Is migraine a signal of unhealthy diet or health?

No: No one knows exactly what causes migraines, but they are felt to be vascular headaches, related to widening and narrowing of blood vessels in the head. What is well-known is that migraines can be triggered by all sorts of things - certain foods, smells, activities, drugs, etc. - which aren't always "unhealthy." being able to identify and avoid triggers is one of the best treatments for migraines.

Possibly: You could merely have some food allergies or be adversely affected by certain other things in your environment. Migraines also have a muscular component and can also be affected by your bite or the way your teeth fit together. Not related to health or lifestyle is a possibility.