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Can Licorice Reduce the Severity of Coronavirus Infection?

Analysis by Dr. Joseph Mercola Fact Checked

licorice root and extract

Story at-a-glance -

  • Liquiritin is a compound found in licorice root and extract that helps prevent the rapid reproduction of SARS-CoV-2, as demonstrated in the lab
  • It also has anti-inflammatory and neuroprotective properties, but no toxicity, based on animal studies
  • Glycyrrhizin, also found in licorice, was found to be active against SARS-CoV-1 with few toxic effects; it has historically been used against flu and pneumonia
  • It’s also important to wash your hands, stay hydrated, get appropriate levels of vitamin D and maintain proper levels of humidity in your indoor environment

Medicinal plants have been a part of human history since the beginning of recorded time. Many pharmaceutical drugs are the result of isolating a plant compound and replicating it in the lab.1 Through many years of fighting illness and disease, people from all over have learned to rely on medicinal plants for healing.

The World Health Organization reports that many nations are continuing to use and rely on herbal treatments to help provide for health care needs. In 133 nations surveyed, 110 reported using herbal medicines.2 In one U.S. survey in 2007 it was reported that 40% of adults used complementary and alternative medicine (CAM) therapies.3

The resurgence of herbal medicine treatments may be driven by an increasing rate of death from all viruses, including influenza4 and SARS-CoV-2.5 Scientists have historically observed medicinal plant use and sought to understand their mechanisms of action. Licorice root offers more than one compound with effects against COVID-19.

Computer Reveals Liquiritin May Be an Effective Antiviral

Liquiritin is a flavanone glycoside6 found in licorice root. Chinese licorice is a flowering plant commonly used in traditional Chinese medicine (TCM) in combination with other herbs. The root has been used to improve the results of the other ingredients in medicine,7 help reduce the harmful effects and improve the flavor.

But, researchers from Peking University and the Academy of Military Science in China have discovered a compound in licorice root that can do more than just boost the effectiveness of other herbs. They analyzed liquiritin, which they found could help prevent SARS-CoV-2 from rapidly reproducing in the lab.

In search of an antiviral treatment against COVID-19, the researchers found licorice root. The study8 has not yet been peer-reviewed, but has been made public in a preprint paper.9

They noticed that past searches for antiviral therapies appeared to focus mainly on blocking the virus and considered searching for a method that boosted the host's protective function. The study began with scientists analyzing natural products and FDA-approved drugs.

An artificial intelligence platform called InfinityPhenotype was used to predict the efficacy of 3,682 drugs and natural products against the gene set of SARS-CoV-2, as reported in previous research. During the analysis liquiritin was revealed to have the top score.

Then, results verified in the lab and showed that liquiritin had the ability to obstruct the growth of SARS-CoV-2 in monkey cells10 by mimicking type I interferon. They moved on to test toxicity in mice and found there were no deaths when the animals were treated with high doses for one week. They also acknowledged that liquiritin:11

"… acts as an antioxidant and has antidepressant, neuroprotective, anti-inflammatory and therapeutic effects on heart system diseases. Liquiritin plays a strong protective effect on vascular endothelial cells in myocardial ischemia-reperfusion injury model. It can also protect smoking-induced lung epithelial cell injury."

In conclusion, the researchers wrote:

"Since liquiritin is also one of the main ingredients of compound licorice tablets, we speculate that it is safe. Indeed, it didn’t show toxicity and side effects in two independent experiments. In summary, we suggest that liquiritin should be assessed in human patients suffering from the COVID-19 …

Because type I interferon is responsive to most viruses that infect vertebrate, we expect liquiritin having a broad and potent antiviral function to other viral pathogens, like HBV, HIV and etc."

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Anti-Inflammatory Effect of Licorice Root Compounds

The compounds in licorice root have demonstrated an anti-inflammatory effect in the body and the ability to modulate the immune system. In addition to fighting viral infections, it is also important to support the body's defenses and reduce respiratory system effects.

For instance, in one literature review of 29 studies, scientists evaluated herbal preparations in the treatment of asthma to improve lung function.12 They found that when the herbal therapies, including licorice root, were used in conjunction with medications, the participants’ asthma outcomes were more improved than when the medications were used alone. Researchers have also studied the anti-inflammatory effects of licorice root extract and wrote:13

"Furthermore, licorice extract inhibited the expression levels of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6) in the livers of t-BHP-treated mice models.

This result suggested that mechanistic-based evidence substantiating the traditional claims of licorice extract and its three bioactive components can be applied for the treatment of inflammation-related disorders, such as oxidative liver damage and inflammation diseases."

