My left eye sometimes twitches on its own.(always left, never right) could certain nutritional deficiency cause this kind of blepharospasm?

No: One sided intermittent twitching is not of nutritional origin. It is most likely due to excitation of a few branches of the facial nerve on that side as it exits from the skull. There is no need to worry unless this is accompanied by hearing loss or facial weakness. Try relaxing the muscles involved in chewing.

Eye twiching: If you mean the eyelid blinking of fluttering, it my be myokymia due to stress or simply dryness of the eye. If the eyelid(s) contract fully, and is very noticeable it could be blepharospasm or hemi-facial spasm. See an ophthalmologist. Most likely stress related.