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After nearly 15 years' absence in Europe, L-tryptophan, one of the essential amino acids in the diet, is back - available to buy once more in an authorised nutritional supplement. 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 with weight loss.
What benefits do studies show about L-Tryptophan?
Serotonin plays a key role in many of the body's functions, and particularly in depression, anxiety, mood and appetite control. 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. Several studies have demonstrated the benefits and efficacy of tryptophan.
- 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.
- 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.
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.
What are the differences between L-tryptophan and 5-HTP?
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 using 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. Besides, 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.
L-tryptophan is available to buy in Supersmart's catalogue, providing benefits as an essential amino acid that is crucial for healthy body function and particularly, for the production of niacin.
What is in L-Tryptophan
january 7 2026
I bought this product for sleep issues and took it for 3 months, it seemed to improve my falling asleep. So I think I'll do another course.
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december 6 2025
Certain effectiveness for falling asleep
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october 15 2025
Help with falling asleep
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october 2 2025
Very effective for falling asleep
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september 25 2025
Same as 5HTP
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Hello Jean,
Thank you for your feedback on L-Tryptophan.
This supplement works by naturally promoting the production of serotonin, and then melatonin, the sleep hormone. It can indeed induce a relaxing effect conducive to drowsiness, sometimes more noticeable during the day (like during a nap) depending on the timing of intake and individual sensitivity.
To optimize its effects at night, we recommend taking it about 30 to 60 minutes before bedtime, away from protein-rich meals.
Feel free to contact our customer service if you wish to explore other natural solutions to improve your nighttime sleep.
Best regards,
Gaëlle - Supersmart team