Solid evidence
Several serious studies, run on humans, all pointing the same way. You can rely on it.
Evidence-based health · 37 products examined
Tell me what's wrong. I'll tell you what actually works.
GUIVONIZ goes through the food supplements sold on Amazon and ranks them in the same order every time: first, what the science has actually shown, then what fits your situation, and only after that, the price. No sponsored content. No superlatives.
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The question we get most
What does “level of evidence” actually mean?
It answers one question only: has the science really shown that this product does what it is said to do?
And one detail changes everything: the rating applies to one specific outcome, not to the product in general.
An example
Magnesium has solid evidence for correcting a magnesium
deficiency. But for “sleeping better”, the evidence is only
emerging.
On this site it is the second rating you see — because that is what people buy it for.
Emerging evidence
Studies exist, but few of them, short, or on small numbers of people. It is promising — it is not established.
Limited evidence
Little or no serious research. We keep it only when it is cheap and carries no risk. Not because it works.
Recommendations
The four supplements with the strongest evidence behind them
Ranked on the strength of the data, not on how many people they concern — two of them are only useful to part of the population, and we say so on each product page. Answer the fifteen questions and this list becomes yours.
Your day, if you follow the protocol
We are not selling you a stack of ten capsules. We spread a minimum of interventions across the moments when they work — and remove everything that does nothing.
Worth reading before you buy
Assessment
Fifteen questions. No sign-up. A protocol that looks like you.
Most health sites sell everyone the same list. Here, your chronotype, your training volume, your diet, your budget and your contraindications genuinely change the ranking — including by removing products from the page altogether.
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Everything is computed in your browser, offline.
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No account, no email, no advertising cookie.
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Exportable and erasable in one click from “My profile”.
The laboratory
How we rank
We don't have a laboratory. We have a grid, and it is public.
The big comparison sites buy products and take them apart. We don't — and claiming otherwise would be dishonest. But for a food supplement, most of what matters about quality can be read off the label, provided you know what to look for. Here are the nine markers we check on every product, where to find them, and what they tell you. You can run the check yourself.
The products, under glass
Spin them around. Behind each object: what the researchers observed, what it does not show, and the three options compared.
Amazon affiliate links: we earn a commission if you buy, at no extra cost to you.
It changes neither the ranking nor the level of evidence shown.
* Budget bands are indicative and change often. Only the price shown on
Amazon at the moment you buy counts: check it before you order.
Our method
Four filters before a product gets onto this site.
Does the claimed result exist in the literature?
We start from the outcome measured in humans — not from the presumed mechanism, not from a cell study. Three levels only: solid, emerging, limited. The level is always shown, including when it is weak.
Is the dose in the product the one used in the trials?
The most common trap in this aisle: the right active ingredient, at 10 % of the dose studied. We compare the real per-unit dose with the published one, chemical form included.
Who must absolutely not take it?
Pregnancy, anticoagulant treatment, kidney failure, thyroid: every product page lists its contraindications, and the engine removes from your ranking whatever you have declared.
What does the result cost, per day?
We think in cost per day of actual use, not in shelf price. A large tub that lasts two months beats a small bottle that lasts ten days, even if it costs more to buy.
What we refuse to write
No product here is “revolutionary”, no supplement “detoxifies”, and nobody on this site will tell you that a capsule replaces a night's sleep. When the evidence is missing, we write that down. When the cheapest supplement is the best documented, we rank it ahead of the expensive one.
Before you go
You don't need thirty products. You need the right three.
Run the assessment: fifteen questions, and this page rewrites itself around your case — your chronotype, your budget, your contraindications. Nothing leaves your browser.