Matin S, et al. - In this clinical trial study, researchers assessed the impact of conjugated linoleic acid (CLA) supplement on oxidative stress levels, and MMP2 and MMP9 serum levels in COPD patients in Ardabil city, Iran. For 6 weeks on a daily basis, 3.2 g of CLA was given to supplement group and 3.2 g of placebo to the control group. For data analysis, Kolmogorov–Smirnov test, independent samples t-test, paired sample t-test, chi-square test, and ANOVA were used. The supplement group had significantly decreased serum level of malondialdehyde (MDA) as well as of MMP9. Overall, CLA supplementation, via inhibiting the production of oxidative stress and controlling MMP9 serum levels, may be helpful for COPD patients.