Hi bumblesue, this passage you quote, from Mark 8, was said by Jesus in relation to a question a Pharisee asked about how what he was doing was "unclean" (read the food laws in Leviticus 11 for more details). Jesus says that what you eat is not important, that just goes through the stomach and out the other side. It's what comes from within - sexual immorality, theft, murder, adultery, greed, malic, deceit, lewdness, envy, slander, arrogance, folly - these are what defile a person.
As for smoking, drinking, drugs, etc, I think it's a little harder to answer than simply "yes" or "no". Paul says in his epistles somewhere that everything is permissable, but not everything is beneficial (not sure of the passage off the top of my head). There's no specific law about smoking or drinking (though the Bible does counsel against drinking to the point of drunkenness - something I've occassionally ignored

), or even illegal drugs. However, if a substance is illegal, regardless of the morality from a biblical point of view (an argument can be made for the medicinal benefits of marijuana, for example) the Bible also asks Christians to follow the laws of the authorities that are placed on earth. If a substance is illegal under earthly authorities then we as Christians should abide by that (see Romans 13 for more details).