Another supplement worth mentioning here is chromium piccolinate....I read a book a while back by a Dr. McLeod, who found a connection with insulin/depression/chromium. I am not sure of the amounts, but it may have been around 400-800mcg dose a day that made many of his patients feel alot better.
Also if you are type O, then low carb is generally good, especially proteins and veggies.

Here's a link to that book:
http://www.amazon.com/s/ref=nb_ss_g...ression&x=0&y=0