The full study is very informative, detailed, and revealing.  It's also gave me a headache reading it!  For those who prefer to read on the layman's level, I've considerably boiled down the study to the bare basics below.  If I have misinterpreted anything, it was unintentional.  The actual study prevails over anything that I boiled down from it.

Disclaimer:  This summary explanation does not include all the legalese and detailed explanation included in the study.  Read the full study for complete details.  Words used in this summary may misrepresent the true meaning conveyed in the study write-up.

Summary:

It’s hard to find a decent treatment for chronic illness caused by a build up metal in the body.  Chelation therapy, for example, has negative side effects and it may not work for everyone.  Use of zeolite, specifically clinoptilolite, may be a safe alternative.  This study will evaluate whether or not Natural Cellular Defense (NCD) (the version of clinoptilolte used in the study) to remove heavy metals from the body without negative side effects.  The study used three treatment groups, each with eleven healthy males aged 35 to 71, two taking NCD and one control group taking a placebo.  Urine samples were collected from all groups at certain times during the study.  Group 1 took NCD for 7 days; Group 2 took NCD for 30 days.  Each person established a baseline urine sample before taking any NCD.  Changes to urine were measured against the baseline.  Five individuals from each group also submitted serum samples which were also analyzed for changes in serum electrolyte levels.  During the study, all participants in Groups 1 & 2 displayed increased levels of heavy metals in the urine, peaking on Day 4.  No one displayed significant changes in electrolyte levels.  (Any change in electrolyte levels would have indicated some sort of side effect.)  In conclusion, the study showed that NCD helps rid your body of heavy metals through urine without harmful side effects.