What the research says
In a large US nutrition survey, 45 out of 100 people got less magnesium than the average requirement, even counting supplements
That's the result of the national NHANES survey for 2003–2006, where 16,110 people reported what they usually eat and which supplements they take. The Institute of Medicine (IOM) defines the average requirement as the amount of magnesium that is enough for half of people, so this is a modest bar. In the fall, as the days get shorter, a lot of people say they run out of energy by evening. Below we look at why your body needs magnesium, how much you need, why a blood test says little about how much you have stored, and how the forms of magnesium in tablets differ.
01Fall
People think of magnesium in the fall, when their energy drops
In the fall the sun comes up late and goes down early, and on forums many people complain about the same things. It's hard to get up in the morning, there's no energy left by evening, and little things get on your nerves.
Next to these complaints you often see the advice to take magnesium. Some hope it will calm them down, others want better sleep, others hope their calf cramps will stop. Most of all, people argue about which magnesium to pick.
The easiest way to check what you can really expect from magnesium is to look at official documents. The European Union has a list of what may be said about the benefits of nutrients on product labels. For magnesium, the list says it contributes to the reduction of tiredness and fatigue, to normal function of the nervous system and muscles, and to normal psychological function.
So magnesium's role in reducing tiredness and fatigue is officially recognized. These words are about how the body works, not about treatment, and the list says nothing about sleep, anxiety, blood pressure or cramps. To see whether we get enough magnesium, next we look at how much people actually get and whether it can be checked.
What people say online
- “Lately I've noticed I have way less energy in the evening than I used to. And it's not like I'm doing anything really demanding.”
- “Just a normal day. Work, chores, my kid, the store, cooking — and by 8 p.m. all I want is to lie down and have everyone leave me alone.”
- “I keep seeing advice to look into magnesium specifically when you get irritable and tense and feel like your body is running on the last few percent of battery.”
- “What would you recommend (which product) for feeling on edge, stressed, apathetic, with no energy to do anything?”
- “Which magnesium is better?? I don't know anything about supplements. I just took whatever the pharmacy gave me”
02How much
You need a few hundred milligrams of magnesium a day, and many people in the US fall short
Your body needs magnesium every day, and the amounts are in the hundreds of milligrams. Under the norms of Rospotrebnadzor, Russia's consumer health agency, an adult needs 420 mg of magnesium a day. In Europe and the US the targets are similar. The European Food Safety Authority (EFSA) sets 350 mg for men and 300 mg for women, and the Institute of Medicine sets 400 to 420 mg for men and 310 to 320 mg for women, depending on age.
How much magnesium people really get has been studied in the most detail in the US. In the NHANES survey we mentioned at the start, 45 out of 100 people got less than the average requirement, and that includes fortified foods and supplements. The work was funded by the food fortification committee of the International Life Sciences Institute (ILSI).
The average requirement is lower than the recommended amount. It's enough for only half of people. For comparison, 38 out of 100 people fell short of it for calcium and 25 out of 100 for vitamin C.
The Institute of Medicine's review shows the same picture. In the 1994 CSFII food survey, American women aged 31–50 had a median magnesium intake of 229 mg a day, below their average requirement of 265 mg. Median means half of the women got even less.
One caveat matters here. These are food surveys, not blood tests, and falling short in them is not a diagnosis. The data come from the US and can't be applied directly to Russia, and we did not find the same kind of data for the whole population of Russia.
03Blood test
A blood test sees less than 1% of all the magnesium in your body
It seems the easiest way to find out if you have enough magnesium is to get a blood test. The problem is where magnesium is stored. According to the Institute of Medicine, an adult's body holds about 25 g of magnesium, and 50 to 60% of it is in the bones.
Outside the cells, by the same estimate, there is only about 1% of the body's magnesium. The authors of a large Russian observational study funded by the company Sanofi add that the blood holds about 0.8% of all magnesium. Of that, 0.3% is in the serum, the liquid part of the blood, and 0.5% is in the red blood cells.
So the test looks where only a small share of magnesium is, while the main supply stays in the bones and inside the cells. The Institute of Medicine writes that serum magnesium may not reflect how much magnesium is inside the cells and has not been confirmed as a reliable marker of the body's magnesium stores. In clinical studies, magnesium in blood cells, bone or muscle was sometimes abnormally low while the serum test stayed in the normal range. This happened in people with diabetes, alcoholism or poor absorption in the gut.
Still, a blood test sometimes does find a shortfall. The same study looked, for example, at women who were taking hormonal birth control or had menopausal symptoms, and 54.8% of women with these conditions had blood magnesium below 0.8 mmol/L. The authors themselves write that they enrolled women who were already suspected of being low, so the share among everyone in Russia may be lower.
