Studies produced at the Kyoto University and the University of Melbourne have shown that capsaicin, the compound that gives chili peppers their hot and spicy flavor, stimulates adrenal glands to release hormones that increase energy and the body's metabolic rate. The studies suggest that this adrenal stimulation is a result of the central nervous system's reaction to capsaicin.
The Adrenal Gland
The adrenal glands are located above both kidneys. Capsaicin causes the adrenal glands to produce two hormones: epinephrine (adrenaline) and norepinephrine. These hormones are thought to be responsible for many of the short-term health benefits of eating hot peppers.
The hormone epinephrine (adrenaline) boosts metabolism by increasing heart rate, helping the body turn sugars into energy and stimulating blood flow from muscle groups to the brain, according to the University of Maryland Medical Center. Epinephrine also relaxes smooth muscle groups. Norepinephrine increases blood pressure.
The burning sensation caused by capsaicin is produced by a compound known as substance P. Nerves react to substance P by sending pain signals to the brain.
Substance P and Adrenal Hormones
In 2000 researchers X F Zhou and B G Livett of the University of Melbourne published a study in The Journal of Physiology about how substance P directly affects the central nervous system. Their work showed that substance P causes the adrenal glands to secrete epinephrine and norepinephrine into the nervous system. This explains why people who eat hot peppers often experience a burst of energy, an increased heart rate and increased body temperature.
Stimulating the release of epinephrine and norepinephrine temporarily increases the metabolism and thus helps the body burn more calories. Alternative medicine advocates recommend eating hot peppers to promote good circulation and weight loss.