Vanquishing Viruses – 10 Natural Antiviral Remedies

Colds, flu and other viral infections are common during the spring. Although prevention is best, when a virus strikes there are a number of natural remedies that can stop it in its tracks. Dr Martin Hum digs up the research on 10 natural antivirals.

At this time of year, when winter seems to have dragged on interminably, our immune systems are often a bit low, leaving us prone to colds, flu, cold sores and other viral infections. Viruses are tiny particles of nucleic acids that invade living cells and divert the resources of those cells in order to make more copies of themselves. We know that some nutrients are immune-supporting and can help build our resistance to viral infections. But what about natural treatments that can actually kill viruses and shorten the duration of the illnesses they cause? Fortunately, there are many products available that have antiviral properties. Most of them are herbs, but we’ll start by looking at two metals – silver and zinc.


Silver has been utilised medicinally since ancient times and from 1900 until 1940 various forms of silver were in mainstream use to treat hundreds of ailments. Recently, there has been renewed interest in the use of colloidal silver. A colloid is a suspension of ultra-fine particles that neither dissolve nor settle out, even with changes in concentration. The colloidal silver used in modern supplements is a suspension of pure metallic silver in water. It is thought to work by interfering with the enzymes that enable viruses, bacteria and fungi to utilise oxygen – to put it simply, it suffocates them. Although clinical trials have yet to be conducted with oral administration of colloidal silver, initial case studies have indicated that injections of a silver-protein compound dramatically reduce the activity of the HIV virus in AIDS patients. There are also numerous anecdotal accounts of colloidal silver’s efficacy against the hepatitis C virus.


Zinc has been shown to be an effective treatment for the common cold in several double-blind, placebo-controlled trials. Both zinc acetate and zinc gluconate lozenges were found to reduce the duration and severity of cold symptoms. Topical application of zinc has also been used to treat cold sores, which are caused by the herpes simplex virus. One study found that using zinc monoglycerolate resulted in complete healing of cold sore lesions in 70 per cent of subjects, whereas zinc oxide only healed 9 per cent. So, clearly, the form of zinc used is important. It appears from other research that it is the positively charged Zn2+ ions that are effective against the herpes and common cold viruses. Zn2+ ions appear to prevent viruses from replicating by blocking the process by which nucleic acid chains split. The amount of zinc available to the body as Zn2+ ions from supplements is greatest with zinc acetate (almost 100 per cent) and zinc gluconate (about 30 per cent) but is almost zero with other forms of zinc such as citrate, orotate and picolinate. You can tell when a supplement contains Zn2+ ions, because it makes your mouth feel dry (due to binding with salivary proteins).


The common black elderberry (Sambucus nigra) has long been used as a food and is also one of nature’s oldest remedies. It appears to be particularly effective against the influenza virus. In a double-blind clinical trial, more than 90 per cent of the 15 patients taking elderberry extract (60 ml a day for adults and 30 ml a day for children) showed a significant reduction in influenza symptoms after two days and complete recovery after three days. However, in the control group it took six days before 90 per cent of patients showed an improvement. The group taking elderberry extract also had higher levels of influenza antibodies in their blood than the control group, indicating an enhanced immune response. In an independent study conducted in Norway, elderberry extract was shown to significantly reduce the duration of influenza symptoms by approximately four days. The use of other medication (pain relievers, etc.) was significantly less in the group receiving elderberry extract than in the placebo group. Elderberry extract is believed to act by binding to, and so disarming, the tiny protein spikes on the surface of the virus, by which it penetrates living cells. Flavonoids, including quercetin, may also be involved in the therapeutic actions of elderberry according to other studies. These flavonoids include anthocyans that are powerful antioxidants and protect cells against damage. The activity of elderberry against other viral infections, including HIV and herpes, has also been studied. It was found to significantly reduce the infectivity of HIV strains in laboratory tests and to completely inhibit the replication of four strains of herpes simplex virus, including two strains resistant to the drug acyclovir (Zovirax).


Olive trees (Olea europea) grow wild around the Mediterranean and were probably first cultivated in Crete around 3500 BC. Olive oil is a staple part of the Mediterranean diet, but it seems the health-promoting properties of the olive tree are not restricted to the well-known benefits of its oil for cardiovascular health. The leaves contain a bitter substance called oleuropein, one component of which, elenoic acid, has been identified as a potent inhibitor of a wide range of viruses in laboratory tests. The calcium salt of elenoic acid destroyed all of the viruses it was tested against, including influenza, herpes, polio and coxsackie viruses. Calcium elenolate also appears to act on the retrovirus for murine leukaemia by blocking its reverse transcriptase enzymes. These enzymes allow the virus to replicate by altering the DNA and RNA of healthy cells. Studies on infected hamsters have shown that calcium elenolate reduces the level of myxovirus parainfluenza type 3 and prevents its spread to the lungs. An uncontrolled clinical trial in Budapest involving over 500 patients concluded that olive leaf extract was extremely effective in treating a wide range of illnesses. Full and rapid recovery after taking the extract was noted in 115 out of 119 patients with respiratory tract infections and 120 out of 172 patients with viral skin infec-tions, such as herpes. Further, placebo-controlled, double-blind trials are needed to confirm olive leaf’s ability to cure viral illnesses in humans.


