During the clinical trials described above, some people taking large amounts of 5-HTP experienced gastrointestinal upset (e.g. nausea) or, less often, headache, sleepiness, muscle pain, or anxiety.
A substance known as “Peak X” has been found in low concentrations in several over-the-counter 5-HTP preparations. Some researchers think this substance may be linked97, 98, 99 to toxicity previously reported100, 101, 102 in a 1989 L-tryptophan contamination incident. However, there is serious question about whether Peak X is actually the toxic agent and it may be unrelated to the problems previously associated with L-tryptophan.103, 104, 105, 106, 107, 108, 109, 110 Although two articles reported possible associations between 5-HTP consumption and toxicity symptoms similar to those attributed to contaminated L-tryprophan,111, 112 evidence linking 5-HTP or Peak X with any toxicity symptoms remains speculative. Although the structure of Peak X has recently been identified, there is no firm evidence that this substance has caused or contributed to any toxicity or disease.113
Very high intakes of 5-HTP have caused muscle jerks in guinea pigs114 and both muscle jerks115 and diarrhea in mice.116 Injected 5-HTP has also caused kidney damage in rats.117 To date, these problems have not been reported in humans. “Serotonin syndrome,” a serious but uncommon condition caused by excessive amounts of serotonin, has not been reported to result from supplementation with 5-HTP; in theory it could be triggered by the supplement.118 However, the level of intake at which this toxic effect might potentially occur remains unknown.
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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2015.