I'm afraid you're wrong (see the irony?)

I do not believe there always is a reason for fear.

I disagree with you, there is always a reason for fear, and in fact, you are already offering a reason for their existence:

It is something of the mind and it can be triggered by a lack of vitamins, minerals, hormone, etc.

Metabolic reasons.

I do believe there are people who never felt afraid

I don't think so. Even Jesus and Buda felt afraid. If you're human, it's normal to be afraid of something.