Magnesium is an essential dietary mineral, one that around 56% of the US population is deficient in (!)
Part of this has to do with diet, but another part has to do with farmers not replacing trace minerals in their soil, leading to magnesium depleted foods.
Magnesium is a co-factor to more than 300 enzymes in the human body, making it crucial for optimal health.
Bioavailability
When supplementing magnesium there are a variety of types to choose from. One way to aid the decision is to understand the bioavailability, which tells us how much gets absorbed by the human body.
| Form | Bioavailability | Notes |
| Oxide | ~4–5% | Very low absorption confirmed in multiple studies |
| Chloride | ~20–30% | High for an inorganic form; easily absorbed orally |
| Citrate | ~25–30% | High; reliable and common, but can cause loose stools at higher doses |
| Glycinate | ~23–25% | High absorption; very gentle on the stomach |
| L-Threonate | ~20–30% | Good overall absorption; uniquely elevates brain Mg more than others |
Based on the above table, for simplicity, we’re going to look specifically at buying options for Magnesium Glycinate and L-Threonate.
Glycinate is a high bioavailability form of magnesium that’s gentle on the stomach. L-Threonate is expensive, but has the highest bioavailability for the brain. Leading to some favouring it for use at night before sleep.
Buying Options
Magnesium Glycinate
Note: if you see the word bisglycinate, be aware it’s the same thing as glycinate. Both are two glycine molecules bound to a magnesium molecule. Bis (meaning two), in bisgylcinate, is the full name, but it’s often shortened to just glycinate.
Reputable brands include:
| Product | Capsules | Price | Cost per 100 mg* |
| NOW - Magnesium Glycinate | 180 x 100 mg | $19 exc. coupon | $0.10 |
| Life Extension - Mag. Glycinate | 90 x 105 mg | $18 exc. coupon | $0.19 |
| California Gold Nutrition - Mag. Glycinate | 180 x 133 mg | $25 exc. coupon | $0.10 |
Magnesium L-Threonate
Reputable brands include:
| Product | Servings | Cost per 100 mg |
| Momentous - L-Threonate | 30 x 144mg | $1.15 |
| Life Extension - L-Threonate | 30 x 144mg | $0.72 |
| NOW - L-Threonate | 30 x 144mg | $0.85 |