The Hierarchy of Evidence Explained: How to Know What to Believe in the Age of Information

We live in an incredible age of information. The upside: an abundance of data at our fingertips, helping us make considered supplement support choices.

The downside? With science, opinion, marketing, and interpretation all competing to shape our decisions, information overload can make it hard to know which evidence-based supplements to trust. 

For Dr Jenna Macciochi, Director of Science and Innovation at Ancient + Brave, when it comes to making sense of supplement claims, the hierarchy of evidence is the tool she turns to. Here, she guides you through what this is and how it can help you make more informed wellbeing support choices.

"The hierarchy of evidence is something I think about constantly, both as a scientist for over 20 years, and as someone responsible for translating research into something people can actually use in their lives." — Dr Jenna Macciochi

What is the hierarchy of evidence?

We have never had access to more health information. We have also never been more misled by it.

Thousands of studies are published every week. Influencers cite them with the same authority as professors. AI generates health content that reads as knowledgeably as a clinician yet may be entirely fabricated. 

That’s where the hierarchy of evidence comes in.  A simple way to map that mountain of evidence in front of you: it helps you to move beyond asking “Is there evidence for this supplement?” towards asking “What kind of evidence sits behind this supplement, and how much weight should I give it?”

At the bottom sit the weakest forms of evidence. At the top sit the strongest. In the next section, I’ll guide you through each stage in detail.

The hierarchy of evidence explained: From weakest to strongest

At the bottom: Expert opinion and anecdote

This is where most wellness content lives. founder's personal story. A before-and-after. A quote from someone with impressive credentials sharing what worked for them. 

This evidence sits at the bottom of the hierarchy partly because one person's experience tells you very little about what will happen to you and partly because this evidence is most vulnerable to bias. That’s not to say it is worthless; far from it, it is simply your sign to use this form of evidence as a starting point.

Near the bottom: Animal and in vitro studies

These are studies conducted in cell cultures or through animal testing. They help researchers understand how a treatment or substance functions so that they can assess if a hypothesis is worth testing in humans.

However, they’re limited. Many things that work brilliantly in a petri dish or in a mouse do nothing or cause harm in humans. If a claim rests primarily on in vitro or animal testing, it's worth digging deeper.

In the middle: Observational studies

Observational studies watch what people do and what happens to them, without intervening. It can be useful evidence, but it generates associations, not proof.

A good example of an observational study is a vitamin D test evaluating vitamin D levels in winter. This can tell us that vitamin D levels fall at a time when respiratory illness rises, but it can’t tell us whether low vitamin D caused the increase in illness, or whether both are simply consequences of the same thing: people spending less time outdoors, moving less, and gathering indoors where viruses spread more easily.

Second from the top: Randomised controlled trials 

Here’s where the evidence gets really robust. A well-designed randomised controlled trial (RCT)  is the gold standard for establishing whether a wellness product works. However, running an RCT is expensive, complex, and time-consuming, which is why there are fewer of them in nutritional science than anyone would like.

An RCT involves taking a group of people, randomly assigning them to receive either the intervention being tested or a placebo, and objectively measuring what happens. 

The randomisation is critical and helps ensure that differences in outcome can be more confidently attributed to the intervention itself.

RCTs should also be double-blinded, meaning neither participants nor researchers know who received what until the data is analysed. This reduces the risk of expectation effects distorting the results.

Our BECOME collagen clinical study is a rare example of a collagen RCT and demonstrates the whole-body benefits of True Collagen. It's one of the ways that we go beyond to bring you the proof outlined in our Evidence Ecosystem, and you can read the results of the trial here.

At the top: Systematic reviews and meta-analyses 

At the top of the hierarchy sit systematic reviews and meta-analyses.

A systematic review identifies every study that meets pre-defined quality criteria on a given question, and analyses them together. A meta-analysis goes further, pooling the data statistically to calculate an overall effect size across studies.

Together, they look at the full body of research, spotting patterns that only become visible at scale, and highlighting where studies contradict each other. When multiple well-designed trials consistently point in the same direction, that is as close to certainty as nutritional science tends to get.

A great example of this is the 2026 Anglia Ruskin University umbrella study, which goes beyond being a single meta-analysis and offers a synthesis of multiple meta-analyses, drawing on over 113 scientific studies involving almost 8,000 people, to demonstrate the many wellbeing benefits of collagen peptide supplementation.

How Ancient + Brave uses the hierarchy of evidence

At Ancient+ Brave, the starting point for every formulation is always to look first to systematic reviews and well-designed human randomised controlled trials when evaluating ingredients. 

We work with independent researchers and academic partners, verifying our decisions with third-party tests that report not only what the evidence shows, but its limitations.

Through our partnership with Light Labs, we provide supplement transparency around our quality test results, and crucially, we don't overstate claims because of our respect for both science and people purchasing our products.

Closing thoughts from Dr Jenna Macciochi 

In a world where a single small study can generate global headlines within hours, where influencers cite research with the same authority as professors, it's clear that the misinformation problem in health and wellness largely stems from selective use of evidence.

The loudest voice in the room is rarely the most rigorous one. Which is why the most important thing is the framework outlined above, which you can use to evaluate the evidence yourself. 

As someone who has reviewed thousands of studies, designed trials, and published peer-reviewed work, I return to this constantly. While it will not solve everything. I hope it gives you the confidence to question us and anyone else making a claim. 

If you’re ever unsure about our claims, or would like to double-check anything with us, we’re here to help. Reach out to our friendly customer service team whenever you need an honest answer. 

References
Ravindran, R., Pizzol, D., López-Gil, J.F., Rahmati, M., Boyer, L., Fond, G., Butler, L., Stellato, A., Gawronska, J., Barnett, Y., Keyes, H., Soysal, P., Eren, R., Onal, B., Yon, D.K. and Smith, L. (2026) ‘Collagen supplementation for skin and musculoskeletal health: An umbrella review of meta-analyses on elasticity, hydration, and structural outcomes’, Aesthetic Surgery Journal Open Forum, 8, ojag018. doi:10.1093/asjof/ojag018.