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Can Garlic Fight Coronavirus (COVID-19)?

Written by Ana Aleksic, MSc (Pharmacy) | Last updated:
Puya Yazdi
Medically reviewed by
Puya Yazdi, MD | Written by Ana Aleksic, MSc (Pharmacy) | Last updated:

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As coronavirus continues to spread, garlic seems to be gaining more popularity than ever. Demands for garlic are increasing, prices are going up, and stores are running low. Should you really be scared if you run out of garlic?

This article is for informational purposes only. The current coronavirus outbreak is an ongoing event and certain details may change as new information comes to light.

Is Garlic Important Amid the COVID-19 Pandemic?

Eating garlic is healthy. This is especially true for raw garlic, which is higher in active compounds and nutrients. However, there’s no evidence that garlic can prevent or treat the new coronavirus.

The WHO (World Health Organization) also says that garlic is “a healthy food that may have some antimicrobial properties” but “there’s no evidence that eating garlic has protected people from the new coronavirus” [1].

Remember that the best preventive measures you can take against the new coronavirus are to stay at home, wash your hands frequently, and avoid touching your face.

Despite some far-fetched claims you may have seen in your social media feed, garlic has never been tested against the new coronavirus. Therefore, we can only review studies that investigated various garlic preparations on similar coronaviruses in this post.

We’ll also take a look at whether garlic has an effect on viruses that cause the common cold, flu, and respiratory infections.

Lastly, limited studies suggest that garlic may strengthen the immune response, reduce inflammation, and help prevent heart disease and diabetes (along with lifestyle changes). We’ll talk a bit about how that might be relevant amid the current pandemic.

All in all, there is a solid amount of small-scale, low-quality research on garlic. But proper clinical trials are lacking and many purported benefits of garlic remain unproven [2].

Based on its overall effects, the only role garlic may play amid the COVID-19 pandemic is promoting general health.

Garlic is a healthy food that may strengthen the immune response and potentially help fight some viruses, but there is no evidence that it can treat or prevent coronavirus.

Garlic as a Natural Antiviral

Activity Against Coronaviruses

Infectious bronchitis virus is a coronavirus that infects birds. Garlic extract reduced its replication in chicken embryos in one experiment [3].

This study doesn’t provide us with much, though. The tested strain is different from the new coronavirus. It’s also impossible to translate findings on chickens to humans. Let’s hope future research on garlic and coronaviruses gives us more clues.

Tests On Other Viruses

In test tubes, garlic extract was active against viruses that cause [4, 5]:

  • Cold sores (herpes simplex virus type 1)
  • Genital herpes (herpes simplex virus type 2)
  • Respiratory infections (parainfluenza virus type 3)
  • Colds (human rhinovirus type 2),
  • The flu (influenza B)

Similar to coronaviruses, most of the listed viruses can infect cells and spread because they have membranes and sticky rod-like structures called viral envelopes [4].

Researchers hypothesize that garlic might help fight viruses by disrupting their membranes and envelopes. If so, garlic might only work before the virus sneaks into cells, but this has yet to be verified [4].

Cytomegalovirus is another common virus, and most people don’t know that they have it. It usually only causes symptoms if your immune system is weakened. In mice infected with cytomegalovirus, a component of garlic (allitridin) reduced virus blood levels and liver damage [6, 7].

Scientists think garlic might shift the immune system to a Th1-dominant state that helps clear viral infections faster, but this hasn’t been confirmed [8].

It’s important not to jump to conclusions based on these experiments. All the viruses mentioned above are different from the 2019 coronavirus.

Garlic was active against some viruses in cells and animals, but its impact on the new coronavirus has never been tested.

Microbe-Fighting Potential

Garlic may have broad antimicrobial activity against bacteria, yeast, fungi, parasites, and viruses. Allicin and sulfur-containing compounds in garlic inhibit DNA, RNA, and protein production in microbes. Clinical data are lacking, however [9, 10, 11].

Against the Cold & Flu

In a study of 120 people, aged garlic extract reduced the severity of colds and the flu. It increased the number of immune cells (T cells and NK cells), boosting the immune system while lowering inflammatory proteins (cytokines) [12, 13].

