Inside each of us exists a diverse community of bacteria, viruses, fungi, and other microbes collectively referred to as the microbiome. These microbial communities vary significantly among individuals and are distributed across various parts of the body, including the skin, mouth, respiratory system, and especially the gut.
The gut microbiome is largely stable over time, but diet plays a key role in shaping it. Since 1919, scientists like John C. Torrey have noted diet’s impact on gut bacteria. These microbes rely on host-provided nutrients to produce various metabolites. Changes in microbiome composition are linked to shifts in immune, metabolic, and mental health, making microbiome research vital for understanding its effects on health and disease. Recent studies continue to explore how these microbes and their byproducts influence overall well-being.
High-protein diets alter the gut microbiome and activate the immune system
Dr. Laurence Macia and researchers at the University of Sydney conducted a study that showed how different foods can impact the microbiome, which can then influence IgA production and immune responses. The study used mice to explore the effects of 10 different diets, each with a unique balance of fats, proteins, and carbohydrates, on IgA levels in the gut.
Findings revealed a link between protein intake and IgA production. Moreover, mice on a high-protein diet released more bacterial extracellular vesicles, which activate the immune system and encourage immune cell movement into the gut. However, the researchers note that these results are yet to be confirmed in humans, and it’s still unclear if these effects are advantageous or harmful to health.
Gut Microbiome Linked to Inflammatory Proteins
When the microbial communities within the gut microbiome become unbalanced, they can trigger abnormal levels of inflammatory molecules known as cytokines. But how does a healthy gut microbiome affect immune signaling?
To explore this, researchers at Radboud University Medical Center in the Netherlands analyzed blood and stool samples from 500 healthy participants to study variations in immune responses to pathogens. The team exposed immune cells from participants to bacterial and fungal pathogens and measured cytokine production to assess these immune reactions. They identified distinct patterns showing that both the types and activities of the microbiome can influence immune responses, with variations depending on the specific pathogen, cytokines, or both. For instance, in some cases, the breakdown of the amino acid tryptophan can suppress the production of the cytokine tumor necrosis factor alpha (TNFα), depending on the pathogen involved.
“We still don’t have all the components, but the overall picture suggests that variations in the gut microbiome change production of the metabolites that go on to educate or influence immune cells, leading to differential outcomes when immune cells are exposed to various infections,” said Dr. Ramnik Xavier, core institute member of the Broad Institute of MIT and Harvard.
Gut Microbiome Can Impact Our Ability To Lose Weight
Research has shown that the gut microbiome can contribute to weight gain in mice, and its composition and diversity have been associated with body mass index (BMI) in humans. Studies involving human diets suggest that the gut microbiome may influence how individuals respond to dietary changes, although the exact mechanisms behind this are not fully understood.
Dr. Christian Diener and his team at the Institute for Systems Biology in Seattle studied the gut microbiome's role in weight loss. They analyzed data from a lifestyle intervention program, comparing participants who lost over 1% of body weight monthly to those with no weight change. They found that those who didn’t lose weight had gut bacteria better at breaking down starches, while those who lost weight had bacteria with genes promoting growth and replication. The team suggests that altering gut bacteria through diet could support weight loss for those struggling to shed pounds.
“Before this study, we knew the composition of bacteria in the gut was different in obese people than in people who were nonobese, but now we have seen that there are a different set of genes that are encoded in the bacteria in our gut that also responds to weight loss interventions,” said Dr. Diener. “The gut microbiome is a major player in modulating whether a weight loss intervention will have success or not. The factors that dictate obesity versus non-obesity are not the same factors that dictate whether you will lose weight on a lifestyle intervention.”
Dog’s Gut Microbiome May Be Transformed Within a Week of Changing Food
When beginning a new diet, the types of microbes in our microbiome can shift, though it’s still unclear how long it takes for these changes to become permanent.
Researchers examining the effects of dietary changes on dogs' microbiomes found that both the microbial species and their metabolic byproducts can transform within a week. Remarkably, dogs’ microbiomes begin producing new chemical compounds within just two days, and their microbial communities stabilize by day six. According to study co-author Dr. Kelly Swanson, this study aimed to establish how long a new diet should be followed before collecting samples in animal nutrition studies, as it hadn’t been definitively tested before. Another important insight from the study supports the advice to gradually transition a dog to a new food brand over a period of seven days.
"Metabolites change really quickly, within a couple of days. Bacteria responsively metabolize and deal with the substrates they're given in the new diet. Then it takes a few more days to sort out the microbial pecking order, if you will,” Swanson says. “Our data show everything stabilizes by day six, so animal nutrition researchers could confidently sample and find a stable microbiome within 10 days."
Much more yet to discover about diet–microbiome interactions
With the importance of the microbiome in our health well-known, and increased awareness of how diet can impact our microbiome, more research than ever is being conducted in this field.The more knowledge we can gain regarding the relationship between diet and our microbiomes, the more likely we are to be able to improve our health by looking after our microscopic guardians.
Reference:
https://www.technologynetworks.com/immunology/
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