Why are oral magnesium supplements so difficult to absorb for most people?

Basically, there are two main reasons for that.First of all, major amount of magnesium from dietary supplements have a tendency to create a laxative effect in most of the users. This reduces transit time through the gastrointestinal tract and decreases overall absorption.
The second reason is when high quantities of magnesium are taken in a single dose, a smaller overall percentage of magnesium is absorbed.