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Information on the latest vitamin D news and research.

Find out more information on deficiency, supplementation, sun exposure, and how vitamin D relates to your health.

Magnesium: A common deficiency that we can’t measure

Dr. Zittermann’s new editorial on magnesium (Mg) and vitamin D is important. We have been saying for the last 7 years that you need to be getting enough Mg.

Zittermann A. Magnesium deficit: overlooked cause of low vitamin D status? BMC Medicine, 2013.

In his editorial, Dr. Zittermann highlights our great need to start looking at Mg deficiency as a serious and common health problem.

However, there are some barriers in making sure people are getting enough Mg, and there are some barriers in being able to measure what their Mg status is, adequate or deficient.

To date, we have no great way to measure Mg adequacy. Unfortunately, serum Mg represents only 1% of Mg stores. Mg is homeostatically controlled in the serum and measuring serum Mg levels miss many Mg deficient people. It is clear that by the time your serum Mg is low, you are very Mg deficient as the body can no longer maintain serum Mg levels.

Douban S, Brodsky MA, Whang DD, Whang R. Significance of magnesium in congestive heart failure. Am Heart J. 1996 Sep;132(3):664-71. Review

Quamme GA. Magnesium homeostasis and renal magnesium handling. Miner Electrolyte Metab. 1993;19(4-5):218-25. Review.

Beyenbach KW. Unresolved questions of renal magnesium homeostasis. Magnesium. 1986;5(5-6):234-47. Review.

In Mg deficient patients, bone Mg is mobilized to maintain serum Mg.

Elin RJ. Assessment of magnesium status for diagnosis and therapy. Magnes Res. 2010 Dec;23(4):S194-8. doi: 10.1684/mrh.2010.0213. Epub 2010 Aug 24.

So that begs the question, how does one know if you are Mg deficient?

Perhaps the ratio of ionized Mg/total Mg in serum or plasma may be a better measurement of Mg depletion.

Durlach J, Pagès N, Bac P, Bara M, Guiet-Bara A. Importance of the ratio between ionized and total Mg in serum or plasma: new data on the regulation of Mg status and practical importance of total Mg concentration in the investigation of Mg imbalance. Magnes Res. 2002 Dec;15(3-4):203-5. Review.

But still, this is probably not reliable enough. As of today, a Mg intake assessment is the only way to know if one is Mg deficient. That means counting all foods in your diet and then looking those foods up on Mg content of foods table.


And when we assess Mg intakes, repeated studies show the average American has inadequate intakes of Mg. Mg consumption is particularly low among adolescent females, adult females, and elderly men, with one study showing that 85%, 80%, and 75%, respectively, of the population groups having mean Mg intakes below their respective RDA.

Morgan KJ, Stampley GL, Zabik ME, Fischer DR. Magnesium and calcium dietary intakes of the U.S. population. J Am Coll Nutr. 1985;4(2):195-206.

In one NHANES study, none of the African Americans studied met the RDA for Mg.

Fulgoni V 3rd, Nicholls J, Reed A, Buckley R, Kafer K, Huth P, DiRienzo D, Miller GD.  Dairy consumption and related nutrient intake in African-American adults and children in the United States: continuing survey of food intakes by individuals 1994-1996, 1998, and the National Health And Nutrition Examination Survey 1999-2000. J Am Diet Assoc. 2007 Feb;107(2):256-64.

In another study, the actual intakes of Mg were 202 mg/day for children from 1 to 5 years old, 228 mg/day for women and 331 mg/day for men, well below the RDA for all three groups.

Lichton IJ.  Dietary intake levels and requirements of Mg and Ca for different segments of the U.S. population. Magnesium. 1989;8(3-4):117-23. Review.

For older Americans, a study showed that both men and women had median diet intakes below the RDA for Mg. That is, less than half had adequate intakes.

Hallfrisch J, Muller DC.  Does diet provide adequate amounts of calcium, iron, magnesium, and zinc in a well-educated adult population? Exp Gerontol. 1993 Jul-Oct;28(4-5):473-83.

But I stress, despite inadequate intakes, few of these people have low blood Mg levels; again, because it’s homeostatically controlled.

