Science
Our approach to evidence
Every ingredient we use carries an evidence level. Every study we cite is appraised for what it shows and what it does not. Where evidence is limited, we say so plainly.
Five levels
How we grade evidence
Following the principles of the Oxford Centre for Evidence-Based Medicine.
Read the explainerTraditional use
Evidence level 1 of 5Documented in classical texts or long practice. Not yet tested in clinical trials. 44 of our ingredients are at this level.
Laboratory evidence
Evidence level 2 of 5Studied in cells or animals. Effects in people are not established. 7 of our ingredients are at this level.
Observational evidence
Evidence level 3 of 5Associations seen in human populations, which cannot prove cause and effect. 1 of our ingredients are at this level.
Clinical evidence
Evidence level 4 of 5Tested in randomised trials in people, usually small or short. 26 of our ingredients are at this level.
Systematic review evidence
Evidence level 5 of 5Several trials pooled and appraised together. 5 of our ingredients are at this level.
Our commitments
Our commitments
- Publish the full ingredient list of every product, with quantities wherever they are declared on the pack.
- Link every statistic and study to its original source.
- Show the strength of evidence, including where it is limited.
- Describe safety concerns, even when they are inconvenient.
- Correct errors openly when we find them.