Fillers: what are they and are they bad for you?

The Vitl Nutrition Team / 22 Aug 2019

Unlike with Vitl, you'll find fillers and bulking agents on many supplement and vitamin ingredients lists. So what are they and why should you be avoiding them?


In recent years there has been a substantial growth in the supplement market. Research on the undisclosed “other ingredients” (aka excipients, inactive ingredients, fillers etc) saturating the supplement industry is often limited, contradictory or controversial. At Vitl, we are committed to ensuring that our ingredients are as pure and absorbable as possible by avoiding the use of fillers, binders or bulking agents that do not provide any nutritional value and may reduce the overall quality and benefit of a product. 

Why are they used?

To reduce manufacturing costs

Many ‘other ingredients’ are used in industry to make the manufacturing and production processes more seamless, resulting in a more affordable end product. With hundreds of supplement companies marketing their products, you may have noticed a vast discrepancy in pricing; in general, when it comes to supplementation, price and quality are synonymous with one another.


Used to achieve desired consistency or texture, either to improve durability or appearance of the capsule itself or within its contents. Excipients can reduce the occurrence of ingredients splitting, separating, cracking or clumping. Often, a combination of stabilisers is more efficient than one used on its own. 


The active ingredient of a supplement often accounts for a small proportion of it, due to the fact that sufficient amounts of vitamins and minerals are visibly pretty tiny (measured in micrograms; 1mcg being 1 millionth of a gram). The majority of supplements consist of bulking agents, adding substance so that you think you are getting your money’s worth. 

Quick stop tour of fillers

  • Magnesium stearate
  • Silicon dioxide
  • Titanium dioxide
  • Starch
  • Microcrystalline cellulose 
  • Stearic acid, simethicone
  • Vegetable gum
  • Talc
  • Propylene glycol

More specifically...

Magnesium stearate (lubricant, stabiliser)

A white powder, often used in the manufacturing process to prevent ingredients from sticking to equipment and machinery. Its sole purpose is ensuring higher output and cycle times of product. As you can see, not a lot to do with nutrition. The European Union and other countries including China, Japan, Australia and New Zealand have permitted the use of Magnesium stearate. The United States also granted the ingredient ‘generally recognized as safe status’ (GRAS). However, some advocate that long-term exposure to the ingredient should be evaluated, as excessive intake of Magnesium stearate has may have a laxative effect on the gastrointestinal system1.

Titanium dioxide

This mineral often used as a colourant to give supplements a bright white colour, making the product more attractive! Titanium dioxide has a number of potential health implications. Research has indicated that titanium dioxide has the capacity to be toxic, it can increase the amount of ‘free radicals’ in our bodies which circulate and cause various levels of trouble to our immune function, metabolism and nervous system to name a few2. There have been studies suggesting that it could be carcinogenic, having exhibited an ability to damage cell structure3.

Silicon Dioxide: Stabiliser (anti-caking), bulking agent

Specifically, this mineral functions as a "flow agent;" used in industry to catalyse the production process. Put simply, silicon dioxide absorbs moisture to help prevent all the active ingredients within the supplement from clumping together. It passes through the body without reacting with the active ingredients within your supplement. It is thought that silicon dioxide is able to sneak across our ‘blood brain barrier;’ a membrane that protects our brain from harmful substances and research is ongoing to investigate the health implications 4,5. Ultimately, we believe the only things we should be putting in our supplements should be beneficial, active ingredients. So, when it comes to silicon dioxide, we think "what’s the point?!”

Hydrogenated Oils: lubricant, stabiliser, binder, bulking agent

In recent years, you may have heard the term ‘trans fats’ being vilified in headlines. Although you might do well to avoid them in your daily life, these can sneak their way into your diet unexpectedly- we help you to reduce the incidence by avoiding the use of hydrogenated oils at Vitl! Used in many products to extend their shelf life, hydrogenated oils have been shown to have harmful health associations6 with a particular correlation between their high intake and complications in those with Coronary Heart Disease7. Evidence has also emerged suggesting adverse effects on the nervous system, potentially reducing mental performance8.

How Vitl does it differently

Our brand differs from numerous others by being 100% committed to avoiding the use of fillers in any of our formulations. To ensure maximum absorption, we only use the highest quality ingredients in our products and avoid using any that are unnecessary. We keep informed about the latest nutritional science and use it to combine the purest form of each vitamin and mineral with food state supplements for maximum efficacy.

The vast quantity of nutritional information online can be overwhelming, with as much advice being anecdotal as it is based on evidential science. Ultimately we have to make informed decisions about what we wish to consume or avoid. We hope however that Vitl’s commitment to evidence-based research can reassure you that you know exactly what you’ve bargained for when it comes to using our products. Click here to start your free 30-day trial of filler-free, personalised vitamins today!