***** ...Lower caste people partake of or otherwise come into contact with substances which are considered polluting. They usually eat meat, will handle flesh, and cleanse the blood of birth or menstruation. The higher castes are vegetarian and do not work in occupations that bring them into contact with polluting substances.... <http://www.rai.anthropology.org.uk/film/catalogue_2/62_caste.html> *****
In Japan (much of whose culture used to be derivative of great Asian civilizations such as India) as well, the lowest caste -- called _eta_ or _burakumin_ or _hinin_ & translated into English as "untouchable" or "outcaste" -- were confined to occupations considered to be polluting: butchering, leather-making, etc.
In general, I think that the more dietary laws & prohibitions exist in a society, the society in question tends to be more hierarchical & plagued by originally pre-capitalist social relations & ideology renovated to fit capitalist modernity. (To look at subcultures, compare Orthodox Jewish practices, Reform Jewish practices, & secular Jewish practices.)
In my opinion, there is something distinctively un-modern or anti-modern about the USA, though at the same time it is hyper-modern when it comes to warfare, polling, marketing, technology in general, etc. So, it is no wonder that dietary prohibitions continue to proliferate here.
Now, the idea of "utopian socialism" in still feudal times was also underwritten by the interlocking notions of caste & purity/pollution. Remember Thomas More's _Utopia_:
***** ...There are also, without their towns, places appointed near some running water, for killing their beasts, and for washing away their filth, which is done by their slaves: for they suffer none of their citizens to kill their cattle, because they think that pity and good-nature, which are among the best of those affections that are born with us, are much impaired by the butchering of animals: nor do they suffer anything that is foul or unclean to be brought within their towns, lest the air should be infected by ill-smells which might prejudice their health.... <http://faculty.wm.edu/rbsche/utopia2.html> *****
Yoshie