Black Garlic (Allium sativum) is produced from fresh garlic (the bulbs of Allium sativum). It is aged under high temperatures (60–90°C) and humidity (80–90%) for several weeks. This unique process softens and darkens the cloves and gives them a sweet, mild flavor.

Black garlic contains significantly less allicin than fresh garlic but more of most other health-promoting compounds, specifically, S-allyl cysteine (SAC). Researchers suggest that these chemical changes may give black garlic some distinct health benefits.

Facts & History

Garlic has been used for hundreds of years as both a cooking ingredient and a medicinal remedy. Throughout ancient Iranian and Chinese medicine, garlic continues to be a significant player (1, 2).

Black garlic originated in some areas of East Asia and today is consumed around the globe, where its fragrance is not as strong as raw garlic, and the flavor is generally mild and sweet (3).

Nutrition & Key Compounds

S-allyl Cysteine (SAC)

The star compound found in black garlic is S-allyl cysteine (SAC), which is a water-soluble organosulfur compound that increases in amount when aged (4). SAC has been associated with antioxidant, anti-inflammatory, and heart-protective activities.

Allicin Bioavailability

The pungent compound in fresh garlic, allicin, is greatly reduced in black garlic, which contributes to its sweeter, milder flavor.

Black garlic has around 5% of the bioavailability of allicin mostly present in fresh garlic, so the health benefits it provides are likely derived from SAC and other converted sulfur compounds (5).

Antioxidant Profile

The fermentation process that black garlic undergoes increases its antioxidant levels. This is due to an increase in the Maillard reaction, also known as browning. This boost in antioxidants is likely one of the main reasons for the health-promoting effects that black garlic has been suggested to have (6).

Summary
Black garlic owes its health benefits primarily to S-allyl cysteine (SAC) and increased antioxidants from fermentation, as it contains significantly less allicin than fresh garlic.

Potential Health Benefits

May Support Heart Health

Research with mild hypercholesterolemia participants found that black garlic may increase HDL (“good”) cholesterol and decrease some bad lipid markers in the blood (7). For those with moderately high cholesterol levels, aged black garlic extract was found to reduce diastolic blood pressure. This was most notable in men with higher baseline blood pressure readings (8).

Aged garlic extract supplements may slow the formation of plaque in arteries and improve arterial elasticity (9, 10). Additionally, a randomized trial reported that aged garlic extract enhanced small-vessel blood flow in older adults at risk for cardiovascular disease after just one dose (11).

Antioxidant & Anti-inflammatory Effects

Due to its high SAC content, black garlic may neutralize harmful free radicals and reduce oxidative stress in the body (12).

Clinical data also suggests that black or aged garlic extracts may reduce inflammatory markers such as CRP or IL-6. Decreasing these markers may help manage chronic inflammation throughout the body (13, 14).

May Enhance Immune Function

Supplementation with aged garlic extract has been shown to enhance natural killer (NK) cells and γδ-T cell activity. These are known to help the body fight cold and influenza infections (15, 16).

Research suggests that people who regularly supplement with aged or fermented garlic experience fewer sick days and less severe cold and flu symptoms (17).

Anticancer Potential

In patients taking high-dose aged garlic extract, researchers observed a potential anti-cancerous effect. They found a decrease in both the size and number of precancerous colon polyps, suggesting a potential tumor-suppressive effect (18, 19).

Some population studies have also found that higher garlic intake was associated with a lower risk of developing certain cancers, including gastric and colon cancer. More large-scale clinical trials, however, are needed to confirm these findings (20).

Additional Emerging Benefits

Due to its high antioxidant content, black garlic is being investigated for potential anti-aging effects (21). Animal studies exploring Alzheimer’s disease have identified possible cognitive benefits of aged or fermented garlic related to memory and brain function. More human research is also needed in this area (22).

Black garlic has shown antimicrobial properties in laboratory studies, demonstrating effectiveness against various fungi and bacteria. This is thanks to its organosulfur compounds (23). Some research suggests garlic may help the body eliminate heavy metals and other toxins. Black garlic’s specific role in detoxification requires further study (24).

Emerging research indicates that aged garlic extract may help regulate blood sugar levels and potentially benefit people with type 2 diabetes, though human trials specific to black garlic are still limited (21).

