hey there garden_gal I have thought about this and tried things out relating to diet and depression. I've never seen a nutritionalist, so I have no 'official' advice.

For ME (I'm sure it's different for everyone):
~Caffeine has had a variety of effects. Earlier it used to be the only thing that kept me OK at times. More recently it's had too many negative effects. Its like deep in depression I needed that extra kick. And now, recovering from it the side effects are worse than the positives if that makes any sense.

~Dairy sometimes messes with my mood so I have to be careful

~Berries/fruit: I find having these instead of dessert or plain sugars does WONDERS for me. Just for the record. I enjoy berries, especially blueberries and strawberries as much or more than ice cream, and I feel better throughout the day when I eat them.

~chocolate used to have a very positive effect on my (dark only, high quality stuff). It doesn't as much anymore =( but when I was deeper in depression it definitely helped my mood a LOT.

Also, for me B12 is really important and I'm taking supplement for it. It's really important to watch your vitamin intake and make sure you're getting what you need because imbalance/deficiency can affect mood. So for B12 you'd need red meats, flax seed among other things :P

Those are my thoughts - you are on a good path!

Also for me exercising does wonders have you tried 30 minutes aerobic stuff about 3 times a week? =)