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Why do we have magnesium deficiency?

March 06, 2021 — BarryK

I posted about cramps in the feet and legs while contorting around inside a small tent on the last hike:

I take a magnesium tablet about every third day, which is effective at preventing leg cramps. if I don't take the tablets, I will wake up in bed with painful cramping. Also, the feet will cramp during the day, especially if they get a little bit cold.

I know of two close relatives who also have to take magnesium supplements, due to cramping. Haven't asked other relatives, but I assume it is a widespread problem.

Sometime ago I investigated iodine deficiency, which is a worldwide problem, or rather, used to be. I don't have the links, but there is an Australian academic who spent most of his life studying iodine deficiency, and he also took part in programs in China and other countries to study and eliminate deficiency.

The fundamental problem is that iodine has leached out of soils and ended up in the ocean. Especially in Australia, which is a very ancient continent. Sea food is rich in iodine. Animals and plants inland are deficient.

Here in Australia, the practice was to wash milk bottles and other food preparation containers, with iodine, which meant that most Australians were getting sufficient iodine, without realising it. The medical fraternity didn't realise it either, until they began discovering iodine deficiency in infants -- then they discovered it coincided with an Australia-wide switch from iodine to chlorine to wash bottles and other food preparation containers.

One of the outcomes was introduction of iodine into salt. Unfortunately, there are those in Australia who only use non-iodized salt, nor do they eat bread and other processed foods that contain added iodine. I know one of those people -- and she mentioned awhile back that her doctor had diagnosed goitre, a symptom of iodine deficiency.

In China, having a totalitarian regime, the government simply ordered that all salt was to be iodized, no exceptions.

Anyway, back onto magnesium. I found a fascinating academic paper:

A few quotes from it:

Because serum magnesium does not reflect intracellular magnesium, the latter making up more than 99% of total body magnesium, most cases of magnesium deficiency are undiagnosed. Furthermore, because of chronic diseases, medications, decreases in food crop magnesium contents, and the availability of refined and processed foods, the vast majority of people in modern societies are at risk for magnesium deficiency.


‘The homeostatic mechanisms to regulate magnesium balance were developed millions of years ago. Investigations of the macro- and micro-nutrient supply in Paleolithic nutrition of the former hunter/gatherer societies showed a magnesium uptake with the usual diet of about 600 mg magnesium/day, much higher than today’. Our homeostatic mechanisms and genome are still the same as with our ancestors in the Stone Age. This means our metabolism is best adapted to a high magnesium intake.

In developed countries, the average intake of magnesium is slightly over 4 mg/kg/day. More than a quarter of obese and non-obese youth have inadequate intakes of magnesium (27% and 29%, respectively). The authors of a study concluded: ‘Even though children may consume an excess of energy, they may not be meeting all of their micronutrient needs’. In other words, children are overfed and undernourished. One expert has argued that a typical Western diet may provide enough magnesium to avoid frank magnesium deficiency, but it is unlikely to maintain high-normal magnesium levels and provide optimal risk reduction from coronary artery disease and osteoporosis. That is, ‘Various studies have shown that at least 300 mg magnesium must be supplemented to establish significantly increased serum magnesium concentrations…’ In other words, most people need an additional 300 mg of magnesium per day in order to lower their risk of developing numerous chronic diseases. So while the recommended daily allowance (RDA) for magnesium (between 300 and 420 mg/day for most people) may prevent frank magnesium deficiency, it is unlikely to provide optimal health and longevity, which should be the ultimate goal.


Since 1940 there has been a tremendous decline in the micronutrient density of foods. In the UK for example, there has been loss of magnesium in beef (−4 to −8%), bacon (−18%), chicken (−4%), cheddar cheese (−38%), parmesan cheese (−70%), whole milk (−21%) and vegetables (−24%). The loss of magnesium during food refining/processing is significant: white flour (−82%), polished rice (−83%), starch (−97%) and white sugar (−99%). Since 1968 the magnesium content in wheat has dropped almost 20%, which may be due to acidic soil, yield dilution and unbalanced crop fertilisation (high levels of nitrogen, phosphorus and potassium, the latter of which antagonises the absorption of magnesium in plants). One review paper concluded: ‘Magnesium deficiency in plants is becoming an increasingly severe problem with the development of industry and agriculture and the increase in human population’. Processed foods, fat, refined flour and sugars are all devoid of magnesium, and thus our Western diet predisposes us to magnesium deficiency. Good dietary sources of magnesium include nuts, dark chocolate and unrefined whole grains.

The magnitude of this problem has been going on "under the radar" by most of us, and even, I read, medical practitioners are not sufficiently aware.

I know an elderly person who was prescribed three tablets per day by her doctor. When she told me that, I thought, wow, isn't that over the top, might she be getting too much? However, from the quote above, our bodies are designed to handle huge intake of magnesium.

The paper also mentions that magnesium intake requirement is higher in the elderly. I found a table showing how recommended intake increases with age:

Birth to 6 months30 mg*30 mg*

7–12 months75 mg* 75 mg*

1–3 years80 mg80 mg

4–8 years130 mg130 mg

9–13 years240 mg240 mg

14–18 years410 mg360 mg400 mg360 mg
19–30 years400 mg310 mg350 mg310 mg
31–50 years420 mg320 mg360 mg320 mg
51+ years420 mg320 mg

I take Blackmores MagMin, the active ingredient per tablet is "Magnesium aspartate dihydrate 500mg (Magnesium 37.4mg)". So what does that mean, am I only getting 37.4mg in each tablet?

A word of warning: despite the above academic paper stating that we can tolerate a large intake of magnesium, I did come across warnings, while browsing online, of possible side-effects if too much is taken.

EDIT 2021-03-07:
Very interesting, I have received emails from Stephen, David and Rodney, advising me that a contributing factor to muscle cramps is lack of salt, that is, sodium chloride. Quoting Rodney:

In 1973 I worked in tropical Indonesia for 10 months. with a company crew of tv transmitter installation engineers.
We were warned while there, to liberally sprinkle extra salt on our meals to supplement the body salt lost through sweating in high temperatures.
Westerners will easily keel over otherwise.
As you say, leg cramp is another side issue of magnesium deficiency.

Quoting from here:

Too little potassium, calcium or magnesium in your diet can contribute to leg cramps.

It is recognised that most of us eat too much salt, however, I will experiment with this on the next hike, maybe take along a packet of potato chips (in the UK, they are called "potato crisps", a fact I learnt when I went into a village general store in England back in the 70s, and asked "do you have any potato chips?" and just got a blank stare).

EDIT 2021-03-07:
The above link mentions lack of potassium as a cause of muscle cramps. See this:

...that link advises not to take potassium supplements, as there is danger if take too much. Potatoes have potassium, so that packet of potato chips is looking good! Yum!  

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