Interesting article about the different types of Magnesium...

The best forms of magnesium are magnesium taurate, magnesium glycinate, magnesium citrate, magnesium malate, magnesium oratate and magnesium oil.

Oral supplements
I will mention some of the oral supplements. Magnesium is available in chelated (bound to) combinations such as alpha-ketogluconate, aspartate, glycinate, lysinate, orotate, taurate and others.

Chelated magnesium is far better absorbed than magnesium oxide but is more expensive. Complementary medicine
practitioners rely on chelated magnesium, such as magnesium glycinate, taurate and oratate (magnesium plus amino acids) to treat serious cases of magnesium deficiency. These kind of magnesiums have less laxative effect on the intestines than magnesium citrate, so they are recomended if you tend to have loose stools.

Magnesium taurate is a combination of the amino acid taurine and magnesium that has special properties for the heart. Taken together in this combination, magnesium and taurine have a synergistic effect, stabilizing cell membranes, making this form of magnesium highly absorbed. Magnesium taurate does not have great laxative effect and is the recommendend form of magnesium for people with heart problems. It appears that the amino acid taurine is important for hearth health and may prevent arrythmias and protect the heart against the damage caused by heart attacks. Magnesium taurate requires oral supplemetation for six to twelve months to restore intracellular levels.

Magnesium citrate is probably the mostly widely used magnesium supplement because it is inexpensive, easily absorbed and only has a mild laxative effect. The best form is magnesium citrate powder mixed in water that can be taken everyday.

Magnesium malate combines magnesium with malic acid, a weak organic acid found in vegetables and fruit, especially apples. The weak bond with magnesium makes it readily soluble in the body. Malic acid is a key component of several energy making chemical reactions in the body. Researchers have used magnesium malate succesfully to treat the chronic fatigue, pain and immsonia of fibromyalgia. Dimagnesium malate increases the amount of magnesium available to the body; it has the same properties as magnesium malate.

Magnesium oxide appears to have high amount of elemental magnesium. One 500 mg capsule of magnesium oxide contains 300 mg of elemental magnesium. But little of that amount is available to the body because it is not absorbed and therefore not biologically available. One recent study reported 4 percent absorption rate of magnesium oxide. This means 12 mg of 500 mg capsule are absorbed and 288 may stay in the intestines, acting like a laxative. Imagine how much favorable the result would be if a more absorbable form of magnesium were used.

Magnesiums to avoid
Avoid magnesium glutamate; it breaks down into the neurotransmitter glutamic acid, which without being bound to other amino acids is neurotoxic. Glutamic acid is a component of aspartame, which should also be avoided.

Avoid magnesium aspartate; it breaks down into the neurotransmitter aspartic acid, which without being bound to other aminoacids is neurotoxic. Aspartic acid is a component of aspartame,which als should be avoided.

How to take magnesium
Take your first dose of magnesium when you wake up in the morning and the last dose at bedtime. Magnesium is most deficient in the early morning and late afternoon. Most people find magnesium as good as a sleepin pill to help them get a good night’s rest.

Magnesium can be taken with or without meals, but it is preferable to take it between meals for better absorption. Magnesium requires stomach acid to be absorbed. After a full meal, your stomach acid is busy digesting food and may not be avaialable to helpl absorb magnesium. Also magnesium is an alkaline mineral and acts like an antiacid: taken with meals, it may neutralize stomach acid and impair digestion. If you develop loose stools while taking magnesium, it does not necessarily mean you are absorbing enough and losing the rest; it may mean you are taking to much at one time. NEVER TAKE YOUR DAILY MAGNESIUM ALL AT ONCE.

Source: http://www.medhelp.org/posts/Heart-Rhythm/Magnesium-supplements----to-avoid---how-to-take-it-and--safety/show/1002415

I found this page about Magnesium. Seems he's done his research.

http://www.worldhairloss.org/index.php/forums/viewthread/93

Recently started using Mag oil topically and in my opinion it does make the hair look healthier.