Myths About 5-HTP

5-hydroxytryptophan (5-HTP) is sold as a “natural antidepressant”, an “appetite pill”, and even as a means for better recovery after training. Some of these promises have a weak but real scientific basis, some do not. The editorial team collected the most common myths about 5-HTP and compared them with what studies actually show.

Why there are so many myths around 5-HTP

5-HTP is an intermediate link on the path from the amino acid tryptophan to the neurotransmitter serotonin. In the body, the enzyme tryptophan hydroxylase converts tryptophan into 5-HTP, and aromatic amino acid decarboxylase converts 5-HTP into serotonin. Commercial 5-HTP is obtained mainly from the seeds of the African plant Griffonia simplicifolia, and it is precisely its plant origin that became the first basis of the marketing legend.

A second reason for the myths is a simple logical scheme that is easy to “sell”: serotonin is linked with mood, appetite, and sleep; 5-HTP raises serotonin; therefore 5-HTP improves mood, reduces appetite, and regulates sleep. In practice, between “raises the level of a substance in the blood” and “gives a tangible clinical effect” lies a long road, which only high-quality randomized studies confirm.

A third reason is the old evidence base. A significant part of the clinical work on 5-HTP was carried out in the 1970s–1990s, had small samples, a short observation period, and often an imperfect design. Systematic reviews, in particular the 2002 Cochrane review, directly indicated that of more than a hundred studies found, only a handful met basic quality criteria.

Finally, in most countries 5-HTP is sold as a dietary supplement rather than as a medicine. This means that manufacturers are not obliged to prove effectiveness the way pharmaceutical companies are, and quality control of the raw material depends on the conscientiousness of a particular brand. Such a situation creates an ideal environment for exaggerated promises.

Myth: “natural means safe” and “replaces antidepressants”

Plant origin does not guarantee safety. The history of tryptophan and 5-HTP illustrates this well: in the late 1980s an epidemic of eosinophilia-myalgia broke out in the USA — a severe systemic disease associated with contaminated batches of L-tryptophan from one manufacturer. Later, impurities were also found in some commercial samples of 5-HTP, in particular the so-called “peak X”, which were discussed as possible risk factors.

The safety review by Das et al. (2004) concluded that there is no convincing evidence of a link between modern 5-HTP and eosinophilia-myalgia, but emphasized the key role of the purity of the raw material. That is, the safety of a product is determined not by its “naturalness” but by the quality of production and control of impurities.

Now about the “natural antidepressant”. Depression is a disease that a doctor diagnoses and treats. The meta-analysis by Javelle et al. (2020) found signs of an effect of 5-HTP in certain types of depression, but the authors assessed the quality of the evidence as low and directly called for new high-quality studies. There is no question of an equivalent replacement of modern therapy.

Something else is also dangerous: people who already take antidepressants of the SSRI or SNRI group or MAO inhibitors sometimes add 5-HTP “for enhancement”. Such a combination can increase the risk of serotonin syndrome — a state with tremor, sweating, tachycardia, and a rise in temperature, in severe cases life-threatening. The clinical review by Boyer and Shannon (2005) describes this syndrome in detail.

So the correct formulation sounds like this: 5-HTP is a biologically active substance with a pharmacological action that requires the same careful attitude as medicines. One must not replace prescribed therapy with the supplement on one’s own or combine them without the doctor’s knowledge.

Myth: 5-HTP is a fat burner

In sports marketing, 5-HTP is sometimes positioned as a means for “cutting”. In reality it has no direct effect on lipolysis or energy expenditure. The idea is based on something else: serotonin participates in the regulation of satiety, so 5-HTP could theoretically reduce appetite and the amount eaten.

The most frequently cited works are small Italian studies by Cangiano et al. from the early 1990s involving people with obesity. In them, 5-HTP against the background of a diet was accompanied by lower food intake and earlier satiety compared with placebo. However, the samples were small, the duration a few weeks, and the doses significantly higher than those typical for supplements.

