Magnesium stearate in D-mannose

When shopping for D-mannose you might see that some manufacturers advertise that their D-mannose is “Magnesium stearate free”. Do you need to be concerned about Magnesium stearate when choosing D-mannose supplement and should you choose the brands that do not use it in their manufacturing processes?

Apparently, magnesium stearate has been a controversial topic for health conscious crowd for ages. Let’s see what are the concerns and if they are fact based.

D-mannose and UTI
Most likely your D-mannose contains magnesium stearate

What is magnesium stearate?

Magnesium stearate is a “flow agent” that is widely used in supplement manufacturing to make sure that ingredients do not stick to the equipment and also stay blended together. If your supplement mentions “vegetable stearate” or “steric acid”, it is pretty much the same thing. So it is everywhere if you look!

Magnesium stearate is a magnesium salt of stearic acid.  It’s a compound containing two stearic acids and magnesium. Stearic acid is a saturated fatty acid found in many foods, including animal and vegetable fats and oils (beef, cocoa butter, coconut oil, and flaxseeds to name a few). Once consumed, magnesium stearate breaks down into it’s components and your body will process stearic acid and the mineral (magnesium).

Concerns rebuffed: toxicity.

One of the concerns you can find online is that magnesium stearate suppresses immune system. Interesting fact: the study that is linked to the majority “toxicity” and “immune suppression” claims (Molecular basis for the immunosuppressive action of stearic acid on T cells) was not even testing magnesium stearate. The experiment was with plain stearic acid and it was used in enormous amounts on the cells of mice. The cells were isolated and were exposed to large quantities of stearic acid. Why does it matter? Well, these were isolated cells, that means the experiment did not mimic normal conditions (our T-cells are not bathed in stearic acid, even if you consume superhuman amounts of coconut oil, tallow, and cocoa butter). Bottom line: this study has nothing to do with reality and you should not be worry about it. It wasn’t even testing the compound in question!

There is no evidence that magnesium stearate is toxic in the amount which is found in the prescription medicines and diet supplements.

Magnesium stearate typically represents 0.25 [percent]–1.5 percent of the tablet weight. Therefore, in a 500 milligram tablet, the amount of stearic acid would probably be about 25 milligrams, and magnesium stearate about 5 milligrams.

You can also find concerns ranging from pesticides and GMOs, to biofilms and drug absorption issues caused by magnesium stearate, but none of the concerns were substantiated so far and I would not be particularly worried about these speculations.

Possible risks: Allergies

A recent study  (“Magnesium stearate: an underestimated allergen”) reported on a 28-year-old woman who had an allergic reaction to magnesium stearate, resulting in hives. Since it hasn’t been clinically tested, let’s agree that pretty much anything could cause an allergy, including magnesium stearate. It is wise to be aware of the common allergy symptoms (skin itching, running nose, breathlessness) especially when taking D-mannose with magnesium stearate in large doses, such as when you are supplementing your UTI treatment. Alternatively, you can choose to purchase D-mannose that is free of this additive.






  1. I am an absolute witness to the reactions that magnesium stearate causes. I was in need of some vitamin D so my doctor prescribed a weekly dose. My hands cramped up so bad I got trigger thumb in my right hand. When I told them where it came from she told me it was out of the question. I stopped taking it until I could investigate only to find the problem as I thought came from the magnesium stearate in the pills. I use gummy bears or nothing. The doctors are telling people it is not this magnesium stearate product but I know it is a dangerous ingredient for some of us.


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