Read this before you buy another probiotic

6 reasons your gut issues may not be a gut problem.

You’ve done the probiotic. Then the better probiotic. The fibre. No bread. And you’re still bloated by four. There’s one part of digestion nothing on that shelf was made for.

Start with reason 1

Developed with a medical and nutrition advisory team. Updated October 2026 · 4 min read

A woman with her hand on her stomach. A line runs from a knot in her gut up through her neck to her head.May start hereFelt here
The short version

It might not be a gut problem. It might be a nerve problem.

Your gut does its own moving. But a nerve from your brain sets the pace: when to start, how fast, when to ease off. Almost nothing on the shelf is made for that part. Here are six reasons it’s worth a look.

01

Everything you’ve tried works on what’s in your gut.

Open the cupboard and look at what’s in there.

A cupboard shelf with a jar of probiotics, a pouch of fibre, peppermint capsules, antacid tablets and a card with bread crossed out.
  • The probioticAdds bacteria.
  • The fibre sachetsAdd bulk.
  • The peppermint capsulesCalm a cramp for an hour.
  • The antacidsSettle acid that has already come up.
  • No bread, no dairy, no onionsTakes food away.

Each of them does a real job, and for plenty of people that’s enough. But every one works on what’s in your gut. None of them works on the signal that tells your gut what to do with it.

That doesn’t make them wrong. It leaves one part of digestion that none of them reaches.

02

Your gut does the moving. A nerve sets the pace.

Your gut is up to nine metres of muscle, with a nervous system of its own that squeezes food along.

But it takes its cues from above. The main line from your brain to your gut is called the vagus nerve.1 It carries the “rest and digest” signal: when to get going, how fast, when to ease off.

A woman in profile with a line running from her brain down to her stomach and gut, arrows showing signals in both directions.The vagus nerve

When that signal is turned down, things can slow. Food sits. And more on the pile isn’t what’s missing.

Fibre adds bulk. It doesn’t set the pace.

03

It’s worse on your worst days.

Fine on holiday. Terrible in a deadline week. Same food.

The same plate of chicken, potatoes and greens twice: once beside a laptop, emails and a clock, once beside a glass of water and a plant.A deadline weekA calm week

When you’re stressed or rushed, your body turns digestion down.2 Lunch can wait when your body thinks it’s under threat.

You’ve felt it. The knot in your stomach before a big meeting. The dash to the loo before a flight.

If it follows your week and not your plate, food is unlikely to be the whole story.

04

The top, the middle and the bottom go wrong together.

Acid coming back up. Food sitting like a brick. Days without going, or a dash to the loo. They feel like separate problems, and you’ve been sold a separate fix for each.

The digestive tract with three numbered points: 1 at the top of the stomach, 2 in the stomach, 3 in the intestines.
  1. 1 · TopThe lid

    The lid at the top of your stomach should stay shut. When it doesn’t, acid comes back up.

  2. 2 · MiddleThe emptying

    Your stomach should empty in good time. When it doesn’t, food sits there and you swell.

  3. 3 · BottomThe pace

    Your gut should move things along at a steady pace. Too slow, and the days go by. Too fast, and you’re looking for the nearest loo.

One nerve has a hand in all three.1

05

Two Nobel Prizes already said so.

This is a hundred years old. It’s in the medical textbooks.

Illustrated portraits of Ivan Pavlov, 1904, and Otto Loewi, 1936.
  1. 1904Nerves direct digestion

    Ivan Pavlov wins the Nobel Prize for showing it.8

  2. 1921The nerve’s messenger

    Otto Loewi finds the chemical the vagus nerve uses to give its orders.3

  3. 1936A second Nobel

    Loewi’s finding wins the prize too.9

It just never made it onto a supplement shelf.

06

A nerve has to be fed. Almost nobody feeds it.

The chemical Loewi found is the nerve’s messenger. Your body has to build it fresh, every day, from raw materials.4

To keep the line to your gut working, the nerve needs three things.

