Also make sure to avoid foods heavy in L-Tryptophan because the conversion to 5-HTP is dangerous before MDMA. *sarcasm*
I've said it before and I doubt anyone will listen, but, I see no strong, convincing scientifical reason why 5-HTP & MDMA is dangerous. Sure 5-HTP is the precursor to serotonin. Sure MDMA releases serotonin. However, 5-HTP doesn't cause anymore serotonin to be released into the synapse than would usually be released. Serotonin Sydrome is a very rare condition resulting from an extreme amount of serotonin in the synapse. It usually occurs when drugs have a strong synergy. E.G. combining MDMA with a Monoamine Oxidase Inhibitor (MAOI). The MDMA releases serotonin and the MAOI blocks the enzyme that breaks serotonin down so it stays in the synapse = dangerously high serotonin. Basically, you can't get rid of the serotonin that has been released. At best, you'd have an extremely long & intense roll. At worst, you could develop SS. Another possible cause is combining MDMA with a drug that also releases serotonin (Tramadol, MKAT maybe? Providing they work through differing mechanisms).
Like I said, rather ironically, if 5-HTP was really dangerous then you could argue that consuming lots of L-tryptophan rich foods before MDMA is also dangerous.
L-Tryptophan > 5-HTP > 5-HT.