Natural antivirals are substances sourced from plants, foods, or other biological origins, investigated for their ability to interfere with or inhibit viruses. These compounds are distinct from synthetic pharmaceutical antiviral drugs, which undergo rigorous development and approval processes. Research into natural antivirals explores their potential to offer supportive or preventive benefits against various viral infections.
How Natural Antivirals Target Viruses
Natural substances combat viruses through several biological mechanisms. Some compounds prevent viruses from attaching to and entering host cells. For instance, certain polyphenols can disturb virus adsorption and attachment, blocking the initial stages of infection. This interference stops the infection before it can establish itself within the body.
Other natural agents inhibit viral replication once a virus has entered a cell. These substances might interfere with enzymes or processes a virus uses to copy its genetic material, such as RNA or DNA synthesis. Essential oils, for example, can disrupt viral enzyme activity or interfere with viral RNA or DNA synthesis within host cells, slowing or halting the virus’s spread.
A different approach involves modulating the body’s immune response. Some natural products promote antiviral cytokine synthesis, increase the activity of immune cells like T-cells and macrophages, and activate antiviral genes. Plant natural products, including flavonoids, terpenoids, and polyphenols, contribute to these immune-supporting effects, helping the body mount a stronger defense against viral pathogens.
Common Natural Antiviral Agents
Elderberry (Sambucus nigra) has been traditionally used to lessen the impact of viral infections, particularly influenza. Its compounds, such as polyphenols and lectins, are thought to inhibit viral entry and replication in human cells, and may also strengthen the immune response. Studies indicate elderberry can reduce the duration and severity of cold and flu symptoms.
Echinacea, especially Echinacea purpurea, is another popular herb often used to shorten the duration of the common cold and flu and reduce symptoms like sore throat and cough. It contains compounds like phenolics and polysaccharides that may boost immune function. Laboratory studies suggest echinacea can protect cultured cells from infection by influenza A virus and herpes simplex virus type 1.
Garlic (Allium sativum L.) has been used for centuries in both food and traditional medicine. Its active organosulfur compounds, notably allicin and ajoene, show potential antiviral activity. These compounds may disrupt viral replication, block viral entry into host cells, and enhance immune response. Garlic has been investigated for its effects against various viruses, including influenza and herpes simplex virus (HSV-1).
Green Tea, particularly its compound epigallocatechin-3-gallate (EGCG), is known for its wide range of health benefits, including potential antiviral effects. EGCG can directly inactivate influenza virions by binding to hemagglutinin (HA) and blocking attachment to host cells. It may also interfere with viral replication and impact viruses like hepatitis B and C, influenza, and herpes.
Licorice Root (Glycyrrhiza glabra) contains triterpenoids such as glycyrrhizin and glycyrrhetinic acid, which are its main active constituents. These compounds have shown inhibitory effects on several viruses, including herpesviruses, influenza virus, and coronaviruses like SARS-CoV-2. Glycyrrhizin may inhibit virus replication, directly inactivate viruses, and reduce inflammation.
Evaluating the Scientific Support
Research into natural antiviral agents spans various levels of scientific inquiry, from traditional use to controlled clinical trials. Laboratory (in vitro) studies reveal the potential of compounds to inhibit viruses in a controlled environment, such as a petri dish. For example, glycyrrhizin from licorice root can inhibit the main protease of SARS-CoV-2 in vitro. These findings are foundational, identifying compounds that warrant further investigation.
Animal studies (in vivo) bridge the gap between lab findings and human application. These studies assess whether a compound maintains its antiviral activity within a living system and evaluate its safety profile. For instance, glycyrrhizin has reduced morbidity and mortality in mice infected with lethal doses of influenza virus.
Human clinical trials provide the most direct evidence of efficacy and safety in people. The evidence varies significantly for different natural antivirals. For elderberry, some human trials suggest it can reduce the duration of flu symptoms, though other studies have yielded mixed results. Many natural antiviral agents primarily have support from laboratory or animal studies, with limited or inconclusive human trials.
Safety and Proper Use Considerations
Despite their natural origin, these agents can have potential side effects and interact with medications. Common side effects may include mild issues like nausea or headaches, but more serious reactions are possible. This highlights that “natural” does not automatically mean “safe.”
Natural antivirals can interact with prescription medications, potentially altering their effects. For instance, garlic compounds may interact with blood thinners. Always consult a healthcare professional, such as a doctor or pharmacist, before starting any new supplement regimen, especially if taking other medications or managing underlying health conditions.
The regulation of dietary supplements, which include many natural antiviral agents, differs from that of pharmaceutical drugs. In the United States, the Food and Drug Administration (FDA) regulates supplements as a category of food, not drugs, and they do not undergo pre-market approval in the same way as medications. Manufacturers are responsible for ensuring the safety and labeling of their products before marketing.