Black garlic

What black garlic is

To make black garlic, fresh garlic is kept for an extended period at 60 to 90 degrees and 80 to 90 percent humidity. The cloves turn black, the allicin content falls, and with it the pungent smell disappears. The process is often referred to as fermentation. The product is rich in S-allylcysteine.

Two other garlic products with their own body of studies must be distinguished from it: aged garlic extract (AGE), for which raw garlic is stored in aqueous ethanol for more than ten months, and garlic powder, which the EMA describes as a traditional herbal medicinal product. Results for these products do not automatically apply to black garlic, and vice versa. In the BK-Score, human evidence stands at 4 out of 10 points.

How it works

S-allylcysteine is considered the main candidate. That sulfur compounds from black garlic are absorbed has been shown in humans: after 20 g of black garlic, 33 sulfur-containing compounds were found in urine, including breakdown products of S-allylcysteine (Moreno-Ortega 2023). In a blood pressure study, nitric oxide in the blood and antioxidant capacity rose, and the activity of the blood-pressure-regulating enzyme ACE fell (Serrano 2023).

These are surrogate markers from a single study. How much of the small blood pressure effect they explain is open; most claims about further mechanisms come from laboratory and animal experiments.

What the studies show

Blood pressure: Valls 2022 and Serrano 2023

Valls 2022 gave 67 people with elevated LDL a standardized black garlic extract (250 mg with 1.25 mg S-allylcysteine) or placebo for 6 weeks each in a double-blind crossover study, along with dietary recommendations. Diastolic blood pressure fell by 5.85 mmHg (95 % interval −10.5 to −1.3), mainly in men with a diastolic value above 75 mmHg. Serrano 2023 tested a low-dose extract over 12 weeks in stage 1 hypertension under blood pressure medication, triple-blinded: an additional −1.8 mmHg systolic and −1.5 mmHg diastolic.

Blood lipids: Jung 2014 and Serrano 2026

In Jung 2014, 60 people with mildly elevated cholesterol took 6 g of black garlic daily or placebo for 12 weeks; 55 were analyzed. Triglycerides, LDL and total cholesterol did not differ, HDL rose and apolipoprotein B fell. Serrano 2026 gave 75 people with stage 1 hypertension 250 mg of extract (ABG10+) or placebo for 12 weeks. None of the usual blood lipid values changed; the authors themselves regard changes in lipoprotein subfractions as hypothesis-generating.

Heart failure: Liu 2018

In a study from China, 120 patients with heart failure due to coronary heart disease were divided evenly between black garlic and placebo and treated for 6 months. Ejection fraction, NT-proBNP and quality of life were better in the garlic group. It is a single study; a replication is lacking.

As a food: Villaño 2023

31 people each with and without elevated cholesterol ate 12 g of black garlic daily, about 4 cloves, for 12 weeks. Apolipoprotein A1 rose and several adhesion molecules in the blood fell. There was no placebo group; the comparison was before versus after.

Where the data stop

• Cardiovascular events. What was measured was blood pressure, blood lipids and blood markers. No study has examined whether black garlic prevents heart attacks or strokes.
• Cholesterol lowering. LDL and total cholesterol remained unchanged in the two placebo-controlled studies on blood lipids.
• Independent replication. The blood pressure data come from a few small studies with standardized extracts. Whether the results can be transferred to bulbs or other preparations is open.
• Transfer from other garlic products. Studies on aged garlic extract (AGE) or garlic powder describe other products with a different composition.

Status, approval and legal

Black garlic is a processed food made from ordinary garlic and is sold as bulbs, paste or in capsules. The EU list of authorized health claims under Regulation 432/2012 contains no claim for garlic.

In its 2017 monograph, the EMA describes garlic powder and dry garlic extracts as traditional herbal medicinal products, as an adjunct for the prevention of atherosclerosis and for cold symptoms, solely on the basis of long-standing use. Black garlic is not specifically covered in it.

Safety

In the study by Jung 2014, no side effects were reported; the longest study ran for 6 months. In the BK-Score, safety stands at 3 out of 10 points; this axis measures how well safety has been studied, not how safe the substance is.

For garlic preparations in general, the EMA names a bleeding risk: caution with anticoagulants and platelet aggregation inhibitors, and discontinuation 7 days before surgery. They are contraindicated during HIV therapy with saquinavir and ritonavir, because drug levels may fall. As side effects, the EMA describes mouth and body odor, gastrointestinal complaints, allergic reactions, headaches and bleeding. Whether this applies to the same extent to black garlic has not been specifically studied. This text is information and does not replace medical advice.

Sources

• Kimura S et al., J Food Drug Anal 2017 – review of the production, constituents and effects of black garlic
• Valls RM et al., Nutrients 2022 – double-blind crossover study, 67 people with elevated LDL, 6 weeks
• Serrano JCE et al., Nutrients 2023 – triple-blinded study in stage 1 hypertension under medication, 12 weeks
• Serrano JCE et al., Front Nutr 2026 – triple-blinded study, 75 participants, blood lipids and lipoprotein subfractions
• Jung ES et al., Nutrition 2014 – double-blind study, 60 people with mildly elevated cholesterol, 12 weeks
• Liu J et al., Front Physiol 2018 – randomized trial, 120 patients with heart failure due to coronary heart disease, 6 months
• Villaño D et al., Nutrients 2023 – before-and-after study, 62 participants, 12 g of black garlic daily over 12 weeks
• Moreno-Ortega A et al., Antioxidants 2023 – sulfur compounds in urine after 20 g of black garlic
• Nakamoto M et al., Metabolites 2026 – production and constituents of aged garlic extract (AGE)
• EMA/HMPC 2017 – European Union herbal monograph on Allium sativum L., bulbus (garlic)