Secret Shopper: How do I know which form of magnesium to take?

Magnesium consistently ranks as one of the most popular supplements among consumers. But its many different forms and dosages can make shopping for a magnesium product a bit overwhelming, especially for a first-timer. Knowing that retailers field lots of customer questions about the mineral, we sent our Secret Shopper into one natural products store to see what kind of help they could offer in the aisles.

Natural Foods Merchandiser: How do I know which form of magnesium to take?

Retailer: There’s not a huge difference between the various forms, but there are some subtleties. Some might cause more GI upset, for example, while others are generally better tolerated. What is your goal in taking magnesium?

Natural Foods Merchandiser: Well, I’m pretty sure I don’t always get the recommended daily amount from my diet, so that’s one reason. I’ve also heard that magnesium can help the body and brain relax and maybe make it easier to fall asleep at night—which I could really use!

Retailer: Great, I think most magnesium forms can be calming. Magnesium citrate is probably the most common form you’ll find in supplements, but magnesium glycinate or other forms may help with that too. But one potential issue with magnesium supplements is diarrhea. Magnesium can have sort of a laxative effect. In general, magnesium glycinate seems to cause fewer issues that way. But that can also depend on the type of supplement—capsule, gummy, liquid, etc.—and whichever your digestive system seems to tolerate best.

Related:Secret Shopper: Why should I look for branded ingredients in supplements?

How did this retailer do?

Our expert educator: Tod Cooperman, M.D., founder and president of ConsumerLab, provider of independent test results and information to help consumers and healthcare professionals identify the best quality supplements. Check out ConsumerLab’s new review of magnesium supplements here.  

Some of the things the retailer said about there being differences among the forms of magnesium are correct. But the retailer could’ve informed the shopper better.

First, the evidence that magnesium helps you relax is pretty weak. No good studies have proven a calming effect. A study that lacked a placebo control suggested a benefit, but a study with a placebo control showed no benefit, and an observational study showed no correlation between low magnesium intake and anxiety. Magnesium may help you fall asleep a few minutes faster, but it won’t help you get more sleep. For falling asleep, the evidence is stronger for melatonin, at low dose, like 1 to 3 mg. 

Second, since the shopper felt that they were not getting enough magnesium from her diet, eating more magnesium-rich foods, like pumpkin seeds, chia seeds or almonds, would be my first suggestion.

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The retailer seemed well versed on the laxative effects of magnesium—and it’s good that this was brought up—although at a lower dosage, laxation is not much of a concern. If a high dose is needed, magnesium chloride (as a powder mixed in a beverage) or magnesium glycinate are preferred. Laxation is avoided when getting magnesium from foods. 

Dose should have been discussed since the shopper may just need a boost to magnesium intake. A dose of 150 to 200 mg of magnesium per day would get most people to the daily requirement of 300 to 400 mg. Also, keeping the dose at this level minimizes the chance of a laxative effect, which is more likely above 350 mg per day.

The glycinate form is OK, but it should be noted that it can taste horrible as a powder, and it is also the form with which problems with quality have been most common. A moderate dose of magnesium citrate in a pill, for example, would likely give the shopper what they want, and such a product can be fairly inexpensive.