Hey, our bodies naturally produce GHB, what could possibly be toxic about it?! And hey, real smart analogy with the oxygen.
The 5-HTP to serotonin conversion occurs with the assistance of l-aromatic amino acid decarboxylase; most cells in your body contain this enzyme, and the net effect is that <1% of 5-HTP actually makes it to your brain. You can do your own research on the effects of a bunch of serotonin floating around where it doesn't belong.
edit:
just a couple quotes from a simple google search..
"5-HTP can cause hypertension by increasing plasma renin activity, when not co-administered with a peripheral aromatic L-amino acid decarboxylase inhibitor, such as carbidopa or benserazide"
"Some clinicians suggest that 5-HTP be administered with a peripheral decarboxylase inhibitor (such as carbidopa) to prevent elevated serotonin levels in the bloodstream (and the subsequent side effects)."
"Safety, Side Effects and Warnings:
5-HTP should not be used by those hypersensitive to any component of a 5-HTP-containing product. It is also contraindicated in people with carcinoid tumors, and during or within 2 weeks after discontinuation of an MAOI.
Large doses of 5-HTP can trigger excess of serotonin formation in tissues other than the target organ and cause significant adverse effects. It should not be used concurrently with any antidepressant, including SSRIS, tricyclics, or MAOIs. Concurrent 5-HTP use with an antidepressant may increase the risk of adverse reactions. 5-HTP should not be used by those with ischemic heart disease, coronary artery spasm, uncontrolled hypertension and any other significant cardiovascular disease."
"At the very best, people who take B-vitamins with 5-HTP, or
who take 5-HTP products with B6, waste their money. All this
would be merely humorous (caveat emptor) were it not for some
other facts. At worst, ignorant people fooling with 5-HTP
actually risk their health, since serotonin in the peripheral
blood is not benign. Serotonin causes not only harmless flushing
and diarrhea, but people with serotonin secreting tumors (hindgut
carcinoids) also have problems with fibrosis of the endocardium
and valves in their right hearts, which can cause heart failure.
This fibrosis is caused by the serotonin. This effect can also
be seen with dietary intake of only modest amounts of serotonin,
and there has actually been described in the medical literature a
tribe of South Sea islanders with right heart fibrosis as a
result of eating green banana mash (matuki), which poisons them
with its serotonin content. No, I'm not making this up. The
hydroxylation of tryptophan is a rate-limiting step in the
peripheral production of serotonin, and one bypasses it at one's
peril.
How much does it take? Several hundred milligrams of 5-HTP
taken per day, if converted to serotonin, would result in a
urinary excretion of the serotonin metabolite 5-hydroxyindoleac-
etic acid (5-HIAA) of several hundred milligrams also-- an amount
well within the urinary excretion range of the average person
with a serotonin producing carcinoid. Such a dose of 5-HTP
certainly would result in a serotonin blood load comparable to
that of green-banana-diet eating people who have
serotonin-induced heart valve disease. Normally, people do not
excrete breakdown products of more than 10 mg of serotonin
metabolites per day. If you take one capsule per day of 50 mg
5-HTP with 10 mg B6, however, you would be expected to go to at
least 50 mg per day of 5-HIAA in the urine. Less metabolism in
the liver (less B6) would result in less 5-HIAA in the urine. If
you are going to take 5-HTP, therefore, you probably need 5-HIAA
urine monitoring, to figure out just how big a dose of systemic
serotonin you're actually getting (and incidentally, how much
5-HTP you're wasting). See a doctor!
For all the reasons outlined above, I am presenting those
vitamin companies who sell 5-HTP with B6, or who sell it alone
but don't warn their customers about 5-HIAA monitoring or B6
intake, a special award: the Green Banana Award. This honor is
for those supplement-sellers who monkey around with people's
health before consulting with some really good nutrition and
medical specialists to make sure they don't f*&% up and hurt
somebody. Hopefully, companies which receive the Green Banana
Award will contemplate its message, and will thereby change their
behavior in order to avoid some of the less-coveted awards which
otherwise await them in the future: the Civil Damage Award, for
instance, or even the All-Expense-Paid Guest of the Federal
Government Award." -Steven B. Harris, M.D.
:D