What is the downside of magnesium oxide?
Answer
It is poorly absorbed, and the unabsorbed portion is what produces the laxative effect the form is known for. A high elemental figure in a poorly absorbed form is not a bargain.
Key takeaways
- Why is it common?
- It is cheap and carries about 60 percent magnesium by weight, so a small amount of compound gives a large elemental figure.
- What is the downside?
- Poor absorption, and a laxative effect at a full serving that is worse than any other common form.
- Is it ever appropriate?
- It is used medically as a laxative, which tells you most of what you need to know about taking it daily.
Why it looks good on a label
Magnesium oxide carries more magnesium per gram than any common form, because oxygen is a small partner. On the arithmetic alone a modest amount of compound produces a large elemental figure, which is exactly what a budget product wants to print.
That is the single most common way a cheap magnesium product appears better than it is, and it is why the elemental figure has to be read alongside the form rather than on its own.
The trade off
Oxide is poorly absorbed. The portion that is not absorbed stays in the gut and draws water into it, which is the mechanism behind the laxative effect and is also why magnesium oxide is used medically for exactly that purpose.
UK guidance sets 400mg a day for supplemental magnesium because of that effect. Futuro Labs Magnesium Glycinate uses bisglycinate, which is chelated and generally the most comfortable of the common forms at a full serving, providing 300mg elemental at 22p a day.
Where it hides
Buffered magnesium bisglycinate is bisglycinate blended with oxide to raise the elemental content per gram cheaply. The front of pack may say bisglycinate while oxide appears in the ingredients.
The tell is an elemental figure well above 20 percent of the stated compound weight, since bisglycinate alone is about a fifth magnesium. Anything materially higher implies something else in the mix.
The full version
- How to compare magnesium forms without the marketingThe three axes that separate the forms.
- How to work out the elemental magnesium in any supplementThe conversion, including the buffered edge case.
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
Why is magnesium oxide cheap?
The raw material is cheap and it carries a high percentage of magnesium by weight.
What is the downside?
Poor absorption, and the unabsorbed portion produces a laxative effect.
How do I spot it in a blend?
An elemental figure well above 20 percent of the compound weight implies something other than bisglycinate.