Is Your Magnesium Supplement What It Claims to Be?
Most of us take supplement labels at face value. If it says “Magnesium Bisglycinate,” we assume that’s exactly what we’re getting. But here’s the kicker: many supplements say one thing and deliver something entirely different.
What Is Buffered Magnesium, Really?
Buffered magnesium refers to a blend—often a cheaper form like magnesium oxide mixed with a more bioavailable one (e.g. bisglycinate, citrate, or malate). While the label might feature the more desirable form, the fine print often reveals otherwise.
Why do companies buffer magnesium? Two reasons:
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Cost savings – Magnesium oxide is inexpensive, so it’s used as a filler to bulk up the dose and reduce production costs.
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More elemental magnesium – Magnesium oxide is dense, meaning you can squeeze more elemental magnesium (the actual magnesium content) into a capsule.
Sounds great, right? More magnesium per capsule must be better. Except—you can’t absorb most of it.
Magnesium oxide is poorly absorbed by the body—research shows bioavailability can be as low as 4%. Due to its low absorption rate, magnesium oxide is often used as a laxative—so much of the elemental magnesium it contains may pass through the digestive system without being effectively absorbed.
How to Spot Buffered Magnesium
Buffered blends can be sneaky. Some labels will list magnesium oxide as a non-medicinal ingredient or just mention “buffered magnesium.” Others may omit it entirely. In fact, some manufacturers may not even know that their raw materials are pre-buffered—if their suppliers don’t disclose it.
Here’s a quick trick:
Check the elemental magnesium per capsule. If a magnesium bisglycinate capsule contains more than 100 mg (120 mg at most) of elemental magnesium, there’s a good chance it’s buffered with oxide. Because magnesium bisglycinate is a bulkier compound, it simply can’t pack as much elemental magnesium into a single capsule.
Want to double-check your bisglycinate supplement? Read our article here.
What Are Fillers and Excipients?
Let’s talk about what’s hiding in your capsules besides magnesium. Ever seen the “Non-Medicinal Ingredients” section on your supplement label? These ingredients are known as fillers and excipients.
They serve several purposes:
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Binders: Hold tablets or capsules together.
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Flow agents: Help powders move smoothly through machines.
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Fillers: Bulk up the capsule so it doesn’t look half empty.
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Preservatives: Extend shelf life.
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Colours and flavours: Improve appearance and taste.
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Sweeteners: Especially in chewables and drink powders.
Some are harmless. Others have raised questions.
Common Additives to Watch For
Magnesium Stearate
A widely used flow agent that prevents powders from clumping during supplement manufacturing. It’s considered safe for use in small amounts by most regulatory bodies. That said, it has been known to cause sensitivities in some individuals, and early lab studies raised theoretical concerns about the immune effects of stearic acid—one of its components. However, there’s no strong evidence that magnesium stearate itself compromises immune function. While likely not a big deal for most, it’s something to be aware of if you're aiming for the cleanest supplement possible.
Cellulose Derivatives
Ingredients like microcrystalline cellulose and hypromellose are common in capsules and tablets. They're derived from purified plant fibers—often from wood pulp—and serve as bulking agents, binders, or vegan capsule shells. While these are widely regarded as safe, some individuals with sensitive digestion may experience bloating or changes in bowel habits. That's why we opt to leave them out of our supplements.
How to Choose a Pure Magnesium Supplement
Not all fillers are harmful, but that doesn’t mean they belong in your wellness routine. When scanning a label, fewer ingredients is usually better. If the ingredient list reads like a science experiment or contains names you can’t pronounce, it’s worth comparing with other brands.
Key things to look for:
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Transparent labeling of both medicinal and non-medicinal ingredients
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Reasonable elemental magnesium per dose (pure forms won’t have sky-high numbers)
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No unnecessary fillers, artificial flavours, or sweeteners
The ITL Health Standard: Pure & Simple
At ITL Health, we don’t believe in fluff. Our magnesium supplements contain only what you need—no magnesium oxide, no mystery blends, no questionable additives. Our capsule products are free of binders and excipients. Even our flavoured MAG365 line uses only real fruit extracts and stevia for taste.
We could cut costs by using fillers or buffered blends—but we don’t. Because we believe you deserve exactly what the label says. Nothing more. Nothing less. Just clean, effective magnesium that actually gets absorbed.
Learn about PrizMAG Pure Magnesium Bisglycinate here.
Learn about MAG365 Ionic Magnesium Citrate here.
Learn about MAG3N8 Pure Magnesium L-Threonate here.
References:
Firoz M, Graber M. "Bioavailability of US commercial magnesium preparations." Magnesium Research. 2001;14(4):257–262.
Tebbey, P. W., & Buttke, T. M. (1990). Molecular basis for the immunosuppressive action of stearic acid on T cells. Immunology, 70(3), 379–384.
Tammaro, A., Abruzzese, C., Narcisi, A., Cortesi, G., Persechino, F., Parisella, F. R., & Persechino, S. (2012). Magnesium stearate: An underestimated allergen. Journal of Biological Regulators and Homeostatic Agents, 26(4), 783–784.