(NaturalHealth365) For 95 percent of human evolutionary history, we have been “hunter-gatherers,” consuming copious quantities of plant-based fiber along with meats and fats. But the advent of industrialization – and the primacy of highly processed and “fast” foods – has caused our consumption of fiber to plummet. Now, an animal study from the Stanford University School of Medicine has disturbing implications regarding the effects of insufficient dietary fiber. Mice on a low fiber diet experienced the loss of certain species of beneficial bacteria – and passed the deficiency down to successive generations.
Low fiber diet caused loss of specific bacterial species
The study, which was published in January in Nature, used mice specially bred in aseptic environments to ensure that their intestines were empty of microbes. They were then populated with microbes from the intestine of a human being and split into two groups. One group received a high-fiber diet and the other was given a low-fiber diet. Except for fiber content, the diets were identical in protein, fat and calories.
Although the groups started the study with identical gut-bacteria profiles, within a few weeks there were differences – described by the researchers as “massive.”
Specifically, the microbial ecosystems of the low-fiber group became depleted – and the diversity of the bacteria populating their guts plunged as well. In fact, over half of the bacterial species were diminished in population by 75 percent – and some species of beneficial bacteria had disappeared without a trace.
After seven weeks, the low-fiber mice were switched to a high-fiber diet. Although some of the animals experienced improvements in their gut-bacteria profiles, the recovery was only partial – and over two-thirds of the extinguished bacteria species never came back.
The findings are troubling, because they show that once a population has experienced the extinction of beneficial bacteria species, proper diet may not be enough to bring them back for individuals in that group.
Internal deficiencies may be passed down the line to future generations
Even more disturbing is the fact that irreversible loss of specific beneficial microbes was apparently passed down to descendants – four generations later.
After mice had been maintained on low-fiber diets for a few generations, researchers found that each generation’s gut-bacteria populations became less diverse. By the fourth generation, the mice only had a quarter of the various bacterial species present in their great-grandparents’ guts – the other three quarters had become extinct.
How do gut bacteria benefit us?
The intestinal ecosystem consists of literally trillions of bacteria – and thousands of different species – which are acquired through exposure over the course of a lifetime. Not only are many of them beneficial — but we couldn’t survive without them.
According to senior study author Justin Sonnenburg, Ph.D., associate professor of microbiology and immunology at the Stanford University School of Medicine, beneficial bacteria ward off disease-causing pathogens, “train” the immune system, guide the development of tissues, and even play a role in mental processes.
As odd as it sounds, beneficial intestinal bacteria – acquired from our mothers during childbirth and infancy – are a valuable legacy.
The standard American diet lacks the fiber needed to fuel friendly bacteria
Fiber, which is actually indigestible by human enzymes, is the main food source for friendly gut bacteria. Good sources of fiber are fruits and vegetables, oatmeal, nuts, bran and whole grains.
Since the 1950’s, the skyrocketing popularity of extremely low-fiber, highly-processed convenience foods in America has resulted in people only ingesting about 15 grams of fiber a day – roughly a tenth of what our hunter-gatherer forefathers consumed.
Studies show that rural agrarian populations have much more diverse bacterial populations than those living in industrialized countries – and often possess bacteria that are absent from the intestinal tracts of those eating a low-fiber diet.
Although low-fiber diets seem to be the primary reason for the depletion of intestinal microbiota, researchers say that widespread use of antibiotics, a decrease in breastfeeding and an increase in C-sections also play a role.
Could our children and grandchildren pay a price for our unhealthy eating habits?
Of course, the study was performed on mice, not people. The rapid reproductive rates and short life span of mice means that three and four generations can be easily studied – a process that would take decades if humans were the subjects.
However, the explosion of low-fiber processed foods has occurred within the past 70 years – roughly two generations for humans. And these study results give rise to a troubling question: within four human generations, will we find that populations of irreplaceable gut bacteria have been lost?
Experts say that the low-fiber American diet is already taking a toll on human health. Researchers have found that less–diverse intestinal microbiota are associated with a range of conditions, including autism, allergies, asthma, diabetes and obesity – all of which are on the rise.
It seems like a no-brainer: eating a high-fiber diet (and avoiding the excessive use of antibiotics) is an easy fix for a situation that could ultimately have devastating consequences for human health.
As lead study author Justin Sonnenburg suggests: “Everybody should be eating more dietary fiber.” Click here to read the entire report about this study from Stanford School of Medicine about the dangers of a low fiber diet.