Effects of Coffee Supplementation on Homocysteine and Leptin Levels: A Systematic Review and Meta-analysis of Clinical Trials.

BACKGROUND: It has been reported that the consumption of antioxidant foods and beverages may benefit the development of cardiovascular risk factors. However, the impact of coffee consumption on some of these factors, such as homocysteine and leptin is controversial. Some clinical trials have suggested that coffee administration increases plasma total homocysteine levels, while others have found no significant changes in leptin concentrations. OBJECTIVE: This study aimed to assess the effects of coffee supplementation on homocysteine and leptin concentrations in a meta-analysis of clinical trials. METHODS: PubMed, Web of Science, Scopus, ClinicalTrials.gov, and Google Scholar databases were searched from inception to September 29, 2021. A fixed-effects model and the generic inverse variance weighting method were used for meta-analysis. RESULTS: The meta-analysis demonstrated that coffee administration significantly increases homocysteine levels (WMD: 0.55 µmol/L, 95% CI: 0.17, 0.93, p = 0.005, I2 = 0%) but has no significant changes in leptin concentrations (WMD: 1.34 ng/mL, 95% CI: -0.78, 3.45, p = 0.21, I2 = 0%). Additionally, the sensitivity analysis was robust for both homocysteine and leptin levels. CONCLUSION: The results of the present meta-analysis revealed that coffee supplementation raises serum homocysteine concentrations but has no effect on circulating leptin levels.

Coffee consumption has no effect on circulating markers of liver function but increases adiponectin concentrations: A systematic review and meta-analysis of randomized controlled trials.

Nonalcoholic fatty liver disease has become the most common liver disorder worldwide, reaching a prevalence of 60% and 24% in patients with chronic liver disease and the general population, respectively. Liver function is often assessed using standard liver tests such as alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase, and alkaline phosphatase. Randomized controlled trials (RCTs) investigating the potential beneficial effects of coffee consumption on liver function are scarce and their results are inconclusive. Some clinical trials have shown a significant increase in adiponectin concentrations following coffee consumption; however, there are few studies in this field. Hence, the hypothesis of this meta-analysis of RCTs is that coffee consumption decreases blood markers of liver function and increases adiponectin concentrations. A systematic search was conducted in PubMed-MEDLINE, Scopus, Web of Science, ClinicalTrials.gov, and Google Scholar databases. Meta-analysis was performed using a random-effects model followed by sensitivity analysis. Meta-analysis of 14 RCTs, including a total of 897 subjects, showed that coffee consumption has no significant effect on alanine aminotransferase (weighted mean difference [WMD], -0.89 mg/mL; 95% CI, -2.90 to 1.12; P = .39), aspartate aminotransferase (WMD, -0.29 mg/mL; 95% CI, -1.25 to 0.66; P = .55), gamma-glutamyl transferase (WMD, .10 mg/mL; 95% CI, -3.94 to 4.15; P = .96), alkaline phosphatase (WMD, -4.60 mg/mL; 95% CI, -9.26 to 0.07; P = .05), and lactate dehydrogenase (WMD, -0.65 mg/mL; 95% CI, -10.80 to 9.49; P = .90). However, coffee administration significantly increased adiponectin concentrations (WMD, 1.19 mg/mL; 95% CI, 0.08-2.31; P = .04). The results of this meta-analysis of RCTs suggest that coffee consumption may improve liver dysfunction through the elevation of adiponectin levels; however, further clinical trials are needed to corroborate our findings.