Research - Colds
Zinc for the common cold
Background: The common cold is one of the most widespread illnesses and is a leading cause of visits to the doctor and absenteeism from school and work. Trials conducted since 1984 investigating the role of zinc for the common cold symptoms have had mixed results. Inadequate treatment masking and reduced bioavailability of zinc from some formulations have been cited as influencing results.
Objectives: To assess the effect of zinc on common cold symptoms.
Search strategy: We searched CENTRAL (2010, Issue 2) which contains the Acute Respiratory Infections Group's Specialised Register, MEDLINE (1966 to May week 3, 2010) and EMBASE (1974 to June 2010).
Selection criteria: Randomised, double-blind, placebo-controlled trials using zinc for at least five consecutive days to treat, or for at least five months to prevent the common cold.
Data collection and analysis: Two review authors independently extracted data and assessed trial quality.
Main results: We included 13 therapeutic trials (966 participants) and two preventive trials (394 participants). Intake of zinc is associated with a significant reduction in the duration (standardised mean difference (SMD) -0.97; 95% confidence interval (CI) -1.56 to -0.38) (P = 0.001), and severity of common cold symptoms (SMD -0.39; 95% CI -0.77 to -0.02) (P = 0.04). There was a significant difference between the zinc and control group for the proportion of participants symptomatic after seven days of treatment (OR 0.45; 95% CI 0.2 to 1.00) (P = 0.05). The incidence rate ratio (IRR) of developing a cold (IRR 0.64; 95% CI 0.47 to 0.88) (P = 0.006), school absence (P = 0.0003) and prescription of antibiotics (P < 0.00001) was lower in the zinc group. Overall adverse events (OR 1.59; 95% CI 0.97 to 2.58) (P = 0.06), bad taste (OR 2.64; 95% CI 1.91 to 3.64) (P < 0.00001) and nausea (OR 2.15; 95% CI 1.44 to 3.23) (P = 0.002) were higher in the zinc group.
Authors' conclusions: Zinc administered within 24 hours of onset of symptoms reduces the duration and severity of the common cold in healthy people. When supplemented for at least five months, it reduces cold incidence, school absenteeism and prescription of antibiotics in children. There is potential for zinc lozenges to produce side effects. In view of this and the differences in study populations, dosages, formulations and duration of treatment, it is difficult to make firm recommendations about the dose, formulation and duration that should be used.
Source : Cochrane Library via Singh M, Das RR. Zinc for the common cold. Cochrane Database of Systematic Reviews 2011, Issue 2. Art. No.: CD001364. DOI: 10.1002/14651858.CD001364.pub3
Link to Full Article
Swiss Echinacea Extract Shown Safe and Effective in Preventing Colds in Largest Echinacea Clinical Trial
Reviewed: Jawad M, Schoop R, Suter A, Klein P, Eccles R. Safety and efficacy profile of Echinacea purpurea to prevent common cold episodes: a randomized, double blind, placebo-controlled trial. Evid Based Complement Alternat Med. 2012:841315. Epub 2012 Sep 16.
Colds and flu, associated with a variety of viral infections, are characterized by symptoms such as sore throat, cough, and nose irritations, as well as systemic complaints such as headache, malaise, and fever. The common cold alone causes great discomfort and is a major reason for school and work absences, as well as physicians visits.1 Preventative strategies have included antiviral agents or vaccines targeted towards infection prevention or inhibition of viral replication; however, common problems arise with adverse side effects (ASE) and/or the failure to protect certain populations.
Echinacea (Echinacea purpurea, Asteraceae) is used widely as an immune system modulator as well as in common cold prevention strategies.2 Many clinical studies investigating the use of echinacea in cold prevention have shown conflicting results or have had too small a sample size to detect significant effects. However, significant preventive effects were observed when 3 trials on standardized echinacea extracts were combined in a meta-analysis.3 (These studies were conducted by Bioforce AG in cooperation with Sebastian Johnston, MD, PhD, from the Imperial College in London.) Finally, tolerability and safety are critical considerations for therapies designed for long-term, preventive use. The most recent randomized, double-blind, placebo-controlled trial investigated the safety profile and efficacy of the long-term usage of a proprietary echinacea formulation for prevention of colds and flu.
