" No one meat for us to be miserable. We actually make "happy hormones" in our brains. These are designed to make us feel good. But there are many things that can turn off these hormones, just as there are many things that can turn them on. And the amount of happy hormones you make in the brain is directly related to the type of diet you ingest. The difficulty is that we are all different in our biochemistry, and hence, also unique in what foods make us the happiest.
In other words, many people feel really mellow and content on a high carbohydrate (vegan or alkaline) diet. Many use this to optimize their athletic performance. While others are carnivores, not vegans, and feel best with meat (acid diet) at every meal. They get weak and lower their zip if they lower their meat content. "

― Sherry A. Rogers , Depression : Cured at Last!