Breaking out is a sweat while eating a spicy meal my ultimately be seen as a good thing by consumers and may lead to increased interest in foods formulated with spices that are gaining increasing interest as much for their health benefits as for their flavour and aroma.
"Consumption of spiced foods or herbal drinks often leads to greater thermogenesis," wrote the researchers in the journal Physiology and Behavior (doi: 10.1016/j.physbeh.2006.01.027).
"Therefore, it is suggested that these ingredients can realistically be considered as functional agents that could help in preventing a positive energy balance and obesity."
Over 300m adults are obese worldwide, according to latest statistics from the WHO and the International Obesity Task Force. About one-quarter of the US adult population is said to be obese, with rates in Western Europe on the rise although not yet at similar levels.
The researchers, from Maastricht University, Wageningen Cnetre of Food Science in Holland, and Laval University in Quebec, reviewed the evidence for capsaicin, black pepper, ginger and mixed spices, with respect to energy balance and heat generation (thermogenesis).
Capsaicin, the compound gives red chilli pepper its heat, has been reported by several studies to boost heat generation by the body, which means people burn more energy.
For example, "clinical research on capsaicin showed for instance that consumption of a breakfast with capsaicin caused an increase in diet-induced energy expenditure (23 per cent) immediately after the meal ingestion in Japanese males," reported the researchers.
Another study reported that people who drank tomato juice with a little bit of red pepper added led to reductions in the amount of energy consumed from meals by ten per cent.
For black pepper, reports can be found of the spice stimulating metabolism. The main irritating component in black pepper, piperine, is said to bind to so-called Transient Receptor Potential Vanilloid (TRPV1)receptors in the brain and other parts of the nervous system.
TRPV1 works as the bodys thermometer and, once activated, turns up the heat by boosting heat production by the body.
Ginger, used extensively as a flavouring agent in foods, only weakly activates TRPV1, but "the pungent principles of ginger, gingerols and shogaols have thermogenic properties," said lead author Magriet Westerterp-Plantenga.
It follows that mixed spices, which consist of mixtures of black pepper, red chilli, turmeric, cumin, ginger and so on, should also have impacts on metabolism.
Animal studies, appear to support this: "Combinations of black pepper, coriander, turmeric, red chili, cumin and ginger or onion, commonly used in Indian households, appeared to have favorable effects on digestion by stimulating digestive enzyme activities, bile flow and bile acid secretion in rats," wrote Westerterp-Plantenga.
Herbs and spices are used primarily for their contributions on flavour and aroma of food, but a growing body of evidence is linking the everyday ingredients to health benefits that could help against obesity.
"Thermogenic ingredients may be considered as functional agents that could help in preventing a positive energy balance and obesity," concluded the researchers.