingredient in lozenges and other products designed to prevent and soothe respiratory tract infections,” explains Clow. “Zinc affects multiple aspects of the immune system, from the barrier of the skin to gene regulation within white blood cells.” Levin agrees, elaborating further that zinc is associated with macrophage and neutrophil functions, natural killer cell response, and the activation of T-lymphocytes. He also adds that, “Even a mild zinc deficiency can impair immune function and wound healing, making the elderly more susceptible to pneumonia, infections and diarrhea, and skin ulcers.”
In a meta-analysis of three randomized trials, it was observed that following the implementation of high-dose zinc acetate lozenges, the duration of several cold symptoms was reduced, including nasal discharge by 34%, nasal congestion by 37%, sneezing by 22%, scratchy throat by 33%, sore throat by 18%, hoarseness by 43%, and cough by 46% (22). The study concluded, “Given that the adverse effects of zinc in the three trials were minor, zinc acetate lozenges releasing zinc ions at doses of about 80 mg/day may be a useful treatment for the common cold, started within 24 hours, for a time period of less than two weeks” (22).
Selenium.“Selenium has what the NIH calls ‘antioxidant’ abilities to help protect against damaging free radicals,” explains Levin. These abilities come from being an integral part of antioxidant enzymes such as glutathioneperoxidase, thioredoxinreductase, and iodothyronine deiodinase, which protect cells during oxidation (23). Further, its role in immune health is to stimulate the immune system to increase the production of antibodies and promote the increase of T cells and macrophages (23). In extreme cases of HIV infection, supplementation with selenium has been shown to help inhibit the progression of the virus into AIDS (23), though one should never consider it to be a cure.
HerbalEchinacea.One of the most popular herbs in the United States, Echinacea is a perennial herb native to Midwestern North America, which evidence suggests had been used by Native Americans for 400 years to treat infections and wounds (24). Clearly, interest has continued into modernity and some research suggest the herb does in fact have immune modulation properties.
In a meta-analysis of six randomized controlled trials comprising 2,458 participants, published in Advances in Therapy, echinacea was observed to reduce the risk of respiratory infections, virologically confirmed recurrent infections, as well as less frequency of complications that included pneumonia and tonsillitis/pharyngitis (24). It was also noted that in those with higher susceptibility from stress or immunological weakness, the herb halved their risk of respiratory infections (25).
One specific randomized, placebo-controlled trial studied the safety and efficacy of echinacea for the prevention of the common cold (26). Results showed a 26% difference in cumulative episodes of illness with 188 cold events with a collective duration of 850 days in the placebo group compared to 149 episodes with collective duration of 672 days in the echinacea group (26). There was also a 59% difference in recurring infections with 65 infections in 28 participants in the echinacea group compared to 100 infections in 43 participants in the placebo group (26).
These results, says Fortin, demonstrate that “those at high risks (elderly, children, smokers, those with high stress, lungs problems, insomnia) should take [Echinacea] every day during flu season to help reduce the risk of developing a cold, flu or any complications they can trigger.”
Black elderberry.Sambucus nigra, more commonly known as black elderberry is a time-honored European cold and flu remedy typically in the form of a tea, explains Clow. Erin Stokes, ND, medical director, MegaFood, Derry, NH, who claims elderberry to be her favorite herb for acute and long term use, describes it as a dark purple berry from an elder tree which is rich in protective antioxidants called anthocyanins.
A few studies have provided evidence for its anecdotal healing properties. One 1995 double-blind, placebo-controlled trial studied the effects of elderberry on individuals living in a kibbutz during an influenza outbreak over the course of six days (27). Results showed a significant improvement of symptoms in 93% of cases in the elderberry group within two days while the placebo group only saw improvement of 91% of cases within six days. Additionally, within three days, 90% of elderberry treated subjects were cured.
