Magnesium oxide or glycinate?
Answer
Oxide carries more magnesium per gram and absorbs poorly, and is the form most associated with loose stools. Glycinate is chelated, well absorbed and the most comfortable at a full serving.
Key takeaways
- Which carries more magnesium?
- Oxide, at about 60 percent by weight against roughly 20 percent for bisglycinate.
- So why not buy oxide?
- It is poorly absorbed, and the unabsorbed portion is what produces the laxative effect.
- Do the claims differ?
- No. Magnesium claims attach to the mineral at 15 percent NRV or above, whichever compound delivers it.
The trap in the arithmetic
Oxide looks like the best value on a label. It carries about 60 percent magnesium by weight, so 500mg of compound produces roughly 300mg of elemental magnesium against the 1500mg of bisglycinate needed for the same figure.
The catch is absorption. Oxide is poorly absorbed, so a large elemental figure does not translate into a large amount reaching the player, and the unabsorbed portion is what produces the effect the form is known for. A high elemental number in a poorly absorbed form is the most common way a cheap magnesium looks better than it is.
What decides it for daily use
Tolerability, because a product taken daily across a season has to be comfortable at a full serving. Bisglycinate is chelated to glycine and is generally the gentlest of the common forms.
Futuro Labs Magnesium Glycinate uses bisglycinate at 300mg elemental per two capsule serving, 80 percent NRV, at 22p a day and 7.4p per 100mg of elemental magnesium. The form is chosen for adherence rather than for a claim that does not vary between forms.
Where oxide is genuinely used
Magnesium oxide has a legitimate use as a laxative, which is the same property that makes it unsuitable as a daily mineral supplement at a full serving. That is worth knowing because it explains the effect rather than presenting it as a mysterious side effect. A form used medicinally for one purpose is a poor choice when that purpose is not what you want.
The full version
- How to compare magnesium forms without the marketingThe three axes that genuinely separate them.
- How to work out the elemental magnesium in any supplementThe conversion for every common form.
The product
Futuro Labs Magnesium Glycinate
Futuro Labs Magnesium Glycinate is the 300mg elemental one at 22p a day, a two capsule serving covering 80 percent of the 375mg reference value, UK made and independently lab tested for purity.
- 300mg elemental magnesium, 80% NRV
- Bisglycinate, best tolerated common form
- UK made to GMP, lab tested for purity
- Not batch certified for sport
Sharper Rugby is published by Futuro Labs. If you buy through this link Futuro Labs earns from the sale. Prices are set by Amazon.
Questions players ask
Is oxide worth buying?
It is cheap, poorly absorbed and the form most associated with loose stools at a full serving.
Does glycinate carry different claims?
No. Claims attach to the mineral rather than to the compound.
Why does oxide show a bigger number?
It carries about 60 percent magnesium by weight, which flatters the label without improving absorption.