Medical & Emotional Fitness (Mental Health) Data

National Library of Medicine
This is the first database I logged onto in 1984. At that time it was the largest database in the world for medical information.

PubMed
This is a division of The National Library of Medicine and is still one of my favorite spots for research.

PubMedCentral
There is a long list of databases in the dropdown at PubMed, but this is the one I refer to most often because it gives you the full text of an article or study. 

MedlinePlus
Another division of The National Library of Medicine where you can find articles on a wide range of medical issues.

National Institute of Mental Health 
As an entity, in my opinion, who has kept itself in the stone age of Emotional Fitness (mental health), I simply do not have a high opinion of this entity.

World Health Organization
Another large database of medical information The National Library of Medicine will reference. 

Centers for Disease Control and Prevention
This site has the latest in disease control and lots of statistical information on virtually any disease or mental health issue. 

Nutritional Data

Examine.com

USDA: National Nutrient Database for Standard Reference 
This is a database for looking up nutritional information. I personally like SELF Nutrition Data because it is easier to read but this one is a good cross reference.

SELF Nutrition Data
You have to tolerate ads, but this database is easier to comprehend than others. 

Functional Medicine

Find a Functional Medicine Doctor 
Functional Medicine practitioners are much more focused on gut health than most other disciplines. 

Naturopathic Doctor

Find a Naturopathic Doctor
If you are unable to find a functional medicine practitioner in your area a naturopathic doctor is a good choice as they also put a focus on gut health. 

Specialty Labs

Genova
This is where you go for comprehensive stool testing.

Center for Digestive Health
This is where you go for SIBO testing.

Cyrex Laboratories
This is where you go for the Intestinal Antigenic Permeability Screen.