Most foods in regular sized servings only contain a small amount of magnesium, unless of course they are foritfied. Nuts are a good source, but you'd have to eat a lot of nuts to get over 300 mg of magnesium.

If you are wanting that much at one time, why not take a supplemet?

I use the powder form and helps your muscles to not twitch and causes me drowsiness.

has anyone heard of magnesium helping with teeth grinding? i grind my teeth in my sleep, and read somewhere that magnesium deficiency may be the cause.