I think that there are very complex issues here but I am sceptical of anything written by Dr Hyman. He has no professional experience of psychiatric medicine.

On the other hand, he is the owner of an entity called "The UltraWellness Center" - a pretentious label is never a good sign.

The titles of some of his books (none of which seem to have been peer-reviewed) include:

The UltraMind Solution: The Simple Way to Defeat Depression, Overcome Anxiety, and Sharpen Your Mind

The UltraSimple Diet: Kick-Start Your Metabolism and Safely Lose Up to 10 Pounds in 7 Days

The UltraMetabolism Cookbook: 200 Delicious Recipes that Will Turn on Your Fat-Burning DNA

He seems to like the term "Ultra" and the notion of "Fat-Burning DNA" is particularly nonsensical for any evidence-based biomedical scientist.

He looks to me to be just another evidence-free complementary/alternative medicine practitioner who makes money by selling books and other products through his "UltraWellness Center".