Some foods may be calming, some may upset your GI system, and others (caffeine) will keep you up. A panic attack is a sudden surge of physiological arousal that occurs unexpectedly. Think heart palps, shortness of breath, dizziness, sweating, tingling in extremities. This is accompanied by psychological symptoms like feeling unreal, feeling trapped and wanting to escape, thinking you're dying or going nuts.
We don't know why this happens, except to say that some people are predisposed to them and it is more common in those who experience other types of anxiety. It also runs in families.