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Fiber Deficiency Western eating habits reduce valuable intestinal bacteria
The variety of beneficial gut bacteria can be irreversibly damaged by the typical Western diet. The low content of fiber and microbiota-accessible carbohydrates in the foods of modern industrial nations leads to increasing loss of gut bacteria from generation to generation, according to US researchers at the Stanford University School of Medicine. Here are corresponding impairments of the intestinal flora and far-reaching negative consequences for the entire organism.
The team led by Professor Justin Sonnenburg of the Stanford University School of Medicine has been able to show in his current research using mice that the low-fiber diet has a direct influence on the intestinal flora and irreversible changes occur over the different generations of animals. According to the researchers, after four generations of low-fiber diets, nearly three-quarters of the beneficial intestinal bacteria species had disappeared. The scientists published their results in the journal "Nature".
Over generations, positive intestinal bacteria die out. Picture: fotoliaxrender - fotolia Thousands of different bacterial species inhabit the colon of every healthy individual and "we would have difficulty living without them," stresses Professor Sonnenburg. According to the microbiologist, the intestinal bacteria "help fight off pathogens, they train the immune system and even influence the development of our tissues." The bacteria also play a key role in the utilization of nutrients.
The individual intestinal bacteria population is influenced by various factors, whereby the intestinal bacteria of the family and in particular of the mother are initially of outstanding importance. They are transmitted to newborn children and babies.
Changes in the intestinal flora during the life course
However, the intestinal flora changes during the lifetime. For example, the intake of antibiotics can cause significant impairment of intestinal bacteria. "Numerous factors, including the widespread use of antibiotics, the increase in cesarean sections and less frequent breastfeeding" have led to a depletion of the intestinal flora, explains Erica Sonnenburg, lead author of the study (and wife of Professor Justin Sonnenburg).
Diet is also of particular relevance to the biodiversity of intestinal bacteria. The scientists therefore wondered what influence the great difference in fiber intake between traditional and modern populations has on gut bacteria.
Low fiber in modern foods
The proliferation of nearly fiber-free, processed food products since the mid-20th century has led to a decline in dietary fiber intake to around 15 grams per day in industrialized societies, report Professor Sonnenburg and colleagues. This is "less than a tenth of the fiber intake of today's hunter-gatherer societies or rural agrarian populations whose living conditions and food intake are likely to most closely resemble those of our common human ancestors," explains Professor Justin Sonnenburg.
Practically all health experts agree that such low-fiber diets are not recommended for health reasons. Also because the fiber, which can not be digested by human enzymes, form the main food source for the intestinal bacteria.
Intestinal bacterial profiles on mice examined
Using mice, the US scientists investigated in their study the effects of low-fiber diet on the intestinal bacteria. Young laboratory mice that were specially bred under aseptic conditions and therefore had viscera without any microbial colonization received microbes from a human donor so that they developed a corresponding intestinal flora.
Subsequently, the mice were divided into two groups, one group receiving a fiber-rich diet and the other group receiving a diet high in protein, fat and calories but with virtually no fiber. During the experiments, the researchers examined the fecal samples of the animals and thus determined the profiles of the intestinal bacteria. In both groups, the bacterial profiles did not differ at first. Already within a few weeks, however, massive changes were noted, reports Professor Justin Sonnenburg.
After a few weeks, many bacteria have already disappeared
The mice in the low-fiber group showed, according to the researchers after about six weeks significantly fewer types of bacteria in the intestine than the animals in the control group. In more than half of the bacterial species, the occurrence had fallen by over 75 percent and many species seemed completely gone, report Professor Sonnenburg and colleagues. After seven weeks of trial period, the diet of the mice had been switched back to a fiber-rich diet for four weeks. Although the intestinal bacteria profiles could be partially recovered, but this restoration was limited, according to the scientists.
"A third of the original species never returned fully, despite the high-fiber diet," said the US researchers in the press release of Stanford University School of Medicine.
Variety of intestinal bacteria decreases with every generation
The real surprise, according to the scientists, however, was the cross-generational effect on the development of the intestinal flora. Thus, the low-fiber diet in each subsequent generation mice caused a decreasing variety of intestinal bacteria. In the fourth generation, almost three-quarters of the original bacterial species had disappeared from the experimental animals. Even when these mice were placed on a fiber-rich diet, more than two-thirds of the bacterial species remained irretrievably extinguished. This equates to an extinction of the species in the fourth generation low-fiber diet.
The dietary habits in the modern industrial nations could therefore bring about an irreversible eradication of many beneficial intestinal bacteria in future generations. The consequences for human health will be difficult to assess. Experts believe that symptoms such as a bloated stomach or permanent abdominal pain are the first signs of a disturbed intestinal flora. In the long run, the negative effects will increase significantly over generations, according to the researchers. (Fp)