Felice grew up in a family of naturopaths, studied arts, then decided to study psychiatry. As she had suffered from anxiety, she wondered if there was a link between mood and food. This book collates parallel lines of evidence from meta data analysis of psychiatric studies, clinical research into animal diet and nutritional information (of which she does not claim to have expertise) to draw correlations between mental health and diet.
The meta analysis of data dredged from other studies is not designed to test her strong belief that there must be links. She notes that proof is impossible to find, as it involves unethical studies on humans. In addition she outlines the caveats of the analysis she uses, discussing sample size (in most studies this is way too low) and confirmation bias (which, ironically, Felice has in spades).
The strength of the book is at the beginning, with the description of large studies and how these observations may direct future research. The middle part outlines her own smaller scale research. Everywhere she looks, it seems, there is some correlation between food and mental health.
The third part of the book is speculative about diet trends today, such as ketones, low carbs, Paleo etc. and a summary of different government messaging about diet. The final part, surprising to me, were recipes, and a description of her eating habits. Essentially she is provides diet advice throughout but says this is not a diet book.
We've always known that diet impacts physical and mental health, but Felice wants to take that one step further. She has set up her own branch of psychiatry and convinced the Australian government to provide better diet messaging. All very good.
Her writing is chatty, but possibly too technical for the general audience. I would have liked some summary tables with sample sizes, the population demographic and some assessment of the accuracy of conclusions (low, I suspect). What was frustrating is that when her studies don't show what she expects, she invents yet another hypothesis. Reverse causality? Well, prove it!
What Felice does show is how complex mental health and diet are, how difficult it is to provide advice to individuals from population studies, and that the impact of one on the other can only be shown at the extremes. Even then, the cause and effect (physiological/psychological basis) is unknown.
Felice mentions the method by which she collected some data, and it would have been good to have those questions or a short version of them in the book. The book as a whole outlines her motivations, passion and interest in this branch of psychiatry, and a lot is common sense.
Claims that a whole food diet can improve your mental health on the back cover mean that it can, but it won't necessarily will. As we know, mental health depends on a lot of factors and the degree to which diet influences it depends on a lot of things too.
Good luck to Felice as she undertakes more research with specific objectives. Hopefully others do the same so that future meta analysis can be as or more useful.