How we grade evidence

Health advice about aging is full of confident claims built on thin research. Every article on Kotsu opens with an Evidence at a glance table, so you can see how solid each claim is before you read a word of explanation.

The four grades

A few rules decide which grade a claim gets:

• Association is not causation. Large cohort studies can show that two things travel together — for example, stronger people tend to live longer. That alone is graded B, however large the study, because it cannot show that changing one changes the other.
• The outcome matters. A trial showing that a supplement changes a blood marker is not evidence that it changes how you look, move or feel. We grade the claim the article actually makes.
• The best evidence wins, including when it disagrees. If good trials find no benefit, the claim is graded D even when smaller studies looked promising.
• Every grade links to its sources. References carry a DOI so you can read the original paper.

Editorial rules

• No affiliate links and no sponsored content. Nothing on this site earns money when you buy a product.
• We check, we don't prescribe. Articles explain what the research shows. They are not personal medical advice, and the author does not give individual advice through this site.
• Conflicts are declared. Where an article discusses a treatment the author provides in clinical practice, it says so at the top, and the evidence is graded by the same rules.
• Outside the author's specialty, we say so. Skin and hair topics are written as evidence checks. Where a specialist reviews an article, their name appears on it.
• Articles are updated. When an important new study changes a grade, the article is revised and its "Updated" date changes.