Read Romans 14:23 Using Other Translations
And he that doubteth is damned if he eat, because he eateth not of faith: for whatsoever is not of faith is sin.
But whoever has doubts is condemned if he eats, because the eating is not from faith. For whatever does not proceed from faith is sin.
But if you have doubts about whether or not you should eat something, you are sinning if you go ahead and do it. For you are not following your convictions. If you do anything you believe is not right, you are sinning.