In a more recent randomized, double-blind, placebo-controlled trial of cold duration and symptoms in air travelers, while the difference in incidence of colds was not significantly different, the duration of symptoms in the elderberry group was reduced by two days (28). There was also a less severe symptom load in travelers taking elderberry.
FungiMushrooms have also been used traditionally to reinforce the immune system and treat symptoms. For immune support, Mark J. Kaylor, founder of the Radiant Health Project, representing Mushroom Wisdom, East Rutherford, NJ, recommends Reishi extract. “Long used as a Shen tonic in traditional Chinese medicine to provide emotional support and nourishment, Reishi also brings decades of research on its ability to modulate our immune system,” he explains.
In China, studies have shown improvement in patients with chronic bronchitis. One study with over 2,000 patients suffering from chronic bronchitis showed 60–90% improvement within two weeks of taking Reishi syrup (29). Reishi has even been used as an adjunctive therapy for cancer. In one placebo-controlled study, 48 patients with advanced tumors were given Reishi mushroom extract for 30 days. Result showed an immune-modulating effect in which T-lymphocytes increased and CD8 counts decreased (29).
For children, Kaylor recommends a Maitake extract (Maitake D-Fraction) as it comes in a liquid form that is pleasant tasting. “If put in the child’s juice or even water, they are likely to not even notice it,” he says. Similar to Wellmune, Maitake’s immune modulation has been linked to the beta glucans in the mushroom (29).
PhytosterolsJay Levy, director of sales, Wakunaga of America Co., Ltd, Mission Viejo, CA recommends phytosterols to support immune health. More specifically, he suggests a well-studied combination of two compounds called sterols and sterolins (Moducare). “Sterols are cholesterol-like fats that are found in all plant-based foods,” explains Levy. “Sterolins are glucosides, which are molecular structures that are fixed to the sterol.”
Studied extensively over the past 30 years, some research, he says, has determined that the combination improves the balance of Th1 and Th2 cells, enhancing cellular immunity when needed and down-regulating overactive immune response. A blend of these two phytosterols was even tested in a randomized, placebo-controlled trial on patients with pulmonary tuberculosis (30). “After six months, those in the treatment group showed a significant increase in T-cells and specialized immune cells called eosinophils,” explains Levy.WF
References
- https://www.statista.com/statistics/308645/reasons-us-consumers-use-vitamin-mineral-nutritional-supplements/, accessed 9/19/2016.
- https://www.statista.com/statistics/473974/monthly-sales-of-otc-drugs-and-supplements-at-large-retailers-in-canada/, accessed 9/19/2016.
- “FDA: Cutting-Edge Technology Sheds Light on Antibiotic Resistance.” www.fda.gov/forconsumers/consumerupdates/ucm519931.htm, accessed 9/19/2016.
- https://www.cdc.gov/drugresistance/biggest_threats.html, accessed 9/20/2016.
- https://www.ars.usda.gov/northeast-area/beltsville-md/beltsville-human-nutrition-research-center/docs/new-jersey/, accessed 9/20/2016.
- H. Hemilä and Z.S. Herman. “ Vitamin C and the common cold: a retrospective analysis of Chalmers’ review.” J Am Coll Nutr. 14(2):116-23. 1995.
- T.C. Chalmers. “ Effects of ascorbic acid on the common cold. An evaluation of the evidence.” Am J Med. 58(4):532-6. 1975.
- Semba, R.D. “Vitamin A as ‘Anti-Infective’ Therapy, 1920–1940,” J Nutr. 129: 783-791. 1991.
- M.R. Bono, et al. “ Retinoic Acid as a Modulator of T Cell Immunity,” Nutrients. 8: 349. 2016.
- A.A. Ginde, et al. Demographic differences and trends of vitamin D insufficiency in the US population, 1988-2004. Arch Intern Med. 2009 Mar 23;169(6):626-32.
- Stachowicz et al. “ The role of vitamin D in health preservation and exertional capacity of athletes.” Postepy Hig Med Dosw. 70: 637-643. 2016.