Another clinical trial on 146 healthy volunteers found that taking an allicin-containing garlic supplement every day helped prevent the common cold and reduce its duration [14].

The latest analysis, however, failed to find any other studies with good quality. Overall, the evidence is insufficient to claim that garlic can prevent or fight the cold and flu [15].

The flu is caused by influenza viruses. Colds can be caused by many different viruses, including other types of coronaviruses. These viruses are not the same as the 2019 coronavirus.

There is not enough evidence that garlic can prevent or fight the cold and flu.

Lung Infections

Secondary bacterial lung infections are a threat to hospitalized COVID-19 patients with breathing difficulties [16, 17].

Yet, there is no evidence that garlic can prevent bacterial lung infections. Garlic has only been tested in small human studies, animals, and test tubes. More research is needed.

In one study on 52 healthy volunteers, garlic powder extract with a cellulose-containing nose spray (Nasaleze Travel) prevented airborne infections better than the spray alone [18].

In mice and test tubes, garlic extract blocked biofilms that cause antibiotic resistance; it also helped clear bacterial infection from the lungs. In other test tube experiments, garlic inhibited several bacteria that may cause upper respiratory infections [19, 20, 21, 22, 23].

In rats, garlic extract, selenium, and antioxidant vitamins (A, C, and E) prevented lung damage in rats. Researchers used a heart disease medication, lisinopril, to cause lung damage. This medication is an angiotensin converting enzyme (ACE) inhibitor — a class of drugs implicated in COVID-19 complications and deaths [24, 25].

However, garlic extract had little or no effect in a clinical trial on 26 people with a bacterial lung infection [26].

Garlic has mixed effects on bacterial lung infections, which are a potential problem in hospitalized COVID-19 patients. Far more research is needed.

Garlic & Immune Health

May Boost the Immune Response

Recent data show that people with weakened immune systems are at a higher risk of catching the new coronavirus. They are also more likely to die from it or experience serious health complications [27].

In animal and cell-based studies, aged garlic extract stimulated white blood cells (lymphocytes, macrophages, monocytes, and neutrophils) by increasing glutathione. White blood cells are immune cells that provide protection against infections, while glutathione is an antioxidant that protects immune cells from free radicals [28, 29, 12].

This suggests that garlic may help strengthen the immune response, but no clinical data are available.

May Reduce Allergies & Inflammation

Inflammation may cause lung and heart damage in later stages of a COVID-19 infection. Scientists use the term “cytokine storm” to describe the widespread inflammatory injury in such cases [27, 30, 31].

Garlic may be anti-inflammatory, but its impact on cytokine storms and COVID-19 outcomes is unknown.

Active compounds from garlic reduced the production of free radicals and inflammatory compounds (TNF, IL-8) in cells infected with dengue virus [32].

In mice with allergic asthma, garlic extract reduced airway inflammation and some inflammatory cytokines. More research is needed [33, 34].

Asthma and other allergic diseases also cause inflammation and have been linked to an increased risk of lung diseases. Over 6% of COVID-19 patients with chronic lung or airway diseases die, compared to under 1% of healthy people [35, 36, 37].

Garlic seems to lower inflammation and boost immunity in animals and cells, but its effects on inflammation-related complications in COVID-19 patients is unknown.

Provides Active Compounds & Nutrients

Garlic has a high concentration of sulfur-containing compounds, which the body can use to make the antioxidant glutathione. The main active components in garlic are thiosulfinates, which include allicin.

Garlic also contains the following nutrients:

Garlic, Disease Prevention & Coronavirus

Along with a healthy lifestyle and diet, garlic may help prevent some chronic diseases and contribute to general wellness.

Chronic diseases — particularly heart disease, lung diseases, and diabetes — are big risk factors for COVID-19 complications and death [27].

Here’s an overview of how garlic affects systems in the body that are particularly important amid the COVID-19 pandemic:

Heart Health

COVID-19 can cause severe heart damage in hospitalized patients. At the same time, having high blood pressure or heart disease predisposes people to complications and death from the virus [39, 40].

