Does the type of food you eat affect your mood?

Studies show that they do.  How far it is true and how proven is this theory, I have no answer.  I read an article online stating that the neurotransmitters in our brain is sensitive to food.  It states that if you want to improve your memory and concentration, you should eat eggs.  Caffeine is known to be an anti-depressant.  Carbohydrates help to reduce stress and protein will boost alertness.  How bizarre!