What You Eat Really Matters to Your Gut Bacteria

Highlights:

There are millions of organisms called the gut microbiome that live in the gut and have been linked to various diseases
The composition of the intestinal microbiota is influenced by a variety of factors, including nutrition and the body's production of the intestinal defense molecule known as defensins
A recent study shows that a healthy diet is more important than defensins when it comes to the health of the gut microbiome

Everyone has heard the phrase, “You are what you eat,” and this has proven to be especially true when it comes to your gut.

A recent study conducted by researchers at Umeå University, Sweden, has found that among the many factors that shape the composition of the intestinal microbiome, diet has a much stronger impact than defensins. Defensins are intestinal defense molecules produced by the body. Instead, they identified a possible role for these molecules in preventing increased blood glucose levels after consumption of a high-caloric “Western-style diet”. The study has been published in the scientific journal Microbiology Spectrum ().

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‘Counting on a healthy diet might be a better bet than your immune system when it comes to your gut.’

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Diet Has a Strong Role to Play in Gut Microbiota

“While the effect of defensins in shaping the adult microbiota composition is rather minor when compared to diet, defensins still have a very important role in protecting us against microbial infections; and our research highlights their protective role against the metabolic complications that can arise after the intake of a high-fat and high-sugar Western-style diet," says Fabiola Puértolas Balint, Ph.D. Student at the Department of Molecular Biology at Umeå University.

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The Importance of Gut Microbiota

The gut microbiota is the trillions of bacteria that live inside everyone's gut. The prevalence of certain bacteria in this community has been intensively examined over the past decades due to its link to various ailments, including inflammatory bowel disease, obesity, diabetes, and even psychological issues.

The community of forms during birth, after which several internal and external factors help shape the community to its final composition. These factors include diet, especially fiber, genetics, medication, exercise, and defense molecules, which are the antimicrobial peptides.

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Defensins: Our Body’s Self-Produced Antibiotics

Our body makes its own antibiotic molecules known as antimicrobial peptides. In particular, the largest group of antimicrobial peptides - the defensins - is produced by all body surfaces, including the skin, the lungs, and the gastrointestinal tract.

Defensins are considered the immune system´s first line of defense against infections but at the same time, they have also been thought to be essential in shaping the microbiota composition in the small intestine.

However, it was so far not known how big their impact is when compared to diet, which has an established impact.

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Healthy Diet vs Low-Fiber Diet for Gut Microbiome

Researchers from Björn Schröder's lab used normal healthy mice and compared their microbiota composition in the small intestine to mice that could not produce functional defensins in the gut, and then both mouse groups were fed either a healthy diet or a low-fiber Western-style diet. "When we analyzed the microbiota composition inside the gut and at the gut wall of two different regions in the small intestine, we were surprised - and slightly disappointed - that defensins had only a very minor effect on shaping the overall microbiota composition," says Björn Schröder.

However, it is important to note that the intestinal defensins still had significant effects directly at the gut wall, where they are produced and secreted. A few distinct bacteria seemed to be affected by the presence of defensins, among them are Dubosiella and Bifidobacteria, likely due to the selective antimicrobial activity of the defensins.

Western-Style Diet - Defensins = Metabolic Disorders

"To our surprise, we also found that the combination of eating a Western-style diet and lacking functional defensins led to increased fasting blood glucose values, which indicated that defensins may help to protect against metabolic disorders when eating an unhealthy diet," says Björn Schröder.

The findings show that efforts aimed at positively modulating the composition of the microbiota should focus on nutrition, while manipulation of the composition via enhanced production of host defense molecules, such as defensins, may have only a minor impact on the overall composition.

Even though it is possible that especially early in life when the microbiota community is not fully matured yet, defensins may have a stronger effect on the microbial composition. Increasing the production of defensins may be a valuable option to prevent the development of metabolic disorders.

Reference:

Intestinal α-Defensins Play a Minor Role in Modulating the Small Intestinal Microbiota Composition as Compared to Diet - (https://journals.asm.org/doi/10.1128/spectrum.00567-23)

Source-Medindia