Microorganisms that live in the human body.

Sukham Blog – A monthly column focused on South Asian health and wellbeing.

The body of an average person weighing 150 lbs. is made up of an estimated 37.2 trillion cells. He or she is also host to more than a 100 trillion bacteria, archaea, eukaryotes, fungi and viruses. While many of these microorganisms reside in the mouth, skin, and other parts of the body, most are found in the gastrointestinal tract or gut and are collectively known as the gut microbiota. Though large in number, these microorganisms together weigh only about 200 grams. Many are harmless, some are beneficial to health, while others can lead to disease.

The entire human genome consists of around 30,000 genes. The rapidly-advancing field of precision medicine is based on an understanding of these genes, the proteins they produce, and their roles in the formation, destruction, and mutation of our cells, enabling scientists and physicians to understand disease and develop diagnostic tools to detect them, as well as effective, targeted treatments of those diseases, based on an individual’s genetic makeup.

The human gut microbiota is estimated to have over 3 million genes. This collection of genes is known as our microbiome. Scientists at Harvard and other research institutions who are compiling a catalog of all the genes in the human microbiome have observed that at least half of these genes appear to be unique to each individual, leading them to speculate that there may be more genes in the collective human microbiome than stars in the observable universe!

The human microbiome was not generally recognized to exist until the late 1990s. We have since learned that bacteria in the microbiome help digest our food, regulate our immune system, protect against other bacteria that cause disease, and produce various vitamins including B, B12, thiamine, and riboflavin, as well as vitamin K which is needed for blood coagulation. The number and kind of bacteria in our bodies can also lead to dental cavities, gastrointestinal infections, and more serious conditions such as chronic inflammatory bowel disease, diabetes and multiple sclerosis. Scientific and medical advances over the past few years are making it clear that the human gut microbiome plays an important role in controlling wellness and disease, and influences our mental state as well. They show how specific microbes related to our diet are associated with biomarkers of obesity, type 2 diabetes, and cardiovascular disease. Unique metabolites – intermediate products of metabolism – associated with some microorganisms protect our bodies against invading pathogens, and regulate various physiological functions, our nervous system, and the development of immunity. The gut microbiome interacts with the central nervous system in complex ways. Microbial diversity and composition are associated with some human personality traits. Conversely, the way we live, and the extent of our social interactions influence the number and kind of microbes in our gut. For example, anxiety and stress are linked to reduced diversity and altered microbiome composition. These bidirectional interactions in the so-called gut-brain axis, influence our mood and mental health – findings that could lead to the development of new treatments for conditions such as autism and depression.

The National Institutes of Health (NIH) initiated the Human Microbiome Project in 2008 as an extension of the Human Genome Project, to map the human microbiome and provide knowledge of uncharted species and genes. The goal is to build a catalog of these genes and examine individual genes for increase in the risk for disease. This project will aid scientists to understand the role of the microbiome in human health, nutrition, immunity and disease, and lead to new, precision, targeted therapies for chronic and other illnesses.

Auto-immune diseases such as diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis, and fibromyalgia are associated with dysfunction in the microbiome. Disease-causing microbes accumulate over time, changing gene activity and metabolic processes, and resulting in an abnormal immune response to substances and tissues normally present in the body. Gut bacteria have recently been shown to play a role in immune suppression in pancreatic cancer, the onset of ALS, and the development of long COVID. Fecal microbiota transplantation (FMT) has proven highly effective for treating recurrent Clostridium difficile infections that cause severe diarrhea and colitis in seniors and others with weakened immune systems.

Your diet aids or diminishes your microbiome.

Our gut microbiome affects all aspects of our health and seems to be a key determinant of a long and healthy life. How do we adjust our diets to support it?

Experts agree that the use of prebiotics and probiotics helps our bodies build and maintain a healthy colony of bacteria and other microorganisms to support the gut and improve digestion. Prebiotics (found naturally in mother’s milk) include non-digestible fibers; they help stimulate the growth of beneficial bacteria, serving as food for probiotics. They are present in fiber-rich foods, such as fruits, vegetables, and whole grains. Probiotics are live or active cultures – these are the “good” bacteria such as Lactobacillus found in our gut. Probiotics are present in fermented foods such as yogurt, sauerkraut, and tempeh, and are also available in supplements. The active cultures help recolonize the gut with beneficial microbial species, improving gut health, boosting immunity and overall health.

Gut microbiota that is more diverse and balanced promote longer, healthier lives, and people with such microbiota are less likely to show early signs of frailty as they get older. Longevity expert Dan Buettner highlights the diet and lifestyle habits of people with longer life spans in Blue Zones. Among habits that directly affect the gut: eating more whole grains, nuts, veggies, beans, and fresh fruit; regular brushing and flossing; eating fermented foods and foods rich in polyphenols; seasoning food with garlic, turmeric, and ginger; limiting artificial sweeteners. You can also seek out other good, professional advice.

What will you do to improve your microbiome and your gut health?


Mukund Acharya is a regular columnist for India Currents. He is also President and a co-founder of Sukham, an all-volunteer non-profit organization in the Bay Area that advocates for healthy aging within the South Asian community. Sukham provides curated information and resources on health and well-being, aging, and life’s transitions, including serious illness, palliative and hospice care, death and bereavement.


Mukund Acharya

Mukund Acharya is a regular columnist for India Currents. He is also President and a co-founder of Sukham, an all-volunteer non-profit organization in the Bay Area that advocates for healthy aging within...