Thanks Dalmeet for the sensible article. I spent several years working with researchers around the world on the interplay between nutrients and cognitive function and the harsh reality is that most studies are far too small, far too short-term, and far too poorly analyzed (the statistical treatments are usually naive at best) for any conclusions to be drawn. Meta-studies merely show en large what the underlying poorly designed studies show, which is like saying we can learn about vehicle accidents by studying many incorrect reports about vehicle accidents.
Everyone wants an easy fix, a simple answer. Biology, however, is complex and we’re only at the very beginning of grappling with its complexity. One good source of well-designed studies (not just double-blind placebo controlled but also longer-term and with statistically valid sample sizes and no p-hacking) is the BPNRC at the University of Northumbria, UK. Most teams, however, fail to meet such adequate standards and their conclusions therefore are worthless.