Where our information comes from

Evidence hierarchy

We prioritise systematic reviews and meta-analyses, followed by well-conducted randomised controlled trials and large prospective cohort studies. Single small studies are treated as preliminary.

Mechanistic and animal research may explain how something might work, but it is not treated as evidence of an effect in people.

Organisations we rely on

World Health Organization (WHO), National Institutes of Health (NIH), NHS, Centers for Disease Control and Prevention (CDC), European Food Safety Authority (EFSA), and university research centres such as the Harvard T.H. Chan School of Public Health.

Where national guidance differs between countries, we note that rather than presenting one country's advice as universal.

What we will not do

We do not invent citations, statistics or expert quotes. If a claim cannot be confidently supported by a credible source, it is qualified in the text or removed.

We do not cite supplement retailers, commercial marketing material or single-source blog posts as evidence.

Reporting an issue

If you believe something on this site is inaccurate or out of date, we would rather know. Corrections are made in the article and reflected in its updated date.