This study took place at the Common Cold Center at Cardiff University in Cardiff, Wales. Healthy subjects were randomized to either echinacea or placebo for 4 months. At the initial clinical visit, subjects received study medication for 1 month in addition to a diary for documenting ASEs, incidences of colds and associated symptoms, and medication use other than given treatments. Subjects brought unused treatments and completed diaries to monthly clinical visits and also were given kits to take nasal swabs for viral identification.
An alcoholic extract of fresh echinacea extract was used in this trial (Echinaforce®, made from E. purpurea, 95% aerial parts and 5% roots, prepared by Bioforce AG; Roggwil, Switzerland). Material was standardized to 5 mg/100 g of dodecatetraenoic acid isobutylamide and tested negative for endotoxin. Placebo was comparable in appearance, smell, and taste, with the same percentage of alcohol and identical packaging. Total dosage was based on Bioforce AG’s instructions and consisted of 0.9 ml of extract or placebo 3 times per day in water; this material was held in the mouth for 10 seconds (2,400 mg of extract daily) in order to achieve maximal local antiviral and anti-inflammatory effects at the pharynx. If subjects had a cold, they were asked to increase dosage to 0.9 ml 5 times per day (4,000 mg of extract). Leftover bottles were weighed for remnant of extract, and diaries were consulted to assess compliance.
Subjects were recruited on campus, at least 18 years old, and in good health with a recent history of 2 or more colds per year. Those pregnant, who had a chance of becoming pregnant, who were breastfeeding, who had a cold at the time of recruitment, who were on either antiviral or antibacterial medication, who abused drugs or alcohol, or who suffered from psychological diseases or epilepsy were excluded. Exclusion criteria also did not permit subjects with the following: a history of suicide attempts, upcoming surgery, chronic or autoimmune diseases, and asthma or allergies, particularly to members of the Asteraceae plant family. A preliminary study showed blinding to be efficient as approximately half the subjects in both the echinacea and placebo groups guessed that they had the echinacea treatment. Additionally, a power calculation based on a beneficial effect of 25% with the echinacea treatment and a protocol deviation and drop-out rate of 20% yielded an ideal sample size of 750 participants for the efficacy variable (number of days with colds).
Blood samples were taken from subjects for screening of blood cell counts and hematological and other measurements. Both subjects and physicians were asked to rate echinacea tolerability. Descriptions for ASEs as related to the treatments ranged from “not related” to “certain.” Those ASEs that were “possibly” associated with treatment were considered adverse drug reactions (ADRs). Parameters for colds included the amount of colds, the total number of days with colds, and colds that required addition medication. Characterization of viral infections was also conducted.
Out of 755 subjects included and randomized, 82 subjects dropped out, leaving 673 who finished the study regularly. Reasons for subject dropout included loss of contact (there was no contact post randomization; n=38), withdrawal of consent (n=16), “technical reasons” (n=3), health or ASE problems (n=3), and unknown reasons (n=22). There were no baseline differences between groups with the exception of cold susceptibility; subjects randomized to the echinacea group were, by chance, significantly more susceptible to colds than those in the placebo group (P<0.05). This was expected to bias the efficacy results against the echinacea group.
ADRs were reported by 9.0% of the echinacea group and 10.0% of the placebo group; the echinacea treatment was identified to be non-inferior to placebo treatment in regard to the rate of occurrence, as even fewer ADRs were observed. In the echinacea group, 177 subjects documented 293 ASEs, and 172 subjects in the placebo group mentioned 306 ASEs. Also, in the echinacea group, 4 ASEs resulted in discontinuation of treatment, while 3 ASEs caused discontinuation in the placebo group. One severe ASE was reported in the placebo group while none were reported from the echinacea group. No significant differences were detected in the amount of ASEs between groups. Also, no significant differences were reported in the blood parameters either after echinacea treatment or between groups. Assessment of tolerability by subjects resulted in ratings of “good” or “very good” in 64% of the echinacea group and 71% of the placebo group.
