Most South African shelves carry three magnesium forms — glycinate, citrate, and oxide. They are not interchangeable. One absorbs well and calms the nervous system. One absorbs moderately and shifts the bowel. One is cheap, common, and largely a waste. Here is the difference, in 1,400 words.
The TL;DR table
| Form | Approx. absorption | Best use case | GI effect |
|---|---|---|---|
| Glycinate (bisglycinate) | ~38–45% | Sleep, anxiety, recovery, daily stack | Gentle, no laxation |
| Citrate | ~25–30% | Constipation, light supplementation | Loosens stools, especially >300 mg |
| Oxide | ~4% | Cheap shelf-filler — short-term laxative only | Strong laxation, cramps |
If you're scanning, that's your answer. Glycinate is the daily form. Citrate works if you tend to constipation. Oxide is mostly there to inflate the milligram number on the bottle for a low price.
Why "magnesium 400 mg" tells you almost nothing
The 400 mg on a label is the weight of the magnesium compound, not the elemental magnesium your body uses. Magnesium glycinate is ~14% elemental by weight. Citrate is ~16%. Oxide is ~60% — but with such poor absorption that the bioavailable magnesium ends up lowest of the three.
This is the single most-abused number in SA supplement marketing. A R110 oxide tablet labelled "400 mg" delivers roughly the same usable magnesium as a R350 glycinate at 300 mg label dose — and the glycinate doesn't send you to the bathroom.
Magnesium glycinate — the daily form
Glycinate (also written as bisglycinate) is magnesium bound to two glycine molecules. Glycine is itself a calming amino acid; it crosses the gut wall easily and pulls the magnesium with it. The result is high absorption with no laxative effect.
Use it for:
- Sleep — most people feel it within 7–14 days at 300–400 mg elemental in the evening.
- Anxiety — modest but real cortisol-buffering effect (Boyle et al., Nutrients 2017).
- Recovery — muscle relaxation, especially after a hard training block.
- Daily multi top-up — most multis contain almost no magnesium.
The catch: the glycinate molecule is heavy, so 60-capsule bottles usually only deliver a 30-day supply at clinical doses. Buy in two- or three-month packs if you can — and check the label is fully reacted bisglycinate, not "magnesium glycinate buffered with oxide" (which is half oxide).
Magnesium citrate — the cycle-and-clear form
Citrate is bound to citric acid. It absorbs reasonably well — better than oxide, worse than glycinate. Its calling card is the gentle osmotic laxation effect: it pulls water into the colon, which makes it a first-line short-term constipation aid.
Use it for:
- Occasional constipation — 300–500 mg in the evening, with water.
- Light daily magnesium top-up if glycinate is out of budget — be aware of the stool-loosening.
- Pre-colonoscopy prep (under clinician direction only).
Skip it for daily sleep support — the laxation outlasts the calming benefit.
Magnesium oxide — the cheap shelf-filler
Oxide is dirt-cheap to manufacture. It looks impressive on a label (high mg number because the compound is mostly magnesium by weight) but the absorption is around 4%. Most of the dose passes through. What does get absorbed often arrives with cramping or loose stools.
Where you'll see it:
- R100–R150 supermarket-aisle magnesium tablets.
- "Magnesium 400 mg" claims on multivitamins where the real bioavailable dose is closer to 16 mg.
- Hospital constipation protocols (where the laxative effect is the goal).
It's not dangerous. It's just inefficient. If you're buying magnesium to sleep better, oxide is not the answer.
What about threonate, malate, and taurate?
Threonate (L-threonate) crosses the blood-brain barrier and has emerging cognitive evidence — useful for focus and age-related cognitive slowing. It's expensive and overkill for a sleep stack. Malate is gentle and energy-supportive — popular with fibromyalgia and chronic fatigue protocols. Taurate is well-tolerated and cardiovascular-leaning. All three are valid; none of them replace glycinate as the daily floor.
South African buying notes
SA shelves are heavy on oxide and citrate. Glycinate is harder to find and usually carries a price premium. Look for:
- Form on the label — "Magnesium (as glycinate)" or "Magnesium bisglycinate". If it just says "Magnesium 400 mg", assume oxide until proven otherwise.
- Elemental milligrams disclosed — a serious brand will give you both the compound weight and the elemental weight.
- No proprietary blend — anything that hides the form behind a blend name is hiding because the blend is mostly oxide.
- Third-party lab tested — heavy-metal and identity testing, batch-traceable.
The Vivid pick
Vivid's Magnesium glycinate is a fully reacted Albion/Balchem bisglycinate at 300 mg elemental per two-capsule serving, third-party batch tested. We list both the compound mg and the elemental mg on the label, and the only other ingredient in the capsule is the HPMC vegetable shell.
If you've been buying R110 oxide for a while and not feeling much from it, the swap is the single highest-leverage change you can make to a supplement routine.