The Entire Case for Magnesium and Testosterone Rests on Thirty Men in Turkey, Four Weeks, and a Dose Twice the Supplemental Upper Limit. The Ten Who Took No Magnesium Went Up Too.
Open any testosterone support formula and magnesium is in it, usually somewhere near the top of the label alongside zinc and vitamin D. The nutritional case for magnesium is stronger than for most things sold to men: it is a required cofactor for hundreds of enzymes, including every reaction that uses ATP, intake in the United States sits below the recommended allowance for a large share of adults, and the standard blood test cannot tell you whether you are short. The hormonal case is much thinner than the shelf presence suggests. One four-week study in thirty men aged 18 to 22, published in 2011 with no placebo group and no blinding, is doing nearly all of the work, and the arm of that study which took no magnesium saw testosterone rise as well. The two placebo-controlled trials that measured testosterone while giving magnesium found no effect on it. What is left is a correlation in 399 older Italian men, a plausible piece of binding chemistry, and two indirect routes through sleep and vitamin D that nobody has tested end to end. This article goes through each study, the measurement problem that makes deficiency hard to detect, the differences between the salts on the shelf, and what a man over 40 can reasonably conclude.
Key Takeaways: What the Magnesium and Testosterone Evidence Actually Shows
No randomized placebo-controlled trial has ever been run with testosterone as its primary endpoint in men taking magnesium. The single study everyone cites is Cinar and colleagues in Biological Trace Element Research in 2011: thirty men aged 18 to 22 in three groups of ten, given 10 mg of magnesium per kilogram of body weight a day for four weeks, in which total and free testosterone rose in all three groups, including the ten tae kwon do athletes who trained without taking any magnesium, which points at the training rather than the mineral. The Cinar dose of 10 mg per kilogram works out to roughly 800 mg a day for an 80 kg man, against a recommended dietary allowance of 420 mg for men aged 31 and older and a tolerable upper intake level of 350 mg a day for magnesium from supplements. Maggio and colleagues reported in the International Journal of Andrology in 2011 that serum magnesium was positively associated with total testosterone and with IGF-1 in 399 men aged 65 and over in the InCHIANTI cohort, which is a single-timepoint correlation and cannot show direction. Wilborn and colleagues in 2004 gave 42 resistance-trained men a zinc and magnesium formula containing 450 mg of magnesium aspartate against placebo for eight weeks and found no change in total or free testosterone, IGF-1, cortisol, strength or body composition. Serum magnesium samples roughly one percent of the magnesium in the body, the rest sitting in bone and muscle, and the body defends the serum value by drawing on bone, so a normal chemistry panel does not rule out depleted tissue stores. Magnesium oxide is 60.3 percent elemental magnesium by weight but the least bioavailable of the common salts, while citrate at 16.2 percent and glycinate at 14.1 percent are absorbed better, which means the milligram figure on the front of a bottle is not comparable across forms. Men with reduced kidney function should not take magnesium supplements without medical supervision, because the kidney is the route by which excess magnesium leaves the body.
Thirty Men Carry the Entire Claim, and Ten of Them Took No Magnesium at All
People enrolled in each human study behind the magnesium and testosterone claim. Amber marks the three uncontrolled supplement arms: Cinar and colleagues in Biological Trace Element Research in 2011 gave 10 mg per kilogram of body weight a day for four weeks to ten sedentary men aged 18 to 22 and to ten tae kwon do athletes of the same age, with no placebo and no blinding, and Brilla and Conte in 2000 gave 27 college footballers a formula containing 450 mg of magnesium aspartate in a study funded by the product's maker. Blue marks the third Cinar arm, ten athletes who trained identically and took nothing, whose testosterone also rose. Grey marks the two placebo-controlled trials: Wilborn and colleagues in 2004 found no change in total or free testosterone in 42 resistance-trained men over eight weeks, and Abbasi and colleagues in 2012 tested 500 mg of magnesium against placebo in 46 older adults with insomnia and measured sleep, not testosterone. Violet marks the largest dataset, 399 men aged 65 and over in the InCHIANTI cohort reported by Maggio and colleagues in 2011, which was cross-sectional and measured a single blood draw. No randomized placebo-controlled trial has ever been run with testosterone as its primary endpoint.
What Did the One Human Study of Magnesium and Testosterone Actually Find?
Cinar and colleagues found that testosterone rose in every group they studied, including the group that received no magnesium, which is the detail that almost never survives the trip onto a supplement label. The study, published in Biological Trace Element Research in 2011, enrolled thirty men aged 18 to 22 and split them into three groups of ten. The first group was sedentary and took 10 mg of magnesium per kilogram of body weight a day. The second group practised tae kwon do for roughly 90 to 120 minutes a day, five days a week, and took the same magnesium dose. The third group trained identically and took nothing. After four weeks the investigators measured total and free testosterone at rest and after exhaustive exercise, and reported increases across all three groups, with the largest increases in the two groups that were training. A design with no placebo, no blinding and ten men per arm cannot separate a mineral effect from a training effect, a seasonal effect, or the ordinary drift of a hormone measured twice in young men. The third group is the control the study accidentally provides, and it went up without magnesium. That single comparison is the reason this study should be read as hypothesis-generating rather than as evidence of an effect.
