Aged garlic extract supplementation modifies inflammation and immunity of adults with obesity: A randomized, double-blind, placebo-controlled clinical trial

Abstract

Background: Obesity is a serious global health issue and often results in low-grade systemic inflammation, increasing the risk for several chronic diseases. If obesity-induced inflammation could be reduced, fewer complications and co-morbidities might occur.

Objective: To investigate whether daily supplementation with aged garlic extract (AGE) could reduce chronic inflammation and improve immune function in adults with obesity.

Methods: Fifty-one healthy adults with obesity (mean age 45.6 ± 1.6 years, mean BMI 36.1 ± 0.9 kg/m²) were recruited to participate in a parallel, double-blind, placebo-controlled, randomized study. After being matched by BMI, participants were randomized into the AGE supplementation or placebo group. Participants were asked to take a divided daily dose of 3.6 g AGE or placebo, with food for 6 weeks. Blood lipid and inflammatory markers were assessed at baseline and after 6 weeks of supplementation. Additionally, peripheral blood mononuclear cells (PBMC) were isolated from whole blood and used to detect changes in immune cell populations and levels of cytokine secretion. A one-way ANCOVA was performed to evaluate differences between the two groups, controlling for respective baseline values.

Results: At the end of study, serum IL-6 (p = 0.04) and TNF-α (p = 0.05) of participants consuming AGE were significantly lower than those consuming the placebo capsules. PBMC flow cytometry results showed that participants from the AGE group had a higher proportion of γδ-T cells (p = 0.03) and a lower proportion of NKT cells (p = 0.02) in the total population of lymphocytes. There was no difference in percentage of NK cells between the two groups. A significant difference in blood LDL concentration was also observed (p = 0.05). Total cholesterol and non-HDL cholesterol tended to differ between participants from the AGE group and those from the placebo group, although values did not achieve statistical significance.

Conclusion: Six weeks of AGE consumption modulated immune cell distribution, prevented the increase of serum TNF-α and IL-6 concentrations and reduced blood LDL concentration in adults with obesity. AGE, taken consistently, may be beneficial in preventing the development of chronic diseases associated with low-grade inflammation in adults with obesity. Registered under ClinicalTrials.gov with the identifier code NCT01959646.

Keywords: Aged garlic extract; C-reactive protein; Interleukin 6; Obesity-induced inflammation; T-cells; Tumor necrosis factor α.