An important detail: in these studies some of the participants reported nausea, which in itself reduces appetite. So it is not always possible to separate “true” satiety from discomfort in the gastrointestinal tract. There are no modern large randomized studies that would confirm a sustained reduction in body weight.

For a person who trains and wants to reduce their fat percentage, the basic tools remain unchanged: a moderate calorie deficit, a sufficient amount of protein, strength training, sleep. 5-HTP in this scheme is at best an auxiliary factor with an uncertain effect, not a “fat burner”.

Myth: 5-HTP increases endurance and speeds up recovery

This myth is especially interesting, because scientific logic here works in the reverse direction. There is a so-called serotonin hypothesis of central fatigue: during prolonged exercise the share of free tryptophan in the blood rises, more of it enters the brain, the serotonin level increases — and this can intensify the feeling of fatigue and reduced motivation.

The review by Meeusen et al. (2006) in the journal Sports Medicine examined this hypothesis in detail. The authors showed that manipulations with the serotonin system can affect performance, but the picture is more complex than the simple formula “more serotonin — more fatigue”: the ratio of serotonin and dopamine, temperature, and the type of exercise play an important role.

One way or another, no theory predicts that taking a serotonin precursor immediately before training will increase endurance. On the contrary, some researchers considered precisely a reduction in serotonergic activity as a potential path to delaying fatigue. The editorial team is not aware of any reliable studies that would show an improvement in athletic performance on 5-HTP.

As for recovery, the discussion here is usually about sleep. If a person falls asleep poorly because of stress, improving sleep quality indirectly affects recovery. However, even here the data on 5-HTP are limited, and for sleep there are better-studied approaches — from sleep hygiene to adjusting the training regimen.

Practical conclusion for athletes: 5-HTP should not be taken as a pre-workout or “endurance” supplement. If the goal is sleep and emotional state, the question is better discussed with a doctor or a sports dietitian, taking into account the drugs the person already takes.

Myth: “the more the better” and “it can be combined with anything”

Part of the 5-HTP is already converted in the intestine and peripheral tissues into serotonin, which does not cross the blood-brain barrier. Peripheral serotonin affects intestinal motility, so the most common side effects of 5-HTP are nausea, abdominal discomfort, and diarrhea. As the dose increases, these effects become more frequent, while the beneficial action does not grow proportionally.

In clinical studies, 5-HTP was sometimes used together with peripheral decarboxylase inhibitors (for example, carbidopa) so that more of the substance would reach the brain. These are medical protocols under the supervision of doctors, not an example for independent repetition: carbidopa is a prescription drug with its own risk profile.

Dangerous combinations are worth knowing by heart:

• antidepressants (SSRIs, SNRIs, tricyclics, MAO inhibitors);
• tramadol and some other opioid analgesics with a serotonergic action;
• triptans used for migraine;
• St. John’s wort and other serotonergic supplements;
• dextromethorphan, linezolid, some antiemetics.

The list is not exhaustive, so before any combination with drugs a consultation with a doctor or pharmacist is needed. Separately it is worth remembering pregnancy and breastfeeding, when the data on the safety of 5-HTP are insufficient, and minors.

Another common myth is that 5-HTP “accumulates” and therefore can be taken continuously for years. There are few data on long-term use, so it is sensible to regard any course as limited in time and to regularly reassess whether it gives a tangible benefit.

Editorial Conclusions

5-HTP is neither a “magic pill” nor a harmless vitamin. It is a serotonin precursor with a real pharmacological action, whose evidence base regarding mood and appetite remains limited and mostly outdated.

The most mistaken notions concern sport: 5-HTP is not a fat burner, and the idea of increasing endurance with it contradicts the central fatigue hypothesis. The real risks are gastrointestinal side effects and serotonin syndrome in the case of combination with drugs.

If you are considering 5-HTP, choose products with verified purity, do not exceed the doses on the label, and do not combine it with serotonergic drugs without a doctor.

The editorial team also recommends familiarizing yourself with our materials “5-HTP: What It Is and How It Works”, “Side Effects of 5-HTP”, and “What to Combine 5-HTP With”.

References

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