Generally, as I understand it, the convention is for that sort of text to mean it’s 200 mg of magnesium, not 200 mg of the compound.
1.4g is more than a tenth of the typical shortfall and there’s a lot of heterogeneity, but also total magnesium need is often estimated at half a gram, so 200mg is a large percentage of that.
That’s a good point, although it still leaves a few hypotheses on the table:
The improvement was due to the magnesium, not the glycine.
I had a severe glycine shortage.
I misinterpreted the label. (i.e. 200 mg is actually the mass of the magnesium itself, so the amount of glycine is unknown.)
If 3 is right, then it’s 1.2 grams of glycine (magnesium glycinate is 14% magnesium by mass)
Generally, as I understand it, the convention is for that sort of text to mean it’s 200 mg of magnesium, not 200 mg of the compound.
1.4g is more than a tenth of the typical shortfall and there’s a lot of heterogeneity, but also total magnesium need is often estimated at half a gram, so 200mg is a large percentage of that.