Anxiety/adrenaline after eating food of any kind. (Possibly postprandial adrenergic syndrome?)

Hi there,
I've had this problem for years, which has caused my life to become a living hell at times. After eating food, of any kind (proteins, carbs, veggies, fruits), within 10-20 minutes I begin having a surge of adrenaline. This adrenaline places my body in a fight-or-flight mode, leaving me in "anti-predator" mode. I usually become quiet, snappy, and have low energy.

The only thing that has helped this condition has been niacin. I must take at least 500 mg after eating meals, or the condition will happen every time I eat something.

Does anyone have any ideas as to WHY this is happening? Is there any permanent way to fix this, or must I use niacin after meals for the rest of my life?