As per my advice to never ingest a supplement without verifying its quality via a Certificate of Analysis, I looked into DoubleWood Magnesium L-Threonate aka “Magtein”.
A ton of credit to DoubleWood for posting the COA documents for their offerings right on their web site. Some companies make you jump through hoops to ask for them eg having to buy the product and produce an order number before they will provide the COA.
This comparison equalizes the single-dose amount of elemental magnesium serving size at 210mg.
DoubleWood: 0.146 mcg lead per 210mg elemental Mg (0.1 mcg per 144mg elemental Mg)
Nutricost: 0.0109 mcg per 210mg elemental Mg
The DoubleWood product has low levels of Pb (lead), Cd, Ar, Hg. It’s a high quality product; many competing products are much higher and some are considerably higher. And... some are considerably lower for lead.
I (active 80kg male) would typically aim for ~400mg to ~600mg elemental magnesium per day, which would mean ~0.4 to ~0.7 mcg of lead from the DoubleWood product. This is low in the context of a 15 mcg per day recommended intake, but it’s not nothing, that is, 0.04 mcg from the Nutricost product suits me better.
Moreover, note that the state of California advises (perhaps unrealistically) no more than 0.5 mcg for pregnant/lactating women and small children. Dosing with the DoubleWood product would hit hit that limit, before any food or environmental exposure.
Compare the heavy metals: Pb (lead), Hg (mercury), Ar (arsenic), Cd (cadmium).
The DoubleWood product is below levels that are concerning for adults. But if you are trying to minimize lead exposure as I am, the Nutricost MgCl product has 13.4X lower lead for the same amount of elemental magnesium (.0109 mcg per 210mg elemental Mg). And it’s much lower on Hg and lower on Ar as well, and only 50% higher on Cd (but Cd is at extremely low levels anyway). I also like the fact that the Nutricost product has only one ingredient vs gelatin + rice powder for the DoubleWood capsules.
|mcg per 210mg elemental Mg||Nutricost MgCl Hexahydrate||DoubleWood Magnesium L-Threonate||RnAReSet ReMag||Heiltropfen Magnesium Chloride Hexahydrate|
"Heavy metals (as Pb)" 5.33