'Let Food Be Thy Medicine': Garlic

This heart-protecting, infection-fighting superstar, may just ward off tigers too!

This is the first entry in a new series, “Let Food Be Thy Medicine”. In it, we’ll do a deep dive plant profile, similar to my other Plant Encyclopedia entries, but focusing on food you can find at the grocery store. I’ll be starting a Fungus Encyclopedia soon as well. Plant Encyclopedia entries will continue to be monthly. The other two series will occur more sporadically as time allows. 

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Garlic feels like a plant that needs no introduction, flavorful, nutritious, unmistakable both in appearance and taste. Because of that I omitted the sections on identification and recipes. If you do want a garlic recipe, hit me up in the comments. But did you know that garlic (aka Russian Penicillin) has been used medicinally for over 5000 years? That it might protect you from tigers? That Chicago bears its name? Legendary herbalist Juliette de Bairacli Levy said of garlic, “The Gypsies worship this plant for its remarkable medicinal powers.” Let’s get to know this healing plant and a little of the magic and history it carries. 

Preparation as Medicine: 

Juliette de Bairacli Levy recommends consuming garlic raw to maximize its medicinal power. Eat either a handful of leaves or 2-3 cloves eaten with a salad. Chopping or crushing raw garlic releases an enzyme that results in the formation of allicin, a powerful medicinal compound. She also recommends chewing leaves of parsley, mint, basil, or thyme to neutralize garlic breath.

Dehydrated garlic/garlic powder is made from garlic cloves that are sliced, then dried at a low temperature to prevent inactivation of medicinal chemicals. These supplements do not contain much allicin, but clinical trials have shown that 600-900 mg/day are beneficial at reducing several risk factors for heart disease. 

Aged garlic extract (AGE) is produced when garlic cloves are soaked in an alcohol and water mix for up to 20 months. Clinical trials have shown these garlic extracts are effective at lowering the blood pressure, reducing cholesterol, and preventing platelet clumping, which can increase the risk of heart attacks.  Garlic oil is both delicious and medicinal. I make this oil, which infuses olive oil with garlic and mullein flowers to help with earaches. 

Black garlic is a form of aged raw garlic exposed to high heat and humidity. The strong flavor of raw garlic becomes mild and sweet and this process also makes beneficial chemicals in the garlic more available to the body. You can make black garlic at home. I haven’t tried it yet, but I hope to soon. 

Cooking garlic does interfere with its medicinal value. Microwaving an unpeeled, uncrushed clove of garlic totally destroyed the enzyme that leads to the production of allicin. Similarly, heating or boiling for 6 minutes or more suppressed garlic’s ability to prevent platelet clumping (aggregation), but crushed garlic kept the ability to prevent platelet clumping better than uncrushed garlic. In animal studies, the cancer prevention effect of garlic was lost after cooking garlic for 60 seconds in the microwave or 45 minutes in the oven. More of the beneficial compounds are retained in cooking if you chop garlic and let it sit for 10 minutes prior to cooking. 

Pencil drawing of the garlic plant, by my talented husband, Joe Donohue

Traditional Uses: 

In traditional use, garlic has been known to have the following properties: 

• Anti-cancer

• Antioxidant

• Antidiabetic

• Kidney protective

• Prevents hardening of the arteries

• Antibacterial

• Antifungal

• Lowers blood pressure

• Lowers fevers

• Relieves intestinal gas

• Sedative

• Aphrodisiac

• Diuretic

It was also used to treat:

• Indigestion

• Respiratory infections

• Urinary tract infections 

• Heart disease

Medical Evidence: 

Infectious Diseases:

• A chemical called allicin in garlic fights multiple kinds of bacteria, including Staphylococcus aureus, Salmonella, E. coli, the bacteria that causes cholera, and antibiotic resistant types of bacteria (specifically MRSA).

• Garlic also eliminates the effects of toxins produced by bacteria.  

• Garlic extracts also kill dozens of varieties of fungi including Candida (which causes yeast infections)

• Garlic extracts also kill several parasites including tapeworms, the parasite that causes malaria, Giardia, and the cause of amoebic dysentery. 

• Garlic extracts also kills multiple kinds of viruses including influenza, rhinovirus (a common virus that causes colds), and herpes. Animal studies showed that garlic increased production of antibodies against influenza. Garlic and/or chemicals in garlic have antiviral properties against at least the 26 viruses found on this chart.

Cardiovascular: 

• Garlic supplementation lowers the top number of the blood pressure by an average of 5 and the bottom number by an average of almost 3. In addition, it lowered blood pressure more in people who had high blood pressure (lowering the top and bottom numbers by an average of 8 and 6 respectively). 

• Garlic supplementation results in 8% decrease in total cholesterol. 

• In addition garlic supplementation decreases the likelihood of “coronary events” (meaning heart attacks and precursors to heart attacks that require interventions like stenting) by 38%. 

• Black garlic extract prevents the formation of platelet clumps (platelet aggregation), which contribute to the process of a heart attack.

• Black garlic plus exercise was found to reduce six different risk factors for heart disease in postmenopausal women.

• Black garlic extract also reduced average blood pressure and stiffness of the arteries. 

• In another study, black garlic extract led to a decrease in blood pressure of, on average, 10 mmHg (e.g. a decrease in blood pressure from 150/90 to 140/84, similar to medications). 

• Black garlic inhibits angiotensin converting enzyme, which is the same way the medication lisinopril works. 

Gastrointestinal: 

• Black garlic extract improves peristalsis (the squeezing of the intestines) this suggests that black garlic extract could be helpful for people who struggle with gastroparesis, a condition where the nerves and muscles of the stomach are damaged and cause the weaker, slower stomach contractions. 

• Black garlic is an effective treatment for stomach ulcers. Compared to raw garlic, black garlic decreased the amount of tissue damage due to acid reflux causing inflammation in the esophagus (reflux esophagitis). 

• Black garlic’s anti-inflammatory and antioxidant effects prevent damage due to NSAID medications (like ibuprofen), and damage due to inflammatory bowel diseases like Crohn’s and Ulcerative Colitis. 

Kidney: 

• Black garlic extract was also found to prevent kidney injury due to an antibiotic called gentamicin and protects the kidneys from injury due to diabetes. 

Liver: 

• Garlic protects against liver injury due to gentamicin or acetaminophen (Tylenol) because of its effect as an antioxidant. 

• Several animal studies also suggest black garlic protects the liver from injury. 

Oncology: 

• Raw garlic was the most effective anti-cancer drug when compared to 33 other raw vegetable extracts. 

• Garlic extracts inhibit the growth of cancer cells, stimulates the death of cancer cells, prevents the development of blood vessels to supply cancerous tissues, and prevents cancer from moving to other areas of the body.

• Garlic extracts also help the body metabolize materials that increase the risk of cancer (carcinogens). 

• Allicin, a chemical in garlic, was found to stop the spread of colorectal cancer to other parts of the body. It also prevents pancreatic and stomach cancer cells from multiplying.

• Garlic powders decreased DNA damage to liver cells in rats by 35%. 

• Continuous garlic consumption decreases the likelihood of developing lung, colon, breast, stomach, and prostate cancer. 

• Z-ajoene, another chemical in garlic slows the growth of breast cancer and glioblastoma (a very deadly brain cancer) cells. 

• Black garlic extract suppresses colon, stomach, lung, and thyroid cancer cell growth. It also makes breast cancer cells more responsive to chemotherapy. 

• A specific chemical in black garlic also has anticancer effects on prostate, liver, bladder, and ovarian cancer. 

Neurologic: 

• Black garlic extract decreased the formation of the proteins and plaques in the brain that lead to Alzheimer’s dementia and decrease cognitive dysfunction because of its antioxidant effects. 

• A chemical in black garlic also slowed the loss of dopamine and improved movement problems in Parkinson’s disease. 

• That same chemical also decreased the amount of neurologic injury from a stroke. It decreased the size of the stroke, how many neurons were lost. 

• Animal studies also support the use of black garlic extract. It protected against brain injury due to stroke. These impacts appear to be due to both antioxidant and anti-inflammatory effects of black garlic. 

Metabolic: 

• Black garlic extract reduced blood glucose, Hgb A1c (a measure of blood sugar over the past several months), and increased insulin levels in rats. 

• Black garlic powder also lowered blood sugar and prevented sugar from being converted to glycogen in the liver. 

• Black garlic also lowered triglycerides and total cholesterol. 

Orthopedic: 

• When joint replacements get infected, treating them is sometimes complicated because the bacteria can develop a “biofilm”, which can prevent antibiotics from getting to the bacteria. Multiple studies have shown that garlic extract is effective at preventing the formation of these biofilms. 

Of note, different preparations of garlic result in different concentrations of the beneficial chemicals. This chart describes the predominant sulfur-based compounds in each preparation. Allicin and alliin are two strong infection-fighting chemicals. I am still learning what the other compounds listed do. 

