Do you sweat out magnesium?
Answer
Some magnesium is lost in sweat, in small amounts next to sodium. It widens the gap between intake and requirement across a season without changing the 375mg daily target.
Key takeaways
- Is it lost in sweat?
- Yes, in small concentrations. Sweat is mostly water and sodium.
- Does heavy training deplete it?
- It raises losses, which makes reaching the reference intake harder rather than raising the intake itself.
- Can it be measured?
- Sweat volume can be, with scales. Magnesium concentration cannot be outside a laboratory.
The scale of the losses
After water, sweat is mostly sodium and chloride, with potassium next and magnesium and calcium in far smaller concentrations.
So a forward losing three litres in a warm pre season session is losing a substantial amount of sodium and a comparatively small amount of magnesium. That ordering is why sports drinks are built around sodium and why the magnesium in them is usually below the threshold at which any claim could be made.
What it means for a daily serving
The losses accumulate across a season and they do not create a separate athlete reference value. None exists.
Futuro Labs Magnesium Glycinate covers 80 percent of the 375mg reference value in one two capsule serving at 22p a day, and that is the same serving in July as in January. Scaling it to session conditions is unsupported and heads towards the 400mg supplemental guidance level.
The salty sweater question
Sodium concentration in sweat varies between players in a way magnesium does not visibly. White marks on kit after a session, sweat that stings the eyes badly, and food tasting bland afterwards all point at the higher end of the normal range. For those players, sodium with food after sessions is worth more than anything else in this category.
The full version
- Magnesium and sweat loss in rugbyHow to measure your own sweat rate, and the salty sweater test.
- Heavy sweat loss: does magnesium help?What a heavy sweater should actually prioritise.
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
Do you lose magnesium in sweat?
Yes, in small amounts relative to sodium.
Does that mean taking more?
No. Losses widen the gap without changing the 375mg daily target.
What should heavy sweaters prioritise?
Fluid and sodium around sessions, which is a hydration decision.
Does a sports drink replace it?
The magnesium in most is below the 15 percent NRV threshold at which any claim could be made.