Preventing and treating influenza with natural medicine By Alan R. Gaby, M.D.
As the flu season approaches, considering that vaccinations and antiviral drugs are only partially effective, it is important to be aware of natural alternatives for preventing and treating influenza.
Sambucol, a proprietary preparation that contains extracts of black elderberries (Sambucus nigra L.) and raspberries (Rubus idaeus L.) has been shown to inhibit the replication of influenza virus in vitro. In addition, an extract of Sambucus nigra L. decreased the infectivity of human influenza virus H1N1 in vitro. The activity of this extract against the H1N1 virus was attributed to two flavonoids (5,7,3',4'-tetra-O-methylquercetin and 5,7-dihydroxy-4-oxo-2-[3,4,5-trihydroxyphenyl]chroman-3-yl-3,4,5-trihydroxycyclohexanecarboxylate), which were shown to bind to H1N1 virions and block the ability of the virus to infect host cells. 1 In clinical trials, treatment with Sambucol decreased the duration of illness in patients with influenza.
Forty patients suffering from influenza-like symptoms during an outbreak of influenza B/Panama in 1993 were randomly assigned to receive, in double-blind fashion, Sambucol or placebo. Children received 30 ml per day and adults received 60 ml per day for three days. Twenty-seven patients completed the trial. After two days of treatment, a higher proportion of patients in the active-treatment group than in the placebo group had experienced significant improvement in symptoms (93% vs. 25%). Symptoms resolved completely after three days in 87% of patients receiving active treatment and in 33% of those receiving placebo. 2
Sixty patients (aged 18-54 years; mean, 30 years) who were suffering from influenza-like symptoms for 48 hours or less were randomly assigned to receive, in double-blind fashion, Sambucol (15 ml 4 times per day during meals) or placebo for five days. The mean time until complete or almost-complete resolution of symptoms occurred was significantly less in the active-treatment group than in the placebo group (3.1 days vs. 7.1 days; 56.3% decrease; p < 0.001). No side effects were reported. 3
N-Acetylcysteine (NAC) is an antioxidant and a precursor to glutathione, which is one of the major antioxidants in lung tissue. There is evidence that oxidative stress contributes to the pulmonary damage that may result from influenza. In a double-blind trial, supplementation with NAC during the flu season reduced the frequency and severity of influenza episodes. This improvement was not due to a reduction in the number of infections but, rather, to a decrease in the number of infections that caused symptoms.
Two hundred sixty-two individuals (78% of whom were 65 years or older) were randomly assigned to receive, in double-blind fashion, NAC (600 mg twice a day) or placebo for six months, beginning in October or November. Compared with placebo, NAC reduced by 42.7% the proportion of subjects who experienced at least one episode of influenza (29.6% vs. 51.7%; p = 0.0006). The percentage of episodes that were mild was higher in the NAC group than in the placebo group (72% vs. 48%; p = 0.06). The mean time in bed per episode was 61.1% less in the NAC group than in the placebo group (p < 0.01). The frequency of seroconversion towards A/H1N1 Singapore 6/86 influenza virus was similar in the two groups, but fewer infected subjects in the NAC group than in the placebo group developed symptoms (25% vs. 79%; p < 0.0001). During NAC treatment, there was a progressive, significant shift of cell-mediated immunity from anergy to normal. The frequency and severity of adverse events was similar in the NAC and placebo groups. 4
Vitamin C has been shown to inactivate influenza virus in vitro. According to one practitioner, supplementation with massive doses of vitamin C can relieve symptoms and enhance recovery in patients with influenza. Vitamin C was usually given 6-15 times per day in amounts just below the dose that produced diarrhea (i.e., the bowel-tolerance dose). Increasing the frequency of administration increased the amount of vitamin C tolerated. The best results were achieved when patients reached at least 80-90% of their bowel-tolerance dose. The amount of vitamin C a patient could take without diarrhea increased with increasing disease severity. Some patients were able to tolerate up to 150 g per day when suffering from influenza, but as they improved the amount of vitamin C they could tolerate decreased. Symptoms recurred in some cases if bowel-tolerance doses were discontinued before the patient was completely well. 5 6
Vitamin D plays a role in immune function. It has been suggested that relatively low vitamin D status during the winter months might explain the higher incidence of influenza in the winter than at other times. 7 In a double-blind trial designed to test the effect of vitamin D supplementation on bone loss, 208 African-American women received vitamin D3 or placebo for three years. The dosage was 800 IU per day for two years, followed by 2,000 IU per day for one year. During the study, 8 women in the vitamin D group and 26 in the placebo group reported cold and influenza symptoms (p < 0.002). It was not stated how many of these episodes were influenza and how many were colds. 8
Green tea extract inhibited the growth of influenza virus in vitro. The inhibitory effect appeared to be due at least in part to (-)epigallocatechin, one of the major catechin molecules in green tea. In a study of elderly nursing home residents, gargling with an aqueous solution of green tea catechins three times per day reduced the incidence of influenza.
One hundred twenty-four elderly residents of a nursing home in Japan (mean age, 83 years) gargled three times per day with an aqueous solution of green tea catechins (polyphenon E; 200 µg per ml) or with a control solution for three months during the winter. The concentration of catechins in the gargles of the active-treatment group was half that of commercially sold green tea beverages in Japan. All study participants received an influenza vaccine. The incidence of influenza during the study was significantly lower in the active-treatment group than in the control group (1.3% vs. 10.4%; p < 0.03). No adverse effects were reported.9
1 Roschek B Jr, et al. Elderberry flavonoids bind to and prevent H1N1 infection in vitro. Phytochemistry. 2009;70:1255-1261.
2 Zakay-Rones Z, 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. 1995;1:361-369.
3 Zakay-Rones Z, et al. Randomized study of the efficacy and safety of oral elderberry extract in the treatment of influenza A and B virus infections. J Int Med Res. 2004;32:132-140.
4 De Flora S, et al. Attenuation of influenza-like symptomatology and improvement of cell-mediated immunity with long-term N-acetylcysteine treatment. Eur Respir J. 1997;10:1535-1541.
5 Cathcart RF. Vitamin C: the nontoxic, nonrate-limited, antioxidant free radical scavenger. Med Hypotheses 1985;18:61-77.
6 Cathcart RF III. Vitamin C, titrating to bowel tolerance, anascorbemia, and acute induced scurvy. Med Hypotheses. 1981;7:1359-1376.
7 Cannell JJ, et al. Epidemic influenza and vitamin D. Epidemiol Infect. 2006;134:1129-1140.
8 Aloia JF, Li-Ng M. Re: epidemic influenza and vitamin D. Epidemiol Infect. 2007;135:1095-1096.
9 Yamada H, et al. Gargling with tea catechin extracts for the prevention of influenza infection in elderly nursing home residents: a prospective clinical study. J Altern Complement Med. 2006;12:669-672.
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