The Capsicum genus of plants contains a number of chemicals that are known as capsinoids and capsicum constituents. Capsaicin, dihydrocapsaicin and nordigydrocapsaicin are pungent capsicum chemicals. These are closely related to three non-pungent capsinoid chemicals capsiate, dihydrocapsiate and nordihydrocapsiate, except that the former contains an amide bond and the latter contains an ester bond. Capsaicin is perceived by the brain as ‘hot’ because it activates TRPV1 receptors (transient receptor potential cation channel, subfamily V, member 1) in the tongue. However, the caspsinoids are hydrolysed in the oral mucosa and so do not possess the same ‘hot’ sensory perception. The capsinoids and capsicum constituents both have thermogenic effects because they activate the TRPV1 receptors in the intestine. This results in increased sympathetic nervous system activation and up-regulation of uncoupling proteins. Evidence suggests that capsicum plants cause weight loss in animals and humans.
Researchers1 have investigated the effects of capsinoids in a double-blind placebo-controlled study involving 40 men and 40 women with a body mass index of between 25 and 35 kg/m2. Subjects were fed 1 mg/d of capsinoids in an oil filled capsule or a placebo, for 12 weeks. The results showed that supplementation with capsinoids caused a weight loss on 0.9 kg compared to 0.5 kg for the placebo. No different in total adiposity was evident, but the capsinoids did cause significant reductions in abdominal adipose tissue compared to the placebo (1.11kg versus 0.18 kg). Total resting energy expenditure was similar between groups, but the capsinoid group showed increased levels of fat oxidation after 12 weeks. Genetic tests showed that two variants of the TRPV1 and UCP2 (uncoupling protein 2) genes correlated significantly with the reduction in abdominal obesity.
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