Green tea (Camellia sinensis) has been considered a medicinal remedy in Chinese tradition for over 4000 years and its many health benefits have recently been validated by scientific methods. Green tea contains a group of flavonoids called catechins, which appear to inhibit viral infections by binding to the haemagglutinin of the influenza virus and so preventing the virus from entering the host cells. Research in China has shown that green tea extract and isolated catechin derivatives also act by blocking the viral enzymes reverse transcriptase and DNA polymerase which allow viruses to replicate. The green tea compounds tested were effective in inhibiting HIV, herpes simplex and hepatitis B virus. So far, no clinical studies have been carried out to further explore green tea’s potential as a treatment for influenza and other viral diseases.


The SARS epidemic last year spurred the search for active antiviral compounds to treat the disease. Researchers at the Institute of Medical Virology at Frankfurt tested four pharmaceutical drugs (including ribavirin, the recommended treatment) and glycyrrhizin, a compound found in the root of the liquorice plant (Glycyrrhiza glabra), against samples of coronavirus from SARS patients. The results, published in The Lancet, showed that glycyrrhizin out-performed all four drugs in inhibiting the virus. Unlike ribavirin, it was also non-toxic to virus-infected cells. Glycyrrhizin was found to reduce replication of the virus and to inhibit both the absorption of viruses on the outside of cells and their ability to penetrate cells. Liquorice has also shown an ability to inhibit reproduction of HIV in laboratory studies. Clinical trials have shown that injections of glycyrrhizin may have a beneficial effect on AIDS and there is preliminary evidence that orally administered liquorice also may be safe and effective for long-term treatment of HIV infection. A preliminary trial involving people with acute and chronic viral hepatitis found that taking 2.5 grams liquorice three times per day (providing 750 mg glycyrrhizin) was superior to the antiviral drug inosine poly-IC. Entire liquorice extract (not de-glycyrrhizinated liquorice or DGL) may well be an effective treatment for other viral illnesses.


Pau d’arco (Tabebuia impetiginosa), also known as lapacho or ipe roxo, is a huge canopy tree native to the Amazon rainforest. It is known as the “divine tree” by indigenous people in Brazil and has long been used in folk medicine to treat a wide range of illnesses, including colds, influenza, herpes and viral stomatitis. The inner bark contains a high proportion of chemicals called quinoids. One of the most studied of these compounds is lapachol, which has been found in laboratory tests to be active against various viruses, including herpes simplex types I and II (responsi-ble for oral and genital herpes), influenza, polio virus, and vesicular stomatitis virus. The mechanism of action of pau d’arco, like that of olive leaf and green tea, is thought to be through inhibition of DNA and RNA polymerase and retrovirus reverse transcriptase. It is reported that lapachol decreases the replication of viruses in human subjects, but no clinical data are available.


St John’s wort (Hypericum perforatum) is a well-known herbal remedy for depression and is used traditionally to help wound healing and to ease the pain of neuralgia, fibrositis and sciatica. Laboratory studies have revealed that it also has antiviral activity against influenza, herpes simplex and HIV. Hypericin and pseudohypericin, chemicals found in St John’s wort, are active against enveloped viruses. These are viruses that tear off a piece of cell membrane when they leave an infected cell and wrap themselves in it, as a way of fooling the body’s immune system. Herpes viruses, HIV and hepatitis C are all enveloped viruses. Hypericin and pseudohypericin appear to attack these fragments of cell membrane (but don’t attack the membranes of living cells). There are as yet no data on clinical trials against viral diseases.


Garlic has been cultivated for more than 5000 years and has been prized for its medicinal properties since the days of the pharaohs. It is used as a folk remedy in many cultures to protect against colds and influenza. In laboratory studies, garlic was found to possess antiviral, antibacterial and antifungal properties. Key to garlic’s antiviral and healing properties are its hundreds of ben- eficial compounds, which work synergistically. The most significant of these is allicin, which produces garlic’s pungent odour. It is produced from another compound, alliin, when fresh garlic is cut or chewed and it can also be obtained from powdered garlic supplements with allicin potential. Allicin in turn produces other sulphur compounds, such as ajoene, allyl sulphides and vinyldithiins. Aged garlic products lack allicin, but may have some antiviral activity due to the presence of S- allylcysteine. Garlic’s cold-preventing reputation has been upheld by laboratory tests in which fresh garlic, allicin and various other sulphur compounds in garlic killed the common cold virus, various strains of influen- za viruses and herpes simplex virus types I and II. Clinical trials are needed to conclusively demonstrate garlic’s effectiveness in fighting colds and flu.


The herb echinacea (Echinacea purpurea) is known to support the immune system and may also have direct antiviral action. Preparations of echinacea roots and flowering parts have been shown in several clinical trials to be effective in reducing the severity and duration of symptoms in patients with common cold, upper respiratory tract infection and viral bronchitis symptoms. The natural antivirals described in this article may provide a welcome (and sometimes more effective) alternative to pharmaceutical drugs. Because some of them have been shown to kill viruses only in the test tube and have not yet been subject to clinical trials, the best approach to take in treating viral illnesses may be a holistic one. This would involve the use of several antiviral products together with immune-boosting nutrients such as vitamins A, C and E, zinc, selenium, CoQ10 and probiotics.

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