Gaby
Despite the fact that fruits and vegetables are a key part of the human diet, scientists are just beginning to understand how our bodies break down the most common organic compound on Earth—cellulose. This sturdy material lines the cell walls of plants.
A new study conducted by an international team of researchers has uncovered previously unknown microbes hiding in the human gut that are capable of breaking down cellulose.
What the Researchers Discovered
For decades, it was believed that cellulose could not be broken down by the human body, unlike in the guts of cows, horses, sheep, and other mammals.
The researchers dedicated their work to searching for the genes of a specific bacterium to identify others similar to it. In their comprehensive analysis, the scientists used stool samples to test the microbiome of people from various eras and regions. The data obtained suggests that we have more in common with agricultural animals than one might think.
It turns out that our gut contains several types of microbes that consume cellulose, which had previously eluded our attention. One type is closely related to hoofed mammals, another to primates, and a third to humans.
All three types belong to the genus Ruminococcus. They are known to have representatives in both healthy (and unhealthy) human guts. They also possess genes involved in cellulose digestion, as reported by Science Alert.
In the stool samples of ancient humans, particularly hunter-gatherers who lived 1,000 to 2,000 years ago, these three types of microbes were abundant. However, in modern industrial societies, these gut microbes have become rare. For instance, one type of microbe (in small quantities) is present in the gut microbiome of only one in twenty residents of the U.S., China, Sweden, and Denmark.
As suggested by the study’s lead researcher, microbiologist Sara Morais from Ben-Gurion University in the Negev (Israel), these species have diminished in the human gut, likely due to the shift to a Western lifestyle. The diets of people in developed countries typically contain less cellulose, which is vital for these microbes.
It is quite possible that if Ruminococcus microbes are deprived of plant fiber, their numbers in the gut decrease. There are concerns that the disappearance of these species somehow contributes to the decline of metabolic health in modern, urbanized individuals.
The authors of the study believe that “there may be potential for enriching these species in the human gut” through dietary supplements or specialized probiotics.
What Else the Team Reported
According to Tom Van de Wiele, a co-author of the study from Ghent University (Netherlands), industrialization may have led to the loss of a vast diversity of microbes in our gut. “We are currently losing microbes that contributed to improving our gut health,” the scientist stated.
The current study represents an important step forward, the researchers noted. It sheds light on previously unknown bacteria that may have historically played significant roles in human gut health.
Evolutionary analysis convincingly indicates that the human-associated strain of Ruminococcus bacteria was passed to us from the guts of ruminant animals, likely during domestication.
So, perhaps at one time, interaction with animals enhanced our ability to digest plants. Since the Ruminococcus microbes settled in our gut, they have claimed the human body as their own.
The results of the study were published in the journal Science.
