This effect is more pronounced with lower-quality magnesium supplements, such as magnesium oxide, magnesium sulfate, and magnesium chloride. These compounds are insoluble in water (magnesium oxide), or their counter-ions are not absorbed (magnesium sulfate). Magnesium + glycine (specifically bisglycinate which is the magnesium salt with two glycine molecules) is more bioavailable and does not have a laxative effect since glycine is easily absorbed by cell walls. Magnesium citrate also does not have a marked laxative effect and is more bioavailable than magnesium oxide, but less bioavailable than magnesium bisglycinate.