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Seasonal Wisdom
OKH Elements Editorial · 2 Jul 2026
Scientists once took a group of mice and removed all their gut bacteria. Completely sterile guts, no microbiome at all. Then they put those mice in stressful situations and measured their reactions. The germ-free mice went to pieces. Way more anxious than normal mice. Way higher stress hormones. Then the researchers did something interesting — they transplanted bacteria from calm, low-anxiety mice into the stressed germ-free ones. The anxiety went down. The stress hormones dropped. The gut bacteria had changed how the brain behaved. This was 2018. Ayurveda had been saying something very similar since around 600 BCE.
Most people think of the brain as the control centre and the gut as a simple tube that digests food. That's not quite right.
Your gut has about 500 million neurons embedded in its walls — more than your spinal cord. It has its own nervous system, called the enteric nervous system, that can operate completely independently of your brain. If you cut the connection between the two, your gut would keep functioning on its own. This is why scientists sometimes call it the 'second brain.'
But the most striking thing isn't the number of neurons. It's what those neurons produce. Your gut makes about 90% of the serotonin in your entire body. Serotonin is the chemical most closely linked to feeling calm, stable, and content. It affects sleep, mood, appetite, and how you handle stress.
Most antidepressants work by keeping serotonin in circulation longer in the brain. But the gut is where most of it is made. If your gut is struggling, your serotonin production goes with it — and your mood follows.
The main communication channel between gut and brain is a nerve called the vagus nerve. It runs all the way from the base of your skull down to your colon, passing through the chest, heart, lungs, and every major organ along the way. 'Vagus' is Latin for wandering, which suits it well.
Here's the part that surprises most people. Of all the signals travelling through the vagus nerve, about 80% go upward — from gut to brain. Only 20% go the other direction. So your gut is sending far more information to your brain than your brain sends to your gut.
Your brain is, in a real sense, receiving a constant live report from your gut — and responding to it. When your gut is inflamed or under stress, those signals go up the vagus nerve and directly affect your mood, your anxiety levels, how well you sleep, and how clearly you think.
The strength of this connection — what researchers call vagal tone — can actually be measured through something called heart rate variability (HRV). People with stronger vagal tone tend to have lower inflammation, better emotional regulation, and more resilience under stress. People with low vagal tone have higher rates of depression, IBS, and cardiovascular disease.
The trillions of bacteria living in your gut aren't just along for the ride. They're actively shaping how your brain works.
They do this through a few routes. One is by producing short-chain fatty acids when they digest dietary fibre. These acids trigger cells in the gut wall to release hormones — including serotonin — that signal up the vagus nerve to the brain. The bacteria are essentially sending chemical messages that influence your mood and stress response.
Another route is through your immune system. About 70% of your immune cells live in and around your gut. The bacteria there constantly interact with those immune cells, training them, calming them, or activating them. When the wrong bacteria take over — from antibiotics, poor diet, or chronic stress — the immune system becomes more reactive. That inflammation doesn't stay in the gut. It crosses into the bloodstream and eventually reaches the brain, where it affects the same pathways involved in depression and anxiety.
The bacteria also control what happens to tryptophan — an amino acid you get from food. Tryptophan is the raw material for serotonin. When your gut bacteria are healthy, more tryptophan goes toward making serotonin. When the balance tips in the wrong direction, tryptophan gets redirected toward a different pathway that produces compounds associated with depression and cognitive decline.
Ayurveda described this connection in completely different language — but the core observation is the same.
In Ayurvedic anatomy, there are five sub-types of Vata, the dosha that governs all movement and communication in the body. Two of them are most relevant here: Prana Vayu (the energy governing the brain, perception, and consciousness) and Samana Vayu (the energy governing digestion and absorption in the gut).
The Charaka Samhita is clear about this: when Samana Vayu is disturbed — through irregular eating, the wrong foods, or stress — Prana Vayu is destabilised as a consequence. Mental restlessness, anxiety, poor concentration, and disturbed sleep follow. The gut goes first. The mind follows.
Ayurvedic treatment of anxiety and mental imbalance has always started in the gut for exactly this reason. Not with sedatives or calming herbs for the mind, but with digestive support, regular meals, warming spices, and herbs like Shilajit that restore depleted tissue. The theory was correct. The pathway — upward through what we now call the vagus nerve — is what modern neuroscience has only recently mapped.
The good news is that vagal tone can be improved with relatively simple habits. And most of them align with what Ayurveda has recommended for centuries.
Slow, deep breathing is one of the most effective. Breathing slowly — around 5 to 6 breaths per minute — directly stimulates the vagus nerve from the diaphragm upward. Even 10 minutes a day has been shown in multiple trials to measurably improve HRV. The Ayurvedic breathing practice called Nadi Shodhana (alternate nostril breathing) naturally lands in this range.
Fermented foods help because they support the specific bacteria — particularly Lactobacillus species — that are most active in signalling to the vagus nerve. Traditional cultures have always included fermented foods: yoghurt, kefir, fermented pickles, idli, dosa. Modern diets largely don't.
Chanting, humming, or even gargling sounds strange, but there's a real mechanism behind it. The vagus nerve passes right through the throat. Vibration in that area — from singing, humming, or gargling with water — literally stimulates the nerve. Ayurveda's tradition of mantra chanting was, incidentally, stimulating vagal tone at the same time.
For herbs: Shilajit and Ashwagandha both show effects on the stress hormone system in research, which indirectly supports gut-brain signalling. Brahmi (Bacopa monnieri) has more direct brain research behind it — multiple trials showing improved memory and processing, with a proposed mechanism involving the same neurotransmitters the vagus nerve uses.
We've spent decades treating the gut and the mind as separate departments. If you had anxiety, you saw a psychiatrist. If you had IBS, you saw a gastroenterologist. The two rarely talked to each other.
But the biology was never separate. The gut makes your serotonin. Its bacteria shape your stress response. Its nerve endings report constantly to your brain. The condition of one is the condition of the other.
Ayurveda never made that split. The concept that mental health begins in the gut — that Prana Vayu follows Samana Vayu — was built into the foundational texts. Treat digestion, and the mind settles. Neglect the gut, and no amount of mental practice will fully hold.
We now have the science to explain exactly why. The vagus nerve, the microbiome, the enteric nervous system. New names. Very old truth.
OKH Elements' Shilajit Resin and Ashwagandha products support both the stress hormone system and gut-brain communication — foundational to vagal tone and mental resilience.
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