If you're subsisting on candy bars and potato chips and not suffering from it yet, it's only a matter of time. It does matter whether it's good food or not. But lots of foods get bad raps, like cheese, meat, and so much other stuff. The name of the ingredient (wheat, beef, rice, cheese) matters less than the quality of it. If food is not very processed that's a good start. If it comes from a local farm, it's probably even better. Cooking a good fraction of your own food, any kind of food, is likely to make a good diet.