Introduction to Firmicutes

This blog post will provide a general overview of another phylum of bacteria present in the human gut: Firmicutes. Alongside the phylum of Bacteroidetes, Firmicutes is the second most abundant and diverse group of bacteria present in humans. These bacteria can span a wide range of functions, but mostly focus on energy extraction efficiency from all incoming food sources. Thus, unlike Bacteroidetes, which like to specialize in carbohydrate metabolism, Firmicutes can grow faster whenever there is more food present.

What are Firmicutes?

Firmicutes is a phylum of bacteria that makes up about 40% of all the bacteria in your gut microbiome. Similar to most other phyla, the exact proportion of Firmicutes in your gut depends on where in the world you live and what kind of diet you follow. Generally speaking, people who eat less fiber relative to energy dense foods have a larger population of Firmicutes in their guts. However, it is important to understand the role of Firmicutes before casting judgment on their utility.

The Evolutionary Mismatch H2
It is obvious to most that our lifestyle as a species has changed dramatically from when we were hunter-gatherers. This rapid shift in lifestyle has consequently thrown our bodies slightly out of whack. For example, we crave fatty, salty, and sweet food all the time because of our ancient drive to obtain energy whenever possible. However, in the modern day, this has generated a mismatch between our genetics and the environment, much to our chagrin. Something similar has happened with regards to Firmicutes in our gut.

Energy Efficiency

When our microbiome initially evolved, we lived in a world of famine and feast. This meant that it was important to extract as much energy from each bit of food as possible. After all, you didn’t know when your next meal would be. As a result, our bodies welcomed bacteria that could pull energy out of food quickly and efficiently. This is exactly what Firmicutes did; for millions of years, these bacteria helped ensure that our ancestors would not starve to death. The problem begins when we fast-forward to the present day.

We are now in the 21st century and more and more nations are becoming developed. The industrial revolution has enabled humanity to feed more people than ever before. Some places in the world have seemingly endless levels of food availability and the future is generally looking upwards. However, when you zoom in and look at this world at an individual’s level, there are many biological problems hidden from view.

In this bountiful world, our guts have had to process food faster than ever in our evolutionary history. The best way to accomplish this would be to sacrifice some energy efficiency so that we can eat without piling on the extra calories. Unfortunately, evolution cannot undo millions of years of work in the span of a few decades. Your body (and its resident bacteria) treat each bit of food as if it is the last one it will see for a long time. As a result, levels of Firmicutes explode in your gut as they proceed to pull as many calories as possible out of your meal. Since there is so much food, these bacteria keep growing, eventually triggering your immune system for population control. This triggering of the immune system can result in chronic problems such as IBS while the extra calories extracted from the food contribute to obesity and diabetes.

Novel Research Disclaimer

The story that is proposed above is backed by recent scientific papers which show that increased numbers of Firmicutes (relative to the numbers of Bacteroidetes) may contribute to diabetes, obesity, IBS, and other chronic issues. This area of research is relatively new, so take this narrative with a grain of salt. There have been some contradictory findings regarding Firmicutes, but the general association between the increase in the Firmicutes-Bacteroidetes ratio and chronic metabolic disorders is notable.

Basically, if you keep your Firmicutes levels low, you can eat the same food and get less calories out of it. However, if you eat energy rich food all the time, these bacteria will begin to grow in number and this effect will disappear.

Conclusion

In conclusion, Firmicutes is a phylum of bacteria that is essential to have in your microbiome for health. However, when left unchecked, these bacteria can begin to dominate the microbiome and have adverse effects. The best way to control the population of these bacteria is to regulate your diet. By eating more high fiber foods like greens, you can limit the amount of Firmicutes that can live in your gut since the fiber dependent Bacteroidetes will take over more of the gut surface. Keeping the levels of Firmicutes low will allow you to enjoy energy rich meals from time to time without impacting your long term health.