About 2400 years ago, Hippocrates said: "All disease begins in the gut"
Do you think that when you walk around or exercise, you are carrying with you only humans cells with your own DNA? Think again. The way we view microbes, especially those that live on and within our bodies, has changed recently to a much more positive perspective. The number of microbes (mostly bacteria, but also viruses, parasites and fungi), tiny microscopic organisms with their own DNA living in each of our bodies has been estimated recently to be as high as 3-fold the number of human cells that contain our own DNA (both in the order of trillions). If we took all of them together this mass would weigh an estimated 2.5-3 pounds - a little over a kilogram. These bacteria (and their bacterial DNA which is present in higher quantities than our own when we look at the number of genes!) are called collectively “microbiome”.
Microbiomes are symbiotic microorganism communities that live within us, and some people view them even as another body organ. In the gut, they may colonize intestinal walls in the form of biofilms (check out my post on biofilms if you want to know more about them). There are microbiomes that colonize different parts of our bodies, thus we have a skin microbiome, an oral microbiome and the most important, abundant, and studied so far, the gut microbiome. Microbiomes are dynamic, and can change over time for example when we move to a new location with different weather, food, environment and living conditions. Each person’s microbiome changes as we grow older, when we move to a different place with different weather, food and environmental and living conditions. They have been shown to affect/be affected by our diet, our birth (whether natural or by Cesarean section), antibiotics we take, anti-cancer therapies we receive, our immune system and many others. Our microbiomes start changing and evolving from the time we are born. Babies acquire a variety of microbe species from the mother when they pass through the birth canal during natural birth, and also from breast milk. It seems that in general the wider variety you get of these creatures, the better it is for your health, and the lack of variety in gut microbiomes for example may result in food sensitivities and allergies.
With technological advances both in science and health/medicine fields and as a result of increased collaboration between researchers and clinicians in different fields and institutions nationally and internationally, an explosion of new discoveries generates quick expanding grounds for new medical applications. The study of the human microbiome and how it affects our health is an emerging and exciting field. The most studied to date, and by far the most dense and abundant and diverse in number of bacterial species is the gut microbiome. These bacteria help us process and extract nutrients from the food we eat as they contain in their genomes genes that encode enzymes that are needed for these process that we (humans) lack, they also produce some good vitamins and prevent the growth of harmful microbes. Correlations have been demonstrated between some human diseases and the presence/absence of specific gut microbial species or species proportions in gut microbiomes, including inflammatory bowel disease, obesity, mood disorders (anxiety, stress and depression), allergy and asthma, colon cancer and others. Autoimmune diseases such as diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis, and fibromyalgia are associated with microbiome dysfunction.
One recent application of microbiomes is the use of “fecal transplants” (yes, feces from one person administered to another) to cure certain conditions such as infections with Clostridium difficile, which cause severe diarrhea and other unpleasant gastrointestinal symptoms. This bacterium kills tens of thousands annually, in part due to its antibiotic resistance occurring in some infections (there is an older post in this blog on this topic, look for “drug-resistant infections”) which makes antibiotics not effective and these would additionally kill good bacteria. A new treatment being used with some success is to administer sick patients diluted feces from a healthy individual (usually a family member) to provide an entire set of good bacteria that can colonize the lower intestine and keep the C. difficile infection under control. As unpleasant as this may sound, this “fecal transplant” technique is working in a majority of cases, especially recurring infections, and new delivery routes especially oral capsules are being explored - currently the options are via colonoscopy, enemas or through a nasogastric tube.
What can we do to try to keep our gut microbiome in good shape and with an ample variety of the “good” bacteria that make us healthy? Besides eating healthy and not taking unnecessary antibiotics that destroy it, we can add pre and probiotics, which help make it stronger or reconstitute it when affected by medications. Probiotics (found in special yogurt labeled as such, aged cheeses and fermented products such as sauerkraut, tempeh and kimchi) contain good bacteria that help control growth of harmful bacteria, while prebiotics are not alive microorganisms but carbohydrates/fiber that cannot be digested by the human body and instead are food for probiotic bacteria. Prebiotics are found in whole grains, bananas, onions, garlic, honey and artichokes.
Hi! This is an attempt to write simply about things I feel passionate about. My name is Judith Recht and I am a scientist by training, a later-in-life mother, and an expat in Bangkok, Thailand and Recife, Brazil (~4 years in each country) now back in the US. I was born in one country (USA) grew up in another (Venezuela) raised by Argentine parents and moved around four more times (NYC to Bangkok to Recife to Maryland). This blog is for those of you who might be interested in the diverse topics so far included and others coming up soon.