1 Tim 4:1-5

4:1 Now the Spirit speaketh expressly, that in the latter times some shall depart from the faith, giving heed to seducing spirits, and doctrines of devils;

2 Speaking lies in hypocrisy; having their conscience seared with a hot iron;

3 Forbidding to marry, and commanding to abstain from meats, which God hath created to be received with thanksgiving of them which believe and know the truth.

4 For every creature of God is good, and nothing to be refused, if it be received with thanksgiving:

5 For it is sanctified by the word of God and prayer.

Note: 1 Timothy 4:3-4 is talking about doctrines of devils and how the false doctrines of stated that we should not eat meat at all. 

In verse three, Paul is speaking about people who "KNOW" the truth of God. They "know" exactly which foods God has created for us to give Him thanks for. They are listed and categorized in Lev. 11 and in Deut. 14. Those who know the truth, know this very well.