A brain joined to a gut by a nerve, with three circles around it: a spark, building blocks and calm waves.FuelBuilding blocksA calm state
  1. FuelA nerve this busy burns through energy all day.
  2. Building blocksThe raw materials it makes its messenger from.
  3. A calm stateA braced body turns the signal down, as in reason 3.

Each one depends on the other two. It’s a chain, and a chain needs every link.

Probiotics feed your gut. Nothing on that shelf feeds the nerve.

If this sounds like you

  • You’re flat at breakfast and tight by teatime.
  • It’s worse in a hard week, whatever you eat.
  • You have more than one of these: the acid, the bloat, the days without going, the dash to the loo.
  • There’s a drawer of half-used probiotics.
  • Your tests came back “normal”.

Then it’s worth looking at the nerve, not just the gut.

What to do about it

So we built what the nerve runs on.

Vagus One is all three links, in one formula. Nine nutrients, each with a job, made to work together. Two capsules a day, with a meal.

Vagus One bottle and two capsules on a stone plinth.
What the nerve needs
What Vagus One gives it
Fuel, to power the line
Four nutrients for the nerve’s own energy supply, in forms your body can use.
Building blocks, to make the messenger
Three nutrients: both halves of the messenger, and what joins them.
A calm state, so the message lands
Two more, for the state your gut does its work in.
Every link, every day
All nine in one formula, balanced to work together.
See all nine, with doses

Fuel. Benfotiamine 200 mg, thiamine 25 mg, active B2 10 mg, magnesium 60 mg.

Building blocks. Citicoline 250 mg, vitamin B5 100 mg, acetyl-L-carnitine 300 mg.

A calm state. L-theanine 150 mg, saffron 30 mg.

Per two capsules. Thiamine, riboflavin and magnesium contribute to normal functioning of the nervous system; pantothenic acid contributes to normal synthesis and metabolism of some neurotransmitters.

Ten years of trying things
“A lot of gut issues… over the last 10 years… I thought, well, that’s different than [a] nutritionist telling me to cut this out, cut that out. So, I thought I would give it a try… Less bloating, less indigestion, but most importantly less food reactions and being able to just eat a variety of foods in peace. The longer I take it, the better I feel.”
Yvonne M. · Yona customer, in her own words
From our advisor, a former NHS doctor

“One thing increasingly frustrated me.”

I worked as a doctor in the NHS, so I’ve seen healthcare from the inside. And medicine is brilliant at diagnosing and treating disease. If something’s seriously wrong, that’s exactly what you need.

But one thing increasingly frustrated me. We often treat the symptom in front of us. Bloating? Something for the gut. Can’t sleep? Something for sleep.

And I kept seeing the same pattern. Digestion that changed with stress. Sleep that fell apart when people couldn’t unwind.

So I started asking: what if these aren’t separate problems at all?

That question led me to the nervous system, and eventually the vagus nerve. What surprised me was that almost everything people were doing for it was stimulation. Cold water. Breathing. Devices. Hardly anyone was talking about what the nerve actually runs on.

I’m not against medicine. I still tell people to see their GP, especially if something’s new or getting worse. I just don’t think the conversation should always stop at the symptom.

That missing half is why we built Yona.

Sana MisraYona advisor · Former NHS doctor
The clinicians who advise us
Dr Alisha Damani
Dr Alisha Damani
MBChB· Clinical adviser

Specialises in autonomic nervous system function and its effect on digestive health: the exact biology Vagus One is built around.

David McCollum
David McCollum
Cert Nat ANP· Clinical nutritionist

Twenty-five years in clinical nutrition, working with people who haven’t responded to conventional approaches.

Vagus One, from 84p a day90-day promise · optional free add-on
See offer
In their words

Hear it from the people taking it.

Videos from Yona customers, including Vagus+, the formula Vagus One grew out of. Individual experiences vary.

Real Yona customers

Thousands now eating with food freedom.

“Less bloating. A lot calmer.”

