What is the difference between 5-htp and l-tryptophan?

The differences between L-tryptophan and 5-HTP supplements

L-tryptophan and 5-HTP are both great dietary supplements that are converted into the same neurotransmitters: serotonin and melatonin. Yet, there are subtle but important differences between the two.


Serotonin is a critical neurotransmitter – it’s looked upon as a natural mood stabilizer. Indeed, from moods to motor skills to managing your stress triggers and efficient digestion, serotonin affects your entire body. It’s not surprising then that there’s an established link to certain disorders of behaviour and cognition such as anxiety, depression and insomnia and serotonin deficiencies.


Melatonin is a neurotransmitter formed by the conversion of serotonin. During daylight hours, production levels of serotonin are high and melatonin low. This changes with night fall. When the light levels in the ambient environment are reduced your brain’s pineal gland starts converting your higher levels of serotonin into melatonin. This activity is at the heart of our circadian rhythms or 24-hour cycle. There are established links between low melatonin levels in the brain and restless sleep or even insomnia.


Tryptophan is the essential amino acid that your body uses to produce serotonin and melatonin and other essential biochemicals such as niacin (vitamin B3) or enzymes. Tryptophan is found in most dietary proteins, especially in seeds and nuts, soya, cheese, meat, fish, beans and eggs. The bacterial fermentation of serine and indole produces the L-tryptophan used in supplements.


5-hydroxytryptophan or 5-HTP is a metabolite of tryptophan. When you consume tryptophan-rich foods or a supplement containing L-tryptophan it’s converted in the body to 5-HTP before it’s used for serotonin synthesis. Supplementing with 5-HTP bypasses the first steps and provides the version ready for serotonin production. 5-HTP is derived from the seeds of Griffonia Simplicifolia, an African shrub.

what is the difference between l-tryptophan and 5-htp
Difference 1: absorption

Both L-tryptophan and 5-HTP are needed to cross the blood-brain barrier for use in serotonin synthesis.
The blood-brain barrier is a defence membrane that protects your central nervous system and brain from the potential toxins, viruses, bacteria or fungi that may be circulating in your blood. It allows only the selected chemicals to enter your central nervous system.

5-htp and l-tryptophan needs to cross blood-brain barrier to enter the brain

L-tryptophan must compete with other amino acids (histidine, isoleucine, leucine, methionine, phenylalanine, threonine, tyrosine, and valine) for the shared transport mechanism to cross the blood-brain barrier [1]. 5-HTP doesn’t need a transport molecule to enter the brain therefore more of it will pass through the barrier and be available for serotonin synthesis [2].

The body uses L-trytophan for a range of purposes such as enzyme creation or niacin (vitamin B3) synthesis [1]. 5-HTP enters the central nervous system without being used up by other processes [2].

In fact, the conversion of L-tryptophan to 5-HTP is a rate limiting step – making it the slowest part of the serotonin pathway. As a result, supplementing with 5-HTP produces more serotonin than supplementing with L-trytophan. In addition, 5-HTP synthesizes the serotonin faster.

Difference 2: effects

Both L-tryptophan and 5-HTP lead to increased serotonin and melatonin levels. This in turn results in improved mood, healthy sleeping patterns and appetite suppression (by increased satiety from food intake) [3] [4] [5]. Yet 5-HTP has stronger and faster effects than L-tryptophan which provides more subtle effects.

On the other hand, because 5-HTP is so effective, there is a theoretical possibility that the body will start to build a tolerance to 5-HTP – which is not the case when using L-tryptophan. Therefore, it’s said that L-tryptophan is safer for long term use while 5-HTP is best short-term use.

High doses of 5-HTP can cause a mild nausea in susceptible persons at the beginning of supplementation. This is not the case with L-tryptophan use.

Co-factors and interactions

Vitamin B6 and magnesium are essential for the conversion of L-tryptophan and 5-HTP to serotonin. Vitamin B6 creates aromatic L-amino acid decarboxylase – an enzyme directly involved in the conversion of 5-HTP to serotonin (alongside L-dopa to dopamine conversion). Without sufficient B6 intake, serotonin synthesis is limited [6] [7].

Serotonin can be also be synthesized outside your central nervous system – in the liver. As a result, there’s a school of thought that suggests simultaneous supplementation with vitamin B6 and L-tryptophan or 5-HTP can cause additional peripheral serotonin synthesis and limit the amounts of L-tryptophan and 5-HTP that cross the blood-brain barrier for serotonin conversion in the brain [8]. Yet additional supplementation of vitamin B6 is advised. It’s better then to allow a time lapse between taking each supplement; take vitamin B6 at least two hours before an L-tryptophan or 5-HTP supplement. Or at a completely different time of day.

Catechnins found in Green Tea Extract (notably EGCG) are inhibitors of peripheral aromatic L-amino acid decarboxylase [9]. This means they prevent serotonin synthesis in the liver by blocking B6-enzyme activity. This leaves more L-tryptophan and 5-HTP to enter the central nervous system. For this reason additional supplementation with green tea extract can boost the effects of L-tryptophan or 5-HTP supplementation.

It’s not advised that you take either of these supplements with SSRIs (serotonin reuptake inhibitors) antidepressants or other medications that influence serotonin levels because of the possibility of dangerous serotonin syndrome [10].


If your goal is long term maintenance of healthy sleep patterns and an increase in positive moods – L-tryptophan is your best choice.

If a strong increase in positive moods and a significant improvement in your sleep patterns are your goals – opt for 5-HTP 300mg capsules. Take prior to sleep on an empty stomach.

And if you’re looking for improvement in mood and an appetite reduction – select 5-HTP 100mg tablets and take one before a meal, three times a day.

The effects of 5-HTP and L-tryptophan supplementation are boosted with vitamin B6 and green tea extract. The latter also has an effect on lowering carbohydrate absorption [11].