Those in the echinacea group experienced 149 colds lasting a combined total of 672 days, while subjects in the placebo group reported 188 colds with a length of 850 days. The total number of days with colds was significantly fewer in the echinacea group than the placebo group (P<0.05, as measured in the intention-to-treat population). Those in the echinacea group also experienced fewer recurring colds than those in the placebo group (65 vs. 100, respectively; P<0.05). In addition, a greater number of subjects with colds in the placebo group used medication such as aspirin, paracetamol (acetaminophen), and ibuprofen as compared with those in the echinacea group (88 vs. 58, respectively; P<0.05).
Of the nasal swabs collected (n=201), viral infection was identified in 54 samples from the echinacea group and 74 in the placebo group. Significantly fewer samples from the echinacea group contained influenza, corona-, metapneumo-, respiratory syncytial-, and parainfluenza viruses as compared the placebo group (24 vs. 47, respectively; P<0.05). Additionally, in subjects with 100% protocol compliance, 36 colds with a combined total duration of 155 days were reported from the echinacea group (n=88) as compared with 58 colds in 268 days in the placebo group (n=99, P<0.0001).
In summary, preventive therapies for colds and flu should be both well tolerated and efficacious. The echinacea preparation used here exhibited a very “good” safety profile for long-term usage. This study reports that echinacea long-term prevention was associated with fewer cold episodes, fewer days with colds, and fewer colds that required additional medication, suggesting efficacy against infection. The study mentions that these data may have been confounded by the significant difference of cold susceptibly between groups and less use of pain-relieving pharmaceutical drugs in the echinacea group. If an adjustment for these co-variables had been conducted, an even more beneficial preventive effect for the echinacea formulation probably would have been shown.
This study also characterized viruses. Although the sample size was small, those in the echinacea group had significantly fewer viral infections than those in the placebo group. This may preliminarily indicate clinical antiviral activity as it agrees with the authors’ in vitro results on the same proprietary extract (Echinaforce). In conclusion, this study claims to be not only the largest ever conducted on the clinical effects of echinacea, but the first to employ the detection of specific viruses in this manner. The conclusions from this well-powered, robust clinical trial contribute substantially to the case for the use of echinacea preparations, particularly this specific formulation, in common cold prevention.
—Amy C. Keller, PhD
1. National Institute of Allergy and Infectious Diseases: common cold overview. August 17, 2012. Available at www.niaid.nih.gov/topics/commonCold/Pages/overview.aspx. Accessed September 9, 2012.
2. Blumenthal M, Goldberg A, Brinckmann J, eds. Herbal Medicine: Expanded Commission E Monographs. Austin, TX: American Botanical Council; Newton, MA: Integrative Medicine Communications; 2000.
3. Schoop R, Klein P, Suter A, Johnston SL. Echinacea in the prevention of induced rhinovirus colds: a meta-analysis. Clin Ther. February 2006;28(2):174-183.
