What Is Magnesium?

Magnesium is absolutely essential for the normal functioning of your body. It is actually used in over 300 biochemical reactions, and is the fourth most abundant mineral in the body.

So, what exactly does magnesium do?

Well, it helps to maintain normal muscle and nerve function, it keeps your heart rhythm steady, it is involved in maintaining a healthy immune system, and it is important for keeping your bones strong. It also helps to regulate blood sugar levels and blood pressure, and is involved in energy metabolism and protein synthesis.

Phew… that’s one important little “macromineral.”


Symptoms of Magnesium Deficiency

Some of the symptoms of magnesium deficiency include:

  • Loss of appetite
  • Nausea
  • Muscle weakness, tremor, or spasm
  • Sleepiness, fatigue
  • Apathy
  • Confusion
  • Vomiting
  • Headaches
  • Insomnia
  • Irritability
  • Poor memory
  • Rapid heartbeat
  • Numbness, tingling
  • Muscle contractions, cramps
  • Softening or weakening of the bone

Note: There is an extremely complex relationship between calcium and magnesium, which we still don’t fully understand. But suffice to say, a healthy diet must contain foods rich in both of these minerals.

Is Magnesium Toxic At High Levels?

As with most things, you can get too much of a good thing.

High levels of magnesium can lead to diarrhea, but this symptom is most commonly linked to magnesium, which is taken as a dietary supplement (1-5 grams, or 1,000-5,000 milligrams).

There is no upper limit set on the intake of magnesium from food, so you don’t need to worry about taking in too much from food sources.

However, if you are taking a dietary supplement containing magnesium, check that it doesn’t contain magnesium above the upper limit, set at 350 milligrams per day.

Dietary Reference Intakes For Magnesium

The Institute of Medicine, at the National Academy of Sciences, have set the Recommended Dietary Allowances for magnesium, these are:

Magnesium RDA for Men

  • 0 to 6 months: 30 milligrams (Adequate Intake)
  • 7 to 12 months: 75 milligrams (Adequate Intake)
  • 1-3 years: 80 milligrams
  • 4-8 years: 130 milligrams
  • 9-13 years: 240 milligrams
  • 14-18 years: 410 milligrams
  • 19-30 years: 400 milligrams
  • 31 years and older: 420 milligrams

Magnesium RDA for Women

  • 0 to 6 months: 30 milligrams (Adequate Intake)
    7 to 12 months: 75 milligrams (Adequate Intake)
  • 1-3 years: 80 milligrams
  • 4-8 years: 130 milligrams
  • 9-13 years: 240 milligrams
  • 14-18 years: 360 milligrams
  • 19-30 years: 310 milligrams
  • 31 years and older: 320 milligrams
  • Pregnant women, 18 years or younger: 400 milligrams
  • Pregnant women, 19-30 years: 350 milligrams
  • Pregnant women, 31-50 years: 360 milligrams
  • Breastfeeding women, 18 years or younger: 360 milligrams
  • Breastfeeding women, 19-30 years: 310 milligrams
  • Breastfeeding women, 31-50 years: 320 milligrams

So, Which Foods Provide Magnesium?

Some of the best sources of dietary magnesium come from foods, like swiss chard, spinach, kelp, summer squash, pumpkin seeds, blackstrap molasses, broccoli, and halibut.

Magnesium can also be found in these foods:

  • Peas, beans and lentils
  • Nuts and seeds
  • Whole, unrefined grains, like brown rice, oats, or wheat bran
  • Fish and meats
  • Dairy foods, like plain yogurt and milk
  • Green, leafy vegetables
  • Fruits like bananas, avocado, and raisins
  • Tap water can be a source of magnesium, but the amount varies according to your water supply (“hard” water contains more magnesium than “soft” water)

You don’t need to get too stressed about whether you are getting the exact RDA of vitamins and minerals each day.

Instead, focus on eating a diet that is rich in color, variety and flavor, and you will normally be giving your body everything it needs to function at it’s very best.

What About Magnesium Supplements?

If you are an alcoholic, or you have a chronic malabsorption condition, such as Crohn’s disease, you may need to take magnesium supplements.

On the whole, however, most adults should try to meet their recommended dietary intake for magnesium through diet alone.

If you are in any doubt whatsoever, speak with your doctors first, as they will be able to evaluate your magnesium status, and give advice personalized to your requirements.

This is the second in a series of short nutrition 101 articles (get the first article on what is iron here) — please let me know if there’s something you would particularly like me to discuss in this series :-)

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About Melanie
Melanie is a Registered Dietitian who started Dietriffic in March 2007. Her aim is to make good health attainable and sustainable, without guilt and torture, making her approach popular with those who desire a level-headed approach to good health. Have you got your copy of her free book yet?

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{ 11 comments… read them below or add one }

Taleen April 6, 2011 at 12:13 am

Wonderful Melanie!! Thank you! You are on the ball….that is one thorough plate of information – perfect!

Magnesium is quite the important little boyo then.

(Notice my pun there….’plate’…..haha!)


Melanie April 8, 2011 at 5:59 pm

:-D You’re welcome!!!


Steve Parker, M.D. April 6, 2011 at 11:22 am

Hi, Melanie.
Just a friendly note that you might want to revise your mention of magnesium being the 4th most abundant mineral in the body. In researching for one of my books, I found it to be our 7th most common mineral.

Thanks for the magnesium review.



Melanie April 6, 2011 at 11:41 am

Hi Steve,
Thanks for your comment. Do you have a source that it is the 7th most common mineral in the body?

My source of info was the Office of Dietary Supplements: http://ods.od.nih.gov/factsheets/magnesium/


Steve Parker, M.D. April 6, 2011 at 12:44 pm

Textbook called “Understanding Nutrition,” 6th ed. (1993) by Whitney and Rolfes, page 368, Figure 11-1, listing “The Amount of Minerals in a 60-kg Human Body” in descending order: calcium, phosphorus, potassium, sulfur, sodium, chloride, magnesium.

That’s a common introductory college nutrition text in the U.S., although more current editions are used. I have the 6th edition in my personal library – got it “used” in a college bookstore in 1997.

Or see “Composition of the human body” at Wikipedia.org. I’ll try to post the link here:

Discrepancies may reflect differences in definition of “mineral.”

I noticed that the rank of minerals in these two lists are discordant.



Melanie April 6, 2011 at 11:41 pm

This is a query. There seem to be lots of different views on, with people stating the 4th, the 7th, the 11th most abundant in the body. I will search my own college text books tomorrow to see what their conclusion is. Thanks for bringing this up anyway :-)


Melanie April 13, 2011 at 9:13 am

Hi Steve,
I cannot find any confirmation regarding your comment. In one of my textbooks from uni it states that magnesium is the 7th most abundant element in the earths crust, but it doesn’t discuss the body. I wonder where the Office of Dietary Supplements source their data?


TheGourmetCoffeeGuy April 7, 2011 at 3:53 am

Enjoyed reading your magnesium review, especially the practical advice about foods considered to be the best sources of magnesium. Not surprisingly, they include dark green vegetables, legumes, nuts and grains. Have always found it very interesting that cooked halibut and cooked tuna contain more magnesium than other sources of the mineral and than meats. Thank you for your detailed overview.


Melanie April 8, 2011 at 8:17 pm

Thanks GCG :-)


good morning mel.... January 16, 2013 at 11:28 pm

just want to know more on your dieting system…..thanks,


Melanie February 7, 2013 at 11:02 pm

Are you talking about The Big Fat Cure?


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