What does evidence mean (state of the research)?
In medicine and science, evidence describes how well a claim is supported. It refers to the state of the research: the quantity, quality and consistency of the studies available. Strong evidence rests on several well-run studies in humans, weak evidence on single cases, cell experiments or animal studies.
Evidence explained simply
In science "evidence" does not mean "obvious", it means supported by data. The state of the evidence describes how reliable our knowledge is on a question, for example: does substance X help with complaint Y? Not every study weighs the same. What matters is the study type, size, duration, quality of conduct and whether several independent investigations reach the same result.
The evidence pyramid: from weak to strong
A simplified ranking of study types. The further down the table, the more reliable the statement for humans.
| Level | Example | Strength |
|---|---|---|
| Level Laboratory experiment (in vitro) | Example Effect on cells in a dish | Strength a hint, but far from humans |
| Level Animal study | Example Experiments on mice or rats | Strength a hint, not directly transferable |
| Level Observational study, case report | Example People are observed, no allocation | Strength can show associations but not prove cause |
| Level Randomised controlled trial | Example Random allocation, comparison with placebo | Strength good strength for an effect |
| Level Systematic review / meta-analysis | Example pools several studies | Strength highest level, if the single studies are good |
Evidence for turmeric and curcumin
For curcumin there are many laboratory studies, but far fewer large, well-controlled studies in humans. In our articles on osteoarthritis, curcumin is considered the best-studied of the spices, above all in knee osteoarthritis, where several controlled trials and reviews exist. For ginger the evidence is thinner, and for spices such as nutmeg there are no large clinical trials demonstrating efficacy and safety.
Even "solid" evidence does not mean that something certainly helps. It means that the available studies point in the same direction, but effects are often moderate and studies can remain small, short or inconsistent. And one preparation tested in a study is not the same as every other product with the same ingredient.
Look for: studies in humans, a placebo group, an adequate number of participants (small studies with a few dozen participants are only of limited value), independent confirmation, and who funded the study. Single reports, cell experiments and mouse studies are interesting but no proof of an effect in you.
Frequently asked questions about evidence
What does "evidence-based" mean? Decisions rest on the best available research, complemented by experience and the individual situation.
Is "no evidence" the same as "does not work"? No. Missing evidence means there are not enough studies, not that an effect has been disproved. Conversely, an effect is not shown either.
Who assesses evidence? Professional societies and bodies such as EFSA evaluate studies by fixed criteria. EFSA also reviews health claims for foods.
