- Organosulfur compounds in garlic inhibited the effect of SARS-CoV-2 on ACE2 in a lab study, suggesting it could help prevent infection
- Garlic has demonstrated antiviral and antibacterial properties; among its merits is its contribution to reducing the common cold
- Garlic compounds may help impact cognitive function, improve glucose control and reduce the risk of stroke and renal failure
While investigating garlic (Allium sativum), researchers have observed a variety of cultures have come to use it in much the same ways.1 Some references are found in Sumerian clay tablets dating back to 2600 BC. In ancient Egypt, the working class were given garlic to help support heavy labor and during the first Olympic Games in Greece, athletes used garlic to improve their stamina.
In ancient China, garlic was prescribed for digestion and to treat diarrhea. In India, it was used for general wound healing and to help allay fatigue, digestive issues, arthritis, heart disease and parasites. Recounting the historical uses of garlic across the globe, researchers wrote in Nutrition Journal:2
“Three ancient medical traditions in India i.e Tibbi, Unani and Ayurveda, made extensive use of garlic as a central part of the healing efficacy of plants. The leading Indian ancient medical text, Charaka-Samhita recommends garlic for the treatment of heart disease and arthritis for over many centuries.
In another ancient Indian medical textbook, Bower Manuscript (~300 AD), garlic was used for fatigue, parasitic disease, digestive disorder and leprosy.
With the onset of Renaissance, increasing attention was paid in Europe to the medical use of garlic. A leading physician of the 16th century, Pietro Mattiali of Siena, prescribed garlic for digestive disorders, infestation with worms and renal disorders, as well as to help mothers during difficult childbirth. In England, garlic was used for toothache, constipation, dropsy and plague.”
Garlic Compounds May Inhibit SARS-CoV-2
Vietnamese scientists have been validating the properties of garlic, including identifying active components and their mechanisms of action. In one study published early in the COVID-19 pandemic, researchers evaluated 17 organosulfur compounds commonly found in garlic essential oil.3
The study included molecular docking to analyze the inhibition garlic may have on host receptor angiotensin-converting enzyme 2 (ACE2). This receptor was identified as a crucial agent for SARS-C0V-2 to infect human cells. The 17 organosulfur compounds included in the study made up 99.4% of garlic essential oil.
The strongest activity against SARS-CoV-2 was found in two organosulfur compounds, allyl disulfide and allyl trisulfide, which represent 51.3% of garlic essential oil. The researchers wrote that the results of the lab study “suggest that the garlic essential oil is a valuable natural antivirus source, which contributes to preventing the invasion of coronavirus into the human body.”4
In a more recent study, researchers from Turkey also wrote about the effect garlic has on the release of the hormone leptin from adipose tissue. This hormone helps regulate satiety but also plays a role in boosting inflammatory cytokines. They concluded that garlic:5
“… may be an acceptable preventive measure against COVID-19 infection to boost immune system cells and to repress the production and secretion of proinflammatory cytokines as well as an adipose tissue derived hormone leptin having the proinflammatory nature.”
The effects it has on leptin levels and its potential to impact obesity have also been studied. In 2018, researchers analyzed the effect of a beverage made from dates, vinegar and garlic juice and found that participants who drank 500 milliliters a day for 10 weeks lost an average of 9.5 pounds (4.3 kilograms) and reduced their body fat ratio and serum leptin levels.6
Despite long-standing evidence that garlic has natural antiviral and antibacterial properties, some are diverting attention away from its use in helping prevent COVID-19, as they seek instead to concoct chemical solutions and pursue the development of a new vaccine.
The World Health Organization warns: “Garlic is a healthy food that may have some antimicrobial properties. However, there is no evidence from the current outbreak that eating garlic has protected people from the new coronavirus.”7
Food researchers have suggested that using a garlic water extract when preparing hamburgers could help reduce the growth of staphylococcus aureus in the burgers.8 The extract may be used as flavoring but it also has antibacterial properties against some Gram-positive and Gram-negative bacteria.
Testing during the COVID-19 pandemic is not the first time garlic has been analyzed for its antiviral effects. In an earlier study from 1985, scientists looked into its effects against influenza B, herpes simplex and Coxsackie viruses, recognizing its centuries-old use to treat various infectious diseases.9 Lab testing showed activity against influenza B and herpes simplex.
In a human trial involving 146 participants, researchers separated the group in two to receive either a placebo or a garlic supplement once a day for 12 weeks.10 This was carried out during flu season and participants filled out a questionnaire to assess their health and cold symptoms on a daily basis.
The data showed that those in the intervention group were less likely to get sick, and if they did catch a cold they recovered faster. Those taking the placebo were more likely to get sick more than once in a 12-week period.