Within the first week I felt a massive difference and have continued using these daily. I have less bloating… Feeling a lot calmer too.
Kathleen M. · Verified review

“Decades rather than years”

…I am no longer constipated (problems in that for decades rather than years!)…
Mary H. · Verified review, September 2025

“I’d had this problem for YEARS”

I have been taking these capsules for a few months to try and stop my excessive burping and after the second/third bottle I realised I’d virtually stopped burping completely.
LBM · Verified review, June 2026

“Nerves, stomach, sleep: all improved”

I was skeptical that this product could support me, but on reflection my general regulation — nerves, stomach, sleep — have all improved and I’ve felt supported.
Jules Z. · Verified review, April 2026

“I can feel the difference”

I have been taking it for nearly a month and I can feel the difference… less bloating, and don’t seem to get any acid indigestion.
Sally S. · Verified review

“Much more settled after 6 weeks”

I didn’t think this would work. I was very suspicious. However after 6 weeks I am much more settled and don’t have the gut issues.
Jane J. · Verified purchase

“A meal without the panic”

…to be able to have a meal and not panic about feeling uncomfortable afterwards.
Liz H. · Verified review

4.6 from 1,000+ reviews

A ninety-day routine, with a money-back promise if nothing changes.
Try it for 90 days

Reviews from Yona customers, including Vagus+, the formula Vagus One grew out of. Headlines are pulled from each review; trimmed for length where marked. Individual experiences vary.

Before you order

Who this isn’t for.

Who it is for

Either you feel the difference, or you don’t pay.

Four in five customers we surveyed reported better digestion. Take it every day for ninety days. If nothing has changed, we refund what you paid, and you don’t send anything back.

“To be able to have a meal and not panic about feeling uncomfortable afterwards.”Liz H. · Verified review

81% of 748 Yona customers, 2026, self-reported. The promise covers your first 90-day supply; you claim between day 90 and day 120. Full terms are below.

The 90-day plan

Feed the nerve for 90 days.

One bottle and two refills: ninety days of nutrition for the nerve, backed by our money-back promise.

The Vagus One 12-week box: one bottle, two refill pouches, the guided plan and a QR card.
A woman holding a Vagus One bottle and a capsule. The image reads: your nervous system needs nutrition too.
A woman with a line of light traced from her head down her neck. The image reads: your brain and body never stop talking.
A Vagus One bottle between a high-alert side and a rest side. The image reads: your body has an on state, it also needs a way back.
A Vagus One bottle being put into a handbag. The image reads: in your bag, for busy days.
An open Vagus One bottle with its lid and three capsules beside it.
4.6from 1,000+ reviews
Vagus One

Daily nervous-system nutrition, designed around the biology of the vagus nerve.

  • Feeds the nerve that sets your gut’s pace
  • Eat with more confidence: 81% of customers surveyed reported better digestion
  • Two capsules a day. Nothing to cut out.
1. Choose your supply
2. Choose how you pay
3. Your order
Today’s total£76.00Free UK delivery · usually 2–3 days
What arrives, renewal and guarantee
What arrives
Vagus One: one bottle and two refill pouches (90 days), with the 12-week handbook and four extras.
Renewal
Renews at £76 every 3 months, the same as today, until you pause, skip or cancel.
Guarantee
Covered by the 90-day money-back promise (your first 90-day supply). Terms

Secure checkout

Visa Mastercard American Express Apple Pay Google Pay PayPalShop Pay Klarna
  • Pause or cancel anytime
  • Third-party tested, every batch
  • Vagus One: vegan, no fillers

Questions before you order? Message us on WhatsApp

“My general regulation — nerves, stomach, sleep — have all improved.”

Jules Z · Verified review
The 90-day promise

A full 90 days. One simple routine.

Your 90 days start when your order arrives. Take it every day for the full 90 days. If nothing has changed, email hello@meetyona.co.uk between day 90 and day 120 and answer a few short questions about how you took it.

We’ll refund what you paid for your first 90-day supply. You don’t need to send anything back.

