Love junk food? Blame the Black Death: Scientists claim plague that killed 60% of Europeans changed our mouth bacteria

The Black Death may have contributed to our love of fast food today, a study suggests.

The second plague pandemic in the mid-14th century, also known as the Black Death, killed up to 60% of people living in Europe and profoundly changed the course of history.

It causes fever, fatigue, and vomiting, in addition to large, painful swellings called buboes in the thighs, neck, armpits, and groin.

But experts now suggest it may be linked to our love of fast food today, due to dietary and hygiene changes during this period.

Analysis of calcified dental plaque from skeletons spanning thousands of years has revealed that the dominant bacteria found in our mouths today are linked to low-fibre, high-carbohydrate diets, as well as dairy consumption.

All of these factors characterize modern diets – such as fast food – and global events such as the Black Death may have led to the dominance of these bacteria, they said.

Changes in diet and hygiene around the plague are thought to have affected our oral microbiome, the community of microorganisms, mostly bacteria, found in our mouths.

This mixture of bacteria within the body is known to be linked to immune, heart and brain health, but can also be linked to certain diseases.

The study, which was published in the journal Nature Microbiology, was supervised by scientists from Pennsylvania State University in the United States and the University of Adelaide in Australia.

Pictured are the remains of people buried in the plague pits at East Smithfield in London, which were used for mass burials in 1348 and 1349.

Professor Laura Weyrich, from Penn State, said: “Modern microbiomes are associated with a wide range of chronic diseases, including obesity, cardiovascular disease and poor mental health.”

“Uncovering the origins of these microbial communities may help understand and manage these diseases.”

Her team collected material from the teeth of 235 people buried at 27 archaeological sites in England and Scotland from about 2200 BC to 1835 AD.

After processing the samples, they identified 954 microbial species that fell into two different bacterial communities.

One was dominated by the genus Streptococcus, which is common in the mouths of modern people, and the other was dominated by the genus Methanobrevibacter, which is now considered largely extinct in healthy people.

The analysis revealed that approximately 11% of the variation in the microbiomes they discovered could be explained by changes over history, including the arrival of the Black Death.

“We know that survivors of the second plague pandemic had higher incomes and could afford higher-calorie foods,” Professor Weyrich said.

“The pandemic likely brought about changes in people's diet, which in turn affected the composition of the microbiome in the mouth.

“This is the first time anyone has shown that the microbes in our bodies may have been affected by things like previous pandemics.”