I think that's why the phrase is "mind over matter", not "matter over mind".
Certainly I completely agree that what one puts into the body is fundamental to good overall health. But in the context of this thread as it concerns matters of mind...mental programming, responsibility and brain function, it's not so much about the fuel that goes into driving the machine, as it is about how the engine is wired.
I know of people who adhere to strict nutritional programs and still got cancer. Who exercise daily and still have high blood pressure. I know first hand what it is to eat well (a pound of yogurt with Grape Nuts every day for 15 years, organically grown greens daily, nothing artificial...and I'm almost never physically ill) and still there's addiction...
Physical nutrition as it applies to overall physical health...no question about how that works. Direct relationship. As it applies to mental hard-wiring, the relationship is far more complex.
In response to your inquiry Autumn, I've not invested nearly enough into exploring CBT or other cognative therapy options. Until very recently I wasn't sure I wanted to leave the drugs behind, and actively engaging mental processing techniques to do so makes addict-thinking quite agitated.