Except for age and lung disease, high blood pressure is one of the biggest risk factors of complications from the virus.

Garlic may support heart health. Limited evidence suggests that it may lower cholesterol, reduce blood pressure, relax hardened blood vessels, and prevent excessive platelet aggregation in patients with heart disease [38, 41].

Scientists think that garlic may lower blood pressure similar to drugs called calcium channel blockers [42].

Theoretically, this may be an advantage over compounds that block angiotensin receptors and increase the receptors coronavirus uses to enter cells (ACE-2). The link between angiotensin and coronavirus is still controversial, though [43, 44].

Blood Sugar & Diabetes

People with diabetes are more likely to die from COVID-19. The death rate in diabetics is currently estimated to be about 7.3%, compared to 0.9% of healthy people of all ages [27].

Garlic might reduce insulin resistance, which often precedes or accompanies type 2 diabetes. Garlic may also lower blood sugar and cholesterol levels in patients with diabetes [45, 46].

Both heart disease and diabetes increase the risk of COVID-19 complications and death. Garlic may support heart health and help keep blood sugar in check, but more research is needed.

Dosage & Precautions

Dosage

The effective dosage of garlic has not been determined. Studies in adults used the following doses [47]:

  • 4 grams (1 to 2 cloves) of raw garlic
  • 300 mg dried garlic powder (standardized to 1.3% alliin or 0.6% allicin) 2 to 3 times per day
  • About 7 grams of aged garlic extract per day

A Word About Allicin

Garlic’s most active compound is allicin, though ajoene is also being researched. Allicin is released when raw garlic is crushed or chopped [48].

Allicin is an unstable compound that degrades quickly, so be sure to chop your garlic right before use. Cooked garlic is less potent than raw garlic [49, 50, 47].

Avoid eating garlic or taking garlic supplements with high-protein meals. This reduces the amount of allicin that can be released and absorbed [48].

Analyses indicate that the allicin content in supplements is highly variable. Supplements with “stabilized allicin” claim to provide higher amounts of allicin that’s resistant to breakdown, but their claims are mostly unverified [48].

Types of Garlic Supplements

Garlic supplements can be classified into five groups [51, 50]:

  • Garlic powder – Used in most studies; may contain alliin and allicin if standardized
  • Garlic oil macerate – Contains allicin, which decomposes quickly
  • Garlic oil – Does not contain allicin
  • Aged black garlic – Allicin decomposes into other antioxidant compounds (including S-allyl cysteine); likely has lower anti-inflammatory, anti-allergy, and immune effects [52, 53]

Precautions & Side Effects

Although eating garlic is safe, it can cause bad breath and body odor. Consuming too much raw garlic, especially on an empty stomach, may cause upset stomach, gas, and changes in gut bacteria [54, 47].

Handling garlic during cooking can cause allergic skin rashes, burns, and blisters in some people [55, 56, 57].

Due to its anti-blood-clotting abilities, high garlic doses may interact with blood thinners like aspirin and warfarin [58].

Takeaway

Garlic is a healthy food that has been researched for fighting viruses in the lab, but human data are lacking. Garlic has never been tested against the new coronavirus and there’s no evidence to claim it can be beneficial.

People often turn to garlic when they feel like they’re coming down with a cold or flu, but no solid evidence supports this practice either.

Limited studies show that garlic may support immune, cardiovascular, and metabolic health. Chronic diseases, on the other hand, increase the risk of COVID-19 complications. Thus, eating garlic may promote general health. For this purpose, be sure to eat raw garlic, as cooking garlic degrades its active compounds.

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About the Author

Ana Aleksic

Ana Aleksic

MSc (Pharmacy)
Ana received her MS in Pharmacy from the University of Belgrade.
Ana has many years of experience in clinical research and health advising. She loves communicating science and empowering people to achieve their optimal health. Ana spent years working with patients who suffer from various mental health issues and chronic health problems. She is a strong advocate of integrating scientific knowledge and holistic medicine.

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