Source : American Botanical Council
Link to Source
A Strategic Call to Utilize Echinacea-Garlic in Flu-Cold Seasons
Tariq Abdullah, MD
Laurel Hill, Florida
The virulent influenza outbreak of 1918, * l twhich was also called the Spanish Flu Pandemic, killed at least 30 million people worldwide."22Some of the most respected influenza experts in the world are predicting that we will face another pandemic in the future. Many think that it will be sooner than later. We are overdue. The recent Avian Flu eruption we saw in Hong Kong
with strain H5N1 portends how it may enter the world stage. Some influenza specialists think that the next virulent strain may come from European pigs infected with an avian strain. The two most recent epidemics killed 90,000 to 100,000 people 40
years ago in 1957 and 34,000 people 30 years ago in 1968. Each year the flu season takes a significant toll on the pediatric, geriatric, and immuno-compromised population. Dr Joshua Lederberg, a Nobel Prize winner in 1959 for his elucidation of bacteria genetics and a specialist in emerging pathogens at Rockefeller University, believes that a new strain of
the influenza virus may pose a greater morbidity and mortality threat than any other previous strain. ' Because of the known pathophysiology and history of influenza infections, perceptibly, it would wreak considerably more havoc than some of the feared hemorrhagic viremias caused by the Ebola and Rift Valley viruses of Africa. When the present world setting is compared to the scenario of 1918, we have a much larger world population and our mobility capacity is much greater. This facilitates transmission and, potentially, may exact a toll beyond our wildest expectations. Coughing and sneezing by victims expel millions of viral particles into the air where they are suspended for hours. The formation of new recombinant genetic strains occurs when a virus jumps from species to species such as from chickens to hogs to humans. This will be the antecedent cycle that will produce a strain for which we are unprepared. The Group for Pandemic Preparedness and Emergency Response
(GRIPPE) is an international flu watch organization composed of scientists and planners from the National Institutes of Health, Centers for Disease Control and Prevention, the Food and Drug Administration, and academic medical centers charged with
planning national strategies for coping with the eventuality of an influenza epidemic. This group conducts vigilant monitoring and surveillance for emerging strains. Efforts are coordinated with those of several nations. These data are used to forecast
strains to cause seasonal infections, produce appropriate vaccines, and determine protocols for administration. Because the recombinant genetic formation of new seasonal strains have not varied drastically this has worked relatively well thus far.
The real danger lies in the sudden emergence of a markedly varied genetic strain caused by sudden antigenic shifts in the viral reservoirs of avian-swine carriers. If such a dreaded happening should come to pass, it would take months to develop a vaccine
and as long to administer it. In the meantime, while this is being done, millions could die. Most people in heavily populated areas would have difficulty avoiding and escaping the pervasive viral contagionladen atmosphere created by the sneezing and
coughing of a progressively larger number of victims. Inhalation in such a contagious atmosphere would seed viral particles in the respiratory system of people and would produce disease in 2 to 4 days. What are some practical things that we can do at
the onset of such a potentially deadly outbreak? Dietary activity and composition, which may offer prophylaxis and aid in curing this infection, should be a prime strategy. Increasingly, people are successfully turning to certain vitamins, foods, and herbs
and alternate lifestyles for their medicinal value (Milton M, personal communication, 1999).3 The old adage, "your food should be your medicine and your medicine should be your food," may never be more applicable than in an influenza pandemic.
Some efficacious dietary medicinal components and activities may include vitamin C, chicken soup, garlic and Echinacea herbs, and abstinence from alcohol. Curing a primary viral pneumonia caused by this pathogen with presently approved medication
would be difficult. Opportunistic secondary microbial infections would respond to antibiotics and other antimicrobials. China is a prime locale to monitor new strains of this virus, because it is, by far, the most populous nation on earth and has farming
practices that bring a tremendous stock of bird and animal carriers into close proximity to a large human population. We must give strong consideration to finding foods and herbal preparations with medicinal value that can be fed to the avian-swine
carriers, hopefully, altering the evolution and production cycle of virulent recombinant genetic strains and their pathogenicity. Many of the medicinal herbs advocated for their medicinal value in humans, probably, would have veterinary application.
