Why do I feel scared?

A nutrient deficiency that’s most likely to put you in a state of fear is a vitamin B1 deficiency (thiamine). Without enough vitamin B1, certain parts of the body can’t work right. For example, you could have problems with the amygdala, the autonomic nervous system, or the adrenals. 

The best source of vitamin B1 is nutritional yeast. You can get this as a powder or tablet. Just make sure it doesn’t come with synthetic fortification.