Tryptophan is toxic. But finding this reference on the internet is not that easy.

"In people who are even marginally vitamin B6 deficient, tryptophan may be rapidly degraded into mildly toxic metabolites such as hydroxykynurenine, xanthurenic acid and hydroxyanthranilic acid."

source:
http://intelegen.com/nutrients/ltryp...nswer_to_p.htm

Tryptophan will not pass the BBB from eating a high protein meal because it has to compete with other amino acids. That is why people craving carbohydrates may be low in tryptophan or serotonin. A high carb snack is the best way to supplement tryptophan or 5-htp so that it gets into your brain. And it is better to take 5-htp with a high carb snack than on an empty stomach. And if you don't have a b6 deficiency you may still want to supplement b6 when you take 5-htp (or tryptophan) just to be safe.

Tryptophan is considered a potentially toxic amino acid. There is no misinterpretation about that statement. HOW it becomes toxic depends on which of several different pathways it can follow in the brain. But this toxicity is not that commonly known about. And if not supplementing enough of ALL necessary b vitamins (in the right doses) then it is likely to become toxic.

I think if anyone wants to increase their tryptophan levels they would be better off taking some form of niacin (with vitamin b6, of course).