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Gut Reactions: U of G Study Finds Food Dyes Can Harm Gut Microbes
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Food dyes might make food look more appealing, but their safety has
long been controversial. New research from the University of Guelph
reveals an unexpected way these compounds may be harming health: by
disrupting the microbial communities in the gut.
In two new recently published papers, researchers from the College of
Biological Science found that commonly used food dyes can break down
in the gut to create potentially toxic byproducts.
Our gut microbiomes contain bacteria, fungi and other microbes that
help break down food and stimulate our immune systems. Imbalances
between good and bad microbes have been shown to result in several
health issues, says Dr. Emma Allen-Vercoe, professor in the Department
of Molecular and Cellular Biology (MCB).
"I don't think that anyone realizes how fragile the gut microbiome
is," says Allen-Vercoe, Canada Research Chair in Human Gut Microbiome
Function and Host Interactions.
"Why are so many of us missing certain microbes, and how did we lose
them? One potential reason is all the artificial stuff we put into our
food, including food colourants, which few people have looked at."
Allen-Vercoe, along with MCB colleague and biochemist Dr. David
Josephy, set out to address this knowledge gap by investigating azo
food dyes, the class of synthetic dyes commonly used in food, drugs
and cosmetics.
Allen-Vercoe's team wanted to investigate how bacteria in the human
gut metabolize or "reduce" azo dyes, and how the resulting compounds
impact the growth of gut bacteria.
Four azo dyes are currently approved for human consumption in Canada:
amaranth, sunset yellow, allura red and tartrazine. Many others are
banned as a result of unacceptable toxicity.
### Food dyes' interaction with gut microbiome not well tested
The food dyes included in the research were amaranth, allura red,
sunset yellow, and tartrazine
While azo dyes have been tested for effects on animal cells, where
they tend to be inert, their ~~~~ interactions with microbial cells
have been mostly ignored and were not considered in the drafting of
current food dye use regulations. That's despite the fact that there
is evidence azo dyes can be reduced by gut bacteria to create new
metabolites that may be toxic.
"Bacteria in particular have had many eons longer than we have had to
evolve. Consequently, they are incredible biochemists and azo dye
reduction is not difficult for them" says Allen-Vercoe.
To evaluate the response of gut microbes to the four azo dyes, Allen-
Vercoe's team grew over 124 human gut bacterial species in culture
media infused with one of the four approved dyes.
Any bacterial strains that could break down the dyes - as revealed by
the disappearance of colour from the growth medium - were further
tested to assess how well they functioned amid the breakdown products
of azo dye reduction.
The study, published in the journal _Anaerobe_ _,_ revealed that many
of the bacterial species typically found in the human gut could
extensively reduce the dyes.
Amaranth was reduced the most frequently by gut bacteria, while
tartrazine was reduced the least, although still by a substantial
number of strains. In many cases, different strains of the same gut
bacterial species showed variability in their reductive capabilities.
### Food dye regulations outdated, say researchers
Molecular biologist Dr. Emma Allen-Vercoe has been researching the
effects of synthetic food dyes on the gut microbiome.
The team also found contrasting growth responses of gut bacteria upon
exposure to azo dyes and their breakdown products. Some gut bacteria
increased in growth while for others, growth was inhibited. For
example, bacterial reduction of sunset yellow and tartrazine led to
the formation of sulfanilic acid which was toxic to some bacterial
species.
The findings might __ help explain why some people are more sensitive
to azo food dyes than others. Everyone has a unique gut microbiome,
and thus some people may harbour more microbes that reduce azo dyes to
toxic metabolites, compared to others.
The team also conducted a second collaborative study with colleagues
in New Zealand, published in the journal _Food and Chemical
Toxicology_ , focusing solely on tartrazine. That study further
revealed the reduction products of the dye in the gut and their toxic
impacts on host cells.
Allen-Vercoe says the studies emphasize the need for food dye
regulations to be updated to include the latest findings. She notes
that most of the current regulations are based on research from the
1950s and '60s that considered only the effects of the dyes on animal
cells, and not the way the compounds are metabolized in the gut.
She adds that the risks from azo dyes concern her. "If I were able to
listen to my gut microbes, they would tell me to stop consuming
artificially coloured foods."
Synthetic food colourings such as azo dyes contain no nutritious
qualities, she points out, and are added to food simply to make it
look more attractive.
"We need the food industry to quickly get on board with this research
and, ultimately, to remove azo dyes and other artificial colours from
their products."
This research was funded by the Canada Research Chair program and the
New Zealand Royal Society.
* * *
_Written by Sujani Rathnayake. Sujani is a writer with SCRIBE, a
program for graduate students in the College of Biological Science to
gain paid experience in translating research results for a non-
specialist audience._
##### Contact:
Dr. Emma Allen-Vercoe
eav@uoguelph.ca
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