Adverse Effects: 

Garlic can interfere with the absorption of certain medications for HIV/AIDS into the body. In fact, two garlic capsules twice a day resulted in a 50% decrease in the availability of protease inhibitors in the body. There have been case reports of uncontrolled bleeding after garlic supplementation. Because of this, doctors often suggest against its use with blood thinners, anti-inflammatories, and diabetes medications. However, the evidence to support those recommendations is weak. Side effects of garlic supplementation occurred in ⅓ of patients in one trial, but were mild and included burping, flatulence, and esophageal reflux (GERD/heartburn). 4-6% of patients experienced more severe GI side effects. They were not described, but I would guess they mean nausea, vomiting, diarrhea. Aged garlic extract, the only water based extract, did not show any toxicity, or medication interactions with blood thinners, cholesterol medications, or cancer medications. It is also important to note that these side effects occurred with supplements that typically have a higher dose than usual dietary intake of garlic. 

Ecosystem Services: 

Garlic is a natural deterrent to common garden pests. It also has high levels of sulfur, which kills fungus and deters aphids. Garlic is a beneficial companion plant to the following plants in your garden: 

• Tomatoes

• Fruit trees

• Potatoes

• Cabbages

• Broccoli

• Cauliflower

• Kale

• Carrots

However, it does stunt the growth of peas and beans. A few garlic cloves in the soil can also deter pests like aphids, snails, and caterpillars from damaging roses too. 

History and Folklore:

Garlic has been used medicinally for at least 5000 years. There are records in Sanskrit of its use. It has been used in Chinese medicine for at least 3000 years. The Egyptian slaves who built the pyramids were given a daily ration of garlic to ward off illness and increase strength and endurance. In fact, when Moses led Hebrew slaves out of Egypt, the things they complained of missing included fish, cucumbers, melons, leeks, onions, and garlic. 

In Ancient Korea, people used to eat pickled garlic before entering mountain passes because they believed the tigers disliked it. According to Mohammed, when Satan was cast out of the garden of Eden. Where his left foot touched the earth garlic grew, where his right foot touched, onions grew. 

Ancient Greeks placed garlic on piles of stones at crossroads to leave dinner for Hecate and protection from evil spirits. Greek midwives hung garlic in birthing rooms to keep evil spirits away. The practice eventually spread through much of Europe. Roman soldiers ate garlic to give them courage and even planted garlic in the fields of lands they conquered, believing that courage was transferred to the battlefield. 

It is believed that the word Allium (the genus name of garlic, onions, chives, leeks, ramps, and others) comes from an ancient Celtic word all, which means monster slayer. Norse mythology linked garlic to Thor. In European folklore, garlic can ward off the evil eye, devils, werewolves, and vampires. There is an old Welsh saying, “Eat leeks in March and garlic in May. Then the rest of the year, your doctor can play”. Garlic was often gathered on the feast of St. John the Baptist (June 24 or around the Summer Solstice). They were kept throughout the year to avoid poverty. 

The city of Chicago was named after garlic. The name is derived from Chicagaoua, an Algonquin word for wild garlic, which was abundant in the area. 

Magical Uses: 

Garlic is known to ward off evil spirits, negative energies, and malevolent forces (including vampires). Burning garlic cloves or garlic-infused incense is thought to purify the environment and facilitate spiritual cleansing. It is considered an herb that increases psychic abilities and spiritual connections.Garlic is included in many spells to increase their potency and effectiveness. 

Flower Essences: 

Garlic helps us fortify ourselves against fear and anxiety. It helps us ward off people who drain our emotional and spiritual energy. 

Blessing: 

Blessed garlic we honor your straight neck, your pungent flavor, and your beautiful flower. 
We praise the protection your provide us inside and out and the protect you provide your plant kin. 
Please help us to release anxiety and protect our energy
Please protect our bodies from infection and our hearts from injury
Please protect us from evil and give us courage 

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Author’s note: Reviewing the medical literature for these plants is great fun AND takes quite a bit of time. Because the knowledge I’m sharing here has a bit more practical use and takes more time than me talking about my feelings I have opened The Nettle Witch, MD up for paid subscriptions. I won’t be putting anything behind the paywall because I want all of this information to be available to anyone who will use it, but if you find it valuable and are willing to support my work, I’d be honored. In addition, I would love to add a fungus of the month and a “Let Food Be Thy Medicine” segment like this garlic one each month. Your paid subscription would help me have more time to do that. As a thank you, I am hoping to start recording a plant spirit meditation for paid subscribers starting with Elderberry in October. Thank you so much!