The Black Death may be responsible for us eating junk food today, suggests new research.
The Second Plague Pandemic of the mid-14th Century, also known as the Black Death, killed up to 60 percent of people living in Europe – and profoundly changed the course of history.
Now new research suggests that the plague, potentially through resulting changes in diet and hygiene, may also be associated with a shift in the composition of the human oral microbiome toward one that contributes to chronic diseases in modern-day humans.
Professor Laura Weyrich, of Penn State, said: “Modern microbiomes are linked to a wide range of chronic diseases, including obesity, cardiovascular disease, and poor mental health.
“Uncovering the origins of these microbial communities may help in understanding and managing these diseases.”
She explained that dietary changes are believed to have influenced oral microbiome evolution through time.
But few studies have directly examined the history of human oral microbiomes in a single population.
Prof Weyrich noted that some studies have used the microbiomes of living indigenous people who practice traditional subsistence lifestyles as a proxy for the microbiomes of pre-industrialised people.
But she says that strategy is faulty because modern-day non-industrialized populations may not have microbes that accurately reflect those that existed in the ancestors of industrialized people.
Prof Weyrich said: “This research places unnecessary responsibilities and obligations on Indigenous communities to participate in microbiome research, where the benefits of these studies may not directly serve Indigenous peoples.”
She said a more accurate and ethically responsible method is to directly examine the oral microbiomes preserved within calcified dental plaque, known as calculus, from the ancestors of Industrialized people.
In the largest study to date of ancient dental calculus, Prof Weyrich and her colleagues collected material from the teeth of 235 people who were buried across 27 archaeological sites in England and Scotland from about 2,200 BC to 1853 AD.
The researchers processed the samples in an ultra-sterile, ancient DNA lab to minimize contamination.
They identified 954 microbial species and determined that they fell within two distinct communities of bacteria – one dominated by the genus Streptococcus – which is common in the oral microbiomes of modern Industrialized people – and the other by the genus Methanobrevibacter – which is now largely considered extinct in healthy industrialized people.
Exploring the origins of the two communities, the researchers found that almost 11 percent of the total variation in microbiome species composition could be explained by temporal changes, including the arrival of the Second Plague Pandemic.
Prof Weyrich said: “We know that survivors of the Second Plague Pandemic earned higher incomes and could afford higher-calorie foods.
“It’s possible that the pandemic triggered changes in people’s diets that, in turn, influenced the composition of their oral microbiomes.”
The team used a new approach to investigate whether a change in diet could have influenced the emergence of the Streptococcus group and the extinction of the Methanobrevibacter group.
They put together a list of functional differences among the bacteria in the two groups that could be linked to diet; for example, functions linked to high or low-dietary fiber digestion, carbohydrate metabolism and lactose metabolism.
The research team found that the bacteria in the Streptococcus-dominated group had more functional traits that are significantly linked with low-fiber, high-carb diets, as well as dairy consumption – all of which characterize modern-day diets.
By contrast, the Methanobrevibacter-dominated group were missing traits associated with dairy and sugar consumption, which characterized the diets of some ancient humans.
The team further determined that the Streptococcus group was associated with the presence of periodontal disease, which is characterized by infections and inflammation of the gums and bones around the teeth.
When the disease progresses, bacteria can enter the bloodstream through gum tissue and potentially cause respiratory disease, rheumatoid arthritis, coronary artery disease and blood sugar issues in diabetes.
The Methanobrevibacter group, on the other hand, was associated with the presence of skeletal pathologies.
Prof Weyrich said: “Our research suggests that modern-day oral microbiomes may reflect past changes in diet, resulting from the Second Plague Pandemic.”
She added: “Importantly, this work helps to inform our understanding of modern-day chronic, non-communicable diseases.”
Produced in association with SWNS Talker
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