Magnesium Stearate: What It Is and Why Health Leads Does Not Use It
If you've ever turned over a supplement bottle and scanned the "Other Ingredients" list, you've almost certainly seen magnesium stearate. It's in the vast majority of capsule and tablet supplements on the market — and it's one of the reasons Health Leads has been doing things differently since 1998.
What Magnesium Stearate Is
Magnesium stearate is a salt formed from stearic acid (a common saturated fatty acid) and magnesium. In supplement and pharmaceutical manufacturing, it functions as a lubricant or flow agent — it prevents powders from sticking to equipment and to each other, allowing ingredients to flow freely through high-speed capsule filling machines without clumping or jamming.
At concentrations of 0.25–1% of the total formula, it makes the manufacturing process significantly more reliable and efficient. For high-volume supplement manufacturers producing millions of capsules, it's essentially standard practice.
Is It Harmful?
Regulatory agencies including the FDA and EFSA consider magnesium stearate safe at the concentrations used in supplements and pharmaceuticals. At these levels — well under 1% of the capsule contents — the evidence for harm is not compelling.
Some researchers have raised questions about whether magnesium stearate could form a hydrophobic film around active ingredients, potentially slowing dissolution and absorption. In-vitro (laboratory) studies have shown reduced dissolution rates at higher concentrations. Human clinical data is limited. At the concentrations typically used, mainstream nutrition science considers the practical impact on absorption to be minimal.
The honest position: it's probably fine in the amounts used. But "probably fine" isn't the same as "preferable" — and there's a reasonable argument for not including it if you don't need to.
What Health Leads Uses Instead
Since 1998 we've used rice flour as our standard filler across the entire range. Rice flour is a straightforward food ingredient — no special classification, no known absorption interactions, suitable for virtually everyone.
Using rice flour instead of magnesium stearate requires more careful manufacturing. Dry powders don't flow as easily without a lubricant, which means tighter control of equipment speed, humidity and batch consistency throughout production. It's more demanding to do well — which is why most manufacturers don't bother.
How to Read a Supplement Label
Excipients appear in the "Other Ingredients" section. Common ones to know:
- Magnesium stearate — lubricant/flow agent, found in the majority of supplements
- Silicon dioxide — anti-caking agent
- Microcrystalline cellulose (MCC) — bulking agent
- Titanium dioxide — whitening agent used in capsule shells
- HPMC (hydroxypropyl methylcellulose) — vegetarian/vegan capsule shell material
- Gelatin — animal-derived capsule shell material
A supplement listing only the active ingredient and a single food-grade filler is genuinely additive-free. Every Health Leads product lists its full formulation on the label and product page — nothing hidden, nothing unexplained.
The Bottom Line
Magnesium stearate isn't a scandal — it's a manufacturing convenience that most of the industry uses because it makes production easier and cheaper. We don't use it because we've always believed you shouldn't need to add something to a supplement purely to make it easier to manufacture. Rice flour does the job, and it's a food ingredient. That's the standard we've held since the beginning.
Health Leads — additive-free supplements since 1998. Every product in our range uses rice flour and nothing else as filler. No magnesium stearate, no silicon dioxide, no flow agents. Made in Wales. Browse the full range →