The Institute of Medicine set the tolerable upper intake level for B6 at 100 mg per day from food and supplements combined. However, the Expert Group on Vitamins and Minerals in the United Kingdom established a safe upper limit from supplements at 10 mg per day -- one-tenth the U.S. limit.

5-HTP, er det håndkøb eller på det grå marked?

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 by means of 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. In addition, 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;
Finally, L-tryptophan is an essential amino acid that is crucial for healthy body function and particularly, for the production of niacin.