Sure there are some edge cases which you can argue the point in
isn't that kind of a big deal, though? either it's not socially constructed and you can't argue in edge cases, or it is socially constructed and you can. as for what you do with this conclusion, it really doesn't matter.......
until you start discussing social constructs with someone and you have to remember that even the concept of food is socially constructed. which should really comfort us and remind us that this means something can be a social construct and still real, meaningful, and important, but instead it seems everyone wants to freak out at the concept! even in this thread.