However, mice that didn’t have any gut bacteria because they had been raised in a sterile environment didn’t become ill when given the same additives, suggesting that it is the emulsifiers’ effect on the microbiome that is to blame. When the ill mice stopped consuming emulsifiers, their gut bacteria gradually returned to normal.
The question is whether the same might be true for humans. The growing use of emulsifiers has coincided with a rise in obesity and diabetes, says Chassaing, while these conditions aren’t as common in countries where less processed food is consumed.
Now Chassaing has supported his findings in mice using a simulation of the human gut. Working with a team in Belgium, he looked at two emulsifiers: carboxymethylcellulose (E566 on EU labels) and polysorbate-80 (E433). When added to a series of flasks that mimic the conditions of the human digestive tract, each caused an increase in the levels of a bacterial protein called flagellin, known to cause inflammation at high concentrations. Chassaing presented the results at a recent meeting at the Royal Society in London.
The simulator results are more convincing than the mouse studies, since lab animals and humans have vastly different gut microbiomes, says Glenn Gibson of the University of Reading in the UK, who studies gut disorders. “The definitive test, however, is obviously a human trial.”
Chassaing is now enrolling volunteers for the first human trial to look at the effects of emulsifiers on gut and metabolic health. Carrying out this study won’t be easy, he says, as the participants’ diets will have to be strictly controlled.
In his earlier work, the mice were given up to 1 per cent of an emulsifier in their water, which Chassaing thinks reflects the levels some people may be consuming. But Patrice Cani of the Louvain Drug Research Institute in Belgium thinks people who eat a balanced diet are unlikely to be exposed to the levels given to the mice.
Nevertheless, Cani says, we should be concerned. Whatever the results of the human trial, regulators need to rethink the way they test the safety of food, he says, as existing tests were developed before we understood the importance of our gut microbiota and how they can be affected by what we consume.
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Once considered the star attraction of a balanced, healthy plate of food, meat is now linked to obesity, heart disease and cancer. Add the environmental concerns over a growing global appetite for meat, and it seems meat should now be an occasional guilty pleasure rather than a daily staple.
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