The Bible has much to say about the food that people consume, there's a guideline given by God regarding what to eat (Gen. 1:29, Gen. 9:3, Lev. 11), Lev. 11 and Deut. 14:3-21 are commonly known as the kosher law, which, to sum it up simply, no pork, shellfish or naturally dead animals. In principle we're not bound by this law, but kosher diet has certain health benefits, all the animals banned on the list are bottom feeders and scavengers with a lot of pathegeons, pork in particular is known for being the carrier of trichinella parasite, the culprit of trichinosis. Therefore, kosher law is not a religious or ceremonial law, but a food safety law, and it's well advanced of its time.
However, kosher law is NOT the topic I wanna discuss, so do me and yourself a favor, don't stretch it out with a wall of theological lecturing. The real challenge we face today is ultra-processed artificial food, that's the junk/fast food most of us eat everyday because it's cheap and convenient, but how does the bible instruct us on diet?
"I have given you every herb that yields seed which is on the face of all the earth, and every tree whose fruit yields seed; to you it shall be for food." - Gen. 1:29
"Every moving thing that lives shall be food for you. I have given you all things, even as the green herbs. But you shall not eat flesh with its life, that is, its blood." - Gen. 9:3-4
When it comes to diet, there're lots of camps like vegan, keto, paleo, asian in addition to kosher, but nearly all of those health gurus agree on one thing no matter what camp they're in - avoid those food-like substance, eat natural, whole food! You see, according to these two principles, God has created and ordained plants and animals for our sustenance. Most plants can be eaten in raw form, all you need is some cleaning and cutting; animals on the other hand have to be butchered, prepared and cooked properly, hence the no blood part. Again, this is common sense regarding food safety.
What God did NOT create or ordain is ULTRA-PROCESSED junk food. He did NOT create any chemical additive, preservative, coloring or flavoring. Question is, are they considered "unclean" like those non kosher meat by biblical standard? Most would say no, and they quote Matt. 15:11 (Not what goes into the mouth defiles a man; but what comes out of the mouth, this defiles a man.), Acts 10:15 (What God has cleansed you must not call common.) and maybe Rom. 14:6 (He who eats, eats to the Lord, for he gives God thanks; and he who does not eat, to the Lord he does not eat, and gives God thanks.) Conclusion: there's no prohibition, follow your own conscience.
I think this is a big mistake that would surely cost our health - both physical and mental, and thus our ability to serve the Lord. Ultra processed food are inherently bad with excessive calories but insufficient nutrients that our body needs, they are created by big corporations for profit, ordained by the FDA and sold out experts, and engineered to be addictive, long term consumption will most definitely defile you. By no means does that prove Jesus wrong, the context of Matt. 15 is about hand washing tradition and the Pharisees' hypocrisy. A little dirt on your hand doesn't kill you or defile you, but excessive amount of those artifical chemicals do, they are slow acting poison, their intake should be minimized.