- H. Lee and G. Ko. “ Antiviral effect of vitamin A on norovirus infection via modulation of the gut microbiome,” http://www.nature.com/articles/srep25835, accessed 9/26/2016.
- http://www.lactospore.com/wp-content/uploads/2016/07/In-vivo-2013.pdf
- M. Moyad, et al. “Effects of Modified Yeast Supplement on Cold/Flu Symptoms.” Urologic Nursing. 28(1): 50-55. 2008.
- M. Moyad, et al. “Immunogenic Yeast-based Fermentate for Cold/Flu-like Symptoms in Nonvaccinated Individuals.” The Journal of Alternative and Complementary Medicine. 16(2): 213-218. 2010.
- S. Possemiers, et al. “ A Dried Yeast Fermentate Selectively Modulates both the Luminal and Mucosal Gut Microbiota and Protects against Infl ammation, As Studied in an Integrated in Vitro Approach.” J. Agric. Food Chem.61 (39): 9380–9392. 2013.
- A. Perez-Martinez, et al. “ Arabinoxylan rice bran (MGN-3/Biobran) enhances natural killer cell-mediated cytotoxicity against neuroblastoma in vitro and in vivo.” Cytotherapy. 17(5):601-12. 2015.
- Jäger, et al., “ Probiotic Bacillus coagulans GBI-30, 6086 reduces exercise-induced muscle damage and increases recovery.” https://peerj.com/articles/2276/, accessed 9/27/2016.
- T. Scheet, et.al.”Increased muscular strength and enhanced muscle repair with hyperimmune egg protein supplement.”
- R. Fuller, et al. “Influence of Yeast-Derived 1,3/1,6 Glucopolysaccharide on Circulating Cytokines and Chemokines with Respect to Upper Respiratory Tract Infections.” Nutrition. 28(6):665-669.
- S. Talbott & J. Talbott. “Effect of Beta 1, 3/1, 6 Glucan on Upper Respiratory Tract Infection Symptoms and Mood State in Marathon Athletes.” Journal of Sports Science and Medicine. 8(4): 509–515. 2009.
- H. Hemilä and E. Chalker. “ The effectiveness of high dose zinc acetate lozenges on various common cold symptoms: a meta-analysis.” BMC Family Practice. 16:24. 2015.
- M. Kieliszek and S. Błazejak. “Current Knowledge on the Importance of Selenium in Food for Living Organisms: A Review.” Molecules. 21, 609. 2016.
- http://umm.edu/health/medical/altmed/herb/echinacea
- A. Schapowal. “Echinacea reduces the risk of recurrent respiratory tract infections and complications: a meta-analysis of randomized controlled trials.” Adv Ther.32(3):187-200. 2015.
- M. Jawad et al. “ Safet y and E fficacy Profile of Echinacea purpurea to Prevent Common Cold Episodes: A Randomized, Double-Blind, Placebo-Controlled Trial.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3457740/pdf/ECAM2012-841315.pdf, accessed 9/28/2016
- Z. Zakay-Rones, et al. “Inhibition of several strains of influenza virus in vitro and reduction of symptoms by an elderberry extract (Sambucus nigra L.) during an outbreak of influenza B Panama.” J Altern Complement Med. 1(4):361-9. 1995.
- E. Tiralongo, et al. “Elderberry Supplementation Reduces Cold Duration and Symptoms in Air-Travellers: A Randomized, Double-Blind Placebo-Controlled Clinical Trial.” Nutrients. 8(4). 2016.
- M. Stengler. “The Health Benefits of Medicinal Mushrooms.” Basic Health Publications, Inc. Laguna Beach, CA. 2005.
- P.R. Donald, et al. “A randomised placebo-controlled trial of the efficacy of beta-sitosterol and its glucoside as adjuvants in the treatment of pulmonary tuberculosis.” Int J Tuberc Lung Dis.1(6):518-22. 1997.