Read the full promise

The 90-day promise applies to the 90-day supply only; the 30-day supply is outside it. Your 90 days start the day your order arrives. Take Vagus One every day, as directed, for the full 90 days. If nothing has changed, email hello@meetyona.co.uk between day 90 and day 120 and answer a few short questions about how you took it.

We’ll refund what you paid for your first 90-day supply. You don’t need to send anything back. On a subscription, your next delivery is billed about three months after you order; if you’re planning to claim, skip or cancel it first. Your statutory rights are unaffected.

CoversYour first 90-day supply
StartsWhen your order arrives
Claim windowDay 90 to day 120
ReturnsNone needed
The science

Over a century of research. One daily formula.

Vagus One is built on what physiology has known for more than a hundred years about the nerve that runs your digestion.

  1. 1921Your gut’s nerve has a messenger.

    Otto Loewi shows that the vagus nerve signals chemically. The messenger is acetylcholine, and the work wins a Nobel Prize.3

  2. 1943That messenger is built from nutrients.

    Acetylcholine is shown to be made from choline and an acetyl group. Later work ties that acetyl group to vitamins B1 and B5.4

  3. 2000sThe ingredients are tested in people.

    Citicoline, saffron and L-theanine go through randomised, placebo-controlled human trials.

What the research shows

Citicoline · 250 mg

In a double-blind trial of 60 women aged 40 to 60, 250 mg a day meant fewer attention errors than placebo after 28 days.5

Read the study
Saffron · 30 mg

In a double-blind trial of 128 adults, 28 mg a day improved mood scores against placebo. In a second trial at 30 mg, heart-rate variability held steady during a lab stress test, where it dropped on placebo.6

Study one Study two
Benfotiamine · 200 mg

In a human absorption study, benfotiamine raised blood thiamine far higher than standard thiamine.7

Read the study

40+ peer-reviewed studies behind the formula, 19 of them in people.

Start my 90 days See every study →
Questions

Questions people actually ask.

Will it stop my bloating?
We can’t promise that, and nobody honestly can. Vagus One is a food supplement, not a treatment. What we can tell you: in our survey of 748 customers, 81% reported better digestion, which means roughly one in five didn’t. That’s why the 90-day supply comes with a money-back promise.
What’s the optional Gut Repair+ add-on?
Vagus One is the plan, and for most people it’s all they’re here for. Gut Repair+ is a separate formula for anyone who’d also like support for the gut lining: sodium butyrate, S. boulardii, zinc carnosine and bovine immunoglobulin. If you want it, tick the box in the order form and one 30-day bottle (90 capsules, three a day), usually £29, is added free to your first 90-day supply on either plan. One per order, not repeated on renewals, while stocks last. Vagus One is vegan; Gut Repair+ contains bovine-derived immunoglobulin, so it isn’t suitable for vegetarians or vegans.
Is this a probiotic?
No. There are no bacteria, enzymes or fibre in Vagus One. It’s nutrition for the nerve side of digestion: vitamins, amino acids and a plant extract. You can take it alongside a probiotic if you already use one. (The optional Gut Repair+ add-on does include S. boulardii, a yeast.)
Why would I need this if I already eat reasonably well?
You might not, and a good diet comes first. Vagus One isn’t there to patch a poor one. Most of what’s in it isn’t something you’d count on meals for in these amounts: citicoline, acetyl-L-carnitine, L-theanine and saffron extract aren’t vitamins, and benfotiamine is a form of vitamin B1 made for supplements. The B vitamins and mineral alongside them are there because the nerve uses them together, in set daily amounts. So the question isn’t whether your diet is good enough. It’s whether a steady daily supply of these particular nutrients makes a difference you can feel. Ninety days is a fair test, and if nothing has changed, the promise covers your first 90-day supply.
Does Vagus One stimulate the vagus nerve?
No. It’s a food supplement. It provides nutrients; it doesn’t stimulate anything. The full formula and every dose are listed above.
How long until I notice a difference?
There’s no first-night effect, because you’re supplying raw materials rather than forcing a response. Of customers who noticed a change, 64% noticed inside four weeks. Ninety days is the fair test. There is no guaranteed timeline or result.
When’s the best time to take it?
Two capsules daily, with a meal. If you’re sensitive to supplements, start with one capsule a day for the first few days.
Do I need to change what I eat?
No. A varied, balanced diet comes first, and if a food genuinely disagrees with you, keep avoiding it. Vagus One doesn’t ask you to cut anything out.
Can I take it with medication or other supplements?
Speak to your doctor or pharmacist first if you take prescription medication, are pregnant or breastfeeding, are under 18 or have a diagnosed condition. Check the amounts across any other supplements you use.
When should I see my GP instead?
If you have blood in your stools, unexplained weight loss, difficulty swallowing, severe or persistent pain, diarrhoea that lasts more than seven days, or a change in bowel habit that lasts three weeks or more, see your GP. Those need assessing, not a supplement.
Do I have to subscribe?
No. Choose One-time purchase for a single payment and nothing renews. A subscription renews at the price in your order summary (every three months for the 90-day supply, monthly for the 30-day), with no minimum term; you can pause, skip or cancel.
How does the 90-day promise work?
It covers your first 90-day supply. Take it daily for 90 days from delivery. If nothing has changed, email us between day 90 and day 120 and answer a few short questions. No return is needed. The 30-day supply is outside the promise.

