What is Black Garlic?
Black garlic, which is essentially fermented or aged fresh garlic, has numerous health benefits that range from its strong antioxidant nature to its potential role in cancer treatment .
With its unique sweet flavor and jelly-like consistency, it is widely known in Asia for its antioxidant properties .
Black garlic (Allium sativum L.) is a fermented product of garlic made by treating fresh garlic for an average of 10 days at high temperatures (40 to 60 °C) and high humidity. It undergoes a Maillard reaction, which causes different compounds to form during the reaction. The reaction also darkens white garlic into a black color .
Processes vary widely across suppliers, with aging treatment ranging from 4 to 40 days. One study found that 21 days of treatment at 70 degrees and 90% relative humidity was best for black garlic’s antioxidant abilities .
While you can add black garlic to your diet, black garlic supplements are also available.
When garlic undergoes treatment to turn into black garlic, allicin, the component that gives fresh garlic its notorious odor, is converted into a variety of antioxidant compounds [R, R].
Black garlic has various antioxidants [R, R]:
- Amadori/Heyns compounds: These are formed during the Maillard reaction. Amadori/Heyns compounds are strong antioxidants, and compared to fresh garlic, black garlic has up to 40 to 100 times more of these compounds .
- 5-hydroxymethylfurfural: This is an antioxidant that also has some anti-inflammatory effects. Compared to white garlic, black garlic has a higher amount of this beneficial component, as 5-HMF is created under very high heat .
- Organosulfur compounds: Diallyl sulfide, diallyl disulfide, diallyl trisulfide, and diallyl tetrasulfide 
- Pyruvate: This is a key antioxidant and anti-inflammatory molecule of black garlic. It reduces nitric oxide and prostaglandin E2, both of which prolong and intensify inflammation [R, R].
- N-fructosyl glutamate
- N-fructosyl arginine
- Other alkaloids, polyphenols, and flavonoids
Black garlic also contains nitrogen oxide, which has strong antiviral and antitumor effects .
It also contains 2-linoleoyl-glycerol, an anti-inflammatory molecule. It lowers levels of prostaglandin E2 and cytokines, which are key promoters and signals of the inflammatory response. They prolong and increase cell death, swelling, and the uncomfortable symptoms of an allergy, infection, or other sicknesses [R, R].
Mechanism of Action
Garlic contains a high abundance of hydrogen-sulfur donating compounds, which are very important for antioxidant properties to be possible. Allicin, an unstable component of garlic, is converted into organosulfur compounds, which are more stable and also contain hydrogen-sulfur donating capabilities .
Hydrogen-sulfur donating compounds are vital to antioxidant effects, as they activate the Nfr-2 factor .
Nfr-2 factors bind to antioxidant response elements, which trigger the release of various enzymes :
All of these enzymes are important because they become powerful antioxidants, transforming damaging oxygens and nitrogens into nonreactive states that can significantly harm cells in the human body .
Health Benefits of Black Garlic
1) Has Anti-Cancer Properties
Black garlic decreases JNK and p38MAPK signaling molecules, which are heavily involved in the onset of cancer. Black garlic is toxic to a variety of cancer cells and can both stop their growth and division, and kill them. Some of these cancer cells are the A549 lung cancer cell, HepG2 liver cancer cell, and MCF-7 breast cancer cell .
Various cell studies have been conducted to analyze the specific anti-cancer abilities of black garlic.
May Treat Leukemia
In a study of human leukemia cells, black garlic stopped cancer cell growth. Black garlic triggered signaling molecules (caspase) to initiate programmed cell death .
Cell death occurs because black garlic increases the death receptor 4 and Fas ligand receptors on human cell membranes. These receptors attach to various other molecules that cause the cell to die. It also increases the number of enzymes that are vital for cell death .
Black garlic also degrades an enzyme called poly (ADP-ribose)-polymerase and in turn prevents DNA in cancer cells from being repaired, further ensuring that the cancer cells die .
May Help Treat Stomach Cancer
In a study of human stomach cancer cells, black garlic at concentrations of 10 mg/mL, 50 mg/mL, and 100 mg/mL successfully killed the cancer cells. This demonstrated black garlic’s potential role in chemotherapy .
In mice, black garlic treatment resulted in smaller tumors and the increase of 2 key defense enzymes (superoxide dismutase and glutathione peroxidase) in the blood. These enzymes are very important because they prevent oxidative damage and remove harmful reactive oxygen species that cause tissue damage .
It also reduces movement, growth, and stability of cancer cells by reducing the enzyme activity of key structural molecules called matrix metalloproteinase-2 and matrix metalloproteinase-9 .
May Treat Colon Cancer
Black garlic treatment led to colon cancer cell death. It also stopped the cell cycle process of growth, replication, and division .