So we are left with the fact that more than half of Americans are Mg deficient, and we have no good way to assess Mg status.  My recommendation is to take supplemental Mg 200-300 mg/day unless you are sure your Mg intake is adequate. Once you assess your Mg intake, you may decide you need even more. Up to 500 mg/day is certainly safe, unless one has renal failure. Too much Mg has a laxative effect, as in milk of Mg.

I’m glad Dr. Zittermann is clearly calling for more research in this area.

  About: John Cannell, MD

Dr. John Cannell is founder of the Vitamin D Council. He has written many peer-reviewed papers on vitamin D and speaks frequently across the United States on the subject. Dr. Cannell holds an M.D. and has served the medical field as a general practitioner, emergency physician, and psychiatrist.

13 Responses to Magnesium: A common deficiency that we can’t measure

  1. Rita and Misty says:

    This is a very challenging task:

    “As of today, a Mg intake assessment is the only way to know if one is Mg deficient. That means counting all foods in your diet and then looking those foods up on Mg content of foods table.”

    And, the reason I think this task is very challenging, is that I often wonder how much of our soil has been depleted of its mineral content….and I wonder, therefore, if we are only making, at best, a giant supposition regarding actual mineral content in our foods…


  2. jimkeller@aol.com says:

    Further confounding assessing mg sufficiency by dietary analysis is the mg wasting effect of excess dietary calcium.

  3. WolverBill says:

    I’ve read the Mg is very important for heart function.

  4. rtfdc1 says:

    If the 70 year old Senate Document 264 is any indication, our soils have been depleted for decades.

  5. GoldieD says:

    I wonder what effect higher amounts of magnesium in one’s diet would have on heart muscle of those with Atrial fibrullation–anyone study this? Sure wish my husband’s otherwise healthy heart and body is still fibrullating. We’d love to see his heart work properly again –there must be a natural way.

  6. Michael says:

    Pizza, cheeseburger, spaghetti — it is all the same stuff, namely


    Is it any wonder 99% of the fast food world is everything deficient.


  7. dew@richardshunter.com says:

    Yes, and even the foods that supposedly have Mg, are often based upon 50 year-old tables and testing. The same foods today don’t have the same Mg content, because: 1) The soil is depleted from continuous cropping; and 2) the application of pesticides, especially Roundup (Glyphosate), greatly impairs the plant’s ability to uptake minerals from the soil, especially Magnesium! So even if the soil does have Mg, you’re still not getting it in your food!

  8. Rita and Misty says:

    Thank you dew ! I had wondered about this.

    A friend of mine had informed me that an organically-grown apple as about 20 mg of Boron, but an apple exposed to pesticide has only 6 mg of Boron.

    Sometimes I wonder about what I hear, as I can be very naive…so, I try to remember to take all that hear with a grain or two of salt 😉

    Magnesium is a wonderful mineral…but so is Boron…and so is Iodine.

    Uncertain if we are all deficient in Boron.

    But, I do know we are all deficient in Iodine.

    BTW–if you do supplement with Iodine, be sure to also supplement with Selenium.

    It is all about balance….imo…. :)

  9. larryr1024 says:

    What about the Red Blood Cell (RBC) magnesium blood tests?

    ARUP Laboratories says:
    “RBC magnesium results reflect the intracellular stores and general homeostasis of magnesium.”

    There are also RBC zinc tests from various labs too.

  10. Ian says:

    Can you supply any references for this?:

    “2) the application of pesticides, especially Roundup (Glyphosate), greatly impairs the plant’s ability to uptake minerals from the soil, especially Magnesium.”

    I am very interested to follow this up. Thanks

  11. JBG says:

    “Too much Mg has a laxative effect, as in milk of Mg.”

    This fact provides a means for titrating Mg intake: Take too much, stools get soft; back off and they get firmer again (assuming you’re healthy otherwise).

    My eating patterns includes a lot of Ca, so I probably need more Mg than most folks. Anyway, I currently take 675 mg every other day, and 450 mg on the alternate days. This works pretty well. Mg Citrate is my preferred form of supplement.

  12. Rita and Misty says:

    Does anyone have thoughts on transdermal Mg?

  13. John says:

    That’s the key Rita! Your skin will only absorb the Mg that it needs.