You’ve spent years on your gut. Give the nerve ninety days.

Nine actives. Two capsules a day. One ninety-day routine.

Try Vagus One for 90 days

90-day money-back promise · optional free add-on

  1. Overton E, Emelyanova A, Bunik VI. Thiamine, gastrointestinal beriberi and acetylcholine signaling. Frontiers in Nutrition. 2025;12:1541054. PubMed 40271433. Browning KN, Travagli RA. Central nervous system control of gastrointestinal motility and secretion. Comprehensive Physiology. 2014. PubMed 25428846.
  2. Konturek PC, Brzozowski T, Konturek SJ. Stress and the gut: pathophysiology, clinical consequences, diagnostic approach and treatment options. Journal of Physiology and Pharmacology. 2011. PubMed 22314561.
  3. Loewi O. Über humorale Übertragbarkeit der Herznervenwirkung. Pflügers Archiv. 1921;189:239–242. doi:10.1007/BF01738910.
  4. Nachmansohn D, Machado AL. The formation of acetylcholine. A new enzyme: “choline acetylase”. Journal of Neurophysiology. 1943;6(5):397–403. doi:10.1152/jn.1943.6.5.397.
  5. McGlade E, Locatelli A, Hardy J, et al. Improved attentional performance following citicoline administration in healthy adult women. Food and Nutrition Sciences. 2012;3(6):769–773. doi:10.4236/fns.2012.36103.
  6. Kell G, Rao A, Beccaria G, et al. affron®, a novel saffron extract, improves mood in healthy adults over 4 weeks. Complementary Therapies in Medicine. 2017;33:58–64. doi:10.1016/j.ctim.2017.06.001. Jackson PA, Forster J, Khan J, et al. Effects of saffron extract supplementation on mood, well-being, and response to a psychosocial stressor in healthy adults. Frontiers in Nutrition. 2021;7:606124. doi:10.3389/fnut.2020.606124.
  7. Xie F, Cheng Z, Li S, et al. Pharmacokinetic study of benfotiamine and the bioavailability assessment compared to thiamine hydrochloride. Journal of Clinical Pharmacology. 2014;54(6):688–695. doi:10.1002/jcph.261.
  8. The Nobel Prize in Physiology or Medicine 1904, Ivan Pavlov, “in recognition of his work on the physiology of digestion”. NobelPrize.org.
  9. The Nobel Prize in Physiology or Medicine 1936, Sir Henry Dale and Otto Loewi, “for their discoveries relating to chemical transmission of nerve impulses”. NobelPrize.org.

Cited as published research on the underlying biology, not as studies of Vagus One. Survey figures are self-reported by 748 Yona customers, 2026.

Policy