Researchers from the Medical University of Vienna found that stools from individuals in Finland, Italy, Japan, the Netherlands, Poland, Russia, the UK and Austria all tested positive for microplastics.
And worryingly, the team discovered that some individuals had up to nine different types of plastic.
Dr Philipp Schwabl, who led the study, said: “This is the first study of its kind and confirms what we have long suspected, that plastics ultimately reach the human gut.”
In the study, eight participants from across the globe kept a food diary for a week, before providing a stool sample.
The diaries revealed that all participants were exposed to plastics by consuming plastic-wrapped foods, or drinking from plastic bottles.
None of the participants were vegetarians and six of them consumed sea fish.
An analysis of the stool samples revealed that up to nine different plastics were present - with an average of 20 micro plastic particles per 10g of stool.
Worryingly, the effect of these plastics on the human body remains unclear.
Previous studies have suggest that they may impact the GI tract, and could lead to a build-up of toxic chemicals in the gut.
Dr Schwabl added: “Of particular concern is what this means to us, and especially patients with gastrointestinal diseases.
“While the highest plastic concentrations in animal studies have been found in the gut, the smallest microplastic particles are capable of entering the blood stream, lymphatic system and may even reach the liver.
“Now that we have first evidence for microplastics inside humans, we need further research to understand what this means for human health."