|Guarana (Guaraná) is a shrub or small tree in the Sapindaceae, native to Venezuela and northern Brazil, known for the high stimulant content of the fruit. The name 'Guaraná' comes from the Guarani tribe that lives in Brazil. Guarana is also known as Paullinia cupana, paullinia, Brazilian cocoa, guarana bread, guarana paste or gum, and zoom. Guarana is an evergreen vine
growing up to 30 feet long in the Amazon rain forest. The vast majority of guaraná is grown in a small area in northern Brazil. The herb is a climbing plant and supports itself in the huge trees of the equatorial rainforest. It has divided compound leaves, flowers yellow panicles, fruit pear shaped, three sided, three-celled capsules, with thin partitions, in each a seed like a small horse-chestnut half enclosed in an aril, flesh coloured and easily separated when dried. Guarana seeds are peeled, dried, roasted, ground, and made into beverages. Guarana gum or paste is derived from the seeds and is used in herbal preparations. In Brazil, a fermented mixture of Guarana, cassava, and water has become a popular national drink.
The seeds of guarana are known to be rich in xanthines (caffeine) and have been widely used as a "tonic" in many South American countries. Caffeine is a stimulant of the central nervous system with psychotropic effects and stimulation of respiration, a stimulant of the heart rate, and has a mild diuretic effect. Caffeine is thought to act on the brain by blocking adenosine receptors. Adenosine, when bound to receptors of nerve cells, slows down nerve cell activity; this happens, among other times, during sleep. The caffeine molecule, being similar to adenosine, binds to the same receptors but doesn't cause the cells to slow down; instead, the caffeine blocks the receptors and thereby the adenosine action. The resulting increased nerve activity causes the release of the hormone epinephrine (adrenaline), which in turn leads to several effects such as higher heart rate, increased blood pressure, increased blood flow to muscles, decreased blood flow to the skin and inner organs, and release of glucose by the liver. In addition, caffeine, similar to amphetamines, increases the levels of the neurotransmitter dopamine in the brain. Caffeine is quickly and completely removed from the brain and, unlike other CNS stimulants or alcohol, its effects are short lived. In many people, caffeine does not negatively affect concentration or higher mental functions, and hence caffeinated drinks are often consumed in the course of work.
As a stimulant, guarana acts on the central nervous system to prevent fatigue and break down lactic acid from muscle stress. Guarana also discourages blood clots, stimulates the urinary system, and promotes production of digestive juices. Guarana was used to treat diarrhea, decrease fatigue, reduce hunger, and to help arthritis. Guarana has been thought as a high energy source that increases mental alertness, slows the pulse, decreases the appetite, fights fatigue, an excellent mood elevator. Guarana has also been used as a nervine tonic for hangovers, neuralgia and menstrual headaches, leucorrhea, diarrhea, and fevers.
As with any caffeinated product, guarana extracts can lead to insomnia, nervousness, anxiety, headaches, high blood pressure and heart palpitations. Excessive stimulation due to caffeine can have a detrimental effect on physical performance and also on aspects of metabolism such as blood pressure and heart rate. Guarana is not recommended for women who are pregnant or lactating, because caffeine may cause miscarriage or may slow the growth of a developing fetus when given in doses greater than 300 mg a day. Guarana contains substances called tannins, which can block the absorption of iron supplements and dietary iron.