Calcium:
Here is a link to that tetany I mentioned. Though don't get bogged down or paranoid about the causes, like any Web-based diagnosis. In most cases, it's a stress response. If we react stressfully, then all sorts of effects follow. Balancing ones thoughts is the key to better health. I sure gained some insights from The Dog Whisperer shows - as more often, responding stressfully to situations, only raises the ante. Cool is a better form of defence because someone will be more wary of you if you show no fear.
<a href=http://www.medterms.com/script/main/art.asp?articlekey=13312>Tetany - Calcium</a>
<a href=http://emedicine.medscape.com/article/241893-overview>Hypocalcemia</a>
Read the paragraph: Pathophysiology
Remembering that, Hypo- anything, is "less". Hyper is more.