The Role of Diet in Gut Microbiota

Introduction

Did you know? The microbes in the guts of animals influence what they choose to eat, and even prompt cravings for different kinds of food. Experts believe that gut bacteria could affect our food choices and cravings. It is said that what you eat affects your health, and that health starts in the gut. A diverse diet is one of the major factors that influences your gut, and the composition and function of your microbiome.

There is growing recognition of the role of diet in regulating the various acts of the human gut microbiota, which in turn can impact health. This blog highlights the influence of diet on gut microbiota.

Diet and Gut Microbiome

The gastrointestinal (GI) tract of humans consists of approximately 100 trillion microorganisms, their type, number, and function vary along the GI tract. The majority of these microbes reside in the large intestine, where they ferment undigested food components to faecal bulk.

The gut microbiome produces a variety of bioactive compounds that can influence your bodily functions, some of which are beneficial while others can be toxic to your health. Fortunately, your immune defences along the intestine prevent these toxic bacteria from causing damage to tissues. By competing for nutrients and colonisation sites, a diverse and thriving population of beneficial gut bacteria helps to keep harmful bacteria at bay. A diverse gut microbiome can be achieved by eating a healthy diet.

Without further ado, let’s shed some light on how major dietary nutrients impact the composition and metabolic activity of the gut microbiota and, in turn, affect both physical and mental health.

Carbohydrates

Carbohydrates are one of the most significant dietary components and are known for their ability to modify the gut microbiome. Non-digestible carbs (such as fibre) are not enzymatically degraded in the small intestine. They undergo fermentation in the large intestine, which produces metabolites called as short chin fatty acids (SCFAs). SCFAs are a major energy source for intestinal cells and strengthen the mucosal barrier.

Proteins

Dietary proteins are an important part of a balanced diet, as they have a significant impact on gut health. They are the primary source of nitrogen for colonic microbial growth and the production of beneficial products such as SCFA. Therefore, a balanced combination of carbohydrates and proteins in the large bowel can contribute to bowel health.

Fats

Dietary fats also greatly impact the composition and metabolic activity of the gut microbiota. High-fat diets induce increased levels of bacteria-derived lipopolysaccharide (LPS) possibly as a consequence of increased intestinal permeability, which is an immune system modulator and potent inflammatory agent and is often linked to the development of common metabolic diseases.

Polyphenols

Dietary polyphenols include flavones, flavonols, catechins, proanthocyanidins, anthocyanins, and phenolic acids. Common foods with rich polyphenol content include seeds, fruits, vegetables, cocoa products, tea, and wine. Unabsorbed phenolics can benefit the host by increasing beneficial microbes and maintaining metabolism once they reach the gut. Polyphenols' prebiotic activity promotes the growth of beneficial bacteria, reducing the availability of nutrients to pathogenic bacteria and acting as antimicrobial agents against them. They promote health and are linked to the prevention of diseases such as cancer and cardiovascular disease.

Probiotics and Prebiotics: Nutritional Strategies to Improve Health

By improving the composition of the colonic microbiota, probiotics and prebiotics promote host health.

• Probiotics are defined as live microorganisms which confer a health benefit on the host when administered in adequate amounts. The most commonly consumed probiotics belong to the genus Bifidobacterium and Lactobacillus. These improve host health by preventing pathogenic bacteria from colonising the intestine, promoting the formation of a healthy intestinal mucosal protective layer, and boosting the immune system.
• Prebiotics are selectively fermented ingredients that induce changes in the composition and/or activity of the gut microbiota, thus benefiting host health. There is mounting evidence that prebiotics modulate the immune system both directly and indirectly, lowering the risk and severity of bowel infectious and inflammatory conditions such as IBD, as well as functional bowel disorders such as IBS. They also play a role in colonic uptake of calcium and magnesium. They can, directly and indirectly, modulate the immune system, and reduce the risk and severity of bowel and systemic diseases.

We shall learn in-depth about probiotics and prebiotics in our upcoming articles. Stay tuned!

Effects of special diets on gut microbiota

Indian Diet

The microbial populations in the gut of healthy Indians are dominated by Firmicutes followed by Actinobacteria, Bacteroidetes, Fusobacteria, Proteobacteria, Spirochetes, and Verrucomicrobia. Although India has many diverse cultures, Indians follow a meal tradition, where a large round platter, the Thali, holds bread or rice along with several smaller bowls (or Katori) which hold a separate curry or condiment to be eaten with the rice or bread as per choice.

Typical dishes include rice, roti, dal, and vegetables and yoghurt. These foods are sources of fibre (prebiotics), protein, probiotics and different classes of phytochemicals. Experts believe this variety helps to restore diversity in the gut bacterial microbiota and may potentially prevent or reverse chronic diseases, such as type 2 diabetes or colon cancer.

Western-Style Diets

Most Western populations over-consume highly refined, omnivorous diets of poor nutritional quality. Also, their diet is high in animal protein and fat and low in fibre. This has led to a significant decrease in total bacteria, and beneficial Eubacterium and Bifidobacterium species. The western diet is also associated with high incidences of chronic diseases, such as cardiovascular disease, colorectal cancer, and type II diabetes.

Mediterranean Diet

It is highly regarded as a healthy, balanced diet across the globe. It is high in monounsaturated and polyunsaturated fatty acids, polyphenols, and other antioxidants; it also contains a lot of fibre and low glycemic carbohydrates. The protein consumed is more from plant-based protein foods than animal sources. Specifically, olive oil, assorted fruits, vegetables, cereals, legumes, and nuts; moderate consumption of fish, poultry, and red wine; and a lower intake of dairy products, red meat, processed meat, and sweets characterise the traditional Mediterranean diet. Studies have shown that foods comprising the typical Mediterranean diet improve obesity, the lipid profile, and inflammation. These changes may be mediated by diet-derived increases in Lactobacillus, Bifidobacterium, and Prevotella, and decreases in Clostridium.

Maintaining a healthy gut microbiome is critical to human health

The above information clearly proves that the integrity of the gut microbiota is of critical importance to human health. So, make sure to have healthy dietary choices when you get those food cravings. You never know which food or diet can modulate your gut microbiota. Maintain your gut’s resilience for better health!

References:

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• Kaitlyn Shondelmyer, Rob Knight, et al. Ancient Thali Diet: Gut Microbiota, Immunity, and Health, online 2018 Jun 28. PMID: 29955222
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• Kaur, Kamaldeep et al. “Metagenomics analysis reveals features unique to Indian distal gut microbiota.” PloS one vol. 15,4 e0231197. 8 Apr. 2020, doi:10.1371/journal.pone.0231197