Posted by Larry Hoover on March 7, 2003, at 23:13:19
In reply to Magnesium Questions., posted by Questionmark on March 7, 2003, at 21:48:43
> Alright, i'm sick of all the contradictory freaking information out there! i've read different sources that say that when taking a mineral supplement one should get a good formulation or whatever (e.g., Calcium citrate or whatever instead of just Ca carbonate, or Mg glycinate instead of Mg oxide). They say that some forms of a mineral compound (or wtvr.) are absorbed much, much better then other forms. Then i read other things that say that it doesn't matter what ion (or whatever) a mineral is bound to (like Mg oxide would be just as good as Mg glycinate, in regard to absorbtion). They say that in the digestive system the mineral compound is seperated anyway (like Mg oxide into Mg2+ ion or something). So does anyone know who the heck is right??? Does anyone KNOW?!
The first abstract shows that magnesium citrate was absorbed in the ballpark of 40 times better than mag oxide (based on urinary excretion), while the second study shows that mag oxide is absorbed at about 4%. It really matters which magnesium salt you use. Solubility is the issue. MgO does not dissolve well, even in pure stomach acid. The only thing mag oxide has going for it is price.
J Am Coll Nutr 1990 Feb;9(1):48-55Magnesium bioavailability from magnesium citrate and magnesium oxide.
Lindberg JS, Zobitz MM, Poindexter JR, Pak CY.
Center for Mineral Metabolism and Clinical Research, University of Texas, Southwestern Medical Center, Dallas 75235.
This study compared magnesium oxide and magnesium citrate with respect to in vitro solubility and in vivo gastrointestinal absorbability. The solubility of 25 mmol magnesium citrate and magnesium oxide was examined in vitro in solutions containing varying amounts of hydrochloric acid (0-24.2 mEq) in 300 ml distilled water intended to mimic achlorhydric to peak acid secretory states. Magnesium oxide was virtually insoluble in water and only 43% soluble in simulated peak acid secretion (24.2 mEq hydrochloric acid/300 ml). Magnesium citrate had high solubility even in water (55%) and was substantially more soluble than magnesium oxide in all states of acid secretion. Reprecipitation of magnesium citrate and magnesium oxide did not occur when the filtrates from the solubility studies were titrated to pH 6 and 7 to stimulate pancreatic bicarbonate secretion. Approximately 65% of magnesium citrate was complexed as soluble magnesium citrate, whereas magnesium complexation was not present in the magnesium oxide system. Magnesium absorption from the two magnesium salts was measured in vivo in normal volunteers by assessing the rise in urinary magnesium following oral magnesium load. The increment in urinary magnesium following magnesium citrate load (25 mmol) was significantly higher than that obtained from magnesium oxide load (during 4 hours post-load, 0.22 vs 0.006 mg/mg creatinine, p less than 0.05; during second 2 hours post-load, 0.035 vs 0.008 mg/mg creatinine, p less than 0.05). Thus, magnesium citrate was more soluble and bioavailable than magnesium oxide.
Magnes Res 2001 Dec;14(4):257-62Bioavailability of US commercial magnesium preparations.
Firoz M, Graber M.
Department of Veterans Affairs Medical Center, Northport, NY 11768, USA.
Magnesium deficiency is seen with some frequency in the outpatient setting and requires oral repletion or maintenance therapy. The purpose of this study was to measure the bioavailability of four commercially-available preparations of magnesium, and to test the claim that organic salts are more easily absorbed. Bioavailability was measured as the increment of urinary maginesium excretion in normal volunteers given approximately 21 mEq/day of the test preparations. Results indicated relatively poor bioavailability of magnesium oxide (fractional absorption 4 per cent) but significantly higher and equivalent bioavailability of magnesium chloride, magnesium lactate and magnesium aspartate. We conclude that there is relatively poor bioavailability of magnesium oxide, but greater and equivalent bioavailability of magnesium chloride, lactate, and aspartate. Inorganic magnesium salts, depending on the preparation, may have bioavailability equivalent to organic magnesium salts.
>Is it better to get a certain formulation of a mineral (Mg, in particular) or does it not matter? Are some formulations absorbed better than others?
Magnesium and calcium are both best absorbed if they're complexed with an amino acid. They're called chelates in that form. Look for second terms such as glycinate or aspartate. Also good are salts with citrate or chloride. Oxides of either one are *not* very bioavailable.
>(Also, i'm just talking about with a supplement. i know that nutrients from a food source are probably much better absorbed than from just a supplement).
Not necessarily. It depends on a lot of factors.
>Finally, in relation to Mg and Ca, does an anxious depressed person want to just get more magnesium, or more calcium And magnesium?
If I was a betting man, I'd say you were unlikely to get enough of either one, but that deficiency in magnesium is far more important to correct.
>Is this whole 2:1 Ca-Mg ratio a good standard, or is this just a crock of balogna?
It's based on assumptions that do not apply to someone who is deficient to begin with (in other words, most everyone).
> If anyone could answer some of this, and state reasons for your answers (i.e., answer "why?"), it would be most appreciated. Mucho thanks in advance.
Some of the confusion about calcium and magnesium supplementation arises because of misunderstanding about how the two minerals interact in the blood, and how they're regulated by hormones. High blood calcium levels block magnesium uptake, but high blood calcium can be caused by magnesium deficiency. What you'll often see posted on the net is that taking calcium and magnesium together blocks magnesium uptake, but that's wrong. It's blood calcium that blocks magnesium uptake, not ingested calcium. High blood calcium shuts down the output of parathyroid hormone, which in turn shuts down the active transport pumping of magnesium ions from the gut (utilizing vitamin D3 in the process).
Best thing is to get a magnesium supplement with good bioavailability, and make sure you're getting enough vitamin D3. Take calcium too, if you feel like it, but I truly believe more people are magnesium deficient than are calcium deficient.
poster:Larry Hoover
thread:206985
URL: http://www.dr-bob.org/babble/20030306/msgs/207021.html