would you try and drink the leech flavored coffee from the Philippines?!
It's probably as reasonable as eating escargot or mussels or other aquatic invertebrates.
I'm not sure what to make of the health claim you mention for leech-flavored coffee though. It's not impossible that leech-flavored coffee contains anticoagulants known to be present in leeches or something else that has an effect on blood or the production of blood cells. Or it may simply be that leeches contain vitamins and minerals that have been useful to people during times of the year when nutrients are scarce.
It's also possible that the health claims are based entirely on "the doctrine of signatures" a form of reckoning based on the similarity of appearances. "Leeches suck blood, so they're strong. If you eat leeches your blood will be strong too." or something equally odd.
Folk remedies and traditional medical practices are often found to work and are studied by pharmaceutical companies searching for new classes of drugs. So who knows?
It sounds like an interesting brew.
http://en.wikipedia.org/wiki/Kopi_Luwak you may find this other kind of coffee, "Kopi Luwak" interesting.