Both magnesium stearate and silica are found on the label of a number of supplements, and the presence of these compounds can be quite concerning and confusing for consumers. This article will explain why magnesium stearate and silica are found in so many supplements, and evaluate their safety for consumption.


Purpose in supplements

Both magnesium stearate and silica are used in the manufacturing process of supplements and many pharmaceuticals. Magnesium stearate acts a lubricant, which stops the product sticking to the machinery. This stops blockages, and ensures that the machinery runs smoothly. Silica plays a very similar role, and acts as an ‘anti-clumping’ agent, this not only prevents the machinery from getting blocked, but also ensures that there is an even distribution of active ingredients throughout the mix. Neither compound actually has a function in the final product, but because they are present in the manufacturing process it is inevitable that they will be in the supplements/ tablets at the end of processing.


Effects on health

Magnesium stearate

Magnesium stearate is formed by binding stearic acid with magnesium, and when ingested, these compounds will be split again. Magnesium is required for a number of biological functions, and has no negative effects in the dosages which supplements and food can provide. The magnesium could actually be considered to be an added bonus seeing as so many people are low in magnesium these days, but the amount of magnesium sterate found in most supplements is so small, that the potential health benefits are negligible.

Stearic acid is a long chain fatty acid, and is is abundant in our diets. When was the last time you had some cheese or a bit of meat? This would provide more steric acid than a few capsules do. Foods highest in stearic acid are animal sourced fats, particularly beef fat, but it can also be found in smaller quantities in vegetables. Steric acid has been shown to posses cardio-protective properties as well as neuro-protective properties. There is also evidence to suggest that stearic acid can inhibit the action of T cells in the body. T cells are a very important part of the immune system, and inhibition of these cells can make our body vulnerable to infection. Bearing in mind the abundance of stearic acid in nature and most peoples diet, the amount that you would consume through supplements/ medicines is very low, and unlikely to have any positive or negative impact on your health.

There is also evidence that supplements containing magnesium sterate slowed down the time taken for the supplement to dissolve, but made no difference to the overall bioavailability of the active ingredients. This could actually be seen as a good thing, because it will help to slowly release the active ingredient into the body, which is part of the reason you should take supplements with food. There is more research needed to understand the actual implication of this, but I cannot see it being a negative thing.

Silica (silicon dioxide)

Silica is found throughout your diet, from water you drink, to the vegetables you eat, and it is chemically inert when consumed. There is some evidence to suggest that silica is actually essential for our body in small quantities, which has lead to silica supplements to appear on the market. The actual benefits of silica are actually poorly understood due to the lack of research. A deficiency is associated with poorly formed bones/ joints but a cause and effect relationship has not been established. There is also some evidence to show that silica may cause inflammation in cells, but because research on silica is largely focused on its effects when inhaled, there is only limited evidence to show that silica can cause inflammation in the digestive system.

Ideally, more research is needed on the implications of silica on our health when consumed to get a complete understanding of the compound. However, as it is present in our everyday diet and lifestyle, and the quantity you obtain from supplements very small, any effects (both positive and negative) from consuming silica in supplements will be negligible.


Why the scare?

Many health professionals (including Dr.Mercola) condemn the use of silica and magnesium sterate in supplements, and quote the study I mention above about stearic acid suppressing T cells in the body, and this understandably causes concern for prospective buyers. However, the study was done in vitro (in a cell culture), and doesn’t translate well into a real world situation where you are eating all kinds of food – most of which will contain some amount of steric acid anyway. The study (the abstract of which you can read here) is interesting for understanding molecular interactions, but is far reach from scientific proof that the tiny amount of steric acid in a supplement has any impact on the body.

I can only imagine that the scare is a marketing ploy released by some companies (such as Dr. Mercola’s) which doesn’t use silica and magnesium sterate in their products, and see it as a way of making their product looks superior to others. In reality, the presence of magnesium sterate/ silica is not an indication of quality in a supplement, and there are much more important things to look out for (least of which is the actual active ingredients used).


Magnesium stearate and silica are compounds used in the manufacturing of supplements and medications to prevent blockages in the machinery, prevent clumping and helping to ensure an even distribution of ingredients. As they are used in the manufacturing process, small amounts make their way into the final product, but do not have a function in the final product. Both compounds are found in nature and our diet, and the small amount that you will consume from supplements/ medications is considered negligible. Having said this, it would be beneficial to have more research on the effects of silica on our health when consumed.
Image courtesy of Virany.

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