A useful evidence hierarchy starts by asking whether the study actually matches the claim being made.
1. Mechanism or Laboratory Research
Cell and laboratory studies can suggest biological mechanisms. They do not demonstrate that people taking a finished supplement experience a meaningful clinical benefit.
2. Animal Research
Animal studies can provide clues, but physiology, dose and metabolism may differ from humans.
3. Observational Research
Observational studies can identify associations but cannot reliably prove that an ingredient caused an outcome.
4. Randomized Controlled Trials
Randomized trials can provide stronger evidence when they are well designed, adequately powered and measure outcomes that matter.
5. Finished-Product Trials
For a branded supplement, the strongest direct evidence would generally come from studies of the actual formulation at the actual dose and for the claimed outcome. That is the evidence most relevant to the question “Does this product work?”