Q and A: Why this microbiologist is warning people not to ingest some food dyes

Apicius, the first-century Roman foodie, is said to have coined the phrase: "we eat first with our eyes," and after just under 2,000 years the sentiment remains true.

But appealing as some modern food may be to the eyes, the food dyes that help make it that way may be harming your gut biome by creating potentially toxic byproducts.

New research from molecular biologist and University of Guelph professor Emma Allen-Vercoe, shows that when microbes in our gut try to break down a particular group of these food dyes, toxic and acidic compounds form.

She joined CBC Kitchener-Waterloo's The Morning Edition with host Craig Norris to talk about where these dyes are found, how to avoid them, and what needs to be done.

This interview has been edited for length and clarity. 

Craig Norris: Tell us more about your study and what you found out about food dyes.

Emma Allen-Vercoe: I'm a microbiologist, I work on the gut microbiome, and the gut microbiome is a key piece in this story. And the reason for that, is that I think in the past it was assumed that artificial food dyes, in particular what we call azo dyes, were thought to be fairly inert and you could consume a lot of them, they're not going to do very much. And I think that's how they've been regulated.

But what we've found is actually that when you ingest these dyes, the human part of your body can't do anything with them. But the microbes that live in your gut are very good at breaking these things down. When they break them down, they turn into not such nice products that can actually be toxic to your cells.

CN: What kinds of foods might these dyes be in?

EA: Well, anything bad. And again, I should point out that natural food dyes are a very different class. They're pretty harmless, but these azo food dyes tend to be used in heavily processed foods.

You'd see them mostly in things like candy, sports drinks, anything brightly coloured that doesn't look natural is probably because it is coloured with azo dyes.

They're also found in cosmetics and in drugs. So some of your cold medication, for example, that brightly red coloured syrup that you take when you're feeling rough is probably coloured with azo dyes as well.

CN: So why are these kinds of dyes used?

EA: That's the question I've always asked. I'm from the U.K. and in the U.K. these aren't used nearly as much. So when I first arrived in Canada, I was kind of shocked by the colour of candy and food in general.

The reason why these things are used is a little bit obscure to me because they actually have no nutritive value. They don't add anything to the food in terms of flavour, taste or nutrition. They only add colour.

So it's all about aesthetics. The kinds of foods that these materials are put into are the kinds of foods that you probably shouldn't be eating anyway. I believe that the reason that they're coloured that way is to make them look more appealing especially to children. That's a big concern that I have.

CN: Who do you think should be paying attention to this research?

EA: Three groups of people.

The first would be the general public. We're always hearing about what we should be eating and what we shouldn't be eating, and it's actually relatively easy to look on a food wrapper and see whether the food contains azo dyes in terms. A few that come to mind, one is called Tartrazine, another one is called Allura Red.

The second group that I think should pay attention to this are the food manufacturers themselves. They're probably going to be the toughest ones to sway because they've been using these kinds of food dyes forever.

They're very easy to use because they're very stable compounds in terms of their chemistry. So it means that you can add them into foods, you can heat them and dry them and expose them to light and all sorts of things, and it won't do anything to the dye,

And then the third group of people that I think should sit up and take notice is probably Health Canada. They're the ones that govern the use of food dyes in foods.They are being good, they're looking at how these dyes are being used. But they're probably using a lot of information based on original studies where, you know, rats were fed a whole bunch of Allura Red or something. We're talking about in the 70s and maybe the 60s even. They weren't looking at the gut microbiome back then.

CN: What then needs to happen moving forward to get to those regulations on food dyes?

EA: I think it's really just awareness. I mean, we just started the process of looking at this, and what our study found was that actually a huge number of microbes live in the guts are actually able to break down these food dyes and they can make compounds which are toxic.

I think we need to do further research to understand what those toxic compounds are actually doing. Everyone has a different gut microbiome, so everyone's going to have a slightly different reaction to these dyes. I mean, in my mind it just makes total sense to remove these things from food entirely because they add nothing to the food apart from colour.

LISTEN | Molecular biologist and University of Guelph professor Emma Allen-Vercoe on food dyes: