Gut Microbiome: How it Keeps You Healthy

Gut Microbiome

Your body is host to an enormous number of microorganisms. We maintain a symbiotic relationship with the many bugs that live in us and on us. We help them. They help us. One fascinating area of research that holds much promise is being done on probiotics – microorganisms that provide a health benefit to the host when administered in adequate amounts.

This article is an overview of the importance of these tiny creatures that live in us and how they affect our health. These microorganisms make up the human microbiome and include bacteria, fungi, viruses, and protozoas.

Now for some staggering numbers.

The Microbiome: How Big is It?

Want to know what a big number is? Try 100 trillion. That’s 100,000,000,000,000. That’s the number of microorganisms that live in our gastrointestinal tracts. Wow, you say? It’s even more than you might imagine because it is nearly three times the 37.2 trillion cells that make up your body or 37,200,000,000,000. That’s right.

We have more of these tiny organisms living in us than we have cells in our bodies. Must be a reason, don’t you think? These microorganisms make us healthy or healthier – if they are in balance and if we have the right ones. These microorganisms are collectively known as the human microbiome. And, they exist for a reason.

The human microbe is estimated to have a 100 fold more genes than our human bodies. It is estimated that there are up to 1,150 bacterial species that comprise the human microbiome. Each of us have around 160 such species that live in our gastrointestinal tracts.

So we all do not share the same micro-organisms. If we did there would be less variation in health among us. More than 90% of these bacteria are from the following four phyla; Bacteroides, Firmicutes, Actinobacteria, and Protebacteria.

How much does the microbiome weigh? Just a mere 7.1 ounces, but it may be the most important seven ounces in the body. Some scientists consider the microbiome as a “new organ” generally not recognized until the late 1990s. The fact that it is now viewed as an “organ” illustrates the significance it plays in our health. Sometimes called “pond scum” this biofilm that coats the intestinal wall is just 30 microns thick.

Just think. Something that is three times the number of our cells that make up the human body that weighs 100 to 200 pounds or more only weighs a mere seven ounces. That should put in perspective how tiny yet powerful the human microbiome is. To a large degree you are as healthy your gut microbiome. Here’s why.

The Role of the Microbiome

Seventy percent of our immune systems resides in our intestinal tract. Might there be a link between immune function and these 100 trillion microorganisms that also live in the gut? Or, is it just coincidence? It’s not coincidence. Our normal gut flora plays a tremendous role in optimizing our ability to fight infection and cancer.

Guess what else? Seventy percent of our serotonin – our happy neurotransmitter – is made in the gut. Not the brain. The gut.  And most likely that production is related to the microbiome. Along those same lines there are 100 million neurotransmitters lining the gut. The same number as there are found in the spinal cord.

We now know the GI tract and brain communiate with one another. In fact the gut is being called the second brain. Interestingly, the same lesions found in the brains of Alzheimer’s patients are also found in the gut.

We are learning that our lifestyle impacts the composition of our gut microbiome. In fact, anything we put in our mouths including the types of foods we eat and any oral medications we might take affect our intestinal flora either positively or negatively.

A low fat and high fiber diet leads to an increase in Bacteroides and decrease number of Firmicutes. Whereas, a high fat and low fiber diet does the opposite. Changing the pH of the stomach via antacids or anti-reflux drugs changes the intestinal flora. Alcohol and smoking changes the intestinal flora.

Human, donkey, and cow milk all effect the gut microbiome differently.

We are learning that each species living in our guts play a specific role in helping us maintain our health or predisposing us to disease. Some species of the microbiome predispose us to obesity and metabolic syndrome. Obesity is associated with a shift in the gut microbiota. In animal studies, leaner animals have higher amounts of Bacteroidies while obese animals have higher amounts of Firmicutes. 

And, some bacteria seem to trigger autoimmune disease. Sufferers of rheumatoid arthritis and psoriatic arthritis, for instance, have an unhealthy amount of Provotella copri when first diagnosed. And, they have lower amounts of healthy intestinal bacteria like Bacteroides, Lachnospiracea, and Clostridia.

Probiotic Interventions for Obesity

Recent studies show the probiotics can improve intestinal microflora balance, decrease food intake, decrease abdominal fat, improve mucosal integrity of the intestinal tract (protecting against acid-reflux and inflammatory bowel disease) by decreasing inflammation. The microbiome helps us digest foods consuming calories in the process and plays a critical role in vitamin production.

Given the magnitude of the obesity epidemic probiotic strategies are being developed to combat this growing problem. One study showed that the probiotic strain of Bifidobacterium animalis lactis improved metabolic syndrome – a constellation of  obesity, high blood pressure, high cholesterol and triglycerides, and diabetes – by counteracting the adverse effects of high fat diets by reducing tissue inflammation.

Another double-blind placebo controlled study show that the addition of Lactobacillus to a traditional yogurt culture reduced abdominal fat and body weight.

Lactobacillus rhamnosus has been shown to reduce stress through its effects on GABA the calming neurotransmitter in the brain.

Studies show that probiotics lower the LDL or bad cholesterol, shorten the duration of flu symptoms, improve insulin sensitivity, and reduce symtpoms of eczema.

For a more in-depth review of studies on probiotics and management of metabolic syndrome and obesity follow this study link.

Probiotics and the Human Genome

The field of human genomics is growing by leaps and bounds. Genes can be turned on or off. In other words, genes are expressed or not. We are beginning to learn how to control the expression of genes by learning how to switch healthy genes on and unhealthy genes off (those that might cause cancer).

Probiotics are one way to control the expression of genes so that we live healthier lives. For more information follow this link human genome research.

Probiotic Foods

Probiotics can be taken as supplements but are naturally found in some founds including:

• Yogurt
• Sauerkraut
• Miso
• Kefir
• Sourdough bread
• sour pickles
• Kombucha
• Kimchi

The Downside of Antibiotics

I see it nearly daily. A patient gets the sniffles for a day or two and wants an antibiotic because “I just can’t afford to get sick” as if anyone can, or “I don’t want to pass this on to my wife or kids”. Ideally, you want your body to fight the infection. It improves your immune function in the long run.

Certainly there are times when it is appropriate for antibiotics but we are learning to be more judicious in prescribing them. One reason is to reduce the likelihood of developing antibiotic resistant bacteria – already a growing problem.

But, there is a second reason and maybe more important reason when it comes to your individual health (antibiotic resistance is more a public health concern). When you take an antibiotic you alter your normal gut flora too as some of your gut flora is killed by the antibiotic and that impacts your health negatively.

We all know people who receive an antibiotic for a sinus infection, then two to three weeks later they are on another antibiotic for bronchitis, then a month later they are on another antibiotic for a urinary tract infection. The antibiotics have altered the normal healthy gut flora compromising their immune function and they have decreased ability to fight an infection on their own. They find themselves in a vicious downward spiral becoming increasingly dependent on antibiotics to fight infections.

So don’t be too quick asking your doctor for an antibiotic when you get an infection and be sure to take probiotics along with it if you do receive a prescription for one.

Those little creatures in our gut are there for a reason. That’s the take home message. In a future post we will discuss what to look for in a high quality probiotic. They are not all the same.