Magnesium is involved in over 300 reactions, and a third of the population eats too little of it. What it does for sleep, muscles, blood pressure and blood sugar, which form the body absorbs, why the blood value says little and when a capsule makes sense.
In short
- Needs of 300 to 400 milligrams daily, from whole grains, nuts, legumes, green vegetables; a third do not reach that.
- Proven: slightly lower blood pressure, better blood sugar, fewer migraines, sleep with deficiency; calf cramps only partly.
- Citrate, glycinate and malate are absorbed well, oxide badly; 200 to 400 milligrams in the evening.
- The serum value shows deficiency late; diet and symptoms are the better measure.
What the body needs magnesium for
Magnesium is a cofactor of over 300 enzymes: energy production, muscle relaxation, nerve conduction, blood sugar regulation, blood pressure, protein synthesis, bone building. Needs sit at 300 to 400 milligrams daily, and whole grains, nuts, seeds, legumes, green vegetables, bananas and mineral water cover them. Whoever consumes white flour, little vegetables and soft water often reaches 250, and alcohol, stress, endurance sport and some medications like proton pump inhibitors and diuretics increase loss.
What is proven
Blood pressure: magnesium lowers it in meta-analyses by about 2 to 4 mmHg, more with deficiency. Blood sugar: in people with prediabetes and low magnesium, supplementation improves insulin sensitivity. Migraine: 400 to 600 milligrams daily reduce attack frequency, which is in guidelines. Sleep: in older people with a low level it improves time to fall asleep and sleep quality, in the well-supplied hardly. Calf cramps: the evidence is weak, many still notice improvement, which may also be down to fluids and stretching. Mood: small studies show an effect with mild depression that is being studied further.
The form decides
Magnesium oxide is cheap and contains lots of elemental magnesium but is absorbed only to a few percent and has a laxative effect. Citrate is absorbed well and is the standard form, may also loosen the bowel in sensitive people. Glycinate, also bisglycinate, is gentle on the gut and preferred in the evening for sleep. Malate for energy during the day, threonate with hints of brain penetration but expensive and little supported. The label should state elemental magnesium, not the weight of the compound.
Dose and intake
200 to 400 milligrams of elemental magnesium daily, in the evening because it relaxes, in two portions if it causes diarrhea. Regulators put the upper limit for supplements at 250 to 350 milligrams; higher doses are unproblematic for healthy people, not with kidney weakness. Two hours apart from thyroid hormones, antibiotics and iron, because magnesium disturbs their absorption.
Why the blood value says little
Only one percent of magnesium is in the blood, the rest in bone and cells. The serum value stays normal for a long time while stores empty. A value under 0.85 mmol/l counts as borderline, but diet, symptoms like muscle twitching, cramps, sleep disturbances and palpitations and a trial over four weeks are the better measure.
Try it
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Does magnesium help calf cramps?
In pregnant women yes, in others the evidence is weak. A four-week trial with 300 milligrams in the evening does no harm; stretching, drinking and potassium from bananas and potatoes often help more.
Can I overdose on magnesium?
With healthy kidneys the body excretes the excess, diarrhea is the first sign. With kidney weakness it can accumulate, then only with a doctor.
Magnesium or zinc or both?
Zinc only makes sense with deficiency, usually in vegans, older people and athletes. Both together are possible but not in one tablet, because they compete for absorption.
This article is general information and not medical advice. If you have symptoms or existing conditions, or before changing any medication, talk to your doctor.
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