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Does Sodium Benzoate react with Vitamin E to form Benzene?

February 8, 2019

Feliz Viernes Mi Amigos!

I’ve got a couple of half-finished posts to put up but this one question flew up this morning and as I had to answer it I thought I’d may as well make that today’s post by sharing it.   Just an aside, for those of you that don’t know, I’m a consultant chemist. I get questions all of the time, I can’t share all of the conversations I have as some are very brand specific and sensitive to their IP. Others though are more generic and I do draw on some of those conversations for my blog posts, when I think there is a shared learning to be had that benefits everyone and yes, I include myself in that.

So here we go.

I have a customer who has been asked to ‘please explain’ why they have vitamin E and Sodium Benzoate in their formula together? Apparently the inter webs state that this is not good, that this will react to form benzene and that we will all die of benzene cancer if the brand doesn’t cease and desist.  Something like that anyway…

So is it true?

In my typical style I could answer that with a quick answer, yes or no, or I could go on a verbal rampage through the chemistry laboratories of history. I prefer the latter but for all of you time-poor people I’ll tell you now that the fact that this information even persists on the internet feeds my theory that humanity is becoming increasingly stupid and that we are all going to die – I have it on good authority that the latter part of that statement is 100% pure and unadulterated 🙂

Let’s dive in.

Me in my polite writing voice:
Thanks for the question.  I’ll answer it as best as I can below.
Firstly I have not come across this concern before.
There has been a long-running ‘warning’ on health blogs etc about sodium benzoate and vitamin C.  This warning is grounded in science and there is a risk of reaction between sodium benzoate and ascorbic acid to liberate benzene. Benzene is a carcinogen.  However,  just because this reaction is possible it doesn’t mean that it is always inevitable.  It can be possible but not probable,  probably but not situationally likely, likely but preventable, highly likely but insignificant in effect (due to it being so small a reaction/ wrong delivery system/ bodies ability to process etc…
In the case that first brought this to the public attention a solution was applied and the problem ceased to be a problem but like the proverbial elephant, the internet never forgot the problem and, more importantly, never moved on with the facts.
Here is what I wrote about that:
And here is the reaction – it is a REDOX reaction – oxidation/ reduction – that’s relevant as that’s the extrapolation that puts vitamin E into the equation.
So back to Sodium Benzoate and Tocopherol. 
A very quick google search brings up a couple of blogs that do make the statement that vitamin E can also react with sodium benzoate to form benzene.  I know some of the writers of those blogs and it is safe to say that they don’t have a background in chemistry.  Others I think may just have copied and pasted.
Taking a step back it is worth noting that many natural and organic certified brands hate the idea that others in their demographic can use sodium benzoate and/or potassium sorbate and still gain certification/ kudos in their space.  These are cheap, effective preservatives that are common to many raw materials that need preserving too so it opens up a world of opportunity that some brand owners can’t access because they can’t get past the reality that is that these chemicals are synthetic.
Now that may be an over-simplification and me projecting what I’ve seen, discussed and read with/ about these people but you can take from it what you will.
Sodium Benzoate is the salt of benzoic acid. Benzoic acid occurs widely in nature in fruits and benzoin resin and it from here that we (the scientific community) first noted the anti-microbial effects of this chemistry.
Sodium Benzoate vs Benzoic acid – I discuss this in this blog post here:
There is a scientific journal article here that also explains how we can use ‘green chemistry’ to convert Benzoic acid to benzene so you can see that the sodium benzoate is not unique in being able to turn into benzene – so it isn’t a case of human interference that has taken something natural and safe and made it less so.

An Efficient Production of Benzene from Benzoic Acid in Subcritical Water Using a Copper (I) Oxide Catalyst

ArticleinGreen Chemistry 17(2) · October 2014 with 302 Reads
A method combining subcritical water technology and a commercially available copper (I) oxide catalyst has been performed for the production of benzene from benzoic acid. The benzene yield reached 91 mol% with 100% selectivity at 350°C and ~25 MPa in 90 min. This is the first time to realize the reaction from benzoic acid to benzene environmental-friendly, efficient and economical. The proposed reaction mechanism indicates that Cu2O was an effective and stable catalyst, and the process was driven by the unique properties of subcritical water: high ion product, the high solubility of products and high diffusivity.
So back to the question:  Vitamin E plus Sodium Benzoate – will they react to form benzene.
The answer to this is no, highly unlikely.
Ascorbic acid is very reactive, low pH, water-soluble.
Ascorbic Acid acts as a reducing agent in this reaction so it takes something away from the sodium benzoate (the sodium) and kick-starts a reaction that leads to benzene.
Tocopherol is a reducing agent, all anti-oxidants are, this is REDOX chemistry and involves the swapping of electrons between chemicals.
But just because something is a reducing agent doesn’t mean that it will want to play with everything that can be reduced.  You must find the right partner for the job and in the case of sodium benzoate, it isn’t the right partner.
This is tocopherol – no  Na group – sodium functional head group. 
Vitamin E will not readily react with sodium benzoate because sodium benzoate is not on its radar (in the oil phase/ right chemistry).  What vitamin E will react with is peroxide and that is formed when fats oxidise.  Vitamin E basically neutralises the peroxide radical thus taking the sting out of its tail and preventing it from going on and turning the whole fatty phase rancid.
The final piece of the puzzle is the vitamin E/ Vitamin C link.
When an antioxidant reacts is is ‘used up’ somewhat.  Some antioxidants can be recycled if they have a little help.  Vitamin C helps vitamin E to recycle by chemically interacting with it to bring the vitamin E back to it’s relaxed state, it’s a chemical pacifier 🙂  
In a formula it is normal to have vitamin E and C together in some shape or form to help maintain product integrity.  
Sodium Benzoate is sometimes part of a formula as a preservative.  It can be kept ‘safe’ by using it at or below the specified levels, using a chelating agent to help prevent it from premature break down and by taking steps with packaging to maintain good stability.   It is not necessary in my opinion to avoid sodium benzoate, especially not as it is one of the most natural options for product preservation, is low-cost,  is used  widely by ingredient manufacturers and is readily available.
Just one other note,  any formulation that contains fruit extracts (water based) and / or the following aromatics has a formula that contains vitamin C and benzene precursors.  Any formula that contains natural oils contains vitamin E.  So, most natural formulations contain all three whether they were formulated in as separate ingredients or brought in by virtue of their natural presence.  
Ylang Ylang
Tolu Balsam
Peru Balsam
Ginger Lily
I hope that helps somewhat.
Before I sign off I want to say a huge Gracias to all of my readers who persist in grappling with this stuff.   We are often talked down to in modern-day society, the media talks to us like we are 12 years old as does politics, we need to stand up for our thinking space and that’s often right slap bang in the middle of a situation.  Things are rarely 100% right or 100% wrong, there is much detail and beauty that is missed by falling into those types of thought pattern.  I hope you continue to hang with me in this middle space as I have personally found much here to be joyful about.
Adios x
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