Research reviewCould capsaicinoids help to support weight management? A systematic review and meta-analysis of energy intake data☆
Introduction
The plant of the genus capsicum produces a fruit (chilli pepper) with unique bioactive compounds (Kwon et al., 2011). The fruit contains a group of chemicals known as capsaicinoids, the most abundant and well known being capsaicin. Capsaicin, along with dihydrocapsaicin, makes up around 90% of capsaicinoids found in a typical chilli pepper (Meghvansi et al., 2010). These compounds are responsible for the fruit’s ‘pungent’ flavour sensation that has made it popular in culinary cultures around the world (Hursel & Westerterp-Plantenga, 2010). This sensation occurs as capsaicinoids bind to the same group of nociceptors (namely the transient receptor potential cation channel subfamily V member 1 (TRPV1), also known as the ‘capsaicin receptor’) which lead to the sensation of pain from heat and acid (Sanatombi & Sharma, 2008).
In recent years, the fruit’s bioactive effects have become of increasing interest within the field of health research (Luo, Peng, & Li, 2011). Clinical trials suggest capsaicinoids may have anti-cancer (Yang et al., 2010), anti-inflammatory (Choi et al., 2011) and antioxidant properties (Henning et al., 2011), while they have been used for pain relief for some time (Szallasi, Cruz, & Geppetti, 2006). Many of these effects are due to the actions of capsaicinoids on the TRPV1 which is found in tissues throughout the body and is the subject of current research (Gunthorpe & Szallasi, 2008). There is also accumulating evidence that capsaicinoid compounds may help to support weight loss (Ludy, Moore, & Mattes, 2012).
Evidence from intervention trials in humans suggests daily consumption of capsaicinoids may increase energy expenditure by around 30 per cent for an hour (Yoshioka et al., 1995) and lipid oxidation by around 20% (Lejeune, Kovacs, & Westerterp-Plantenga, 2003). A number of human intervention trials have also investigated capsaicinoids’ ability to regulate energy intake, although findings have generally been contradictory (Whiting, Derbyshire, & Tiwari, 2012). For example, one study found significant reductions in ad libitum energy intake of 24 subjects after consuming a capsaicinoid invention prior to a meal, compared to a placebo (Westerterp-Plantenga, Smeets, & Lejeune, 2005). However, another trial found no reduction in energy intake in 36 participants during a 4-week intervention with fresh chillies compared with a control diet (Ahuja, Robertson, Geraghty, & Ball, 2007).
As the effects of capsaicinoids on energy intakes can be difficult to establish from one meal, one trial investigated the effects of hot spices on energy intake and appetite after participants received five meals of fixed portion sizes, served with or without five hot spices followed by a buffet (Reinbach, Martinussen, & Moller, 2010). While hot spices were not found to significantly affect energy intake, the ingestion of hot spices appeared to induce changes in sensory specific desires e.g. an increased desire for sweet foods after ingesting chilli.
While pharmacological solutions have been created to help people control appetite, a number of medications (such as sibutramine, fenfluramine and dexfenfluramine) have been withdrawn from the market due to harmful cardiovascular side-effects and the options for treatment with drugs are currently limited (McGavigan & Murphy, 2012). Capsaicinoids have therefore the potential to be an innovative approach in terms of helping people trying to manage their weight; however, patent legislation provides little monetary incentive for the pharmaceutical industry to develop a plant compound for a medical application. Thus this present article sets out to combine findings from studies investigating inter-relationships between capsaicinoid ingestion and energy intake using a meta-analytical approach and form evidence-based conclusions about possible weight management roles.
Section snippets
Identification of relevant studies
Studies were identified by searching Web of Knowledge, PubMed and Scopus (1990-Present). The initial search was performed in June 2012 and updated in May 2013. The following search terms were used in all databases: ‘capsaicin*’ ‘red pepper’’, ‘chilli*’, ‘chili*’. These four terms were each combined (using Boolean ‘AND’) with ‘energy intake’ and ‘satiety’. Trials were initially selected based on their abstract; full content was then reviewed to determine final inclusion.
Inclusion and exclusion criteria
Inclusion was based on
Results
A total of 74 clinical trials were identified from the database searches. Fifty-five trials were excluded for being duplicates and a further 9 were excluded for methodological reasons (as listed in Fig. 1), leaving a total of 10 trials. The 10 studies investigated the role of capsaicinoids on weight management in relation to effects on energy intake, hunger and hormone levels. Studies assessing ad libitum energy intake after a capsaicinoid intervention were most common, and were therefore used
Discussion
The results suggest adding capsaicinoids to the diet could have a beneficial effect for weight management, by reducing energy intake; caution should be applied to this result however, due to the high heterogeneity. A reduction of around 309.9 kJ (74 kcal) per meal, repeated three times a day may have the potential to lead to beneficial weight loss. A calorie imbalance of 2100 kJ (500 kcal) per day is often suggested as ideal for weight loss (Stern et al., 2004), although smaller imbalances can also
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Acknowledgements: The authors would like to acknowledge the support of Manchester Metropolitan University for funding this research. Conflict of interest statement: There are no conflicts of interest.