What is the Human Microbiome?

Posted on Monday, July 27th, 2015

Written by Megan Scarth, AHN Student

Bacteria often get a bad rep in our society. We wash our hands with anti-bacterial soap, spray our counters with Lysol, and typically throw out food that’s been dropped on the floor. But in spite our efforts to keep them at bay, these much-maligned organisms are already housed in our own bodies. Approximately one hundred trillion microbes live in our guts, making up a unique ecosystem dubbed the “human microbiome.” For an idea of just how large the microbiome is, it has been estimated that humans contain ten times more bacterial cells than human cells! 

But unlike the strains of bacteria you may find in old, rotten food, these microbes are not there to harm us — in fact, they are absolutely essential to our survival. Our gut bacteria perform a huge array of functions in our bodies, such as helping digest food and absorb nutrients, creating physical barriers against “bad bacteria” and viruses, neutralizing toxins, supporting the immune system, aiding in sleep, and controlling inflammation.

One of the most important functions that bacteria perform is their vital role in the gut-brain connection. These two major parts of the body are linked through the vagus nerve, which is the longest of the twelve cranial nerves, and stretches from the brain stem to the abdomen. Both the gut and the brain can directly communicate through chemical messengers called neurotransmitters. But contrary to popular belief, not all neurotransmitters are made in the brain; 80-90% of serotonin, a natural antidepressant, is produced by the nerve cells found in the gut! The microbiome’s vital role in regulating our mental state has caused many to dub it as the body’s “second brain."

Hence, it’s not difficult to understand why keeping your gut flora happy is essential to overall health. That’s why foods that contain beneficial bacteria (probiotics) and nutrients to sustain these bacteria (prebiotics) can be a great addition to your diet. One of the best-known probiotic foods is yoghurt, and indeed, there’s a reason why there are so many health claims behind this popular and versatile food. That’s because when yoghurt is made from milk, it’s first cultured with two strains of beneficial bacteria called Lactobacillus bulgaricus and Streptococcus thermophilus, both of which make great additions to our microbiomes.

Yoghurt may be one of the most popular probiotic foods here in Canada, but it’s far from your only option. A close cousin of yoghurt is Kefir, which is a drink made from fermenting milk with the kefir grain. There’s also sauerkraut, which is made from cabbage, and is easy to make yourself, since the only ingredients are cabbage and salt. Miso soup packs a surprisingly hefty dose of 160 bacteria strain. Tempeh, which is similar to tofu and consists of packed, fermented soybeans, is another good source. Other good bets are most canned and fermented foods, such as kimchi, pickles, or even fermented hard-boiled eggs.

Scientists are only just starting to learn the importance of the human microbiome on our physical, mental, and emotional health. The wide-reaching health impacts may still be under study, but it’s never too early to start introducing some of these tasty and unique foods into your diet!

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