IDK. Magnesium sulphate is the one thats in the ocean, if that helps at all! It seems river water has a variety of types: sulphates and carbonates, chlorides?
It seems magnesium is highly water soluble, and an ideal way to take it would be in water. Alot of the european mineral waters have a decent amount. Evian has something like 24mg/L of magnesium. S.pelligrino has 52.5 mg /l!
If I was rich, id just drink some select european mineral waters and that would be the end of the story :P
If you do happen to be rich, heres a magnesium versus water brand list:
And trust me if its in water, or pure supplement, it will absorb alot moreso than in foods (especially if you eat high fat with them). I was eating load and loads of spinach, nuts, berries etc....to no avail in my case, with my high fat diet, and screwed digestion. Maybe in normal healthy folks this is a non issue with high fat diets, IDK.
(I had low magnesium recently. Tried the supplements, which worked great, immediate relaxation, but they made me have "stomach issues", if u catch the drift. Not fun side effect )
But if your not rich, and you want something more natural, or at least less pills, you either eat, like a serious bucketload of magnesium foods each day, or take the odd epsom salts bath/footbath (or spend lots of time in the ocean, if your coastal and its sunny).
Ive been doing the epsom salt baths now. So long as you dont overdo it, theres definately less stomach issues than supplements. It still seems pretty well absorbed, like quite strong versus food. I think you need to make sure u dont use too much too often, bathwise, and dont soak for longer than say 20 mins. I am still new to this epsom salts bath thing. Relaxing!
After being wound up and anxious from high fat, low carb, magnesium was a godsend. So glad I found it!
I suspect that this and perhaps other electrolyte minerals like potassium and sodium is where a lot of low carbers go wrong. Magnesium is only really partially absorbed from food in the small intestine (less with fat in foods IMO, more with water).
Its very very hard to get your minimum intake from foods regardless of dietary preferances/lifestyle (420mgs for men my age! Id have to be siphoning blended spinach into my mouth all day long!).
And doesnt even seem to be the ideal form to get it in (It seems to work much better in drinking water, or in water to absorb through ur skin, at least for me, but then I have somewhat compromised digestion)
Its just crappy they take it out of tap water :/ Water would normally be plenty of mg in nature...When I find a cheap water with decent magnesium in it, I am on it. In the mean time, the baths are awesome, so no worries i suppose!