[quote=@Fallenreaper]
<Snipped quote by Thundercrash>

Considering humans have been isolated while Asari, Turian, Krogan and others have been in close range with one another or at least interacting, you think they would have similar biological needs. OR have a food made that they all could eat without issues. 
[/quote]

http://forum.bioware.com/topic/319407-dextrolevo-food-split-makes-no-sense/ I don't know how accurate this guy's science is, but I do know that food and nutrients are a lot more complicated than one would think. I imagine that it's just hard to create non-Earth sentient species, since it's so heavily dependent upon the environment they evolve in.