Higher mushroom consumption is associated with a lower risk of cancer
I don't put any credence on this. As the authors say this study merely suggests a possible relationship that needs to be investigated in a proper RCT.What I don't like1. Passive observational studies only. Therefore a huge risk of confounders (e.g. people who generally live a healthy lifestyle).2. The effect size is not very large, making it much harder to winnow out confounders.3. Invariably attempts to 'control' for confounders use simple linear models that that come nowhere close to actually controlling for confounders.4. They generally only control for known confounders. If there is an unknown confounder it will get through and mess up the results.5. It is really hard to tell what is a confounder and what is a legitimate node in the causal chain. As a simplistic example consider 'controlling' for lung cancer in a study of whether smoking is bad for you. Of course this would take away much of the reason why smoking is bad for you. You need a proper causal model informed by data - something that is hard to do. See Judea Pearl "Causality".6. Note the heterogeneity of results. This suggests that things are going on that are not captured by the studies. Note also that the types of mushrooms don't seem to matter - a strange thing if there were some magic factor in mushrooms, given how mushrooms vary greatly in nutrient content.7. Misuse of the term "significant" usually a shorthand for statistically significant. A very different thing from "practically significant, large enough to matter".