Serotonin, an important brain neurotransmitter, regulates appetite, mood and melatonin production. The presence of serotonin in the brain is associated with a balanced emotional state. This is achieved in part by decreasing the activity of certain excitatory hormones, including dopamine and noradrenaline. Serotonin also acts as a satiety signal in the brain, thereby naturally regulating food intake. Additionally, as a precursor of melatonin, serotonin is involved in regulating sleep patterns. Serotonin is unable to cross the blood-brain barrier and is therefore synthesized in the brain. Tryptophan, an essential amino acid, is a precursor for the synthesis of serotonin. Tryptophan crosses the blood-brain barrier and is converted to L-5-hydroxytryptophan, which, in turn is converted into serotonin. As a metabolic intermediate in the conversion of tryptophan into serotonin, 5-HTP can also serve as a precursor of serotonin. Although St. John’s Wort has a variety of traditional uses, extracts of this flowering perennial are best known for their mood balancing properties. St. John™s Wort extract is widely recognized for its positive, supportive effects on mental and emotional function. As co-enzymes, the B vitamins are essential components in most major metabolic reactions. They play an important role in energy production, including the metabolism of lipids, carbohydrates, and proteins. B vitamins are also important for blood cells, hormones, and nervous system function. As water-soluble substances, B vitamins are not generally stored in the body in any appreciable amounts (with the exception of vitamin B-12). Therefore, the body needs an adequate supply of B vitamins on a daily basis.