The inhibition of proinflammatory cytokines may be an important effect as early studies have demonstrated an increased number of cytokines IL1B, IL6, IL12, IFNγ, IP10, and MCP1 in those with COVID-19.14 Two (IL1B, IL6) are the same cytokines researchers found were inhibited when licorice extract is used.

In an animal study from 2008 liquiritin showed an antidepressant-type effect.15 The research team said the mechanism of action was an increase in norepinephrine and 5-Hydroxytryptamine (serotonin).16 This is interesting since norepinephrine plays an important function in enhancing the expression of COX-2.17 Researchers believe their findings demonstrated:

"… the role of NE [norepinephrine] in CNS inflammation. NE via COX-2 and PGE-2 [prostaglandin] induction may have a protective physiological function rather than being purely detrimental."

Serotonin is also enhanced with licorice root18 and plays a role in mediating immune cell function.19 For example, it modulates cytokine secretion and can suppress TNFα and IL1B, both important cytokines released in a COVID-19 infection.

Glycyrrhizin: Another Compound With Antiviral Effects

A second compound in licorice root that has demonstrated an effect against SARS-CoV-1 in 2003 is glycyrrhizin. The active compound was discovered in a search for antiviral therapies that may reduce the severity and mortality from the SARS coronavirus infection.

In a study20 published in the Lancet, scientists evaluated antiviral activity in patients with SARS-CoV-1 admitted to Frankfurt University in Germany. After evaluating the result of each of the compounds, they found that glycyrrhizin was the most active in stopping the reproduction of the SARS-CoV-1 virus. They concluded:

"However, although high doses of glycyrrhizin have been used in clinical trials, this compound had few toxic effects compared with the other regimens, and the drug was reported to be clinically effective."

Results from another study21 showed the antiviral capacity of glycyrrhizin against coxsackievirus A16 and enterovirus 71 responsible for hand, foot and mouth disease. This is a contagious viral infection that children are susceptible to. The extract was used in the lab and showed a dose-dependent ability to block the reproduction of enterovirus 71 and coxsackievirus A16.

Historically, glycyrrhizin was a valuable asset in the treatment of coughs and viral respiratory tract infections in China, India and Greece.22 Current research has shown it to be a formidable antiviral with demonstrated effects against herpes, HIV, hepatitis, influenza and pneumonia. In animal studies glycyrrhizin reduced mortality from herpes encephalitis and influenza A pneumonia.

Licorice Root Has a Long History of Medicinal Use

Licorice is also known as "sweet root" because it’s about 50 times sweeter than regular sugar.23 Topical preparations have been used to treat eczema and other skin conditions. In Eastern and Western medicine, it has been used as an expectorant and to treat common colds.

When the Greek historian Herodotus was in the Black Sea area, after being exiled from Athens,24 he observed how licorice root was used in the Scythian Empire. He suggested it may be useful to the Greeks. Theophrastus advocated use in the 3rd century B.C. in asthma and respiratory diseases. In combination with honey, he suggested it for topical uses on wounds and ulcers.

Between 1400 and 1650, herbalists noted licorice had positive effects in the mouth and discovered different extracts had different potencies. To ensure the same benefits with each plant or extract, it would be necessary to standardize the growth and use of the plant.

Reduce Infection Potential and Support Your Immune System

While it is encouraging that licorice root has demonstrated the potential to positively affect the SARS-CoV-2 virus, you may also seek ways to reduce your potential for getting sick and the severity of the illness if you do get infected. Here are some suggestions:

Hand-washing — Using proper hand-washing techniques can help reduce your risk of a respiratory infection, as proven by the military. They were able to reduce the number of upper respiratory infections by 45% in a class of new recruits.25

Humidity and Hydration — Keeping the room humidity between 40% and 60% can reduce the transmission of viruses and may support your immune system.26 Thomas Pietschmann from the Center for Experimental and Clinical Infection Research explains it this way:27

“Viruses have greater stability at low temperatures. This is similar to food that keeps longest in the refrigerator. On cold and usually dry winter days, the small droplets, together with the viruses, float in the air longer than when the air humidity is high."

Keeping your body hydrated is another way of protecting your mucus membranes. It has additional benefits as well as I discussed in “This Could Prevent 3 Million Cases of Degenerative Disease.”

Vitamin D — An increasing number of analyses of the data is showing people with adequate levels of vitamin D are experiencing infections with less severity and have lower mortality. You don’t have to go to a lab, but can easily test your vitamin D levels at home.

Vitamin C — This vitamin has a history of reducing the damaging effects of respiratory viruses and is being used by doctors in New York to reduce the mortality rates in people with COVID-19.28

Sleep — Sleep plays an integral role in your immune system and has a curious bidirectional link to your gut microbiome. If you need help getting quality sleep each night, here are my Top 33 tips to optimize your sleep routine.