Kimchi kills anxiety

and so does miso, yogurt, and other fermented foods

TL;DR: Researchers showed that germ-free mice exhibit exaggerated anxiety and hyperactive neurons because their SK-channel is almost gone. Reactivating those channels with an SK agonist or simply giving the mice the microbial metabolite indole found in kimchi, restores the brake, neutralises neuron excitability, and kills anxiety-like behaviours by about half.

So eat your kimchi.

I still remember the first time I tried kimchi. It was ten years ago, and it was horrendous. I hated it. I pushed it aside and swore I’d never touch fermented cabbage again.

Fast-forward a decade: I popped into a full-blown Korean food culture, and somehow that same kimchi became my favourite part of the meal. I was expecting the worst, but now I can’t imagine grabbing K-Bbq without some kimchi on the side.

Now science shows those tangy little cabbages are beneficial for our brains.

Let’s dive into it.

How fermented foods calm the brain’s fear centre

Published in February this year, Weonjin Yu and colleagues investigated the effects of microbial metabolites towards anxiety-linked behaviours in mice.

First, the team compared completely germ-free mice (raised without a single microbe) to normal mice in anxiety tests. The germ-free mice froze more in open arenas and spent less time exploring the “risky” parts of a raised maze. When they peeked into the brains of those mice, they saw a flood of c-Fos (a marker of neuronal “wakefulness) lighting up in the basolateral amygdala, i.e., our built-in alarm system.

(A) Total distance traveled in the open field test in GF and SPF mice. (B, C) Total time spent in the open arms of the elevated zero maze (B), and the number of transitions between the two closed arms (C) in GF and SPF mice, SPF N = 9, GF N = 10. https://www.embopress.org/doi/full/10.1038/s44321-024-00179-y

Next, they snipped out that exact amygdala slice, and used tiny electrodes to measure how easily its neurons fired. Think of this like a sensitivity test for neurons. In germ-free mice, just a small jolt of current made those cells shoot off far more spikes than usual, despite the basic parts (voltage-gated channels) all looked normal.

So… why did it happen?

The researchers found out that those germ-free mice were missing a neuron “brake” called the medium after-hyperpolarisation (mAHP), which are normally driven by SK potassium channels. In germ-free neurons, that brake was almost gone. And to further prove this point, the authors bathed the tissue in 1-EBIO (an SK-channel activator) which activated the brake and tamed the firing.

The point is, simply restoring normal gut bacteria can dial the amygdala back to sanity, and even better, it was found that giving germ-free mice a steady dose of indole (a metabolite you get from fermented foods like kimchi) did the same job on its own! Indole crossed into the brain, reactivated SK channels, and reinstated the mAHP brake, which cuts anxiety behaviours nearly in half!! Isn’t that cool?!

After reading this week’s journal paper in its entirety, it never ceases to amaze me just how connected our whole body is. The human body is an incredible assembly of systems that somehow just know how to get things done.

Right now my brain feels like it needs a bandage after rapid learning electrophysiology and the amygdala. Or maybe I could just open the fridge, grab a quick bite of kimchi, and call it a day.

Talk soon,

Krish

Help us keep sharing relatable science

▶ Know someone who’d love this? Forward it their way.

▶ Was this forwarded to you?

▶ Got something cool? Let’s get it out there.

Reply

or to participate.