Similarly, while direct evidence for black garlic is still developing, studies on garlic’s compounds suggest they may help protect liver function from toxins and heavy metals (24).

Summary
The potential benefits of black garlic, improved cardiovascular markers, enhanced immune support, anticancer effects, and beyond, are due to the transformation it undergoes. Additionally, emerging evidence indicates that black garlic may reduce oxidative stress and promote detoxification, providing benefits for blood sugar control and liver protection.

Possible Risks & Side Effects

Black garlic is generally well-tolerated by most people and is easy on the digestive system. However, some considerations are worth noting. Some users report mild headaches, fatigue, or dizziness after consumption, though studies suggest these occur at rates similar to placebo groups (25).

As with fresh garlic, black garlic can have mild blood-thinning effects. People taking anticoagulant medications or preparing for surgery should consult with their healthcare provider before using black garlic supplements (26). Research indicates no significant bleeding risk with moderate intake, even for those taking warfarin, but medical guidance is still recommended (25, 27).

Allergic reactions to black garlic are uncommon, but people with known allergies to garlic or other members of the Allium family should be cautious. Finally, consuming large amounts of black garlic might cause gas or mild digestive discomfort in some individuals.

Summary
In general, black garlic is well tolerated by the majority of individuals. Due to the potential blood-thinning effects, those on anticoagulant medications or those who are anticipating surgery should speak with their physician. Mild adverse effects, such as headache or fatigue, are rare, with most occurrences being similar to those seen in placebo groups of studies.

Buying & Storage Tips

Black garlic is available in whole bulbs, peeled cloves, or paste and should be purchased without mold or extreme dryness. Once opened, keep them in an airtight container in a cool, dry place or refrigerated. When correctly stored, black garlic can last for several weeks to months.

How to Eat Black Garlic

  1. Spread on Bread/Crackers: The jam-like consistency makes it a great option for spreading on toast or crackers.
  2. Blend into Sauces or Dressings: For a sweet-savory addition to dips, vinaigrettes, or marinades, mash or puree it.
  3. Mix into Stews & Soups: Add it toward the end of cooking to maintain a subtle flavor.
  4. Create Custom Sauces: Mix it into black garlic aioli, mayonnaise, or butter.

FAQs

Does Black Garlic Contain Allicin?

Not much, just about 5% bioavailability compared to fresh garlic. Instead, it contains higher levels of compounds like SAC that may deliver similar or even stronger benefits (5).

Can black garlic be consumed while taking blood thinners?

In most cases, yes since garlic can potentially act as a mild anticoagulant. It’s recommended to consult your physician first if you are taking warfarin or other similar medications (25, 26).

How is black garlic different from aged garlic extract (AGE)?

Black garlic is created through the slow fermentation of whole garlic bulbs under high temperatures and humidity. This process results in a soft, sweet, and umami flavor and texture. On the other hand, aged garlic extracts are usually made by soaking garlic in alcohol or water. Both forms are rich in S-allyl cysteine but yield different final products and manufacturing methods (3).

Can black garlic aid immune function?

Yes. Research has shown that garlic extracts that were fermented or aged may enhance the function of immune cells (such as NK cells) and may decrease the severity of cold and flu (15, 17).

Does it have any anticancer properties?

Preliminary research suggests that those who consumed aged garlic extract had smaller and fewer precancerous lesions in the colon. However, more extensive studies are warranted to determine the full extent of black garlic’s anticancer effects (18).
Fact
Black garlic, a fermented form of garlic, carries symbolism related to health, resilience, and even immortality, particularly in Taoist mythology.

Conclusion

Black garlic is made from raw garlic bulbs and aged for weeks under conditions of heat and humidity. This process alters the texture, flavor, and chemical composition of garlic, increasing compounds like S-allyl cysteine and decreasing others such as allicin.

The higher antioxidant activity and growing evidence of black garlic’s potential effects on heart health, immune support, and cancer prevention make it an interesting functional food to consider. However, while many studies are promising, they are often conducted with small populations or short durations. Further research is needed to validate these results, but more studies are ongoing.

For most people, black garlic is a simple, low-risk food to experiment with in the kitchen or as a supplement. For specific concerns, especially those taking blood thinners or other medications, consult a healthcare provider for further guidance. All in all, black garlic is a tasty way to incorporate the potential health benefits of garlic, supported by credible research.

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