When there is mental illness there is almost always a poor diet. These are problems that go hand in hand, and poor nutrition is frequently overlooked by medical and mental health professionals alike. This is likely due to the fact that MD's and mental health professionals receive very little training in the area of nutrition.
The divide between medical, psychological, and dietary needs seems greater than ever in our modern society and are viewed as separate entities. However, in my experience adults and children alike, as the phrase states, are what they eat. And it's not just what they eat, the types of foods they prefer, but it's also how they eat.
When I was trained to become a therapist there was very little training about assessing for proper nutrition. The problem with this is that poor nutrition will have an effect on mood, thoughts, and even the brain. To give an extreme example, a person with an eating disorder such as anorexia who comes into my Malibu office for therapy may be unable to benefit from the therapy because they are starving themselves. Now, in this example someone who is actively starving themselves would likely need a referral to an inpatient treatment setting, and the reason for this is that the lack of nutrition has also starved their brain, the gray matter actually shrinks. They are unable to use the tools provided to them in therapy because they literally can't think. As I prefaced, this is an extreme example, but I believe in every case of mental illness, poor nutrition works together, exacerbating or causing symptoms, not just with a diagnosis of an eating disorder.
A holistic understanding about health is paramount as a psychotherapist. It's not enough to only attempt to understand people through fancy philosophical theories. Though I am not a nutritionist, I can ask about diet and look for some of the red flags. I have found these to include but are not limited to: diets restricting excessive amounts of calories, measuring calories, fasting, restricting certain food groups, binge eating, fear of certain foods, creation of intolerances or allergies to certain foods where there is none, and trying to be overly controlling with food (overly concerned about health so that a balanced diet is not achieved).
It is important to consider nutrition when trying to understand mental illnesses such as depression, anxiety, PTSD, Bipolar Disorder, and ADD as well as eating disorders as something not quarantined within the mind.