In a historical review of the literature, it was found that in addition to reducing high blood pressure, helping prevent diabetes and offering protection against cancer, garlic was active against a number of viruses, including flu, the common cold, HIV, herpes types I and II and rhinovirus.11
Another study was conducted to test the effect of garlic powder tablets in preventing acute respiratory diseases in children.12 The study took place over a period of five months and produced results showing that the infection rate was reduced by 2.4 times in the school children treated as compared to the controls.
The researchers went on to a second stage in which they compared 42 children ages 10 to 12 to 41 children who were given a placebo and 73 who were treated with benzimidazole. The results again showed garlic performed better than placebo at the same ratio and 1.7 times better than the benzimidazole. The researchers concluded:13
“The results of this study have demonstrated that garlic powder tablets Allicor are effective in non-specific prevention of acute respiratory infections in children and possess no side effects. Additionally, the commonly used ARD prevention with benzimidazole turned out to be entirely ineffective in placebo controlled study, so the development of new useful and safe efficient drugs like garlic-based preparations is of ultimate importance.”
Your Brain Benefits From Raw Garlic
Garlic may offer protection to your brain as it helps fight age-related changes in your gut microbiome which are linked to cognitive function. This is according to researchers from the University of Louisville who presented their study at the American Physiological Society’s 2019 meeting.14
A high diversity of gut microbiota is associated with better health. Yet, as you age, this diversity can decline.15 The researchers used 24-month-old mice; this corresponds to about 56 to 69 human years. Some of the mice received allyl sulfide — a compound in garlic — and others got a placebo.16
The researchers discovered that the mice who got the garlic compound had better memory function and a greater expression of neuronal derived natriuretic factor (NDNF), which is a gene required for memory consolidation.
This link between gut bacteria and neurological health is not new. Scholars have found people with dementia have a different population and diversity of gut microbiota compared to others.17
Researchers have also highlighted the benefits of aged garlic extract (AGE) for brain health. In a 2017 study from Thailand, it demonstrated a strong anti-inflammatory effect and improved short-term memory in rats with Alzheimer-type disease.18
Garlic Supports a Healthy Heart and Blood Sugar Levels
With age your arteries stiffen. This happens to nearly everyone to varying degrees.19 In this short video, bestselling author Dr. Michael Greger, a Fellow of the American College of Legal Medicine and a general practitioner specializing in clinical nutrition, reviews the benefits of garlic associated with your heart.
Arterial stiffness leads to poor blood circulation in the microvasculature of the renal system and brain. This can increase the risk of stroke and renal failure. In a meta-analysis of the effect of garlic consumption, researchers found it helps optimize cholesterol levels and reduce the risk of coronary events.20
In addition, Greger notes the blood-thinning properties of garlic are so pronounced that the American Society of Anesthesiology recommends that patients avoid all garlic in the week leading up to surgery.
However, if you’re a candidate for surgery and you want to go ahead and have your garlic, make sure it’s cooked first since cooking inactivates the blood thinning property. Greger suggests adding raw garlic to pesto, salsa and other dips.
Raw garlic also has an effect on high blood sugar, which is a symptom of Type 2 diabetes. According to “The National Diabetes Statistics Report 2020,” 13% of the U.S. population has diabetes and the number skyrockets to 26.8% for people over 65.21 A U.K.-based diabetes organization reports that:
“… scientists found that moderate amounts of garlic supplements could offer benefits to diabetes patients, and that raw or cooked garlic or aged garlic extract can help to regulate blood glucose and potentially stop or lower the effects of some diabetes complications, as well as fighting infections, reducing bad cholesterol and aiding blood flow.”22
They caution, however, that excessive amounts should not be taken and that patients should check with their doctors on this and other measures to improve health.
Growing Garlic From Grocery Store Cloves
You can enjoy the benefits of harvesting your own garlic cloves or scapes from your garden free of pesticides and other chemical toxins. Growing a full head of garlic must be done outside since the plant needs the cold winter to produce the bulb.23 Garlic plants have few requirements other than a sunny location with fertile soil.
The bulbs are planted in the fall before the first freeze.24 You can use a good quality head or two of garlic from the store. Gently break it apart and use the larger outer cloves for planting.
Place them in the soil 3 inches to 4 inches deep and approximately 6 inches apart with the pointy side pointing up. Water the area gently and cover with 4 inches of straw. The following summer, keep the area weeded and watered until harvest time.
However, if it’s the scapes you’re after, then an indoor container will work just fine.25 These are the gently curled green tops that sprout from the garlic clove after planting. If you’re aiming for a full head of garlic outdoors, trim them back like many gardeners do so the plant puts all energy into producing the head.
The green scapes have a gentle garlic flavor and can be eaten raw, sauteed or cooked. You may notice a bulge in the middle of the scapes. This is the unopened flower that is also edible. At the farmer’s market they are available in the early spring, but by planting your own bulbs indoors you can enjoy garlic scapes all year round.
You can plant three to four cloves in one small pot and harvest the scapes in about 10 days. If you’d like to keep greens at home, you’ll need to plant the cloves in succession since the greens do not grow back after clipping.
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