Anecdotal and growing scientific data about the herbs, garlic and Echinacea, suggest that the administration of herbal preparations derived from them should be part of any international planning to prevent virulent seasonal and pandemic strains of the flu virus. It is not far-fetched to propose that fresh and aged preparations of those herbs should be stockpiled for administration to all victims, if investigations confirm and warrant use. Empirically, these herbal preparations should be utilized in case we are caught before ideal confirmatory studies can be completed. There are old and recent data suggesting
further studies of the value that these herbs may hold for our presently feared and suspected inadequacy to cope with this threat.4'6-8 PROPHYLACTIC AND CURATIVE EFFICACY Anecdotally, the prophylactic and curative value
of both herbs has been noted by avid consumers during the cold-flu season. This has especially been noted among health care workers who are exposed to the contagious environs created by patients who are infected.3 These two herbs, together and singularly, have been noted for their prophylactic and curative efficacy. How did these health providers administer
these two herbs for the prophylaxis and cure of the common cold and influenza? They relayed to me that they orally administered crude, raw, or manufactured preparations of these herbs at the beginning of the predicted cold-flu season. The
oral administration of raw garlic involved masticating or mincing a clove with honey once daily for prophylaxis and twice daily for cure. This garlic preparation is chewed and retained in the oral cavity as long as possible for the liberated volatile
compounds to penetrate and be absorbed by the tissues of the mouth, nasopharynx, and sinuses. Many inhaled these fumes into the pulmonary spaces and exhaled them with a closed mouth through the nostrils. Before ingestion, many related
directly of inhaling sliced or minced garlic into the nostrils or from a container that could be opened and closed. After nasal administration and oral retention, they would swallow the raw or crude preparation where numerous beneficial compounds and components would be absorbed by the gastrointestinal tract. Manufactured or processed preparations would be administered as directed by the manufacturer. In its crude or raw form, Echinacea was administered orally with a cup of tea sweetened with honey or unsweetened once daily for prophylaxis and twice daily for cure. As with garlic, manufactured or processed preparations were administered as directed by the manufacturer. Many who had worked with cold-flu patients through several seasons gave impressive accounts that they had never had an acute upper respiratory tract infection. Many of these advocates
further related that they didn't smoke or drink alcohol. If they did, they reduced their indulgence during the cold-flu seasons. Smoking and alcohol use are believed by many to decrease cell-mediated immunity in general, and especially, in the respiratory
JOURNAL OF THE NATIONAL MEDICAL ASSOCIATION VOL. 92, NO. 1, JANUARY 2000 49
INFLUENZA AND ECHINACEA-GARLIC IMMUNE MODULATORS
Echinacea and garlic are immune modulators.' In vivo studies years ago in Japan revealed how laboratory mice could not be inoculated with the influtenza virus, intranasally, when garlic was administered. 7 Further data revealed that mice given a flu
vaccine and administered garlic produced a much more significant titer of neutralizing antibodies than those administered the vaccine alone. Other studies, including anecdotal, in vitro, and in vivo have confirmed the broad antiviral spectrum of garlic
encompassing all species of the herpes family, including Kaposi's sarcoma virus VIII.'i 8 ') These data also suggest that garlic may have therapeutic applications for the post-vaccine flu-like syndrome noted in some vaccine recipients. Garlic may reduce
the pathogenicity of the attenuated influenza virus in the immune response to the vaccine.3-57 Recent scientific reports in the media have touted how the oral and parenteral administration of Echinacea in Germany have reduced the frequency and severity of infections during the cold-flu season. The antimicrobial and immune modulatory legacy of these Echinacea and garlic are reflected in their medicinal use over millennia to prevent and cure infectious diseases. That potency is being confirmed
and verified in medical research labs and in clinical trials conducted all over the world. In vitro and in vivo studies have shown the tremendous antimicrobial, especially, antiviral activity of compounds in both herbs.3,4,6-12,37 Perhaps, more impressive