The Only Trial Used Roughly Twice the Recommended Intake and More Than Twice the Supplemental Upper Limit
Daily elemental magnesium in milligrams, comparing the Cinar 2011 dose with the intakes a man is ordinarily held to. Cinar and colleagues gave 10 mg per kilogram of body weight a day, which works out to about 800 mg for an 80 kg man and about 700 mg for a 70 kg man. The Food and Nutrition Board sets the recommended dietary allowance at 400 mg a day for men aged 19 to 30 and 420 mg for men aged 31 and older, and sets a tolerable upper intake level of 350 mg a day for magnesium from supplements and medications, a limit based on diarrhea rather than on serious toxicity and one that does not apply to magnesium from food. Mean intake from food among US adult men sits close to 350 mg a day, below the recommended allowance, and roughly half of Americans take in less than the estimated average requirement. A common magnesium capsule delivers 100 to 200 mg of elemental magnesium, so reproducing the trial dose would mean four to eight capsules a day, well past the point where most men would be dealing with loose stools.
Was That Dose Safe, and Is It What Is in a Magnesium Supplement?
The Cinar dose was roughly twice the recommended intake and more than twice the upper limit that applies to supplements, and it is not what a commercial capsule delivers. Ten milligrams per kilogram a day comes to about 700 mg for a 70 kg man and about 800 mg for an 80 kg man. The Food and Nutrition Board sets the recommended dietary allowance at 400 mg a day for men aged 19 to 30 and 420 mg for men aged 31 and older, and sets a tolerable upper intake level of 350 mg a day for magnesium taken from supplements and medications. That upper limit is based on diarrhea rather than on organ toxicity, and it does not apply to magnesium obtained from food, because the kidney handles dietary loads spread across a day without difficulty. A typical magnesium capsule contains 100 to 200 mg of elemental magnesium, so a man trying to reproduce the trial would be taking four to eight capsules a day and would likely meet the upper limit's defining side effect before he met the four-week mark. Anyone quoting the Cinar result as support for a 200 mg capsule is quoting a dose four times larger than the one in the bottle.
The Blood Test Samples About One Percent of the Magnesium in a Man's Body
Approximate distribution of the roughly 24 to 25 grams of magnesium held in an adult body. Bone holds somewhere between half and sixty percent of it, skeletal muscle holds around a quarter, other soft tissue holds most of the rest, and the extracellular fluid that a blood draw samples holds about one percent, with serum itself accounting for a fraction of that. Serum magnesium is defended within a narrow band of roughly 0.75 to 0.95 mmol per litre by pulling magnesium out of bone and by adjusting how much the kidney excretes, which means a man can run down his tissue stores for years while his serum value stays comfortably normal. This is the central measurement problem in the field. Studies that screen participants with a serum magnesium test are not identifying who is depleted, and a normal result on a standard chemistry panel does not rule out inadequate intake. The measurements that track tissue status better, such as red blood cell magnesium, ionized magnesium or a magnesium retention test after an intravenous load, are rarely ordered and were not used in the testosterone studies.
- Bone
- Skeletal muscle
- Other soft tissue
- Extracellular fluid, including serum
Does a Normal Magnesium Blood Test Mean You Are Not Deficient?
No. A normal serum magnesium result is compatible with substantially depleted tissue stores, because serum holds about one percent of the magnesium in the body and the body works hard to keep that one percent stable. An adult carries roughly 24 to 25 grams of magnesium. Somewhere between half and sixty percent of it is in bone, around a quarter is in skeletal muscle, most of the remainder is in other soft tissue, and only about one percent is in the extracellular fluid that a blood draw samples. When intake falls, the kidney reduces excretion and bone releases magnesium into the circulation, which holds serum inside its usual range of roughly 0.75 to 0.95 mmol per litre while the reserves behind it come down. This is why chronic magnesium inadequacy is often described as subclinical. Tests that reflect tissue status more faithfully exist, including red blood cell magnesium, ionized magnesium and a magnesium retention test measuring how much of an intravenous load the body holds onto, but they are rarely ordered in ordinary practice and none of the testosterone studies used them. In practical terms, dietary intake history is a better guide to magnesium status than the number on a standard chemistry panel.
Do Older Men With More Magnesium Have Higher Testosterone?
