The ratio of microbial cells to human cells in the human body appears to be 1:1, with as many microbes living in our bodies as the number of humans cells, which is why our health depends a lot on what microbiomes we carry and how they behave; they crowd in our gut

Human beings and their health are predetermined by their genomes, some argue their proteome, and yet others claim other codes carried in our biological makeup like miRNome. Recent studies like The Human MicroBiome Project and MetaHIT indicate, however, that humans are affected as much by their microbiome (the flora of the human gut) as the inherent genetic makeup! The findings of these studies so far have been astounding, to say the least.

The literature around microbiome in various illnesses is exploding. The microbiome’s role pervades realms that have never been explored before. The examples below are just some of the exciting discoveries that have started to be made.

Mental health

The gut microbiome has been implicated in emotional well-being. A study was performed involving two groups of women, one with more Bacteroides bacteria and another with Prevotella bacteria in their microbiome. The MRIs of their brains revealed that that the group with Bacteroides bacteria had a thicker grey matter in the frontal cortex, which plays a part in complex behaviour and decision making, and a high-volume hippocampus, which plays an important role in memory. Conversely, the group with higher Prevotella bacteria showed lower-volume hippocampus, but more connections in regions of the brain associated with emotion, attention and sense. Not surprisingly, therefore, the latter experience more negative emotions when dealing with negative circumstances.

The microbiome also finds significant mention in autism with autistic children showing an increased bacterial diversity compared to controls.

Brain health

The gut is connected to the brain through millions of nerves, making the brain an obvious target of the role of the microbiome. Preliminary studies have revealed that individuals with psychological disorders have a different microbiome in their guts as compared to healthy individuals. Also, some studies have shown that certain probiotics can improve symptoms of depression and other mental health disorders.

Can altering the microbiome help alter emotional and mental well-being? Preliminary studies definitely indicate so.


The gut microbiota is also directly related to so-called lifestyle illnesses like obesity. Studies in mice have shown that transferring microbiota from a lean mouse to its obese twin led the obese twin to become lean — all other factors, including diet remaining constant. In human beings, interactions between the gut phyla Bacteroidetes and Firmicutes appears to have a significant impact on obesity. The obese population shows a decrease in the Bacteroidetes population as compared to the population of Firmicutes.

Hope for the obese, therefore, presents itself in tiny packages of probiotics.

Cardiac wellness

The microbiota is also implicated in heart health. A study with 1,500 individuals revealed that the gut microbiome played a crucial role in promoting HDL cholesterol, the so-called “good cholesterol”, and triglycerides. On the flip side, certain gut microbiota are responsible also for producing trimethylamine N-oxide (TMAO) from choline and L-carnitine, which contributes to blocked arteries, which may lead to stroke and cardiac arrests. Lactobacilli, on the other hand, may help reduce cholesterol.

Blood sugar

A recent study on 33 infants, who were genetically predisposed to developing type 1 diabetes, revealed that just before the onset of the disease, the microbiota changed, with a spike in the number of unhealthy bacterial species.

The much-celebrated discovery of the direct relationship between Helicobacter pylori and gastric cancer, which fetched discoverer Barry Marshall the Nobel Prize in 2005, is not unknown to many.

A disbalance between the microbial populations in the microbiome is implicated in many diseases including various autoimmune and allergic diseases, like inflammatory bowel disease (IBD), Crohn’s disease.

The scientific community has described The Human Microbiome Project as “a logical conceptual and experimental extension of the Human Genome Project”. The outcome of the study showed that the ratio of microbial cells to human cells in the human body appears to be 1:1 with as many microbes living in our bodies as the number of humans cells confirming the scientific community’s prediction. Health certainly demands that we look within: our guts.

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