Magnesium Glycinate vs Citrate: Which Magnesium Should You Take, and How Much?
Someone on a Reset Room call last month asked me whether they should take magnesium, since everyone seems to be raving about it. The short answer is yes, almost certainly. The longer answer is that the form matters more than the brand, the dose on the front of the bottle is not the dose you are getting, and the one real side effect tells you exactly when you have had enough.
Should you take magnesium?
For most people, yes. I run a lot of blood work, and magnesium has become a lot like vitamin D: almost everyone is suboptimal. Not deficient in the way a lab would flag, but below where I want to see it. It has a hand in more than 300 enzyme reactions in your body, from making energy inside your cells to letting a muscle relax after it contracts. When a muscle contracts it needs calcium. When it relaxes, it needs magnesium.
You do not have to look much further than the food supply to see why so many of us run low. The soil our food grows in is depleted compared with what our grandparents ate from, and the modern diet leans on foods that carry very little of it. Almost half of Americans get less magnesium from food than the amount the government says they need, according to the NHANES survey data Andrea Rosanoff’s group analysed in 2012.
Magnesium is also one of the few supplements I am comfortable telling people to take without a blood test first. You are not going to harm yourself with it. You can only help yourself, and the only question left is cost: do you really need it? The one exception is anyone with kidney disease, because the kidneys are what clear the excess. If that is you, talk to your doctor before adding any.
Magnesium glycinate vs citrate: what is the difference?
Magnesium glycinate is magnesium bound to the amino acid glycine, and it is the form I reach for first. Magnesium citrate is magnesium bound to citric acid. It absorbs well, but it pulls water into the bowel, and at a high enough dose it is what some bowel-prep kits use to clear you out before a colonoscopy. If you had to pick one bottle, glycinate gives you the most for your money.
Here is why the carrier matters at all. Magnesium on its own is a reactive metal, so it has to be attached to something to be delivered. That is why you see magnesium oxide, glycinate, citrate, malate, threonate, and so on. The thing it is attached to decides two things: how much of the magnesium your gut absorbs, and which part of you feels it most.
Glycine is interesting in its own right. It is an inhibitory neurotransmitter, one of the chemicals in your brain that turns nerve activity down, and it reaches the brain. So magnesium glycinate tends to be the form people notice at night. It helps sleep come, it dials down that anxious, wired feeling, and it is gentle on the stomach. It still helps the gut and the muscles, because every form reaches every system to some degree. The difference between forms is emphasis.
Citrate’s strength is absorption. In a 60-day trial from the University of Reading, citrate produced the highest blood magnesium of the three forms tested, ahead of an amino-acid chelate and well ahead of oxide. Its weakness is the bowel. If you are constipated, that is a feature. If you are not, it is the reason you will not want to take much of it.
If you had to pick one, you would get the most bang for your buck with magnesium glycinate.
Magnesium glycinate vs threonate: is threonate worth the extra money?
For most people, no. Magnesium L-threonate is the patented form marketed for the brain, and it costs several times what glycinate does. The idea that it reaches the brain better comes from a 2010 study in Neuron, where it improved learning and memory in rats. That is genuine science, and threonate is a good form. But glycinate also gets into the brain, it is not patented, and in my practice it does the job at a fraction of the price.
The blend I formulated for my own patients uses a little threonate alongside glycinate and a third form, so one product covers the muscles, the gut and the nervous system. That is a sensible way to go if you want all three bases covered. If you are buying a single bottle, buy glycinate.
Which form of magnesium should you avoid?
Magnesium oxide. It is the cheapest form, the one in most drugstore bottles, and the least absorbed. In that same Reading trial, people who took oxide for 60 days had no more magnesium in their blood than people taking a placebo. Most of it stays in the gut, which is why oxide works as a laxative and not for much else. If the label says oxide, put it back.
How much magnesium per day?
About 400 mg of elemental magnesium a day is the dose I give most people. If your blood work shows you are low, 800 mg a day for a while. That usually does not cause loose stools, though it can. The official recommended intake for adults is 310 to 420 mg a day, and most of that is supposed to come from food, so the supplement is topping up what your diet is not supplying.
The word that trips people up is elemental. Someone on the call read a label out loud: magnesium glycinate 750 mg, magnesium 95 mg. Both numbers are correct. The 750 mg is the weight of the whole compound, glycine included. The 95 mg is the magnesium you get. Glycine is a bulky carrier, so it delivers less magnesium per milligram than a small one like oxide does. That is why one capsule rarely gets you to 400 mg, why you might need three capsules to reach 300 mg, and why so many magnesium products come as a powder to stir into water.
For the record, the Institute of Medicine sets an upper limit of 350 mg a day from supplements. That limit is based entirely on the loose-stool effect. Nobody has shown toxicity at those doses in people with working kidneys. Above it you are in bowel-tolerance territory, which is the next section.
What happens if you take too much magnesium?
You get diarrhea, and for someone with healthy kidneys that is the whole side effect. It is not a health problem. It is a signal. You dial back to the dose that did not do it and stay there.
Almost anything gives you loose stool past a certain dose. Vitamin C does the same thing. What is interesting is that the line moves. Say 800 mg is fine and 1,000 mg sends you to the bathroom. Stay at 800 for a while, then go back up, and 1,000 may be fine, and now 1,200 is the new line. Your body adapts to the increased dose. Linus Pauling, who did more vitamin C research than anyone, is said to have started getting loose stool at a couple of grams a day and worked his way up to 18 grams. I am not suggesting you do that with anything. I am saying the threshold is not fixed, so if a dose bothers you today, it may not in a month.
What else is magnesium good for?
Sleep, muscle cramps, that anxious edge, headaches, and the stiff joints I covered in the joint-health post. Magnesium has a real track record in preventing migraines, which I have written up separately in magnesium for migraines, including which form and how much. It also has a part in how your body handles blood sugar, and it is one of the nutrients that quietly disappears when people take acid blockers for years, because you cannot absorb what your stomach cannot break down.
So, should you take it? Yes. Buy glycinate, aim for 400 mg of elemental magnesium a day, read the small number on the label, and let your bowel tell you if you have overshot.
References
- Rosanoff, A., Weaver, C. M., & Rude, R. K. (2012). Suboptimal magnesium status in the United States: are the health consequences underestimated? Nutrition Reviews, 70(3), 153–164. https://doi.org/10.1111/j.1753-4887.2011.00465.x
- Walker, A. F., Marakis, G., Christie, S., & Byng, M. (2003). Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnesium Research, 16(3), 183–191.
- Slutsky, I., Abumaria, N., Wu, L. J., Huang, C., Zhang, L., Li, B., Zhao, X., Govindarajan, A., Zhao, M. G., Zhuo, M., Tonegawa, S., & Liu, G. (2010). Enhancement of learning and memory by elevating brain magnesium. Neuron, 65(2), 165–177. https://doi.org/10.1016/j.neuron.2009.12.026
- Institute of Medicine. (1997). Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. National Academies Press. https://doi.org/10.17226/5776
