Health headlines are almost always misleading. Not always through malice — often through the natural process of compressing complex, uncertain science into a shareable sentence.
The Hierarchy You Need to Know
- Systematic reviews & meta-analyses — Pooling multiple studies reduces the impact of any single outlier. Start here.
- Randomised controlled trials (RCTs) — The gold standard for causation. Look for large sample sizes, pre-registration, and industry independence.
- Prospective cohort studies — Can establish correlation, not causation. Still valuable for long-term outcomes.
- Case-control and cross-sectional studies — Hypothesis-generating. Do not draw strong conclusions from these alone.
- Animal and in-vitro studies — Interesting mechanistically. Cannot be directly applied to humans without replication.
The Questions to Ask
- Who funded it? Industry-funded studies are 4× more likely to show favourable results.
- What was the effect size? Not just "significant" — how much of a difference did it make?
- Was it pre-registered? Registration before data collection prevents p-hacking.
- Has it been replicated? A single study proves very little.
Critical appraisal is a learnable skill. It takes practice, but it's one of the highest-value things you can develop as a health consumer.