Health Care Iranian Style

Oh, that's all right then, Iran is doing this for their health..... MEMRI here.

UPDATE: Uh.....Here's the "straight dope" from the Chicago Reader staff, which does not vouch for its accuracy, but, hey, it's close enough, in case you were sorta confused:

Despite the fact the light water and heavy water are chemically identical, heavy water is mildly toxic. How can this be? Since heavy water is heavier than normal water, the speed of chemical reactions involving it is altered somewhat, as is the strength of some types of bonds it forms. This affects certain cellular processes, notably mitosis, or cell division, due to the difference in binding energy in the hydrogen bonds needed to make certain proteins. Mouse studies have shown that drinking only heavy water along with normal feed eventually causes degeneration of tissues that need to replenish themselves frequently, and leads to cumulative damage from injuries that don't heal as quickly. One study likens the effects to those suffered by chemotherapy patients. Heavy water toxicity manifests itself when about 50% of the water in the body has been replaced by D₂O. Prolonged heavy water consumption can cause death.