After nearly 15 years absence in Europe, L-tryptophan, one of the essential amino acids in the diet, is back - available once more in an authorised nutritional supplement.

In 1990, its use in supplements was banned, after a single contaminated batch of tryptophan supplied by one Japanese manufacturer apparently led to the development of a deadly condition. Its use in drugs, infant formulas and parenteral food products, however, continued unhindered. It should be noted that this ban coincided with the launch of Prozac. A precursor of serotonin, melatonin and niacin, tryptophan is a vitally important substance. Discovered in 1901, it has been used for decades to relieve depression, promote sleep or aid weight loss.

A number of studies have demonstrated the benefits and efficacy of tryptophan, in particular:

• in improving serotonin levels. Serotonin plays a key role in many of the body's functions, and particularly in depression, anxiety, mood and appetite control. Furthermore, serotonin cannot cross the blood-brain barrier, so when levels are inadequate, only supplementation with either of its two precursors - tryptophan or 5-HTP - can raise them effectively;
• many people eat excessive amounts of carbohydrates when they feel stressed, depressed or anxious. This results in a rise in cerebral serotonin and a temporary feeling of well being and security, but at the same time, an increase in fat stores. Tryptophan supplementation improves psychological state without inducing increases in the amount of stored fat;
• the first studies using tryptophan to influence mood were conducted in the Fifties. Tryptophan supplementation was shown to be effective and free of side-effects in subjects suffering from mild to moderate depression;
• both on its own and combined with phototherapy, tryptophan is also an effective treatment for SAD (Seasonal Affective Disorder);
• in cases of mild insomnia, tryptophan promotes drowsiness and good quality sleep.

L-Tryptophan and 5-HTP are converted into serotonin following the same metabolic pathway. However, certain people react better to supplementation with L-tryptophan than with 5-HTP.

This may be for a number of reasons:

• with L-tryptophan supplementation, the body maintains control over the amount of serotonin produced by means of the enzyme L-tryptophan hydroxylase;
• when 5-HTP is taken, some of it may find its way to the intestine where it can cause nausea. In addition, since serotonin cannot cross the blood-brain barrier, any serotonin produced outside of the brain is unable to penetrate it;
  
• In some individuals, certain conditions, including severe depression, can prevent the passage of 5-HTP across the blood-brain barrier - this does not happen with L-tryptophan;
• Finally, L-tryptophan is an essential amino acid that is crucial for healthy body function and particularly, for the production of niacin.