Normal colonoscopy, chest cta, & brain/neck/upper back mri. but get left arm numbness sensation when i take any medicine/supplements and foods high in fat/sugar/grease/dough make me feel fainty. even just 1 bite.not diabetic. what should i look for?

With all the complex tests you have done and yours doctors could not make a diagnosis, it is impossible for us to provide an accurate assessment. Please follow with your doctors and trust them.

With respect to the left arm numbness, the usual causes are poor circulation from blocked or compressed artery,radiculopathies from neck vertebral spurs or disc disease,cardiac ischemia, cererbral vascular disease,thoracic outlet syndrome,certain type of migraine,& perpheral neuropathy which is what I think you experience. An EMG might demonstrate this. Discuss with your MD or neurologist.