Garlic

garlic

The strongest evidence available for garlic supplementation, specifically AGE, is lowering blood pressure. A 2016 meta-analysis evaluated 20 trials (970 subjects) in which study duration ranged from 2 to 24 weeks. A variety of garlic preparations included garlic powder and AGE. Mean systolic and diastolic pressure decreases were 5.1 mm Hg and 2.5 mm Hg, respectively (1). A 2020 meta-analysis of 12 randomized control trials (553 hypertensive subjects) lasting at least 2 months found a mean decrease of 8.3 mm Hg in systolic pressure and 5.5 mm Hg in diastolic pressure (2).

Results of the lipid-lowering effects of garlic supplementation have been quite inconsistent. A 2013 meta-analysis of 39 randomized controlled studies (2298 participants) found that garlic lowered total cholesterol by 17 mg/dL (0.4 mmol/L) and LDL (low-density lipoprotein) cholesterol by 9 mg/dL (0.2 mmol/L) (3).

A 2015 meta-analysis of 7 studies (513 subjects) has verified efficacy of garlic in lowering fasting glucose (4). Other studies are needed to assess impact on hemoglobin A1C.

A randomized, placebo controlled trial found that garlic5).

Scientific evidence of either garlic intake or garlic supplement use shows limited or no protection against cancer. A 2016 systematic review and meta-analysis evaluating garlic intake in relation to colorectal cancer incidence did not find any protective effect (6).

7). In a randomized controlled trial, 146 participants were treated with an allicin-containing garlic supplement or placebo, one capsule a day, for 12 weeks. During the 12 weeks of the study, those treated with garlic had significantly fewer colds than the placebo group (24 versus 65, P < .001). The authors concluded that an allicin-containing garlic supplement can prevent attack by the common cold virus (8).

Most of these studies lack the specific details with regard to the supplement and/or concentration of active ingredients in the supplement, which may account for the variable results.

Breath and body smell and nausea may occur; high doses may cause burning in the mouth, esophagus, and stomach.

Theoretically, garlicSome Possible Dietary Supplement–Drug Interactions.)

1. 1. Ried K: Garlic lowers blood pressure in hypertensive individuals, regulates serum cholesterol, and stimulates immunity: an updated meta-analysis and review. J Nutr 146(2):389S-396S, 2016. doi: 10.3945/jn.114.202192

2. 2. Ried KExp Ther Med 19(2):1472-1478, 2020. doi:10.3892/etm.2019.8374

3. 3. Ried K, Toben C, Fakler P: Effect of garlic on serum lipids: an updated meta-analysis. Nutr Rev 71(5):282-299, 2013. doi: 10.1111/nure.12012

4. 4. Hou LQ, Liu YH, Zhang YY: Garlic intake lowers fasting blood glucose: meta-analysis of randomized controlled trials. Asia Pac J Clin Nutr 24(4):575-582, 2015. doi: 10.6133/apjcn.2015.24.4.15

5. 5. Soleimani D, Paknahad Z, Rouhani MH: Therapeutic effects of garlic on hepatic steatosis in nonalcoholic fatty liver disease patients: a randomized clinical trial. Diabetes Metab Syndr Obes 13:2389-2397, 2020. doi:10.2147/DMSO.S254555

6. 6. Chiavarini M, Minelli L, Fabiani R: Garlic consumption and colorectal cancer risk in man: a systematic review and meta-analysis. Public Health Nutr 19(2):308-317, 2016. doi: 10.1017/S1368980015001263

7. 7. Filocamo A, Nueno-Palop C, Bisignano C, et al: Effect of garlic powder on the growth of commensal bacteria from the gastrointestinal tract. Phytomedicine 19(8-9):707-711, 2012. doi: 10.1016/j.phymed.2012.02.018

8. 8. Josling P: Preventing the common cold with a garlic supplement: a double-blind, placebo-controlled survey. Adv Ther 18(4):189-193, 2001. doi:10.1007/BF02850113

The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

1. National Institutes of Health (NIH), National Center for Complementary and Integrative Health: General information on the use of garlic as a dietary supplement