Dietary supplementation of transient receptor potential vanilloid-1 channel agonists reduces serum total cholesterol level: a meta-analysis of controlled human trials

Figures & data

Table 1. Summary of study characteristics for publications included in the meta-analyses.

First author (year)	Study design	Country	Control/ treatment (n)	Age^a (years)	BMI^a (kg/m^2)	Administered substance	Dosage of capsaicin (mg/day)	Duration (weeks)
Ahuja and Ball (2006)	RCRT	Australia	27/27	46.0 (12.0)	26.6 (4.9)	Chili supplement	approx. 22^b	4
Arent et al. (2018)	RCT	USA	18/18	36.9 (10.2)	NR	METABO pill^c	NR	8
Cha et al. (2013)	RCT	China	30/30	42.6 (1.9)	27.1 (0.7)	Kochujang pill	NR	12
Kang et al. (2016)	NRCRT	China	12/12	27.8 (3.8)	22.4 (3.2)	Chili supplement^d	5	6
Kim et al. (2010)	RCT	China	14/14	NR	26.4 (2.5)	Chili supplement	NR	12
Lim et al. (2015)	RCT	China	13/13	42.0 (7.7)	26.9 (4.5)	Kochujang pill	NR	12
Qin et al. (2017)	RCT	China	17/18	43.5 (5.4)	26.3 (2.9)	Pod pepper powder	4	12
Taghizadeh et al. (2017)	RCT	Iran	25/25	33.7 (7.2)	32.4 (4.6)	Dietary supplement^e	100	8
Urbina et al. (2017)	RCT	USA	28/22	29.0 (2.0)	27.5 (6.0)	Chili supplement	4	12
Yuan et al. (2016)	RCT	China	22/20	30.4 (4.5)	27.0 (3.6)	Chili powder	4	4

BMI, body mass index; NR, not reported; NRCRT, non-randomized cross-over trial; RCRT, randomized cross-over trial; RCT, randomized controlled trial.

^a Data are reported as mean (standard deviation).

^b Based on the reported capsaicin concentrations in cayenne pepper (Al Othman et al. 2011).

^c Containing capsaicin, caffeine, raspberry ketone, garlic organosulfur, vitamin B, chromium, and gingerols.

^d Containing 1.05 mg/g capsaicin, 0.58 mg/g dihydrocapsaicin, and 0.12 mg/g nordihydrocapsaicin.

^e Consisting of 125 mg green tea, 25 mg capsaicin, and 50 mg ginger.

Figure 1. Flow chart of study selection and inclusion.

Figure 2. Forest plot of the effects of capsaicinoids (top) and capsaicinoid-containing mixtures (bottom) on serum total cholesterol level. Here, and in Figures 3–5, for each study, we calculated the difference between serum cholesterol levels in the capsaicinoid-treated group and the control group at the end of the intervention period. For all studies, the differences in means were standardized (based on variances) to obtain standardized mean differences (SMDs). The SMDs and 95% confidence intervals (CI) are used as primary measures of effect size and are shown in the forest plot. Black circles represent the SMD for each study, while the left and right horizontal arms of the circles indicate the corresponding CI. The size of the gray box is proportional to the sample size and inversed variance. The rhombus represents the average SMD calculated from the SMDs of the individual studies in a subgroup (top and middle) and in all studies (bottom). The horizontal diagonal of the rhombus represents the CI, while the vertical diagonal of the rhombus points at the SMD value of the subgroup or of all studies. The dashed line is determined by the vertical diagonal of the bottom rhombus and indicates the SMD of all studies in the forest plot. There was no significant difference between the two subgroups (Q = 0.709; p = 0.400). SD, standard deviation.

Figure 3. Forest plot of the effects of capsaicinoids (top) and capsaicinoid-containing mixtures (bottom) on serum low-density lipoprotein (LDL) cholesterol level. There was no significant difference between the two subgroups (Q = 0.006; p = 0.940). CI, confidence interval; SD, standard deviation; SMD, standardized mean difference.

Figure 4. Forest plot of the effects of capsaicinoids (top) and capsaicinoid-containing mixtures (bottom) on total serum triglyceride level. There was no significant difference between the two subgroups (Q = 0.216; p = 0.642). CI, confidence interval; SD, standard deviation; SMD, standardized mean difference.

Figure 5. Forest plot of the effects of capsaicinoids (top) and capsaicinoid-containing mixtures (bottom) on serum high-density lipoprotein (HDL) cholesterol level. There was no significant difference between the two subgroups (Q = 1.115; p = 0.291). CI, confidence interval; SD, standard deviation; SMD, standardized mean difference.

Ahuja, K. D., and M. J. Ball. 2006. Effects of daily ingestion of chilli on serum lipoprotein oxidation in adult men and women. British Journal of Nutrition 96 (2):239–42. doi: 10.1079/BJN20061788.

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Lim, J. H., E. S. Jung, E. K. Choi, D. Y. Jeong, S. W. Jo, J. H. Jin, J. M. Lee, B. H. Park, and S. W. Chae. 2015. Supplementation with Aspergillus oryzae-fermented kochujang lowers serum cholesterol in subjects with hyperlipidemia. Clinical Nutrition 34 (3):383–7. doi: 10.1016/j.clnu.2014.05.013.

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Taghizadeh, M., N. Farzin, S. Taheri, M. Mahlouji, H. Akbari, F. Karamali, and Z. Asemi. 2017. The effect of dietary supplements containing green tea, capsaicin and ginger extracts on weight loss and metabolic profiles in overweight women: A randomized double-blind placebo-controlled clinical trial. Annals of Nutrition and Metabolism 70 (4):277–85. doi: 10.1159/000471889.

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Yuan, L. J., Y. Qin, L. Wang, Y. Zeng, H. Chang, J. Wang, B. Wang, J. Wan, S. H. Chen, Q. Y. Zhang, et al. 2016. Capsaicin-containing chili improved postprandial hyperglycemia, hyperinsulinemia, and fasting lipid disorders in women with gestational diabetes mellitus and lowered the incidence of large-for-gestational-age newborns. Clinical Nutrition 35 (2):388–93. doi: 10.1016/j.clnu.2015.02.011.

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