Magnesium: The Magical Mineral

We have know for years that many people with diabetes have too little magnesium in their bodies. So why don’t all of us take supplements of this magical mineral?

Everyone seem to recommend magnesium, mostly to reduce the insulin resistance and hence help counteract diabetes. But how much magnesium we have in our bodies is almost impossible to test, because most of it resides in our bones and very little in our blood, according to Dr. Barkat Charania in Dubai, United Arab Emirates. He practiced orthopedic surgery for more than 30 years, now blogs at Dr. Barkat Charania, and helped me research this article.

Since our blood levels of magnesium don’t tell us if we have enough, researchers have reported few human studies, he told me. Still, he brought to my attention 41 studies of magnesium, most of them in relation to diabetes.

Citing just three of these studies is enough to make my point:

1. “Magnesium deficiency is not uncommon among the general population: its intake has decreased over the years especially in the western world [emphasis added]. The magnesium supplementation or intravenous infusion may be beneficial in various diseased states. Of special interest is the magnesium status in … diabetes.” This comes from “Magnesium: An update on physiological, clinical and analytical aspects” in Clinica Chimica Acta.

2. Mean serum magnesium levels were significantly lower in participants with prevalent cardiovascular disease, hypertension, and diabetes than in those free of these diseases. This comes from “Associations of serum and dietary magnesium with cardiovascular disease, hypertension, diabetes, insulin, and carotid arterial wall thickness: The aric study” in the Journal of Clinical Epidemiology.

3. “A reduced intracellular magnesium content might contribute to the impaired insulin response and action which occurs in Type 2 (non-insulin-dependent) diabetes mellitus.” This comes from “Hypomagnesaemia in Type 2 (non-insulin-dependent) diabetes mellitus is not corrected by improvement of long-term metabolic control” in Diabetologia.

Even so, the Institute of Medicine has standard age- and gender-related recommended levels of magnesium. In its Dietary Reference Intatkes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride the IOM sets the Recommended Dietary Allowances of magnesium for males 19 to 30 at 400 mg/d, males 31 and up at 420, females 19 to 30 at 310, females 31 and up at 320, and pregnant or lactating women somewhat higher.

Even worse, the fact that it’s almost impossible to tell how much magnesium we have in our bodies hasn’t stopped some so-called authorities, like Celeste Robb-Nicholson, M.D., Editor in Chief, Harvard Women’s Health Watch,
from writing that “magnesium deficiency … is rare in the United States” and that we get most of the magnesium we need from “whole grains, legumes, and dark-green leafy vegetables.”

But that doesn’t work for us when we follow a very low-carb diet that excludes whole grains and legumes. One cup of spinach, for example, has only 24 mg of magnesium, according to the USDA’s National Nutrient Database.

But even Dr. Robb-Nicholson admits that magnesium deficiency “can cause muscle weakness, cramping, or heart rhythm disturbances.” Leg cramps are what it took to bring me back to magnesium supplements after skipping them for years.

Getting enough magnesium on a very low-carb diet isn’t easy. One correspondent wrote me recently that she takes one tablespoon of molasses a day, “since it is high in magnesium.” I replied that since molasses is also very high in fructose, it’s hard on our liver, as I wrote here in “The Trouble with Fructose.” Besides, it ranks only No. 135 in Nutrition Data’s list of “Foods highest in Magnesium.”

In The Art and Science of Low Carbohydrate Living, which I reviewed here at “Low Carbohydrate Living,Stephen Phinney and Jeff Volek recommend taking magnesium for leg cramps, which I had at the time. They focus their recommendation taking the magnesium supplements for just 20 days, unless the leg cramps return, which they did for me.

They recommend slow-release tablets, although not the expensive proprietary brand-name product, “Slow-Mag.” “Mag-64 or Mag-Delay” are “equally effective generics at a fraction of the brand-name price.”

But I couldn’t find either of these recommended brands.  When I wrote Dr. Phinney for advice where to buy one of them, he instead sent me two bottles of 120 capsules of Mag 64. Subsequently I found it on at “rising mag64.”

I have been taking two tablets daily ever since and now almost never have leg cramps. I am continuing to take this magnesium supplement to prevent the common leg cramps that I once had, because my diabetes indicates that I probably need more magnesium than most people, because I follow a very low-carb diet, and because of a chronic muscle weakness I have in my left leg. That started when I took statins many years ago and has never disappeared, although I am still hopeful that magnesium will eventually overcome this side effect of that drug.

Most people who have diabetes probably do need to take supplemental magnesium. But not everyone.

Like any drug or supplement, magnesium can have those unintended consequences that we call side effects. In the case of magnesium the only known contraindication is severe renal failure. So if you have any history of kidney problems or know of any loss of kidney function, be sure to check with your doctor before taking any magnesium supplement.

For the rest of us, however, the mineral known as magnesium might well be magical.

This article is based on an earlier version of my article published by HealthCentral.

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  • Rhonda at

    This was a great article. But I have only one kidney so I will talk to Dr. about the mag. But my heart dr. says statin’s don’t cause leg cramps. I believe they do because I never had any until I had heart attack. Thanks, David, you really help us with all the stuff we have to deal with!