Diet changes following Black Death linked to chronic diseases 

A new study has linked the second plague pandemic, infamously known as the Black Death, with shifts in human oral microbiomes. 

The research suggests that the long-term consequences of the plague may reach far beyond what we initially understood, possibly shaping our current struggle with chronic diseases.

“The prevalence of chronic, non-communicable diseases has risen sharply in recent decades, especially in industrialized countries. While several studies implicate the microbiome in this trend, few have examined the evolutionary history of industrialized microbiomes,” wrote the study authors. 

Black Death

The second plague pandemic was a catastrophic event in the mid-14th century that killed 30 to 60 percent of the European population. 

The repercussions of this mass mortality event are well-documented, but a recent study from Penn State and the University of Adelaide sheds new light on the legacy of the Black Death.

Modern microbiomes 

The researchers found that the plague may be associated with a shift in the composition of the human oral microbiome due to the resulting changes in diet and hygiene.

“Modern microbiomes are linked to a wide range of chronic diseases, including obesity, cardiovascular disease and poor mental health,” said study co-author Professor Laura Weyrich. “Uncovering the origins of these microbial communities may help in understanding and managing these diseases.”

According to Professor Weyrich, 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. 

Faulty strategy 

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-industrialized peoples. 

Yet, this strategy is faulty, said Weyrich, because modern-day populations may not have microbes that accurately reflect those that existed in the ancestors of industrialized peoples. 

“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.”

Comprehensive analysis 

The team examined dental calculus from 235 individuals spanning from 2200 B.C. to A.D. 1853 across 27 archaeological sites in England and Scotland. 

The researchers identified 954 microbial species, falling into two distinct bacterial communities: one dominated by Streptococcus, common in modern industrialized populations, and the other by Methanobrevibacter, now nearly extinct in healthy industrialized people.

Dietary influence

The research team explored how dietary changes, possibly following the Black Death, could have influenced these microbiome shifts. 

The experts found that the Streptococcus-dominated group aligns with modern diets that are high in carbohydrates and low in fiber, while the Methanobrevibacter group lacked traits associated with such diets.

Implications for modern health

The experts discovered that the Streptococcus group is associated with periodontal disease, which has far-reaching health implications. Conversely, the Methanobrevibacter group correlated with skeletal pathologies. 

This indicates that changes in diet, potentially stemming from the Black Death, might reflect in today’s oral microbiomes, influencing the prevalence of chronic diseases.

“Our research suggests that modern-day oral microbiomes may reflect past changes in diet, resulting from the second plague pandemic,” Weyrich said. “Importantly, this work helps to inform our understanding of modern-day chronic, noncommunicable diseases.”

The research is published in the journal Nature Microbiology.

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