Actually, 1 Corinthians 6:19 has nothing to do with smoking or tattoos or eating foods. Here is what it says.
1 Corinthians 6:12-20
12 “All things are lawful for me,” but not all things are helpful. “All things are lawful for me,” but I will not be dominated by anything. 13 “Food is meant for the stomach and the stomach for food”—and God will destroy both one and the other. The body is not meant for sexual immorality, but for the Lord, and the Lord for the body. 14 And God raised the Lord and will also raise us up by his power. 15 Do you not know that your bodies are members of Christ? Shall I then take the members of Christ and make them members of a prostitute? Never! 16 Or do you not know that he who is joined to a prostitute becomes one body with her? For, as it is written, “The two will become one flesh.” 17 But he who is joined to the Lord becomes one spirit with him. 18 Flee from sexual immorality. Every other sin[e] a person commits is outside the body, but the sexually immoral person sins against his own body. 19 Or do you not know that your body is a temple of the Holy Spirit within you, whom you have from God? You are not your own, 20 for you were bought with a price. So glorify God in your body.
We need to read the whole thing in context. Paul is saying just the opposite of how most people use this verse. He is saying that it does NOT matter what we put into our bodies. All things are allowable, but not all things are beneficial. He does point out that he will not be dominated (addicted) to anything. So it is okay to have the occasional drink or cigar if you can do so without becoming addicted. He then specifically says that it doesn't matter what foods we eat (verse 13).
Then he moves on to the main point. What does defile the body is sexual immorality, and here is why. When two people are joined together sexually, they become "one flesh". They are joined together physically and spiritually (verse 16). You can study more about this in Ephesians 5:25-33, Matthew 19:5 and Genesis 2:24.
Since Christians are the temple of God, we are joined to Christ spiritually. Here is the main point. If we as Christians have sex with a non-believer (prostitute in this case), we are therefor joining Christ with a prostitute. This is what the passage is about. The Corinthians were using God's grace as an excuse to have sex with prostitutes, and Paul is saying that they can not do that. It has nothing to do with foods, smoking or tattoos.