We use garlic to season foods from entrees to french fries. For those who love garlic but always wished it just wasn’t so pungent, black garlic may be the ideal solution. Black garlic doesn’t have the same pungent odor as fresh garlic, and it could have a variety of health benefits.
What is Black Garlic?
Black garlic, a type of fermented or aged 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 other compounds .
Black garlic has various antioxidants :
- 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 .
- 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 .
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
Black garlic is a safe foodstuff which can be used in the same way as fresh garlic, but it has not been approved by the FDA for medical use and generally lacks solid clinical research. Talk to your doctor before using black garlic as a supplement.
Possibly Effective For
1) Heart Health
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 decreased by 11.8 mm Hg [6, 7].
Insufficient Evidence For
The following purported benefits are only supported by limited, low-quality clinical studies. There is insufficient evidence to support the use of black garlic for any of the below-listed uses. Remember to speak with a doctor before using black garlic, and never use it in place of something your doctor recommends or prescribes.
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].
Animal & Cell Research (Lacking Evidence)
No clinical evidence supports the use of black garlic for any of the conditions listed in this section. Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
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 cell 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].
4) 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 .
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 .
These potential effects have not been investigated in humans.
6) Brain Cells & MSG
You’ve probably heard of the seasoning MSG (monosodium glutamate). In rat brain cells, MSG damaged the Purkinje cells in the brain (cerebellum and hippocampus), but its effect on humans is unclear [2, 1].
The cerebellum and the hippocampus are vital parts of the brain, as they control muscle coordination and make memory retention possible. In rats, black garlic extract helped decrease Purkinje cell damage caused by MSG [2, 1].
Scientists are investigating whether any of the active compounds of black garlic have an effect on cancer cells. This is very early research on cells only, and no particular conclusion can be drawn from it about the effect of black garlic on cancer in a living animal or human. Many compounds have “anti-cancer” effects in cells which do not pan out in a living system.
In some cancer cells, direct exposure to black garlic decreases JNK and p38MAPK signaling molecules, which are heavily involved in the onset of cancer. Some of these cancer cells are the A549 lung cancer cell, HepG2 liver cancer cell, and MCF-7 breast cancer cell .
Black garlic and its active compounds are currently being investigated in:
Supplementing with Black Garlic
Forms of Supplementation
Black garlic is taken in tablet form as supplements, or in bulb form in Asian supermarkets. Purées or jellies are also available to use as spreads.
There are no known major side effects of black garlic, which is considered safe to use as food.
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
Few extensive human clinical trials have been conducted, so it is difficult to predict the long-term effects of black garlic. Many more clinical trials will be required.
Differences Between Fresh Garlic and Black Garlic
In a study of immune cells from 21 volunteers, black garlic showed stronger antioxidant activity than fresh garlic .
Fresh garlic, however, had stronger anti-inflammatory properties because of its lower sugar content .
Black garlic is made through the slow fermentation of fresh garlic via the Maillard reaction. This reaction reduces the pungency of garlic and produces antioxidant Amadori/Heyns compounds.
Multiple clinical studies have found a potential benefit of black garlic for heart health, reducing cholesterol and blood pressure in humans. Other studies have indicated that black garlic is mildly anti-inflammatory.
Black garlic is available as whole bulbs, spreadable purée or jelly, or in supplement form. It is considered safe to eat as food.