Q In reading about insomnia and daytime sleepiness elsewhere, I encountered the following statement: “Avoid taking vitamin B6 supplements within 6 hours of taking 5-hydroxytryptophan (5-HTP) because vitamin B6 can cause the conversion of 5-HTP to serotonin in the blood before it has a chance to cross the blood-brain barrier to increase serotonin in the brain. Excessive serotonin in the blood can be dangerous.”

It doesn’t say what the danger is. I take 5-HTP twice daily and a multivitamin that has B6 in it twice daily, and I feel so much better on the 5-HTP. It has reduced my achy feelings and lifted my sour mood. Can you enlighten me about what the problem might be?

CINDY, Rodman, NY

A We answered this question for you in the January 2005 issue, but perhaps you didn’t see it. Because some urban legends live on, and we are often asked this question, the answer is worth repeating.

Although some literature suggests that vitamin B6 may cause 5-HTP to convert rapidly to serotonin before it even reaches the brain, thus inhibiting an increase in brain serotonin, it is actually quite the opposite. In one notable study on rats, vitamin B6 deficiency was deliberately induced, and it was discovered that very little serotonin was produced in the rats’ brains in that condition.1 In other experiments with monkeys and rats, the presence of ample amounts of B6—even to the point of “moderate excess”—increased production of serotonin (in the brain) from 5-HTP by up to 60%.2,3

Once again, it is clear that 5-HTP raises brain serotonin levels—with or without carbidopa or benserazide, and with or without vitamin B6. But the evidence indicates that it’s better to take 5-HTP without carbidopa or benserazide, and with vitamin B6.4

More recent research shows that vitamin B6 helps to convert 5-HTP to serotonin more efficiently because it plays a role in tryptophan metabolism, thereby increasing production of 5-HTP.5

Regarding too much peripheral serotonin, we are not aware of any literature showing any connection between 5-HTP consumption and this problem.


  1. Dakshinamurti K, LeBlancq WD, Herchl R, Havlicek V. Nonparallel changes in brain monoamines of pyridoxine-deficient growing rats. Exp Brain Res 1976;26:355-66.
  2. Hartvig P, Lindner KJ, Bjurling P, Langstrom B, Tedroff J. Pyridoxine effect on synthesis rate of serotonin in the monkey brain measured with positron emission tomography. J Neural Trans 1995;102:91-7.
  3. Dakshinamurti K, Sharma SK, Bonke D. Influence of B vitamins on binding properties of serotonin receptors in the CNS of rats. Klin Wochenschr 1990;68:142-5.
  4. Siow YL, Dakshinamurti K. Effect of pyridoxine deficiency on aromatic L-amino acid decarboxylase in adult rat brain. Exp Brain Res 1985;59: 575-81.
  5. Calderon-Guzman D, Hernandez-Islas JL, Espitia-Vazquez I, Barragan-Mejia G, Hernandez-Garcia E, Santamaria-del Angel D, Juarez-Olguin H. Pyridoxine, regardless of serotonin levels, increases production of 5-hydroxytryptophan in rat brain. Arch Med Res 2004 Jul-Aug;35(4):271-4.

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