In one large cross-sectional dataset they do, though the design cannot establish which way the arrow points. Maggio and colleagues, publishing in the International Journal of Andrology in 2011, analysed 399 men aged 65 and over from the InCHIANTI study in Tuscany and found that serum magnesium was positively and independently associated with total testosterone and with IGF-1 after adjustment for age and other covariates. The association held across the normal range rather than only at the deficient end. What that analysis cannot say is whether magnesium status raises anabolic hormones, whether anabolic status affects magnesium handling, or whether both track a third factor such as muscle mass, diet quality, physical activity or the burden of chronic disease, all of which move serum magnesium and testosterone in the same direction. Older men who eat more leafy greens, nuts, legumes and whole grains are different from older men who do not, in ways that no covariate adjustment fully removes. A correlation in 399 men is the strongest human dataset in this field, and it is still not an experiment.
What Did the Placebo-Controlled Trials Find?
The two controlled trials that gave men magnesium and measured the relevant outcomes found nothing on testosterone. Wilborn and colleagues, publishing in the Journal of the International Society of Sports Nutrition in 2004, randomized 42 resistance-trained men to a zinc and magnesium aspartate formula supplying 30 mg of zinc and 450 mg of magnesium, or to placebo, for eight weeks of training. The formula raised nothing that mattered: no significant change in total testosterone, free testosterone, IGF-1, cortisol, strength or body composition against placebo. That trial exists because of an earlier one, by Brilla and Conte in 2000, which reported a 32 percent rise in free testosterone in 27 college footballers over eight weeks on the same category of formula. The earlier study was funded by the product's manufacturer, whose founder was the second author, and its placebo group showed unusually steep declines that account for much of the between-group gap. Abbasi and colleagues in 2012 ran a placebo-controlled trial of 500 mg of magnesium for eight weeks in 46 older adults with insomnia and reported improvements in insomnia severity, sleep efficiency and sleep onset latency, but that trial measured sleep, not testosterone. The pattern here matches what the zinc literature shows: the positive results come from uncontrolled or interested studies, and the controlled ones come back flat.
How Could Magnesium Affect Testosterone At All?
There are three mechanisms that are biologically reasonable, and none has been carried through to a hormonal endpoint in a controlled trial. The first is binding. Work by Excoffon, Guillaume and colleagues using molecular chromatography, published in the Journal of Pharmacy and Pharmacology, reported that magnesium reduces the binding affinity of testosterone for sex hormone binding globulin, which would leave a larger bioavailable fraction without changing the total. That is an in vitro observation about a protein interaction, not a demonstration that free testosterone rises in men. The second is vitamin D. Magnesium is a required cofactor for the enzymes that hydroxylate vitamin D in the liver and kidney and for the vitamin D binding protein that carries it, so magnesium status conditions how much usable vitamin D a given intake produces, and vitamin D repletion has its own modest and contested relationship with testosterone. The third is sleep. Magnesium has placebo-controlled evidence for improving sleep quality in older adults with insomnia, and sleep restriction has the cleanest experimental link to falling testosterone of anything in men's health: one week of five-hour nights cut daytime testosterone by 10 to 15 percent in healthy young men. If magnesium helps a man sleep and sleeping better protects his testosterone, the mineral is working two steps removed. Nobody has run the study that would connect those steps.
Which Form of Magnesium Is Worth Taking?
Choose a form for absorption rather than for the milligram figure on the front of the bottle, because the two run in opposite directions. Magnesium oxide is 60.3 percent elemental magnesium by weight, the highest of any common salt, which is why it produces impressive label numbers cheaply, but it is poorly soluble and poorly absorbed. Firoz and Graber compared four preparations in healthy volunteers in Magnesium Research in 2001 and found oxide the least bioavailable of the group, with organic salts and chloride absorbed considerably better. Calculated from formula weights, magnesium citrate is 16.2 percent elemental magnesium, glycinate 14.1 percent, chloride hexahydrate and lactate 12.0 percent, sulfate heptahydrate 9.9 percent, aspartate 8.4 percent and L-threonate 8.3 percent. Citrate and glycinate are the reasonable defaults for repletion, glycinate being the gentler of the two on the gut. The unabsorbed fraction is not inert: it stays in the intestine, draws water in osmotically and produces the laxative effect for which magnesium oxide, hydroxide and sulfate are actually marketed. Doses are better split across the day than taken at once, and there is no evidence that any exotic form outperforms citrate or glycinate for the purpose of correcting an ordinary dietary shortfall.