04What it does
Low magnesium can lower calcium and potassium in the blood
To understand what falling short can mean, it helps to know what magnesium does. Rospotrebnadzor describes its role like this. Magnesium is needed by many enzymes that run carbohydrate and energy metabolism, it takes part in making proteins and nucleic acids, and it's needed to keep calcium, potassium and sodium in balance in the body.
When magnesium is low, it affects other substances too. According to EFSA, magnesium deficiency can cause lower calcium and potassium levels in the blood.
This fits the European list we mentioned at the start. According to it, magnesium contributes to normal energy metabolism, normal muscle and nervous system function, and the maintenance of normal bones and teeth.
We covered how magnesium is linked to vitamin D in detail in our vitamin D article. Here we focus on magnesium itself and the forms you can get it in.
05Forms
In a tablet, magnesium is always bound to something, and that affects how much gets absorbed
In supplements, magnesium never comes on its own. It's bound to another substance. That can be oxide, citrate, chloride, lactate, or a chelate, where magnesium is bound to an amino acid.
How much the form matters was tested in a placebo-controlled trial where healthy people took different forms of magnesium for 60 days. The organic forms, citrate and amino acid chelate, were absorbed better than oxide, and oxide did no better than the placebo.
The groups in this trial were small, and the abstract of the study doesn't say which amino acid chelate was used. In this test, oxide fell behind the organic forms, citrate and amino acid chelate, and the authors named citrate the best.
06Chelate
Bisglycinate is magnesium bound to the amino acid glycine
Bisglycinate is a chelate in which magnesium is bound to two molecules of the amino acid glycine. It belongs to the amino acid chelates. In the placebo-controlled trial, amino acid chelate along with citrate was absorbed better than oxide, but the study doesn't say whether that chelate was bisglycinate.
Bisglycinate was also tested on its own, in people who have an especially hard time absorbing magnesium. After bowel surgery they absorb little magnesium, and in a small trial almost as much was absorbed from bisglycinate as from oxide, 23.5% and 22.8%. The authors write that for these patients bisglycinate may be a good alternative to regular supplements.
We did not find large, long trials comparing bisglycinate with other forms. In one short comparison, blood magnesium did not rise noticeably in the first hours after bisglycinate. But that study was commissioned by a maker of a different form of magnesium, and measurements like these don't show well how much magnesium the body stored.
In the countries of the Eurasian Economic Union, which includes Russia, magnesium bisglycinate is listed among the forms allowed in supplements. The form in a tablet is always stated in the ingredients on the package.
07Myths
What people believe about magnesium, and what the sources say
- Myth
A blood test will show whether you have enough magnesium
FactThe blood holds only about 0.8% of all the body's magnesium, and the serum 0.3%. These are data from a Russian observational study funded by the company Sanofi.
Source 06 - Myth
All forms of magnesium in tablets are the same
FactIn a placebo-controlled trial, citrate and amino acid chelate were absorbed better than oxide after 60 days, and oxide did no better than the placebo.
Source 07 - Myth
If you get calf cramps at night, just add magnesium
FactA Cochrane review (Cochrane is an international organization that reviews medical research) says magnesium supplements are unlikely to noticeably prevent muscle cramps in older adults. After 4 weeks, the number of cramps per week was almost the same as with placebo (5 trials, 307 people).
Source 12 - Myth
You can't get too much magnesium
FactFor magnesium not from food, the Institute of Medicine set an upper level of 350 mg a day for teens and adults. In the EU, the upper level for easily dissolved magnesium salts and magnesium oxide in supplements, water and fortified foods is 250 mg. The first sign of too much is diarrhea. Magnesium from regular food has not shown harmful effects.
Source 02 - Myth
Heartburn pills don't affect magnesium
FactIn a review of 16 observational studies with 131,507 patients, low magnesium was found in 19.4% of people taking proton pump inhibitors and in 13.5% of those not taking them. This is a link seen in observations, not a proven cause.
Source 13
08What to do
What to do this fall
Know how much you need
Under Rospotrebnadzor norms, an adult needs 420 mg of magnesium a day. Under EFSA norms, it's 350 mg for men and 300 mg for women. The amount is counted in milligrams of magnesium itself, so on a supplement label look for that number, not the weight of the whole tablet.
Don't fear magnesium from food
According to the Institute of Medicine, magnesium from regular food has not shown harmful effects. The upper limit applies only to magnesium from supplements and medications.
