The effects of capsaicin and capsiate on energy balance: critical review and meta-analyses of studies in humans

Abstract

Consumption of spicy foods containing capsaicin, the major pungent principle in hot peppers, reportedly promotes negative energy balance. However, many individuals abstain from spicy foods due to the sensory burn and pain elicited by the capsaicin molecule. A potential alternative for nonusers of spicy foods who wish to exploit this energy balance property is consumption of nonpungent peppers rich in capsiate, a recently identified nonpungent capsaicin analog contained in CH-19 Sweet peppers. Capsiate activates transient receptor potential vanilloid subtype 1 (TRPV1) receptors in the gut but not in the oral cavity. This paper critically evaluates current knowledge on the thermogenic and appetitive effects of capsaicin and capsiate from foods and in supplemental form. Meta-analyses were performed on thermogenic outcomes, with a systematic review conducted for both thermogenic and appetitive outcomes. Evidence indicates that capsaicin and capsiate both augment energy expenditure and enhance fat oxidation, especially at high doses. Furthermore, the balance of the literature suggests that capsaicin and capsiate suppress orexigenic sensations. The magnitude of these effects is small. Purposeful inclusion of these compounds in the diet may aid weight management, albeit modestly.

Figure 1

Chemical structures of capsaicin and capsiate vary only at the center linkage. Capsaicin (top) contains an amide bond between the vanillyl group and the fatty acid chain, whereas capsiate (bottom) contains an ester bond. This figure appears in color in the online version of Chemical Senses.

Figure 2

Forest plots comparing studies on the effects of capsaicin on EE by low (1), intermediate (2), and high (3) dose. The weight that the study received in the overall association is indicated by the size of the gray squares. SMD was used as an effect size indicator. The 95% CIs are represented by error bars. The pooled estimates for each analysis are represented by diamonds. SMD ± 95% CIs show that capsaicin increases EE (indicated by SMD > 0) at high doses. Capsaicin had no significant effect on EE overall or at low or intermediate doses. I-squared was used to assess heterogeneity. All I-squared values (subtotal and overall) were not statistically significant when subdivided by dose. This indicates that SMD with 95% CI can be interpreted separately by dose or when all 3 dose levels are combined into a single overall estimate. Multiple subscripts following author name indicate the use of more than one pepper dose within the same study. This figure appears in color in the online version of Chemical Senses.

Figure 3

Forest plots comparing studies on the effects of capsaicin on substrate oxidation (RQ) by low (1), intermediate (2), and high (3) dose. The weight that the study received in the overall association is indicated by the size of the gray squares. SMD was used as an effect size indicator. The 95% CIs are represented by error bars. The pooled estimates for each analysis are represented by diamonds. SMD ± 95% CIs show that capsaicin enhances fat oxidation (indicated by SMD < 0) overall as well as at intermediate and high doses. Capsaicin had no significant effect on substrate oxidation at low doses. I-squared was used to assess heterogeneity. All I-squared values (subtotal and overall) were not statistically significant when subdivided by dose. This indicates that SMD with 95% CI can be interpreted separately by dose or when all 3 dose levels are combined into a single overall estimate. Multiple subscripts following author name indicate the use of more than one pepper dose within the same study. This figure appears in color in the online version of Chemical Senses.

Figure 4

Forest plots comparing studies on the effects of capsiate on energy expenditure (EE) by low (1), intermediate (2), and high (3) dose. The weight that the study received in the overall association is indicated by the size of the gray squares. SMD was used as an effect size indicator. The 95% CIs are represented by error bars. The pooled estimates for each analysis are represented by diamonds. SMD ± 95% CIs show that capsiate increases EE (indicated by SMD > 0) overall as well as at intermediate and high doses. Capsiate had no significant effect on EE at low doses. I-squared was used to assess heterogeneity. All I-squared values (subtotal and overall) were not statistically significant when subdivided by dose. This indicates that SMD with 95% CI can be interpreted separately by dose or when all 3 dose levels are combined into a single overall estimate. Multiple subscripts following author name indicate the use of more than one pepper dose within the same study. This figure appears in color in the online version of Chemical Senses.

Figure 5

Forest plots comparing studies on the effects of capsiate on substrate oxidation (RQ) by low (1), intermediate (2), and high (3) dose. The weight that the study received in the overall association is indicated by the size of the gray squares. SMD was used as an effect size indicator. The 95% CIs are represented by error bars. The pooled estimates for each analysis are represented by diamonds. SMD ± 95% CIs show that capsiate enhances fat oxidation (indicated by SMD < 0) overall as well as at high doses. Capsiate had no significant effect on substrate oxidation at low or intermediate doses. I-squared was used to assess heterogeneity. All I-squared values (subtotal and overall) were not statistically significant when subdivided by dose. This indicates that SMD with 95% CI can be interpreted separately by dose or when all 3 dose levels are combined into a single overall estimate. Multiple subscripts following author name indicates the use of more than one pepper dose within the same study. This figure appears in color in the online version of Chemical Senses.