Garlic is an herb that has been used for medicinal purposes by various cultures throughout history. Some of the earliest documented therapeutic use of garlic dates to the 6th century BC in the Zoroastrian culture. The Sumerians and ancient Egyptians, as well as the Greeks, have used garlic therapeutically. In addition, garlic’s healing properties have been revered in traditional Chinese, Ayurvedic, and Unani medicine for centuries.(1)
Modern science has validated garlic’s traditional use, showing its benefits for a variety of health conditions. From a mechanism-of-action standpoint, garlic has been found to possess antioxidant, nitric oxide–enhancing, and angiotensin-converting enzyme (ACE)–inhibiting properties.(2) Further studies have shown garlic’s ability to reduce inflammation through its action on various enzymes, including cyclooxygenase (COX) and lipoxygenase (LOX), while also potentially acting against a master switch for inflammation in nuclear factor kappaβ (NF-κβ).(3) Garlic also normalizes platelet aggregation, reduces lipid peroxidation, and supports healthy levels of blood lipids.(4) These mechanisms make garlic well suited for supporting cardiovascular function, immune wellness, and a bevy of other health conditions. And the research goes on. Several recently conducted studies highlighted here showcase garlic’s broad healing potential.
1. Bayan L et al., “Garlic: a review of potential therapeutic effects,” Avicenna Journal of Phytomedicine, vol. 4, no. 1 (January–February 2014): 1–14
2. Shouk R et al., “Mechanisms underlying the antihypertensive effects of garlic bioactives,” Nutrition Research, vol. 34, no. 2 (February 2014): 106–115
3. Jeon YY et al., “Comparison of anti-oxidant and anti-inflammatory effects between fresh and aged black garlic extracts,” Molecules, vol. 21, no. 4 (March 30, 2016): 430
4. Khatua TN et al., “Garlic and cardioprotection: insights into the molecular mechanisms,” Canadian Journal of Physiology and Pharmacology, vol. 91, no. 6 (June 2013): 448–458
Coronary Plaque Reduction
Coronary plaque is a well-known risk factor for heart disease. Plaque can be characterized as calcified and non-calcified. Studies suggest that the presence of non-calcified plaque―also known as soft plaque―along with calcified plaque may be a stronger predictor of coronary risk than either plaque alone.(5)
While earlier studies showed the benefits of garlic on calcified plaque, a newer study aimed to evaluate aged garlic extract’s effects on reducing non-calcified arterial plaque.(6) In the study led by Suguru Matusumoto of UCLA Medical Center (Torrance, CA), 55 individuals with metabolic syndrome were asked to supplement with aged garlic extract (2,400 mg/day of Kyolic extract from Wakunaga of America in Mission Viejo, CA) or placebo for one year. Baseline measures included the assessment of plaque burden via cardiac computed tomography angiography (CCTA).
The results of the study showed that the aged garlic extract significantly reduced the percentage of low-attenuation plaque versus placebo. Low-attenuation plaque is a lipid-rich plaque that is considered a subset of non-calcified plaque. Thus, the study results suggest an important additional benefit of aged garlic extract in supporting cardiovascular health by reducing the presence of this plaque.
5. Nasir K et al., “Calcified versus noncalcified atherosclerosis: Implications for evaluating cardiovascular risk,” Current Cardiovascular Risk Reports, vol. 3, no. 2 (March 2009): 150–155
Garlic isn’t readily associated with benefitting liver function; however, recent studies suggest that garlic extracts may in fact support liver health.
Ha-Na Kim and colleagues from the Catholic University of Korea (Seoul, Republic of Korea) conducted a study in which 75 adults with mild liver dysfunction, but no diagnosed liver disease, were randomized to receive two sachets of a fermented garlic extract, or a placebo, daily for 12 weeks.(7) At baseline, all individuals participating in the study had elevated serum gamma-glutamyl transpeptidase (GGT), a liver enzyme.
Researchers evaluated the serum changes in GGT as well as alanine aminotransferase (ALT), another liver enzyme, over the 12-week period. In the garlic group, ALT and GGT levels improved from baseline over 12 weeks and improved compared to placebo, indicating the potential therapeutic benefits of garlic supplementation on mild liver dysfunction.
Pending further research, the changes in liver enzymes may also indicate the utility of fermented garlic extract for addressing more severe cases of liver dysfunction.
7. Kim HN et al., “Efficacy and safety of fermented garlic extract on hepatic function in adults with elevated serum gamma-glutamyl transpeptidase levels: a double-blind, randomized, placebo-controlled trial,” European Journal of Nutrition. Published online October 14, 2016.
Several compounds in garlic may interact with the immune system and serve to boost the function of diverse components that comprise our immune defenses.
A recent study led by Susan Percival of the University of Florida (Gainesville, FL) aimed to evaluate the effects of aged garlic extract on activity related to immune cell proliferation, activation, and on the inflammatory process.(8) In the study, 120 healthy adults were recruited to participate in a double-blind placebo-controlled trial in which they supplemented with 2.56 g of aged garlic extract or a placebo daily for 90 days during the height of the cold and flu season. Peripheral blood mononuclear cells (a type of immune cell) were isolated before and after the 90-day intervention, and the function of T- and natural killer (NK) cell function was also assessed at 45 and 90 days.
At the end of the study, aged garlic extract significantly improved T- and NK-cell proliferation and reduced cold and flu severity (though not the number of illnesses). Symptomatic improvement was noted, and there was a reduction in the number of days of work or school missed in the group supplementing with aged garlic extract.
The study indicated multiple beneficial effects of the garlic preparation on immune health and supports its prophylactic benefits in healthy adults.
Weight Management and Body Composition
Previously, studies in animals have found that garlic may support a weight-loss benefit; however, whether this effect occurs in humans has been unclear.
A recent study conducted in Iran aimed to assess the effects of garlic on weight and body composition parameters in individuals with non-alcoholic fatty liver disease (NAFLD). As being overweight is a risk factor for the development of NAFLD, reducing weight is associated with benefits for liver health.
In the current study, 110 individuals were recruited from the Metabolic Liver Disease Research Center at Isfahan University of Medical Sciences (Isfahan, Iran) and randomized to receive 400 mg of a garlic powder supplement (1.5 mg allicin) twice daily or a placebo for 15 weeks.(9) Both groups were monitored for dietary intake and physical activity, while both also received basic dietary and exercise advice. Body composition parameters of all participants were evaluated during the trial.
The garlic group showed a significant average decrease in body weight of 2.59% from baseline, while the placebo group had a decrease of 0.75%. Garlic supplement consumption also led to a mean decrease of 2.91% in body fat, while the average decrease in the placebo group was 0.42%. These results support the concept that garlic supplementation can be a useful adjunct to lifestyle modification for weight management in overweight individuals with NAFLD.
9. Soleimani, D., Paknahad, Z., Askari, G., Iraj, B. & Feizi, A. Effect of garlic powder consumption on body composition in patients with nonalcoholic fatty liver disease: A randomized, double-blind, placebo-controlled trial. Adv. Biomed. Res. 5, 2 (2016). Published online January 27, 2016.