I would not be afraid to use my pocket knife to cut apples or clean fish or cut a steak even if I used something like 3 in 1 on the joint. After all, I do keep my blade clean and dry not runny wet with 3 in 1 or mineral oil. I would think any possibility of contamination of food to be very small compared to the amount of foreign material allowed in our food, and pesticide contamination of fruits and vegetables.
Not to mention the acetaminophen and aspartame that we consume in our food and/or medications. I'm not saying that you can use anything you want, but why do we think that our knives don't see more serious contamination potential in manufacturing and packaging?
If I think my knife is dirty, then I wash it and dry it before using it on food. I clean it again after using it on food to protect it from the harsh environment of food. Then I re-lubricate the joint, wipe the blade with oil, then wipe off oils and put it away or back in my pocket as needed. Occasionally, I will thoroughly clean it just to get any dust, pocket lint, or other pocket nastiness off of it and out of it.
I think it is prudent to use something that is not so toxic that you have to wear a respirator and chemical gloves and lab apron to handle it. For example, PCB might make a decent knife preservative, but it is so toxic and chemically stable that it has been banned from manufacture.
Please don't think I am saying that "it's okay to use anything you want", because I'm not. Ballistol was mentioned above and it is a good lubricant, but I won't use it on my knives because I think it stinks (literally).
Ed J