Magnesium L-Threonate

What it is

Life Extension’s Neuro-Mag is magnesium L-threonate, sold under the trademarked ingredient name Magtein. A serving supplies 2,000 mg of Magtein, which works out to 144 mg of elemental magnesium — a low yield by weight, and the reason a bottle delivers less actual magnesium than its size suggests. Vegetarian capsules, non-GMO.

The compound came out of research at MIT led by Guosong Liu. The premise: bind magnesium to L-threonate and it crosses more readily into the central nervous system, raising magnesium concentrations in the brain, where ordinary magnesium salts do a poor job of reaching.

Why it’s on this list

The premise is genuinely interesting, and it is not made up. Rodent work showed brain magnesium rising and measures of synaptic density improving. In humans, a 2016 randomized controlled trial in older adults with cognitive impairment reported benefit, and a handful of more recent randomized trials report improvements in sleep quality and on cognitive test batteries in adults.

Here is the honest accounting. That trial base is small, short in duration, and closely tied to the company that sells the ingredient. Nothing about magnesium L-threonate is settled, and anyone telling you it is has skipped the reading. This is a bet on a specific and unproven hypothesis about brain magnesium, and it should be placed with open eyes.

If your actual goal is to correct a magnesium shortfall in your diet, this is the wrong product: magnesium glycinate is cheaper, better characterized, and gives you far more elemental magnesium per dollar. Buy threonate only if the brain hypothesis is the specific thing you want to test.

What to know before you buy

• You pay a great deal for a modest amount of magnesium. 144 mg of elemental magnesium per serving is well under half a day’s requirement, at several times the price of ordinary magnesium.
• The evidence is thin and interested. Small trials, short follow-up, and funding connected to the ingredient’s manufacturer. That is not proof of nothing — it is a reason to hold your conclusions loosely.
• Glycinate does the ordinary job for less. If you want general magnesium repletion, buy that instead and put the difference somewhere useful.
• Count your total magnesium. If you also take a multivitamin, a greens powder or another magnesium product, add them up. The tolerable upper intake for supplemental magnesium in adults is 350 mg a day; magnesium from food is not capped.
• Kidney function changes everything. Impaired kidneys clear magnesium poorly. If yours are compromised, do not supplement magnesium without medical supervision.
• Talk to a doctor before starting this or any supplement, especially alongside prescription medication.