Black garlic accomplishes this by stopping proteins from being made that help with cell processes, such as structure and communication. Specifically, black garlic stops a signal (phosphatidylinositol 3-kinase̸protein kinase B transduction pathway) that promotes protein synthesis and thus prevents cancer cell survival .
Black garlic also increased PTEN (a tumor suppressor), which prevents mutations in the DNA from accumulating that could then cause cancer .
May Treat Endometriosis
In human endometrial cancer cells, 50 μg/mL of black garlic impeded the growth of the cancer cells by stopping important signals (c-Jun N-terminal kinase) .
2) Benefits the Heart
In a 12-week human study (placebo) involving 60 people, 30 people were given 6 g of black garlic 2 times daily before meals. It increased HDL (good) cholesterol levels compared with the placebo group at the end of the study. However, there were no changes in LDL (bad cholesterol) [2, 1].
Black garlic’s high levels of organosulfur compounds also relax blood vessels, which leads to lower blood pressure. In a 12-week study of 79 high blood pressure patients, they took either 2 or 4 black garlic tablets daily. Their average blood pressure significantly decreased by 11.8 mm Hg [7, 8].
3) Is a Strong Antioxidant
Black garlic reduces allicin content by converting allicin, an unstable compound, into more stable compounds that turn out to be great antioxidants. The Maillard reaction causes brown discoloration of garlic and generates various compounds that have antioxidant properties .
Black garlic is 10 times more effective than fresh garlic in its antioxidant power. The garlic mimics an enzyme (superoxide dismutase) by defending cells from hydrogen peroxide, a reactive oxygen species that can cause tissue damage .
4) Can Reduce Inflammation
In a cell study using macrophages (immune cells), black garlic decreased the production of nitric oxide, TNF-α, and prostaglandin E2, which are all key promoters of inflammation. It accomplished this by decreasing various protein and enzyme levels, specifically of NO synthase, TNF-α, and cyclooxygenase-2 protein [1, 2].
5) Can Help Lower Severity of Allergies
Allergies are related to immunoglobulin E (IgE) antibodies and mast cells that all contribute to promoting long-term inflammation. Specifically, a type I allergy response is activated by the IgE receptor that is on the outside surface of immune cells [2, 1].
In another study, 50 μg/mL of black garlic inhibited key allergy-promoting molecules (prostaglandin E2, leukotriene B4, and cyclooxygenase-2), and prevented signaling (phosphorylation of Syk, phospholipase A2, and 5-lipoxygenase) that can lead to cell attack by immune system cells called macrophages [2, 1].
6) May Reduce Liver Damage
Black garlic also increased the normal activity and metabolism of the liver as the garlic increased levels of a molecule called CYP2E1. The black garlic also decreased fatty liver deposits and rebalanced liver cell diameters to optimal size .
7) Can Help Reduce Obesity
In a rat study, black garlic significantly decreased bodyweight, stomach fat, and fat cell (adipocyte) size. The rats experienced the benefits of overall decreased fat. Black garlic also lowered triglyceride and LDL (bad) cholesterol levels and increased HDL (good) cholesterol levels .
8) May Protect Brain Cells from MSG
The cerebellum and the hippocampus are vital parts of the brain, as they control muscle coordination and make possible human memory retention. In rats, black garlic extract helped decrease Purkinje cell damage caused by MSG [2, 1].
Supplementing with Black Garlic
Forms of Supplementation
Black garlic is taken in tablet form as supplements, or in bulb form in Asian supermarkets.
There are no known major side effects of black garlic. However, a toxic dose of garlic is 1,000 μg/mL. It is less toxic compared to raw garlic .
A rare case has been reported, in which black garlic has led to a case of pneumonia. It could not be determined if it was an immune reaction or a case of toxicity .
Limitations and Caveats
Various cell studies have proven the antioxidant nature of black garlic, and it is this main property that further extends to its other consequent benefits. Few extensive human clinical trials have been conducted, so it is difficult to predict the long-term effects of black garlic.
Differences Between Fresh Garlic and Black Garlic
In a cell study of immune system cells from 21 volunteers, black garlic showed stronger antioxidant and anticancer activity than fresh garlic .
Another study showed that black garlic is the optimal choice as an antioxidant for neutralizing reactive oxygen species. Fresh garlic, however, had stronger anti-inflammatory properties because of its lower sugar content .
Multiple users have claimed that they did not recognize any major changes, as they had not taken black garlic for a substantial period when reviewing it.
However, many remarked that they were pleased it did not have a smell and that they were taking it for its many antioxidant effects.
One user who has been taking garlic supplements regularly for years remarked that black garlic supplements seemed to be more potent. Some users felt the black garlic reduced appetite.