Bodies do absorb magnesium, even when cleansing.

Interesting concept - that a body deficient in the essential nutrient magnesium would not absorb it when it is in the organs responsible for absorbing nutrients. Perhaps whomever gave you this information is misinformed? I suspect that if you were to consult with an expert whether or not any magnesium is absorbed when massive amounts of magnesium are administered, the experts would say YES!