Dietary Capsaicin: A Spicy Way to Improve Cardio-Metabolic Health?

Abstract

Today's sedentary lifestyle with too much food and too little exercise has made metabolic syndrome a pandemic. Metabolic syndrome is a major risk factor for type-2 diabetes and cardiovascular disease. New knowledge of medical and nutraceutical intervention in the early stages of metabolic syndrome is central to prevent these deadly complications. People who eat chili pepper on a regular basis seem to stay healthier and live longer than those who do not. Animal experiments suggest a therapeutic potential for dietary capsaicin, the active principle in hot chili pepper, to reduce the risk of developing metabolic syndrome. This is an attractive theory since capsaicin has been a culinary staple for thousands of years, and is generally deemed safe when consumed in hedonically acceptable doses. The broad expression of the capsaicin receptor TRPV1 in metabolically active tissues lends experimental support to this theory. This review critically evaluates the available experimental and clinical evidence for and against dietary capsaicin being an effective dietary means to improve cardio-metabolic health. It comes to the conclusion that although a chili pepper-rich diet is associated with a reduced risk of dying due to cardiovascular disease, dietary capsaicin has no clear effect on blood glucose or lipid profiles. Therefore, the reduced mortality risk may reflect the beneficial action of digested capsaicin on gut microbiota.

Keywords: capsaicin; cardio-metabolic health; dyslipidemia; gut microbiota; hyperglycemia; insulin resistance; low-grade inflammation; nutraceutical.

Figure 1

The complex molecular mechanism of action by which capsaicin may prevent the development of metabolic syndrome. In humans, TRPV1 activation may up-regulate Signal Transducer and Activator of Transcription-3 (STAT-3), a key member of the JAK/STAT pathway. Stimulation by cytokines of STAT-3 expressed in hepatocytes prevents steatosis. In animal studies, TRPV1 activation was linked to reduced fat accumulation and improved serum triglyceride (TG) and total cholesterol (TC) levels. Dietary capsaicin stimulates glucagon-like peptide-1 (GLP-1) secretion in the gastrointestinal tract. Furthermore, capsaicin supports the growth of the “anti-obesity bacterium”, Akkermansia muciniphila, by increasing mucin production, acting on the mucin-2 (Muc2) gene Activation of TRPV1 in preadipocytes results in lipid accumulation and increased insulin sensitivity via up-regulation of the Peroxisome Proliferator-Activated Receptor-γ (PPARγ), PPARγ-coactivator-1α (PGC-1α), and Uncoupling Protein-1 (UCP1) genes. Reproduced with permission from [95].