than these herbs' outstanding antimicrobial activity data are the data confirming that the immune modulating activity components of garlic and Echinacea have profound effects on the cellmediated and humoral armamentariums of the immune
system. '-24 These components have included organically bound selenium and germanium, amino acids, several other sulfur compounds, lectins, polysaccharides (poly- and heteroglycans), mitogens, vitamins A and C, saponins, etc. Many of these components, in isolated, combined, or crude extract form from which they originate, have induced natural killer cell, macrophage, T-cell, and B-cell prolif'eration and activation and have enhanced their ftunctional activity. Echinacea and garlic components stimulate phagocytosis and nonspecific and specific cellular immunity.25-32 Poly- and heteroglycans in
garlic have provided protection in immunosuppressed mice against Listeria monocytogenes and Candida albicans. Glycans from both herbs enhance macrophage activation. Extracts from Echinacea by assay studies increased natural killer cells isolated from patients with AIDS and chronic fatigute syndrome. Components of garlic and Echinacea have increased cytokine production of immune system cells such as interleukins and tumor-necrosis factor. Both herbs have enhanced the production of antigen-specific IgG and IgM antibodies. The message in a Japanese investigator's report' 2 about garlic and influenza in 1973 was clear and has been confirmed in very recent studies. (omponents of garlic have been shown to enhance the membrane functions of lymphocytes and macrophages such as receptor site activity and sensitivity. Anecdotal, experimental, and clinical data more than substantiate the value of these herbal roots as first-time therapeutic defenses and cures for primary upper respiratory tract infections caused by the common cold and influenza viruses, but for secondary bacterial invaders.2733-36"
It is only fitting and proper for appropriate monitoring and planning strategists such as the World Health Organization, GRIPPE, and others to strongly consider evaluating the constructive role the herbs Echinacea and garlic and others may play
in helping us cope with potential biological disasters. This should be done before too many more cold-flu seasons pass. If a virulent influenza nightmare should come to pass before we can investigate the worth of these herbs and are unable to successfully treat ourselves with approved allopathic and vaccine therapies, the empirical use of these herbal
preparations may have infinite survival value.
1. Johnson HJ. Killer Flu. 7heRollingStone. 1998;778:47, 51, 65.
2. Larson E. The flu hunters. 7ime. 1998;15(7):54-73.
3. Abdullah TH, et al. Garlic Revisited: Therapeutic for the Major Diseases of Our Time? J Nail Med Assoc. 1988;804:439.
4. Abdullah TH, Kirkpatrick D, Carter j. Enhancement of natural killer cell activity in AIDS with garlic. Onkologie. 1989;21:
5. Abdullah TH. In vitro efficacy of a compound derived from garlic against Pneumocystis carinii. J Natl Med Assoc. 1996;88:
6. Nagai K. Experimental studies on the preventable effect of garlic extract against infection with influenza virus. JpnJInfect
7. Esanu V, Prahoveanu E. The effect of garlic extract, applied as such or in association with Naf, on experimental
influenza. Virologie. 1983;34:7-17.
8. Tsai Y, Cole LL, Davis LE, et al. Antiviral properties of garlic: in vitro effects in influenza B, herpes simplex-I and Cocksackie
viruses. Planta Medica. 1985;5:460-461.
9. Weber ND, et al. In vitro effects of Allium sativa (garlic) extracts and compounds. Planta Med. 1992;58:417-423.
10. Thompson KD. Antiviral activity of Virascea (echinacea) against acyclovir susceptible and acyclovir resistant strains of the
herpes simplex virus. Antiviral Res. 1988;39:55-61.
11. Nagai K. Preventive effect of garlic extract against influenza. Kansenshosgaku Zasshi. 1973:47:111-115.
12. Wagner H,Jurcic K. Immunlologic studies of plant combination preparations: in vitro and in vivo studies on the stimulation
of phagocytosis. Arzneittelforchung. 1991;41:1072-1076.
13. Coeugniet EF, Elek E. Immuno modulation with viscum album and Echinacea purpurea extracts. Onkologie. 1987;10(3
14. RoeslerJ, Steinmuller C, Kiderlen A, et al. Application of purified polysaccharides from cell cultures of the plant Echinacea
purpura to mice mediates protection against infections with Listeria monocytogenes and Candida albicans. Int J Immunopharmacol. 1991;13:27-37.
15. RoeslerJ. Application of purified polysaccharides from cell cultures to the plant Echinacea purpurea to test subjects mediates activation of the phagocyte system. IntJ Immunopharmacol. 1991;13:931-941.
16. Burger RA, Torres AR, Warren RP, et al. Echinacea-induced cytokine production by human macrophages. Int JImmunopharnacol. 1997;19:371-379.
