It's clear to me that there is a great deal of nutritional advice grounded in weak or worthless evidence. A few reasons that the evidence is weak: Long-durations RCTs are very hard to run (they would ideally run for decades, it's generally hard to blind people to what they are eating, it's hard to make people stick for long periods to diets they haven't chosen themselves). Observational studies are badly confounded and you can't control perfectly for all confounders. The usual "Why Most Published Research Findings Are False" problems are exacerbated by the existence of food producers with big budgets and huge incentives to influence the findings.
Is there any trustworthy guide to... (read more)