The phrase “gut health” has been all over health programs and magazines for the past few years.

At first it sounded vaguely trendy to me. But after six months of eating fermented foods and starting to sense real changes in my body, I finally wanted to understand properly: why is the gut such a big deal?

The Ecosystem Called the Gut Microbiome

The human gut is home to approximately 1,000 species and more than 100 trillion bacteria. Their total weight reaches about 1.5 kilograms.

This community of bacteria is called the “gut flora” (or gut microbiome). The name apparently comes from the fact that under a microscope, it looks like a field of flowers (flora).

The gut flora is broadly divided into three types: “beneficial bacteria,” “harmful bacteria,” and “opportunistic bacteria” — the ones that side with whichever group has the upper hand. Keeping the beneficial bacteria in the majority is the basic idea behind gut health.

Why Fermented Foods Help

The lactobacillus, yeast, and other microbes in fermented foods do, to some extent, join the gut flora directly after being consumed — but more importantly, they seem to play a supporting role in improving the gut environment overall.

Specifically, the microbes in fermented foods can serve as food for the gut’s beneficial bacteria, and can stimulate the gut lining to strengthen immune function. The organic acids produced during fermentation (such as lactic acid) also keep the gut mildly acidic, creating an environment where harmful bacteria have a harder time multiplying.

More recent research has also revealed that the gut and brain are deeply connected through a neural network called the “gut-brain axis.” When the gut environment is disrupted, it’s been shown that stress resilience can decrease and mood can drop.

It Doesn’t Work “Right Away”

What I learned from researching this is that improving the gut environment doesn’t happen quickly.

The gut flora varies enormously from person to person, and the same foods produce different effects in different people. Changing the balance of gut bacteria requires sustained changes in eating habits.

“Dramatic improvement in one week” is unfortunately something you can basically rule out.

On the flip side, that means people who stick with it longer are the ones most likely to feel gradual, steady changes.

I Understand a Little Better Why I’ve Been Feeling What I Feel

The changes I noticed over six months — a more settled stomach, feeling cleaner and more awake in the morning — now make a little more sense to me scientifically. I can’t explain all of it, but I’ve come to feel that it’s not unrelated to improvements in my gut environment.

It’s not “just my imagination.” Something inside me may genuinely be shifting.

Thinking that made me trust fermented foods one level deeper.

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Next time: Six months of eating fermented foods. A careful inventory of the changes.

※ This article is based on personal experience and publicly available information. It is not intended to diagnose, treat, or prevent any disease. If you have health concerns, please consult a doctor or registered dietitian. See our Disclaimer.