Zechstein (Magnesium Chloride) vs Epsom (Magnesium Sulfate): The Health Benefits
According to the National Institute of Health, Magnesium Chloride has approximately 12 percent magnesium available for absorption. Alternatively, Magnesium Sulfate, or that found in Epsom salt, contains only 10 percent Magnesium available for absorption.
Daniel Reid, author of The Tao of Detox, cites that Magnesium Sulfate, commonly known as Epsom salts, is rapidly excreted through the kidneys and therefore difficult to assimilate. This would explain in part why the effects from Epsom salt baths do not last long and why you need more Magnesium Sulfate in a bath than Magnesium Chloride to get similar results. Magnesium Chloride instead is easily assimilated and metabolized in the human body.