Gut Microbiome 101: What is it, Why is it so important and How to feed it

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The mighty microbiome. You can’t glimpse into the wellness world without hearing mention of this exciting area of research. Although scientists discovered gut bacteria in the late 1800’s, it wasn’t until the early 21st century (2001) that the term microbiome was described. So the concept of the microbiome is really in its infancy and what’s so exciting is that there is still so much to learn and I’ll be ready and waiting to geek out on all of it.

What exactly is this microbiome that everyone is buzzing about? It is defined as all of the trillions of microorganisms (bacteria and fungi) and their genetic material that line the digestive tract. It is commonly thought the ratio of bacteria to human cells exist in a 10:1 ratio, however now it is believed to be closer to 3:1 or 1:1. Why? Well two reasons- 1) it can depend upon whether non-nucleated cells are considered in the overall body cell count (think red blood cells) and 2) the microbiome has drastically changed since earlier counts which is likely due to the evolution of the western diet, changes in our soil and the constant use of hand sanitizer to name a few. Bottom line: these ratios show the magnitude of bacteria in our body and thus should have us thinking about the important role these bacteria play in our overall health.

Why is the gut microbiome important to our health?

The gut microbiota are involved in a number of metabolic and immune functions as well as manufacturing neurotransmitters, enzymes and vitamins like vitamin K.

Healthy gut bacteria also help to maintain the lining, or mucosa, of the gut so that the bad stuff such as toxins and waste do not leak out into our body. If this should happen a whole host of problems occur such as inflammation, allergies, etc. The following are the benefits of a healthy gut flora:

· Improved immune function – At least 70% and up to 80% of our immune system resides in our gut. The good bugs in our tummies fight the bad bugs therefore we want to keep them populated and thriving.

· Management of blood sugar – Research is being conducted to show the link between gut bacteria and glucose metabolism and homeostasis. This area of research is exciting and can provide a new way to treat diabetes.

· Reduced weight- Crazy as it sounds, our microbiome may be more responsible for our cravings than our head. When we crowd out the bad, sugar-craving bacteria (that result from the consumption of sugary, processed foods) with fiber-filled, whole foods we find less cravings and usually a reduction in weight. Further, our healthy gut bacteria metabolize fiber and produce chemicals that help us feel full.

· Reduced inflammation- As mentioned before healthy gut bacteria maintain the integrity of our gut lining. Without a healthy gut lining, toxins escape into the bloodstream and lead to chronic inflammation (the underlying cause of chronic diseases).

· Improved mood- Our gut bacteria communicate with our brain along what is called the gut-brain axis or HPA (Hypothalamic–pituitary–adrenal) axis. Our microbiota secrete neurotransmitters such as dopamine and GABA that work to boost mood and calm anxiety.

What disrupts the gut microbiome?

Dysbiosis is the term used to describe instances when our gut microbes are out of balance. Symptoms of dysbiosis include upset stomach, bloating, diarrhea, constipation, depression, anxiety, skin issues, gas, fatigue and so on. Here are some factors leading to imbalance:

-Overuse of antibiotics – I can’t stress enough, don’t take them unless you need them! Antibiotics fight the bad bacteria and kill the good bacteria as well. It can takes months to repopulate the good bacteria that we lose.

-Processed foods, especially processed meats

-High fat foods such as fried foods, fatty meats and cheeses

-Artificial sweeteners

-High sugar diets

-Diets high in animal protein

-Food additives such as emulsifiers, which wreak some serious havoc on our gut mucosa and have been indicated as major culprits in chron’s and inflammatory bowel disease

-Psychological and physical stress

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How do we feed the microbiome?

Research suggests that the growth of the microbiome begins as early as when we are in our mother’s womb. Factors such as vaginal versus cesarean birth or breast versus formula feeding are the first determinants of further growth and diversity. So what can we do to maintain a healthy gut flora and promote growth and diversity?

Here are my top tips:

1. Plant number and diversity in the diet- Plant diversity is KEY when ramping up your gut microbiome. A plant based diet is more effective than taking a probiotic to build/restore gut bacteria.

2. Fiber- Fiber has countless health benefits. In terms of the microbiome, fiber is paramount to growth of the good gut bacteria. When fiber hits the large intestine it gets converted through fermentation to short chain fatty acids (SCFA’s)- butyrate, acetate and propionate. The SCFA’s are the primary fuel, or food, for our beneficial gut bacteria. Good sources of fiber are fruits, vegetables, nuts, seeds and legumes. PRObiotic fiber supply our gut with the good bacteria, PREbiotic fiber feed the gut bacteria. The best prebiotic fiber rich foods are asparagus, leeks, onions, garlic, spinach, beans, bananas and oats. Aim to get at least 35-40 grams per day.

3. Spend time outdoors – Being outside exposes you to different microbes and can help build your microbiome diversity.

4. Exercise – Studies have shown that exercise can increase the number and diversity of the gut flora.

5. Eat fermented foods – Fermented foods such as kefir, kimchi, tempeh, yogurt and kombucha may play a role in the gut bacteria number and diversity. A special consideration when choosing products, such as kombucha and yogurt, is whether the products have undergone the process of pasteurization. The good bacteria would not survive the pasteurization process and therefore would not have a beneficial effect.

6. Sleep – A positive correlation exists between sleep quality and number of gut flora.

7. Probiotics- I tread lightly on this one. The science is weak on whether probiotic use has an overall impact on the gut microbiome. Keep in mind that the probiotic industry is a multi-billion dollar industry on this one with major marketing heft. The instance where I would definitely recommend a probiotic supplement is following a course of antibiotics. Consumers must also be aware that not all probiotics are created equal. Probiotics contain different bacteria strains that address some problems but not others. Know which strain you need for your specific issue, otherwise the benefit is null.

Bottom line:

Our gut microbiome consists of trillions of cells, weighing up to five pounds. It is so vast and carries out important metabolic and immune function that it is considered as a separate organ in the body. Research is growing on how the microbiome impacts our health and how it might work to prevent and treat disease. Stay tuned for more on the mighty microbiome because it is going to be a hot area of research for years to come. In the meantime, feed yours right with a variety of pro- and prebiotic foods because diet is the number one determinant of gut health.


The NIH Human Microbiome Project

Revised Estimates for the Number of Human and Bacteria Cells in the Body

20 Things you Didn’t Know About the Human gut Microbiome

Exercise Modifies the Gut Microbiota with Positive Health Effects

A preliminary examination of gut microbiota, sleep, and cognitive flexibility in healthy older adults.

Role of the gut microbiota in nutrition and health

Gut-Brain Axis and Mood Disorder

Mechanisms Linking the Gut Microbiome and Glucose Metabolism

Jaime Shelbert