Lipid-Lowering Efficacy of the Capsaicin in Patients With Metabolic Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Abstract

Background: Patients with metabolic syndrome (MetS) have increased cardiovascular risk. Capsaicin (CAP) has been shown to reduce lipids, but efficacy for patients with MetS is unknown.

Methods: A systematic review was performed according to PRISMA guidelines, to compare the effects of CAP against a placebo. Differences in the weight mean difference (WMD) with 95% confidence intervals (95% CI) were then pooled using a random effects model.

Results: Nine randomized controlled trials including 461 patients were identified in the overall analysis. CAP significantly decreased total cholesterol (TC) (WMD = -0.48, 95% CI: -0.63 to -0.34, I ²= 0.00%) and low-density lipoprotein cholesterol (LDL-C) (WMD = -0.23, 95% CI: -0.45 to -0.02, I ² = 68.27%) among patients with MetS. No significant effects of CAP were found on triglycerides (TG) or high-density lipoprotein cholesterol (HDL-C) (WMD = -0.40, 95% CI: -1.50 to 0.71, I ² = 98.32%; WMD = -0.08, 95% CI: -0.21 to 0.04, I ² = 86.06%). Subgroup analyses indicated that sex and intervention period were sources of heterogeneity. The results revealed that CAP decreased TG levels in women (WMD = -0.59, 95% CI: -1.07 to -0.10) and intervention period <12 weeks (WMD = -0.65; 95% CI: -1.10 to -0.20). And there was no potential publication bias according to funnel plot, Begg' test and Egger regression test.

Conclusions: CAP supplementation is a promising approach to decreasing TC and LCL-C levels in patients with MetS. However, short-term (<12 weeks) use of CAP in women may also reduce TG levels.

Systematic review registration: Identifier: CRD42021228032.

Keywords: capsaicin; lipid levels; meta-analysis; metabolic syndrome; randomized controlled trials.

Figure 1

PRISMA 2009 flow diagram for study selection process.

Figure 2

Graph of bias risk assessment for included studies by the Cochrane Collaboration's tool. (A) Risk of bias graph. (B) Risk of bias summary.

Figure 3

Forest plot for lipid levels: capsaicin vs. placebo (random-effect model). (A) Funnel plot for total cholesterol (TC). (B) Funnel plot for triglycerides (TG). (C) Funnel plot for high-density lipoprotein cholesterol (HDL-C). (D) Funnel plot for low-density lipoprotein cholesterol (LDL-C).

Figure 4

Sensitivity analysis. (A) Total cholesterol (TC). (B) Triglycerides (TG). (C) High-density lipoprotein cholesterol (HDL-C). (D) Low-density lipoprotein cholesterol (LDL-C).

Figure 5

Results of subgroup analysis. (A,E,I,M) Effect of capsaicin (CAP) on total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low density lipoprotein cholesterol (LDL-C) in different races. (B,F,J,N) Effect of CAP on TC, TG, HDL-C and LDL-C in different genders. (C,G,K,O) Effect of dose of CAP on TC, TG, HDL-C and LDL-C. (D,H,L,P) Effect of duration of CAP intervention on TC, TG, HDL-C and LDL-C. WMD, weighted mean difference.

Figure 6

Publication bias. (A) Funnel plot for total cholesterol (TC). (B) Begg' test for TC. (C) Egger test for TC. (D) Funnel plot for triglycerides (TG). (E) Begg' test for TG. (F) Egger test for TG. (G) Funnel plot for high-density lipoprotein cholesterol (HDL-C). (H) Begg' test for HDL-C. (I) Egger test for HDL-C. (J) Funnel plot for low-density lipoprotein cholesterol (LDL-C). (K) Begg' test for LDL-C. (L) Egger test for LDL-C.