Keep the upper limit for supplements in mind
Upper levels for magnesium from supplements differ. The Institute of Medicine sets 350 mg a day and names diarrhea as the first sign of too much. In the EU, the upper level for easily dissolved magnesium salts and magnesium oxide in supplements, water and fortified foods is 250 mg, and in the Eurasian Economic Union countries it's 800 mg for supplements. These are limits, not recommended doses.
Don't judge your stores by one blood test
According to the Institute of Medicine, serum magnesium may not reflect how much magnesium is inside the cells. If something worries you, work out the causes with your doctor rather than going by a single number.
Tell your doctor about heartburn medicine
In observational studies, low magnesium was found more often in people taking proton pump inhibitors, medicines that lower stomach acid. If you take them, ask your doctor whether your magnesium should be monitored.
If you choose a supplement, check the form
In a trial, magnesium oxide was absorbed worse than citrate and amino acid chelate. The form is listed in the ingredients on the package. Decide which supplement to choose and at what dose together with your doctor.
09Sources
What the sources actually say
In NHANES 2003–2006 (16,110 people), total usual intake was below the Estimated Average Requirement (EAR) for vitamins A, C, D and E in 34, 25, 70 and 60% of the population, for calcium in 38%, and for magnesium in 45%. The work was funded by the Fortification Committee of the North American Branch of the International Life Sciences Institute (ILSI).
The Estimated Average Requirement (EAR) is the daily intake that meets the needs of 50% of people of a given age and sex. The recommended magnesium intake is 400 mg a day for men 19–30, 310 mg for women 19–30, 420 mg for men 31–50 and 320 mg for women 31–50. In CSFII 1994, the median magnesium intake of women 31–50 was 229 mg a day, below the EAR of 265 mg. The Tolerable Upper Intake Level for teens and adults is 350 mg a day, and it applies to magnesium not from food. Diarrhea is considered the first sign of excess magnesium not from food. Magnesium from regular food has not shown harmful effects. The body holds about 25 g of magnesium, 50–60% of it in bone, and about 1% outside the cells. Serum magnesium may not reflect how much magnesium is inside the cells and has not been confirmed as a reliable marker of the body's magnesium stores.
Magnesium is a cofactor of many enzymes of carbohydrate-phosphorus and energy metabolism, takes part in the synthesis of proteins and nucleic acids, and is needed to maintain calcium, potassium and sodium homeostasis. The updated physiological requirement for adults is 420 mg a day.
The adequate intake of magnesium is 350 mg a day for men over 18 and 300 mg a day for adult women. Magnesium deficiency can cause lower calcium and potassium levels in the blood.
Claims about magnesium authorized in the EU. Magnesium contributes to the reduction of tiredness and fatigue, electrolyte balance, normal energy-yielding metabolism, normal functioning of the nervous system and muscles, normal protein synthesis, normal psychological function, and the maintenance of normal bones and teeth, and has a role in cell division. There are no claims about sleep, anxiety, blood pressure or cramps among them.
The blood holds only about 0.8% of all the body's magnesium, 0.3% in the serum and 0.5% in the red blood cells. Among women with hormone-related conditions, low blood magnesium at a cutoff of 0.8 mmol/L was found in 54.8%. The study enrolled women suspected of magnesium deficiency, so the true share of low magnesium in Russia may be lower. The observations and analysis were funded by the company Sanofi, and three of the authors are its employees.
After 60 days, the organic forms of magnesium (citrate and amino acid chelate) were absorbed better than oxide, as measured by 24-hour urinary magnesium. Magnesium oxide did not differ from placebo.
In patients after removal of part of the ileum, magnesium absorption was low and did not differ between the supplements, 23.5% for the chelate and 22.8% for the oxide. Magnesium diglycinate may be a good alternative to regular magnesium supplements for these patients.
After taking magnesium bisglycinate, no significant rise in plasma magnesium was seen. The study was commissioned by a maker of a different form of magnesium (Lubrizol).
The upper permissible level of magnesium in dietary supplements is 800 mg a day. The forms of magnesium allowed in supplements include magnesium bisglycinate, magnesium citrates and magnesium amino acid complexes.
The Tolerable Upper Intake Level of magnesium for adults is 250 mg a day. It applies to readily dissociable magnesium salts and compounds like magnesium oxide in supplements, water, or added to foods. Magnesium naturally present in foods and beverages is not included.
Magnesium supplements are unlikely to provide clinically meaningful prevention of muscle cramps in older adults. After 4 weeks, the difference in the number of cramps per week was −0.18 (5 studies, 307 participants).
16 observational studies with a total of 131,507 patients were found. Among people taking proton pump inhibitors, low magnesium was found in 19.4%, and among those not taking them in 13.5%. Higher doses were linked to higher odds of low magnesium than lower doses. These are observations showing a link, not a proven cause.