Many evidence-based proponents will be quick to judge clinicians who claim that food can “improve symptoms of mental health disorders”, or when clinicians say that a good diet can “reverse” or even “cure disease”.  Let’s take a look at some of the literature to see what the “evidence” tells us.

Does food/glycemia/nutrition affect mood, depression, anxiety?
There are quite a number of studies implicating various nutritional disorders with mental disease, namely b12 deficiency, diabetes, and high glycemic diets.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3317401/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5532289/
https://www.ncbi.nlm.nih.gov/pubmed/11375373
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3022608/
https://www.nature.com/articles/s41598-017-05649-7
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3856388/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4515860/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5154680/
https://www.ncbi.nlm.nih.gov/pubmed/29189904

What about Food Quality and Food Security?
It seems as if food quality and food security play an intimate role in anxiety and depression.
https://www.ncbi.nlm.nih.gov/pubmed/30588894
https://www.ncbi.nlm.nih.gov/pubmed/30269866

Is there any evidence that a well-constructed, ketogenic diet could be beneficial?
Anecdotally, I can tell you many of my patients have been able to slowly taper their anxiolytics and antidepressants with weight loss and diet improvement. There does seem to be some early evidence that a well constructed Ketogenic diet can help mood and mental health.
https://www.ncbi.nlm.nih.gov/pubmed/30075165
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5357645/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5863039/
https://www.ncbi.nlm.nih.gov/pubmed/28808808

Is diet a cure for any of these disease?
Probably not, but it seems as if a bad diet can exacerbate symptoms while a well-constructed diet can improve symptoms.

Can a well-constructed diet ERASE childhood trauma, abuse or neglect? Can a diet cure you of a job that is stressing you out, or decrease your financial burdens?
Absolutely NOT! It can’t, sorry. I am making NO conclusions here, as more studies need to be done to understand the exact impact of diet on mental health. But clearly a nutritionally replete diet seems to be associated with a decreased burden of mental health issues and treating nutritional deficiencies seems to alleviate symptoms of depression and anxiety. And, this is only the tip of the iceberg. There is plenty of more evidence of iron excess, copper excess, folate deficiency, and other nutritional disorders that are implicated in psychiatric and mental health.

Bottom Line:
Can food be thy medicine?
Probably…
I know that for my myself, my family and my patients, I will recommend a low-sugar, real-food diet for overall health and wellness.