All disease begins in the gut,’ said Hippocrates. It’s time we redefine our relationship with the gut bacteria.
Gut health is key to overall health. Every food and meal we eat influences the bacteria present in our gut for better or worse. Gut microbiota function like an organ within an organ. Emerging evidence sheds light on the complex mechanism of action between gut microbiota, diet and disease manifestation that need attention. A diverse, whole food based, probiotic diet is recommended to keep the gut microbiota healthy in the long run.
What constitutes the gut
A human body houses trillions of microorganisms or gut flora. In a recent study, Ron Sender and colleagues estimated that the number of bacteria in the human body is the same as the number of human cells, and their total mass is about 0.2 kg. Almost 1,000 species of bacteria live in the human gut and each type plays a crucial role in our body. Microbes in our gut weigh 1 to 2 kg, carry more than 150-fold genes than the human genome itself and weigh almost the same as our brain. Gut microbiota functions as the second brain or an extra organ in executing multiple functions.
Before we dive into the existing evidence to understand the connection between alteration in gut microbiota and metabolic syndrome such as obesity and type 2 diabetes (T2D), the concept of dysbiosis needs to be discussed briefly.
According to the Textbook of Natural Medicine, “dysbiosis can be defined as a reduction in microbial diversity and a combination of the loss of beneficial bacteria such as Bacteroides strains and butyrate-producing bacteria such as Firmicutes10 and a rise in pathobionts12 (symbiotic bacteria that become pathogenic under certain conditions), including Proteobacteria, which encompasses gram-negative Escherichia coli. Simply put, dysbiosis is the condition where harmful gut microbiota outnumbers beneficial bacteria and leads to several disease outcome.
Also read: We are consuming up to 5 gms of plastic every week – in our water, apples, fish, beer
Obesity to diabetes–all come from the gut
A pile of original research studies, meta-analysis and comprehensive reviews compelled researchers to register the huge contribution of gut microbiota towards health and disease outcome.
Multiple studies have found that endotoxin, a bacterial waste product, leaks through the gut lining and enters the bloodstream, causing metabolic endotoxemia. Endotoxins are countered by the body’s immune system, which treats them as foreign molecules that lead to autoimmune response and low-grade systematic inflammation linked to obesity.
Diet shapes gut microbiota and gut microbiota shapes obesity, Elaine Patterson and others explain in a comprehensive review. The authors mentioned metabolic endotoxemia has considerable effects on host adiposity and insulin resistance. They also said dysbiosis may contribute to weight gain.
A 2019 review cited multiple studies that reported microbiome dysbiosis-induced insulin resistance as the cause for nearly 90 per cent of all T2D cases worldwide.
A Lancet summary of 42 human studies reporting microbial connection with disease, identified that the bacteria colony of Bifidobacterium, Bacteroides, Faecalibacterium, Akkermansia and Roseburia were negatively associated with T2D, while Ruminococcus, Fusobacterium, and Blautia were associated with T2D disease occurrence and progression.
Also read: 3rd Covid wave fears should make Indians cut down on sugar, salt and alcohol
The gut-heart connection
Gut microbiota influences your heart health too. Trimethylamine N-oxide (TMAO), a metabolite produced by some gut microbiota, is a potential biomarker of poor cardiovascular outcomes in patients living with heart diseases.
A review by researchers from the University of Cambridge explained some gut bacteria convert choline, a nutrient found in red meat and legumes, into trimethylamine (TMA), which gets converted into TMAO, a much more harmful version of TMA.
Similarly, L-carnitine, another nutrient found in red meat gets converted into TMAO and enhances the risk of atherosclerosis, a condition that occurs when plaque accumulates inside arteries.
Also read: Mustard oil is good for kitchen but no clean chit yet on whether it’s good for heart
The diet that harms
Combinations of high trans-fat, high-refined carbs, and low dietary fiber diets lead to alteration in gut microbial composition linked to harmful metabolic health outcomes.
A 2021 review concluded overconsumption of sucrose or table sugar had more deleterious effects on metabolic alterations. Fructose, a sugar found in honey and fruits, affects gut barrier function and leads to subclinical inflammation that overall contributes to adiposity and sugar addiction.
A study conducted by the Yale University and National Institutes of Health reported that high intake of both sucrose and fructose, two different forms of simple sugar, were associated with compromised function of gut microbiota in lean and healthy people.
Higher consumption of sugar also leads to leaky gut syndrome, increases the number of pathogenic bacteria, eliminates beneficial bacteria and promotes inflammation.
A typical western diet contains multiple ultra-processed foods that are loaded with refined carbs, trans fat and preservatives. These diets disturb the balance between good and bad bacterial culture in our guts, change their composition and lead to inflammation.
Dr Subhasree Ray is Doctoral Scholar (Ketogenic Diet), certified diabetes educator, and a clinical and public health nutritionist. She tweets @DrSubhasree. Views are personal.
This is the first of a three-part series on gut health. The second article will focus on the relation between gut and mental health. The third will explain the relation between gut microbiota and the immune system, and provide detailed dietary guidelines.