So here's the breakdown of the different types of magnesium :
Magnesium oxide: Often used in milk of magnesia products since this form has a strong laxative effect. It has poor bioavailability and readily causes loose stools; therefore it is considered the least optimal form to use as a supplement but great for constipation.
Magnesium sulfate: is not used in oral formulations, but it does have some absorbability through the skin, so it is found in Epsom bath salts. It’s great for muscle relaxation and although it can be used as a laxative, I recommend magnesium citrate for that.
Magnesium Citrate: has a better bioavailability compared to oxide, but does have a stool loosening effect.
Magnesium Aspartate: has some promising clinical trials that found a combination of magnesium and potassium aspartates had a positive effect on fatigue and may reduce muscle hyper-excitability.
Magnesium Glycinate: Glycine is a well-known calming amino acid. This combination has good bioavailability and does not have a laxative effect since glycine is actively transported through the intestinal wall. This is the magnesium I recommend for sleep.
Magnesium Malate: Since malate can help improve ATP production; there is some preliminary evidence that it may reduce muscle pain and tender points, especially in fibromyalgia patients.
Magnesium Orotate: has good bioavailability and has had been studied specifically for heart health. It has been shown to improve heart failure, symptoms of angina and exercise performance in clinical trials.
Magnesium Taurate: has a potentiating effect on insulin sensitivity and also a calming effect on neuromuscular excitability. It has been shown to reduce blood pressure, stabilize nerve cells, improve the contraction of the heart muscle and have an anti-thrombotic effect.
Magnesium-L-Threonate: This form of magnesium has recently been studied to improve memory and brain function.

Well, I hope that clears up any confusion. Take this chart into the Martin’s pharmacy the next time you need to pick your magnesium or ask the wellness consultant to assist you with your magnesium needs.