Benefits
HDL cholesterol and apolipoprotein B in a placebo-controlled trial
In a 12-week double-blind trial of 60 adults with mildly raised cholesterol, 6 g a day of an aged black garlic preparation did not change LDL cholesterol, total cholesterol or triglycerides compared with placebo. HDL cholesterol rose and apolipoprotein B fell. These are blood markers from one small trial, not health outcomes.
Blood fats and vessel markers after eating whole cloves
Adults who ate four black garlic cloves (12 g) a day for 12 weeks, with no placebo group, saw apolipoprotein A1 rise and some blood vessel adhesion markers fall. Total and LDL cholesterol rose in those who started with normal cholesterol, and blood pressure did not change, so these within-group shifts show no clear benefit.
Walking distance and heart pumping measures in a cardiac patient trial
In 120 adults with heart failure from coronary disease, 20 g of black garlic a day for six months on top of standard care was reported to improve walking distance, quality of life and ejection fraction versus control. Blinding was not described and the stated primary endpoint was not reported, so this needs confirmation and is not a treatment.
Absorption of garlic sulfur compounds
After a single 20 g serving, healthy adults excreted 33 organosulfur compounds in urine, including breakdown products of S-allylcysteine, showing these compounds are absorbed. A separate breath test study found black garlic delivers only about 5% of the allicin that raw garlic does, so it is not an allicin source.
Antioxidant activity in laboratory tests
Laboratory analyses find black garlic has more sugars, polyphenols and S-allylcysteine than the fresh garlic it is made from, and higher antioxidant capacity in test tube assays. A review of lab studies reports weaker anti-inflammatory and anti-clotting activity than raw garlic. Test tube antioxidant readings are not health outcomes in people.
Milder taste and smell than raw garlic
The aging process gives black garlic a sweet and sour taste and a soft, jelly-like texture without the strong odor of raw garlic, which makes it easy to eat whole. This is a matter of taste and convenience rather than a health effect.
Mechanism of action
Maillard reaction during aging
Holding whole bulbs at roughly 40 to 90 degrees C and 60 to 90% humidity for days to weeks drives the Maillard reaction between sugars and amino compounds. This browns the cloves, raises sugar and polyphenol content and changes the flavor. The exact profile depends on time, temperature and garlic variety.
Shift from allicin to S-allylcysteine
Aging converts pungent, unstable sulfur compounds such as allicin into stable water-soluble ones, mainly S-allylcysteine and S-allylmercaptocysteine. S-allylcysteine is reported four to eight times higher than in fresh garlic, rising more with aging time than with temperature, while allicin delivery falls to a small fraction of raw garlic.
Antioxidant and anti-inflammatory activity in lab and animal work
Cell and animal studies report antioxidant and anti-inflammatory effects of black garlic extracts and of compounds such as S-allylcysteine. These findings come from laboratory models, often at concentrations not reached by eating black garlic, and have not been confirmed as health effects in people.
Clinical trials
Double-blind randomized placebo-controlled trial; 6 g/day of an aged black garlic preparation taken as two doses before meals for 12 weeks; stated aim was the blood lipid profile; no registry number in the abstract; one author was affiliated with Doul Farming Corporation (Jung et al. 2014, Nutrition)
60 adults with mildly raised cholesterol; 28 on black garlic and 27 on placebo were analyzed after 5 dropouts.
Total cholesterol, LDL cholesterol, triglycerides and free fatty acids did not differ from placebo. HDL cholesterol rose versus placebo, apolipoprotein B fell and the LDL to apolipoprotein B ratio rose. These are blood markers, not health outcomes. No adverse effects were reported.
Randomized trial of 20 g black garlic daily versus a placebo group for 6 months, added to standard treatment and a walking program; blinding and the placebo are not described; registered as ChiCTR1800017999; the stated primary endpoint was deaths, strokes and heart attacks, which the results do not report; authors declare no commercial conflicts (Liu et al. 2018, Front Physiol)
120 adults aged 35 to 75 with chronic heart failure caused by coronary heart disease, NYHA class II to III, screened May 2016 to June 2017 in China.
The authors report better heart function class, quality of life scores and 6-minute walk distance, ejection fraction about 14% higher and NT-proBNP about 18% lower than control, and higher blood antioxidant enzymes. With unclear blinding and an unreported stated primary endpoint, this single trial needs confirmation; black garlic is not a treatment for heart conditions.
Single-center before-and-after study with no placebo; 12 g (4 cloves) of black garlic daily for 12 weeks; registered as NCT05082350; publicly funded, authors declare no conflicts (Villaño et al. 2023, Nutrients)
62 adults aged 40 to 65 with overweight: 31 with raised cholesterol and 31 with normal cholesterol.
Apolipoprotein A1 rose in both groups, MCP-1 and ICAM-1 fell in both groups and VCAM-1 fell only in the raised-cholesterol group, all as within-group changes. Total and LDL cholesterol rose in the normal-cholesterol group, apolipoprotein B rose in the raised-cholesterol group, triglycerides did not change and the authors report no blood pressure effect. Without a placebo arm, cause cannot be assigned.
Single-dose absorption study; urine collected for 24 hours after 20 g of black garlic, following two days without allium vegetables; publicly funded (Moreno-Ortega et al. 2023, Antioxidants (Basel))
12 healthy adults, 7 women and 5 men, average age 29.
Thirty-three organosulfur compounds and metabolites were found in urine, mainly methiin, isoalliin, S-(2-carboxypropyl)-L-cysteine and S-propyl-L-cysteine, plus N-acetylated metabolites of S-allylcysteine. This shows absorption, not a health effect.
Branded extract, listed here for comparison and not counted as evidence for generic black garlic. Randomized triple-blind placebo-controlled parallel trial (NCT04915053); one tablet a day containing 250 mg of extract and providing 0.25 mg S-allylcysteine, versus maltodextrin placebo, for 12 weeks after a 2-week placebo run-in; primary outcome office and home blood pressure; funded by Pharmactive Biotech, with three Pharmactive employees as authors (Serrano et al. 2023, Nutrients)
81 adults with Grade I hypertension already on blood pressure drugs were randomized; 77 completed.
Office blood pressure did not differ from placebo. In daily home readings, pressure drifted down in the extract group by an estimated 1.8 mmHg systolic and 1.5 mmHg diastolic over 12 weeks, a trend that differed from placebo, although the paper's confidence intervals for these changes include no change. Endothelial function did not change, and of seven cytokines only IL-2 differed from placebo. Nitric oxide, antioxidant capacity, uric acid and ACE activity changed within the extract group but not versus placebo. Withdrawals for intolerance, mainly reflux, occurred in the extract group.
Branded extract, listed here for comparison and not counted as evidence for generic black garlic. Randomized double-blind crossover (NCT04010565); one tablet a day containing 250 mg of extract and providing 1.25 mg S-allylcysteine, or placebo, for 6 weeks each with a 3-week washout, plus dietary advice; the paper names cardiovascular risk factors as its main objective without a single primary outcome; funded by Spain's CDTI, with two Pharmactive employees as authors (Valls et al. 2022, Nutrients)
67 adults with LDL cholesterol of 115 mg/dL or more.
Diastolic blood pressure fell 5.85 mmHg more than placebo (95% CI 1.3 to 10.5 mmHg lower), mainly in men with diastolic pressure above 75 mmHg. Total cholesterol did not differ between treatments. Adverse events did not differ.