Is Magnesium Stearate Safe in Supplements?

Magnesium stearate is a compound made up of two components: magnesium and stearic acid.

Magnesium is used hundreds of different enzymatic reactions. You know this.

Stearic acid is a saturated fatty acid found in all animal foods and some plant foods such as cocoa butter and shea butter. Stearic acid, FYI, was found to lower cholesterol in this study.

Stearic acid is obtained from fats and oils by the saponification of triglycerides using hot water (about 100 °C). The resulting mixture is then distilled.

Conclusion: If you want to skip the entire article, the gist of it is simple: magnesium stearate is safe, and even beneficial.

Why is Stearic acid and stearates used in supplements?

Before they’re assembled into pills, most supplements and drugs exist in powder form. And as those powders travel through the pill-making machines, they can clog and clump, and gum up the works. Magnesium stearate is added to the powders to keep them flowing smoothly. Of course, it is possible to make pills without magnesium stearate, but it’s harder, it takes longer, and it costs more.

Even if you disagree with the benefits of mag stearate or the need for making pills, you can hardly argue that it’s a source of anything that isn’t normally found in the diet.

Either way, you’re not getting that much.

The amount of mag stearate in a capsule is tiny…. around 10 mg. If you took 100 capsules, that means you are getting 1 gram of mag stearate or 1/28th of an ounce.

Now, of that magnesium stearate, about 7% of it is magnesium, or 70 mg. Consider that a bonus. We need plenty of magnesium to keep the cellular wheels turning.

The other 93% of that magnesium stearate is stearic acid. Again, doing the math — again, assuming you’re taking 100 pills a day — you’re getting 930 mg of stearic acid – less than a gram of fat. You get that much stearic acid in a single ounce of cashews, or a 1/4 of an ounce of 65% dark chocolate. To think of it another way, you’re getting as much stearic acid in a single 3-ounce chocolate bar as you are in 1,200 standard capsules.

And we see study after study showing stearic acid is heart healthy. So, what’s the problem?

Let’s address some other concerns voice on the internet.

Magnesium Stearate blocks nutrient absorption. Stearates can slow down absorption, but not decrease absorption. Big difference. If anything, fat soluble nutrients like A, D, E and K should be better absorbed because of the fatty acid, stearate.

Generally, things that break down more slowly don’t spike blood levels as dramatically, but they tend to maintain steady, consistent blood levels over a longer period of time. A number of studies have been conducted to examine total absorption of drugs prepared with stearates (in much higher levels than you’d see in supplements, added deliberately to slow tablet break-down). Stearates did not decrease total bioavailability.

Magnesium Stearate contains stearic acid, a dangerous saturated trans-fat. No. Not only is this untrue, it is chemically impossible: if it’s saturated, it cannot be trans.

Magnesium stearate contains stearic acid, which if not from animals, is produced by hydrogenation. And hydrogenation is bad because it uses toxic metals which leave residues in the finished product. This sounds like a legitimate concern. But the contamination left behind is largely theory. Stacked against theory and suspicion is lab testing: legitimate supplement manufacturers test for heavy metals.


There are plenty of concerns in the supplements industry. That is why we research our products and manufacturers, even visiting their facility. But mag stearate is not one of those concerns.

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