Did you know that most DNA found in your body is not human?
For years scientists were baffled with the fact that most DNA isolated from human specimens is not only non-human but belongs to unknown species.
To put this fact into numbers, consider this: our DNA is organized in genes, we have about 20 thousand of them. Researchers studying human samples taken from the mouth, nose, skin, vagina and feces of healthy volunteers have found anywhere between 2 million and 20 million genes!
Amazingly, the vast majority of these non-human genes belong to species of microbes that we have never been able to isolate, let alone study. We don’t know what they look like, we don’t know what they do.
By now, if you are a germaphobe (with extreme fear of germs) like Michael Jackson and Donald Trump, you are probably curling into a ball and rocking back and forth asking yourself, “Why…why …why?” . Stay calm, you might end up turning into a germaphile or germ lover. Seriously.
To address this issue, in 2008, the National Institute of Health decided to establish a project called the Human Microbiome Project (HMP) with the intention to characterize all the microbes that live in the human body and shine some light on their role in human health and disease. So far 2,200 strains (types or sub-type of microbes) have been identified and there is still much more work to do. It turns out that a healthy individual (shower or not) harbors around 100 trillion microbes in their body, vs. only 10 trillion human cells that make us up.
But what are all these germs doing in our body?
Nature is all about balance and efficiency, therefore, it is not surprising that all these microbes called your microbiome and that represent 3% of our body weight, are doing something quite important.
It is no secret that the bacteria in our intestines help us digest food, produce vitamins that we wouldn’t be able to obtain, and help keep bad bacteria like Clostridium difficile at bay. But what we have learned in the past decade is simply amazing and quite unexpected.
Your microbiome and obesity
If you have a DNA sample of a person, you can tell with 60% of accuracy whether or not that person will be obese. If you have a sample of the microbiome of a person, you can tell with more than 90% of accuracy whether or not that person will be obese. In other words, the bacteria that live in your intestine are more important to define obesity than your own genetic makeup.
The first hints of this fact came from an unexpected source. In 1948 a British scientist named Thomas Jukes found that by adding a small dose of antibiotics into poultry feed the chickens grew 2.5 times faster and bigger than those on a regular diet. That opened the flood gates of antibiotics in the food industry to such extent that now a days 75% of all antibiotics used in the USA are used in animals.
Jukes had no idea why this was happening but today we know that specific types of bacteria in our intestine regulate the rate of absorption of nutrients in the food we eat and therefore prevent us from storing excessive amounts of fat. Even more interesting, these microbes have an important role in the eating behavior of the host, helping produce the feeling of satiety and limiting the amount of food consumed. Being exposed to antibiotics or any other factor that can change the composition of our intestine’s microbiome, especially in our infancy, increases a person’s chance of being obese by up to 60%.
Your microbiome and your mental health
Do you remember when we said that there are literally thousands of different types of microbes in your intestines? Well, microbes tend to be very different from one another in two things: a) the type of nutrients they use as their own food and, b) the waste products of their metabolism (their excretions). So, you can imagine that an environment of such diversity as our intestines is a complex soup of hundreds or thousands of compounds produced by our microbiome, some of which are neuroactive, meaning they can affect our nervous system influencing the way we feel, our memory, attention, etc.
In recently published studies it was found that severely depressed patients were lacking two types of bacteria in their intestines: Coprococcus and Dialister. These species of bacteria produce a substance called DOPAC, which is closely related to dopamine which is a neurotransmitter important for our mental health. Similarly, patients with other psychiatric disorders were found to have different populations of gut microbes compared to microbes in healthy individuals.
What should we expect in the future?
A lot of research is being done to learn exactly how can we identify and repair altered microbiomes. Fecal matter transplants (poop transplants) from healthy individuals are one way this is being done and positive results have been seen in patients with autism, Chron’s disease, ulcerative colitis, etc.
For now, understand this, your microbes are an important part of who you are. They might be right now preventing you from getting a terrible infection or a metabolic disease. Treat them with respect by not taking antibiotics unless prescribed by your doctor, and by eating healthy.