The Form With the Most Magnesium on the Label Is the One the Gut Absorbs Worst
Elemental magnesium as a percentage of compound weight, calculated from formula weights, for the salts sold on supplement shelves. Magnesium oxide is 60.3 percent magnesium by weight, which is why a 500 mg oxide tablet can advertise 300 mg of magnesium, but it is barely soluble and absorbed poorly: Firoz and Graber, comparing four preparations in healthy volunteers in Magnesium Research in 2001, found oxide the least bioavailable of the group, with the organic salts and chloride absorbed considerably better. Magnesium citrate is 16.2 percent magnesium by weight, glycinate 14.1 percent, chloride hexahydrate and lactate both 12.0 percent, sulfate heptahydrate 9.9 percent, aspartate 8.4 percent and L-threonate 8.3 percent. The practical consequence is that the number on the front of the bottle tells you very little on its own. A label claiming 400 mg of magnesium as oxide may deliver less absorbed magnesium than one claiming 200 mg as citrate or glycinate, and the poorly absorbed fraction stays in the gut, draws in water osmotically and produces the laxative effect that magnesium oxide and magnesium sulfate are actually sold for.
Can You Get Enough Magnesium From Food?
Yes, and for most men food is the better route, because the foods that carry magnesium carry other things worth having and because dietary magnesium has no upper limit attached to it. Magnesium sits at the centre of the chlorophyll molecule and concentrates in the seed and bran fractions of grains, so the reliable sources are leafy greens, seeds, nuts, legumes and whole grains. Using the values in the National Institutes of Health Office of Dietary Supplements fact sheet, an ounce of roasted pumpkin seeds supplies 156 mg, an ounce of chia seeds 111 mg, an ounce of almonds 80 mg, half a cup of boiled spinach 78 mg, an ounce of cashews 74 mg, an ounce of dark chocolate at 70 to 85 percent cocoa 65 mg, half a cup of cooked black beans 60 mg and half a cup of cooked brown rice 42 mg. Against a requirement of 420 mg a day for men over 30, a handful of pumpkin seeds, a serving of spinach and a cup of beans covers most of it before anything else on the plate is counted. Refining removes most of the magnesium from a grain along with the bran, which is a large part of why intake in the United States sits where it does.
Two Ounces of Pumpkin Seeds and a Plate of Spinach Cover Most of a Day's Requirement
Magnesium in milligrams per ordinary serving, using the values published in the National Institutes of Health Office of Dietary Supplements fact sheet, against the 420 mg a day recommended for men aged 31 and over. An ounce of roasted pumpkin seeds supplies 156 mg, an ounce of chia seeds 111 mg, an ounce of almonds 80 mg, half a cup of boiled spinach 78 mg, an ounce of cashews 74 mg, an ounce of dark chocolate at 70 to 85 percent cocoa 65 mg, half a cup of cooked black beans 60 mg, a cup of cubed avocado 44 mg, half a cup of cooked brown rice 42 mg and a cup of milk 24 mg. Magnesium sits at the centre of the chlorophyll molecule and in the seed and bran fractions of grains, so the foods that carry it are leafy greens, seeds, nuts, legumes and whole grains, and the refining that strips the bran from a grain strips most of the magnesium with it. Food magnesium also carries no upper limit, because the kidney handles dietary loads that the same amount from a supplement would not tolerate in one sitting.
Who Should Not Take Magnesium Supplements?
Men with reduced kidney function should not take magnesium supplements without medical supervision, because the kidney is the organ that clears excess magnesium and impaired clearance is the main route to genuine hypermagnesemia. That risk is small in men with normal renal function, where surplus magnesium is excreted and the practical ceiling is gastrointestinal rather than toxic. Magnesium also interferes with the absorption of several drugs, most notably tetracycline and quinolone antibiotics and bisphosphonates, which should be separated from a magnesium dose by at least two hours. Certain medications push the other way and deplete magnesium: loop and thiazide diuretics increase urinary losses, and prolonged proton pump inhibitor use has been associated with hypomagnesemia serious enough to prompt a Food and Drug Administration safety communication. Heavy alcohol intake and poorly controlled diabetes also increase urinary magnesium loss. A man on a diuretic or a long-term acid blocker has a better reason to pay attention to magnesium than a man hoping to move a hormone, and he is also the man most likely to have a normal serum result while running low.
What Does the Evidence Justify for a Man Over 40?
The evidence justifies correcting a magnesium shortfall for its own sake and does not justify expecting a testosterone response from doing so. A man whose intake is below the recommended 420 mg a day, or who takes a diuretic or a proton pump inhibitor, or who drinks heavily, has a reasonable case for improving intake through food and, if that is impractical, for a supplement of 200 to 400 mg of elemental magnesium as citrate or glycinate, kept at or under the 350 mg supplemental upper limit unless a clinician directs otherwise. The plausible returns are on sleep quality, muscle cramps and the many enzymatic processes that require magnesium regardless of what any hormone does. The testosterone claim rests on thirty men, four weeks, no placebo, a dose no commercial product delivers, and a control arm that rose without the mineral. Set against that, the two controlled trials that looked found nothing, and the cross-sectional correlation in 399 older men cannot tell direction. Magnesium belongs in the category of things worth not being short of, which is a smaller claim than the label makes and a more defensible one.
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