Effect of curcuminoids on oxidative stress:A systematic review and meta-analysis of randomized controlled trials
J Funct Foods. 2015, DOI: 10.1016/j.jff.2015.01.005.
Oxidative stress is now considered as a precursor of many human disorders and health conditions. It is defined as the disturbance in balance between production of ROS and the inability of the body’s defence system to neutralize them. Oxidative stress can be induced by a number of factors including intrinsic and extrinsic. Free radicals are commonly formed in the body as an outcome of aerobic cellular metabolism as well introduced in the body from environment, food, toxins etc. One such reactive oxygen intermediate is superoxide anion, which may produce related toxic products in the body. Superoxide dismutase can convert superoxide into hydrogen peroxide, which is later converted into water by catalyses and glutathione peroxidase. However, over production of the super oxide in the body can lead to oxidative stress. The chronic over production of free radicals can promote disease conditions, even leading to cancer due to oxidative damage to DNA.
Meta–analysis is a powerful tool, which helps in assessing the clinical effectiveness of an intervention by combining the results of two or more randomized clinical trials using statistical tools.
To perform meta-analysis on Curcumin formulations to assess the effect of Curcuminoids supplementation on oxidative stress in health as well as in disease conditions.
The meta-analysis was based on the guidelines of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analysis) statement, 2009. The data was searched using PUBMED, Cochrane Library, Scopus and EMBACE databases. The search was limited to randomized-controlled human trials done from January 1, 1970 to September 1, 2014. Inclusion criteria for the studies were; randomized-controlled trials (RCTs) with parallel or cross-over design, investigation of serum/plasma SOD activities and sufficient information on serum SOD activities at the beginning and at the end of the study for control and active groups. The data was extracted and quality of studies, which were included in this meta-analysis was done using Jadad scale. Meta-analysis was done by Review manager version 5.2 (Cochrane collaboration) and Comprehensive Meta-Analysis (CMA) V2 software (Biostat, NJ). All information related to serum activities of SOD and catalyses and concentration of lipid peroxides and GSH were collected and (SD) standard deviation and mean difference were calculated. Sensitivity analysis was done to estimate the overall effect size of individual studies.
This was an 8-week, randomized, double-blind, placebo-controlled trial involving 33 patients over 18 years old, who were diagnosed with CAD and were enrolled in the study after CAD was confirmed by angiography by a cardiologist. All patients were randomized to receive either one capsule (500 mg) of Curcumin C3 Complex® (n=17) four times a day or equivalent placebo (n=16) for 8 weeks.
The parameters evaluated during the trial (i.e. at baseline and at the end of the study) included fasting glucose level and lipid profile (total cholesterol, LDL-C, HDL-C and Triglycerides) along with liver and kidney function tests.
- Six studies were selected, in total 396 subjects were randomized out of which 197 subjects received Curcumin supplementation in dose range of 80-1500 mg/day for 4-8 weeks.
- All the studies selected in this meta-analysis showed that Curcumin supplementation was safe and very well tolerated by the subjects with no serious adverse events.
- The data received from meta-analysis of the 6 RCTs involved showed that Curcuminoids supplementation was significantly able to increase serum SOD activities. Sensitivity analysis showed that effect size was robust for individual studies.
The results of the meta-analysis showed that Curcumin supplementation was able to significantly affect all the parameters of oxidative stress. There was a significant increase in serum activities of SOD and catalase, serum GSH concentration and decrease in serum lipid peroxides. The meta-analysis results indicated that Curcumin supplementation is able to alleviate the symptoms of oxidative stress, thus this phytochemical may be useful in treating ailments for which oxidative stress is involved in pathogenesis.