17. Brown L. Scientific review-natural approaches to the cold and flu season. Vitamin Retailer. 1999;6:51-54.
18. Leuettig B, Steinmiller, Gifford GE, et al. Macrophage activation by the polysaccharide arabinogalactan isolated from
plant cell cultures of Echinacea purpurea. J Natl Cancer Inst. 1999; 81:669-675.
19. Bauer VR,Jurcic K, PuhlmainnJ, et al. Immunologic in vivo and in vitro studies on Fchinacea extracts. Arneimittelforchung.
20. Buckovsky M, Vaverkova S, Kost'alova D. Immunomodulating activity of Echinacea gloriosa L. Echinacea augustifolia DC,
and Rudbeckia speciosa Wenderoth ethanol-water extracts. Polish J Pharmacol. 1995;47: 175-177.
21. Jeong HG, Lee YW. Protective effects of dially sulfide in garlic on N-nitrosodimethylamine-induced immtino-suppression
in mice. Cancer Lett. 1998; 134:73-79.
22. Smeets K, Van Damm EJ, Van Leuven F, et al. Isolation,characterization, and molecular cloning of the mannose-binding
lectins from the leaves of garlic. Plant Mol Biol. 1997;33:531-535.
23. Stimpel M, Proksch A, Wagner H, et al. Macrophage activation and induction of macrophage cytotoxicity by purified
polysaccharide fractions from the plaint Echinacea purpurea. Infect Immun. 1999;46:845-849.
24. Herber D. The Stinking Rose: Organosulfur compounds and cancer. AmJ Clin Nut. 1997;66:398-405.
25. Lersch C, Zeuner M, Baur A, et al. Nonspecific immunostimulation with low doses of cyclophosphamide (LOCY), thymostimulin, and Echinacea ptirpurea extracts (echinacin) in patients with far advanced colorectal cancers: preliminary results. Cancer Invest. 1992;10:343-348.
26. Rehman J, Dillow JM, Carter SM, et al. Increased production of antigen specific immunoglobins G and M following in
vivo treatment with the medicinal plants Echinacea angustifolia and Hydrostis canadensis. Immunol Lett. 1999;68:391-395.
27. Tang Z, Sheng Z, Lui S, et al. The preventing ftinction of garlic on experimental oral precancer and its effects on natural
killer cells, T-lymphocytes, and interleukin-II. Hunan I Ko TaHsueh Hsueh Pao. 1997;22:246-248.
28. Lau BH, Yamascki T, Gridley DS. Garlic compounds modulate macrophage and T-lymphocyte functions. Mol Biother.
29. Romano EL, Montano RF, Brito B, et al. Effects of Ajoene (garlic) on lymphocyte and macrophage-dependent functions.
Immunopharmacol Immunotoxicol. 1997;19:15-36.
30. Feng ZH, Zhang GM, Hao TL, et al. Effect of daillyl trisulfide on the activation of T-cell and macrophage mediated
cytotoxicity. J Tongji Univ. 1994;14:142-147.
31. Wagner H, Proksch A, Riess-Mauner I, et al. Immunostimulating action of polysaccharides (heteroglycans) from
higher plants. Arzneimittelforshung. 1985;35:1069-1075.
32. Brinkeborn RM, Shah DV, Degenring FH. Echinaforce and other Echinacea fresh plant preparations in the treatment of
the common cold: a randomized, placebo controlled, doubleblind clinical trial. Phytomedicine. 1999;6:1-6.
33. Melchart D, Walther E, Linde K, et al. Echinacea root extracts for the prevention of upper respiratory tract infections:
a double-blind, placebo-controlled randomized trial. Arch Fam Med. 1998;7:561-565.
34. Gunning K. Echinacea in the treatment and prevention of upper respiratory tract infections. West j Med. 1999;171:198-
35. Uchida Y, Takahashi T, Sato N. The characteristics of the antibacterial activity of garlic. JpnJAntibiot. 1975;28:638-642.
36. Farbman KS. Antibacterial activity of garlic and onions: a historical perspective. Pediatr Infect Disj 1993;12:613-617.
JOURNAL OF THE NATIONAL MEDICAL ASSOC