Here's another reason to eat your vegetables. Trillions of microbes in the large intestine known as the human microbiome-dependent fiber prosper and give us energy. As the consumption of fibers decreases, so, too, is the range of bacteria which can survive in the intestine. Now a new study of several generations of mice fed a diet low in fiber indicates that this diversity dives deeper with each generation, a hint of what might occur in the human intestine as we continue to eat a diet of contemporary refined foods. The work may also help explain the rise in many Western diseases, such as inflammatory bowel disease and obesity.
"This is a seminal study," said Jens microbial ecologist Walter of the University of Alberta in Canada. "The extent by which the weak [fiber] supply depletes the microbiome in mouse experiments is striking."
For much of human history hunter-gatherer and early agricultural times, the daily fiber intake was probably at least three or four times the officially recommended today (something like 100 grams against 25 grams) -and several times higher than the average consumption in the United States today (15 g). the tendency has led many researchers, including Erica Sonnenburg microbiologist from Stanford University in Palo Alto, California, to suspect that the low well documented diversity of gut microbes in people in developed countries, 30 % less diverse than modern hunter-gatherers- is in part a product of considerably reducing the consumption of fibers.
the new study confirms this relationship in rodents. Sonnenburg and his colleagues raised mice in a germ-free environment, then fed them human faeces, giving them the human intestinal bacteria. When fed a diet low in fiber (about 30% less fiber than the chow control high fiber), animals experienced a significant dip in the gut microbial diversity (with about 60% of microbes lose at least half their populations). The mice then maintained on the food poor in fiber and have helped raise the offspring produced with a diversity even lower, the team announced today online Nature . And subsequent generations of mice fed low fiber continued to lose whole groups of microbes such as bacteria have reached these reduced numbers in the parents that they could not be transmitted through birth, nursing, or even tend to eat'S mouse droppings on the other.
by the fourth generation, mouse microbiota seemed to have reached a new normal, low steady microbiota diversity, accommodation only over a quarter of the diversity enjoyed by the first generation. In particular, no low generations fiber could be "saved" by reintroducing foods rich in fiber. To reach the bacterial variety of their grandparents, mice need a fecal transplant group rich in fiber and a diet rich in fiber.
The results raise questions about how our diet affects our own offspring. "As we move relatively little change in our human DNA for each generation, this study indicates that we potentially pass on huge changes in our gut microbiome," Sonnenburg said. Because the mice in this study started with microbes of a Westerner, the microbiome was already low in diversity, the study also suggests that "it may be possible for Western microbiota to lose the extra diversity," she adds. Microbiologist Eric Martens, University of Michigan Medical School in Ann Arbor, amazed by the extent of the loss. "The surprise is that the proportion of organizations can actually be driven to extinction," he said.
The researchers have yet to prove that the same rapid reduction of microbial diversity occurs on rights generations and if it is, what it means for health. "in these complex ecosystems, it is very difficult to know the exact result of the loss of biodiversity," said Sonnenburg. But, she notes, "it is likely that these extinctions in the microbiota have big effects." For example, other research has shown that obese people are more likely to have the lowest microbial diversity in their guts that their lean peers. and our more macroenvironments studies teach us that a diverse ecosystem is heartier and quicker to bounce to another less diversified.
Meanwhile, as Martens suggests in an accompanying commentary in Nature , "you might consider choosing a salad ... or an additional portion of beans."
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