You have the right idea. There hasn't been a lot of reserch to back up this theory. I know studies have proven to show in HS's that the students were better behaved etc when they ate healthy. Good foods are good for your body and brain. They will also help you feel better and keep you healthier. Either way you win.
As for drinking, it is a depressant. I feel awesome right when I drink. My symptoms go away and I'm normal again. I have a glass of wine to calm my nerves, it's also healthy for you (red). But, I have been told by my psychologist when he suggested meds, that alcohol screws with the chemicals in your brain. We have anxiety/depression because of a chemical imbalance. When you throw that off even more, the affect is more anxiety or depression overall. My anxiety is the worst part of my hangover. Ugh! I hate it. I'm tired but never puking or sick. My anxiety is what keeps me on the couch all day.
I have learned to not really drink when my anxiety is acting up. I have also learned that when my anxiety goes away (went away for about 4 months), I don't get the anxious hangovers. It was awesome. So, this goes to show that the state you are in before you drink should be a warning sign.
There are a lot of theories and studies that go into the causes and magnifiers of anxiety. Eating healthy does have its benefits. I have tried to eat healthier and I have noticed a marked improvement and attitude in the way I feel. I also exercise regularly and that helps tremendously as well. I do agree that diet and exercise has a lot to do with controlling one's anxiety.